1610773947_FundamentalsofPlantPhysiology3.1Theory-LectureNote-Jan2021.pdf

It has all the basic concepts of plant physiology which are needed for a beginner level to understand how the science behind it works.
Great! Here’s a 2000-word comprehensive description of your plant physiology PowerPoint presentation covering all major concepts. The description will follow a structured format, breaking down each topic into key ideas to give a clear overview of the depth and breadth of the content.

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## **Plant Physiology: A Comprehensive Overview**

Plant physiology is the study of how plants function, focusing on all the vital processes that keep them alive. Your PowerPoint presentation aims to provide a detailed exploration of these processes, combining theoretical understanding with experimental evidence. The PPT will cover a wide range of topics from water relations to the mechanisms of photosynthesis, plant growth, hormonal control, and stress physiology. Below is a breakdown of each major section.

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### **1. Water Relations in Plants**

#### a. Water Absorption and Transport
This section of your PPT focuses on how plants absorb water through their roots and transport it to different parts of the plant. It highlights the structure and function of root hairs, which increase surface area for absorption. The movement of water from the soil into the root xylem via osmosis is explained, along with concepts like the apoplast and symplast pathways.

#### b. Water Potential
Water potential (Ψ) is critical in understanding water movement in plants. The PPT explores the components of water potential—solute potential (Ψs) and pressure potential (Ψp). The role of water potential in determining the direction of water movement, from roots to leaves via the xylem, is described. The concept of turgor pressure and its impact on plant rigidity and growth is also highlighted.

#### c. Transpiration and Water Loss
This section discusses transpiration, the loss of water vapor from plant surfaces, particularly the stomata. It covers the role of stomata in regulating water loss and gas exchange, along with the physiological and environmental factors affecting stomatal opening and closing. The cohesion-tension theory is detailed, explaining how water is pulled upward through the xylem as water evaporates from leaf surfaces.

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### **2. Photosynthesis**

#### a. Overview of Photosynthesis
Photosynthesis is the cornerstone of plant physiology, converting light energy into chemical energy. The PPT introduces the overall photosynthetic equation, describing the inputs (carbon dioxide, water, light) and the outputs (glucose and oxygen).

#### b. Light Reactions
This section provides an in-depth explanation of the light-dependent reactions occurring in the thylakoid membranes. Key processes include the absorption of light by chlorophyll and other pigments, the flow of electrons through the electron transport chain, and the generation of ATP and NADPH. The role of photosystems I and II, proton gradients, and photophosphorylation are emphasized

1. THEORY
Chapter-1:Introductiontocropphysiologyanditsimportancein
Agriculture;
Chapter-2:Plantcell:anOverview;
Chapter-3:Diffusionandosmosis;
Chapter-4:Absorptionofwater,ascentofsap,transpiration,
antitranspirantsandStomatalPhysiology;
Chapter-5:MineralnutritionofPlants:Functionsanddeficiencysymptoms
ofnutrients,nutrientuptakemechanisms;
Chapter-6:Photosynthesis:LightandDarkreactions,C3,C4andCAM
plants;
Chapter-7:Respiration:Glycolysis,TCAcycleandelectrontransportchain;
Chapter-8:Plantgrowthregulators:Physiologicalrolesandagricultural
uses,
Chapter-9:Physiologicalaspectsofgrowthanddevelopmentofmajorcrops:
Growthanalysis,RoleofPhysiologicalgrowthparametersincrop
productivity.
Chapter-10:PhotoperiodismandVernalization
Chapter-11:Translocationofsolutes

2. PRACTICAL:
Practical-1:Studyofplantcells
Practical-2:Structureanddistributionofstomata
Practical-3:Imbibitions
Practical-4:Osmosis
Practical-5:Plasmolysis
Practical-6:Measurementofrootpressure
Practical-7:Rateoftranspiration
Practical-8:Separationofphotosyntheticpigmentsthrough
paperchromatography
Practical-9:Photosynthesis
Practical-10:Respiration
Practical-11:Tissuetestformineralnutrients
Practical-12:Estimationofrelativewatercontent
Practical-13:Measurementofabsorptionspectrumof
chlorophyll

3. Lecture-1
(A)Introduction to crop physiology
&
(B) Importance in Agriculture

4. PlantPhysiology:
Itisstudyofinternalprocessesandtheirfunctional
aspectssuchasphotosynthesis,respiration,transpiration,
translocation,nutrientuptake,plantgrowthregulation
throughhormonesandotherbiologicalprocesses.
Hereditary
potential
External
environment
Internal
processes &
conditions
Plant growth
&
Development
(A) Introduction to crop physiology

5. Crop:
Itisgroupofplantsgrownasacommunityina
specificlocalityand,foraspecificpurpose.
Cropphysiology:
Itisastudyinwhichplantphysiological
processesareintegratedtocausewholeplant
responsesincommunities.

6. BRIEF HISTORY OF CROP PHYSIOLOGY:
1627-SirFrancisBaconpublishedoneofthefirstplantphysiology
experimentsinthebook,SylvaSylvarum.
1648-JanBaptist&VanHelmontpublishedwhatisconsideredthe
first“quantitativeexperimentinplantphysiology.”
1699-JohnWoodwardpublished“experimentsongrowthof
spearmintindifferentsourcesofwater”.
1771-JosephPriestly:Plantscouldgenerateoxygeninthe
atmosphere.
1779-Ingenhouz:Studiestheroleoflightinphotosynthesis.
1727-StephenHalesisconsideredtheFatherofPlantPhysiologyfor
themanyexperimentsinthefieldofPlantPhysiology.
1865-Juliusvon Sachs published “Experimentelle
Pflanzenphysiologi”whichunifiedthespiecesofplant
physiologyandputthemtogetherasadiscipline.His
“LehrbuchderBotanik”wastheplantphysiologybibleofits
time.

7. Hecalculatedinfluxof
waterintotheplantwith
theamountofwater
leavingtheplantby
transpirationthroughthe
leaves.
Healsomeasured'the
forceofthesap'orroot
pressure.
Halescommentedthat
"plantsveryprobablydraw
throughtheirleavessome
partoftheirnourishment
fromtheair".
STEPHENHALES
Hestudiedtranspiration:Thelossofwaterfromtheleavesofplants.
Heestimatedthesurfaceareaoftheleavesoftheplantandthelength
andsurfaceareaoftheroots.

8. 1915-W.L.Balls:Stateddynamicsofyielddevelopmentincrops.
1947-D.J.Watson:TheconceptofLAI(leafareaindex)was
developed.
1950-D.J.Watson:DevelopmentofInfraRedGasAnalysis
(IRGA)methodforestimationofphotosynthesisand
respirationbycropsinthefield.
1953-MonsiandSaeki:Heexplainedlightinterceptionbythe
cropcanopy(Conceptoflightinterceptioncoefficient)
1963-HeskethandMoss:ResearchonphotosyntheticCO2
fixationpathwayslikeC4andCAMmechanisms.

9. (B) IMPORTANCE OF CROP PHYSIOLOGY IN
AGRICULTURE AND HORTICULTURE:
1.Itprovideunderstandingaboutseedgermination,seeding
growth,cropestablishment,vegetativedevelopment,
flowering,fruitandseedsettingandcropmaturity.
2.Itprovidesknowledgeofseedphysiologythathelpsin
understandingofphysiologicalandmorphologicalchanges
occurduringgermination.
3.Ithelpsinpredictshigheryieldincropsishightotaldry
matterproductionperunitarea(CGR).
4.Itgivestheestimatesofphotosynthetesusedinrespiration
processandphotosynthetessynthesizedduring
photosynthesis.
5.Theknowledgeofnutrio-physiologyhashelpedin
identificationofessentialnutrients,ionuptakemechanisms,
theirdeficiencysymptomsandcorrectivemeasures.

10. 6.Photoperiodism
7.Ithelpstoknowrequirementofconcentrationof
hormoneapplication.
8.Physiologicalapproacheshelpsincalculatingwateruse
efficiency(WUE).
9.Knowingphysiologicalchanges,helpsinreductionin
postharvestlossesofagricultureandhorticulturecrops.
10.Usefulinunderstandingthevariousaspectsof
metabolism,growthanddevelopment.
IMPORTANCE OF CROP PHYSIOLOGY IN
AGRICULTURE AND HORTICULTURE:

11. Lecture-2
(A) Introduction to Plant Cell
(B) Cell Theory &
(C) Cell wall

12. Plantcellsareeukaryoticcellsthatdifferinseveralkeyaspectsfromthecellsofothereukaryoticorganisms.
Thesedistinctivefeaturesincludethefollowing:
Alargecentralvacuole,awater-filledvolumeenclosedbyamembraneknownasthetonoplastthat
maintainsthecell'sturgor,controlsmovementofmoleculesbetweenthecytosolandsap,storesuseful
materialanddigestswasteproteinsandorganelles.
Acellwallcomposedofcelluloseandhemicelluloses,pectinandinmanycaseslignin,issecretedby
theprotoplastontheoutsideofthecellmembrane.Thiscontrastswiththecellwallsoffungi,whichare
madeofchitin,andofbacteria,whicharemadeofpeptidoglycan.Cellwallsperformmanyessential
functions:theyprovideshapetoformthetissueandorgansoftheplant,andplayanimportantrolein
intercellularcommunicationandplant-microbeinteractions.
Specializedcell-to-cellcommunicationpathwaysknownasplasmodesmata,poresintheprimarycellwall
throughwhichtheplasmalemmaandendoplasmicreticulumofadjacentcellsarecontinuous.
Plastids,themostnotablebeingthechloroplast,whichcontainschlorophyll,agreen-coloredpigmentthat
absorbssunlight,andallowstheplanttomakeitsownfoodintheprocessknownasphotosynthesis.
Othertypesofplastidsaretheamyloplasts,specializedforstarchstorage,elaioplastsspecialized
forfatstorage,andchromoplastsspecializedforsynthesisandstorageofpigments.Asinmitochondria,
whichhaveagenomeencoding37genes,plastidshavetheirowngenomesofabout100–120
uniquegenesand,itispresumed,aroseasprokaryoticendosymbiontslivinginthecellsofan
earlyeukaryoticancestorofthelandplantsandalgae.Celldivisionbyconstructionofaphragmoplastasa
templateforbuildingacellplatelateincytokinesisischaracteristicoflandplantsandafewgroupsof
algae,notablytheCharophytesandtheChlorophyteOrderTrentepohliales.
Themotile,free-swimmingspermofbryophytesandpteridophytes,cycadsandGinkgoaretheonlycells
oflandplantstohaveflagellasimilartothoseinanimalcells,buttheconifersandfloweringplantsdonot
havemotilespermandlackbothflagellaandcentrioles.
(A) Introduction to Plant Cell

13. DIFFERENT TYPES OF CELLS:
Parenchymacells:
Theyarelivingcellsthathavefunctionsrangingfromstorageandsupport
tophotosynthesisandphloemloading(transfercells).
Apartfromthexylemandphloemintheirvascularbundles,leavesarecomposedmainlyof
parenchymacells.
Someparenchymacells,asintheepidermis,arespecializedforlightpenetrationandfocusing
orregulationofgasexchange,butothersareamongtheleastspecializedcellsinplanttissue,
andmayremaintotipotent,capableofdividingtoproducenewpopulationsofundifferentiated
cells,throughouttheirlives.
Parenchymacellshavethin,permeableprimarywallsenablingthetransportofsmallmolecules
betweenthem,andtheircytoplasmisresponsibleforawiderangeofbiochemicalfunctions
suchasnectarsecretion,orthemanufactureofsecondaryproductsthatdiscourageherbivory.
Parenchymacellsthatcontainmanychloroplastsandareconcernedprimarilywith
photosynthesisarecalledchlorenchymacells.Others,suchasthemajorityoftheparenchyma
cellsinpotatotubersandtheseedcotyledonsoflegumes,haveastoragefunction.
Collenchymacells:
collenchymacellsarealiveatmaturityandhaveonlyaprimarywall.
Thesecellsmaturefrommeristemderivativesthatinitiallyresembleparenchyma,but
differencesquicklybecomeapparent.
Plastidsdonotdevelop,andthesecretaryapparatus(ERandGolgi)proliferatestosecrete
additionalprimarywall.Thewallismostcommonlythickestatthecorners,wherethreeor
morecellscomeincontact,andthinnestwhereonlytwocellscomeincontact,thoughother
arrangementsofthewallthickeningarepossible.

14. Sclerenchymacells:
Sclerenchymacells(fromtheGreekskleros,hard)arehardandtoughcellswithafunction
inmechanicalsupport.Theyareoftwobroadtypes–sclereidsorstonecellsandfibres.
Thecellsdevelopanextensivesecondarycellwallthatislaiddownontheinsideof
theprimarycellwall.
Thesecondarywallisimpregnatedwithlignin,makingithardandimpermeabletowater.
Thus,thesecellscannotsurviveforlong'astheycannotexchangesufficientmaterialto
maintainactivemetabolism.
Sclerenchymacellsaretypicallydeadatfunctionalmaturity,andthecytoplasmismissing,
leavinganemptycentralcavity.
Functionsforsclereidcells:
Hardcellsthatgiveleavesorfruitsagrittytextureincludediscouragingherbivory,by
damagingdigestivepassagesinsmallinsectlarvalstages,andphysicalprotection(asolid
tissueofhardsclereidcellsformthepitwallinapeachandmanyotherfruits).

15. Inbiology,celltheoryisthehistoricscientifictheory,nowuniversallyaccepted,thatliving
organismsaremadeupofcells,thattheyarethebasicstructural/organizationalunitofall
organisms,andthatallcellscomefrompre-existingcells.
Cellsarethebasicunitofstructureinallorganismsandalsothebasicunitofreproduction.
Withcontinualimprovementsmadetomicroscopesovertime,magnificationtechnology
advancedenoughtodiscovercellsinthe17thcentury.
ThisdiscoveryislargelyattributedtoRobertHooke,andbeganthescientificstudyofcells,
alsoknownascellbiology.Overacenturylater,manydebatesaboutcellsbeganamongst
scientists.Mostofthesedebatesinvolvedthenatureofcellularregeneration,andtheideaof
cellsasafundamentalunitoflife.
Celltheorywaseventuallyformulatedin1839.ThisisusuallycreditedtoMatthias
SchleidenandTheodorSchwann.However,manyotherscientistslikeRudolf
Virchowcontributedtothetheory.
Itwasanimportantstepinthemovementawayfromspontaneousgeneration.
Cell theory are as described below:
(i)Alllivingorganismsarecomposedofoneormorecells.
(ii)AllCellsarisefrompre-existingcells.
(iii)Allcellsarebasicallyalikeinchemicalcompositionandmetabolicactivities.
(iv)Thecellisthebasicunitofstructureandorganizationinorganisms.
(v)Thefunctionofanorganisationasawholeistheoutcomeoftheactivitiesandinteractionsof
theconstituentcells.

18. Lecture-3 & 4
Protoplasm and Cell
Membrane
Cell organelles and its
functions

20. Sr. No. Details Animal Cell Plant Cell
1
Cell wall
Absent Present (formed of cellulose)
2 Shape Round(irregular shape) Rectangular (fixed shape)
3
Vacuole
One or more small vacuoles
(much smaller than plant cells).
One, large central vacuole taking
up 90% of cell volume.
4
Centrioles
Present Only present in lower plant forms.
5 Chloroplast
Absent Plant cells have chloroplasts
because they make their own
food.
6 Cytoplasm Present Present
7
Endoplasmic Reticulum
(Smooth and Rough)
Present Present
8 Ribosomes Present Present
9 Mitochondria Present Present
10 Plastids Absent Present
11 Golgi Apparatus Present Present
12
Plasma Membrane
Only cell membrane Cell wall and a cell membrane
13 Microtubules/
Microfilaments
Present Present
14
Flagella
May be found in some cells Not found
15
Lysosomes
Lysosomes occur in cytoplasm. Lysosomesusually not evident.
16 Nucleus Present Present
17 Cilia Present It is very rare

22. Sr. No.Details Eukaryotic Cell Prokaryotic Cell (Bacteria)
1 Nucleus Present Absent
2 Number of
chromosomes
More than one One--but not true chromosome:
Plasmids
3 Cell Type Usually multicellular Usually unicellular (some
cyanobacteriamay be multicellular)
4 Membrane
bound Nucleus
Present Absent
5 Example Human, Animals, Plants,
Amoeba, Paramecium,
Euglena etc.
Cyanobacteria, Staphylococcus aureus
E. coli, Lactobacillus and Salmonella
6 Genetic
Recombination
Meiosis and fusion of
gametes
Partial, undirectionaltransfers
DNA
7 Lysosomes and
peroxisomes
Present Absent
8 MicrotubulesPresent Absent or rare
9 Endoplasmic
reticulum
Present Absent
10MitochondriaPresent Absent
11CytoskeletonPresent May be absent

23. Sr. No.Details Eukaryotic Cell Prokaryotic Cell (Bacteria)
12 DNA wrapping on
proteins.
Eukaryotes wrap their DNA around
proteins called histones.
Multiple proteins act together to fold
and condense prokaryotic DNA. Folded
DNA is supercoiledand wound around
tetramers of the HU protein.
13 Ribosomes larger smaller
14 Vesicles Present Present
15 Golgi apparatusPresent Absent
16 Chloroplasts Present (in plants) Absent; chlorophyll scattered in the
cytoplasm
17 Flagella Microscopic in size; arranged as nine
doublets surrounding two singlets
Submicroscopic in size, composed of
only one fiber
18 Permeability of
Nuclear
Membrane
Selective not present
19 Plasma membrane
with steroid
Yes Usually no
20 Cell wall Only in plant cells and fungi
(chemically simpler)
Usually chemically complexed
21 Cell size 10-100um 1-10um

24. NUCLEUS CYTOPLASM
1. Nuclear
membrane
1. Plasma
membrane
6. Mitochondria
2. Nucleoplasm 2. Endoplasmic
reticulum
7. Plastids
3. Chromatin 3. Ribosomes 8. Lysosomes
4. Nucleolus 4. Golgi body 9. Microtubules
5. Vacuoles

25. NUCLEUS
Functions :
(1) NUCLEAR MEMBRANE :
It protect the chromosomes from cytoplasmiceffetcts
It permits transport of electrons and exchange of
materials between nucleus and cytoplasm
It give rise to some cell organelles
(2) NUCLEOPLASM :
Functions :
Its watery substances in higher nucleolus
It is also known as nucleoplasmor nuclear sap or
Karyolymph
It is shapeless and contain dissolved phosphorous ribose
sugar proteins, nucleotides and had nucleic acid

26. (3) CHROMATIN OR NUCLEAR RETICULUM:
Functions :
1.Chromatin is the basic unit of chromosomes contain
genes and thus play important role in the inheritance of
the character from the parents to offspring.
(4) NUCLEOLUS:
Functions :
1. Formation of ribosome and synthesis of proteins
2. It provide energy for all nuclear activities

27. CYTOPLASM
(1)Plasmalemmaorplasmamembrane:
Functions
1.Itregulatesthepassageinandoutofthecell
2.Itactasselectivepermeablemembrane
3.Itcheckstheentryoftoxicelementsfromoutsideintocytoplasm
4.Itpermitspassageofmoleculeslikemineralsintothecellandrestrict
theiroutwardmovement
(2)EndoplasmicReticulum(E.R.):
Functions:(E.R.)
1.Itisassociatedwiththesynthesisofproteins(roughE.R.),lipidsand
phospholipids(BothE.R.)
2.Providechannelsforthetransportationofsynthesizedmaterialto
variousparts
3.Providecontrolledpassagefortheexportofm-RNAfromnucleusto
roughE.R.
4.Severalenzymesareembeddedinthemembraneeg.Glucose-6-
phosphate,ATPaseetc.

28. (3) Ribosomes:
Functions :
1.To carry out protein synthesis with the help of m-RNA
(4) Golgi complex :
Functions :
1. Packaging food materials such as proteins, lipids and
phospholipids for transport to other cells
2. It secrete many granules and lysosomes
(5) VACUOLES:
Functions :
1.Storageandtransmissionofthematerialsand
maintenanceoftheinternalpressure

29. (6) Mitochondria:
Functions :
1. It involved in respiration, oxidation and metabolism of
energy (Power house of the cell)
2. They contain circular DNA and ribosomes, so they are
capable of synthesis of certain proteins
3. They contain DNA, so also contribute to heredity by the way
of cytoplasmicinheritance

30. (7) Plastid :
They are the self replicating cytoplasmicorganelles founds in plant cell
They are absent in bacteria, cerainfungi and animals
Mainlythreetypes:Leucoplast,ChromoplastandChloroplast
1.Leucoplast:
Theyarecolourlessandassociatedwithstorageofstarch,proteinandfats
2.Chromoplast:Colouredbutotherthangreenviz.,PlucoxanthinandPhycocynin.
Therefunctionsarestillnotclear.Theycontainpigmentsofdifferentcolour–
Yellow,orangeandred.ThecoluringmatterisassociatedwithXanthophylland
Carotene.
3.Cloroplast:Theyaregreenincolourduetochlorophyllpigment.Theyareacting
asthesitesofphotosynthesis.Theultrastructureofchloroplastconsistthreeparts
–Membrane,StromaandGranna
Stroma: It consist the enzymes related to dark reaction of photosynthesis
Granna: It is associated with electron transport and photophosphorilation

31. (8) Lysosomes:
Functions:
1.Itisresponsiblefordigestionofintracellularsubstances
andforeignparticles.
2. When cell dies lysosomesreleases its enzymes, which
digest the dead cell resulting in cleaning of debris.
(9) Microtubules :
1. Complex structure made up of 13 individual protofilaments
arranged to form hallow cylinder
2. Responsible for transportation of small molecules

32. Lecture-5
(A)DiffusionProcesses
(B)OsmosisProcesses
(C)Cellasanosmoticsystem
(D)Importanceofosmosis

33. (A) Diffusions:
Whensugarcubeorpieceisputinsidealiquid,thesugarmoleculesarediffusedthrough
theliquid,givinguniformlysweettaste.
Thefragrancefromanopenedbottleofperfumediffusingthroughofair.
Thismainlyduetothekineticpropertiesofmatterpossescertainamountofenergy.
Definition:
Ingeneral“themovementofanyparticles/moleculesfromaregionofhighconcentration
toaregionoflowerconcentrationduetotheirownkineticenergyinordertoequalizethe
concentrationofthetworegion”iscalleddiffusion.
Factorsdeterminedtherateofdiffusion:
Relativedensity,Temperature,ConcentrationGradientandConcentrationofmedium
Hydrogendiffuse4-timesfasterthanoxygen
Riseintemp.increasediffusion
Stepper(risingorfallingsharply)theconc.gradientincreasediffusion
Highconc.Ofmediumreducediffusionrate
Diffusionpressure:
 Thepotentialabilityofagas,liquidorsolidtodiffusefromanareaofitsgreatest
concentrationtoanareaoflowerconcentrationthatcreatepressureiscalledasdiffusion
pressure.AgasfilledinballoonhasgreaterDiffusionpressurethanthegassurroundsit.

34. OSMOSIS and DIFFUSION

35. ExamplesofDiffusionsofdifferentstatesofMatter:
FORMS EXAMPLES
Gas intogas Diffusion of Ammonia into air
Gas intoLiquid Foam
Gas into Solid Precious stone
Liquid into Gas Clouds
Liquid into Liquid Alcohol in to water
Liquid into Solid KOH solution into Solidified Agar
Solid into Gas Smoke
Solid into Liquid KMnO4 crystalplaced into water
Solid into Solid Copper into zinc metals are kept
press with one another.

36. Osmosisisaspecialtypeofdiffusion,whichinvolvesthemovementofwater
throughadifferentiallypermeablemembrane,fromanareawhereitisinhigh
concentrationtoanareawhereitisinlowconcentration.Osmosisissimilartodiffusion,
theonlydifferencebeing,andthepresenceofadifferentiallypermeablemembrane.
OsmosisProcessorPhenomenon:
Itisthespontaneousnetmovementofsolventmoleculesthroughaselectivelypermeable
membraneintoaregionofhighersoluteconcentration,inthedirectionthattendsto
equalizethesoluteconcentrationsonthetwosides.Itmayalsobeusedtodescribea
physicalprocessinwhichanysolventmovesacrossaselectivelypermeablemembrane
(permeabletothesolvent,butnotthesolute)separatingtwosolutionsofdifferent
concentrations.Osmosiscanbemadetodowork.
Osmoticpressure:
Itisthepressuredevelopedbythepresenceofsoluteparticlesinasystem.
Theosmoticpressureisdirectlyproportionaltothenumberofsolutemoleculesina
givenamountofsolvent.
Eg:1molarsolutionofanundissociatedsubstanceat0Chasatheoretical
osmoticpressureof22.4atm.

37. Turgorpressure/wallpressure:
Thepresenceofcellwallandplasmamembraneinplantcell
allowsittoexistinarelativelywiderangeofosmoticconcentration.
Whenplantcellsareplacedinpurewater,theyswellsupto
smallextent,butdonotburst.Becauseofthehighosmoticpressureof
thecellcontent,waterwillmoveintothecellresultinginthecell
membranesbeingpressedagainstthecellwall.Simultaneouslythewall
alsoexertsanequalamountofpressuretowardstheinnersideofthe
cell.ThispressureiscalledasTurgorpressureunderthisconditionsthe
plantcellissaidtobeturgid.

38. Osmosis Diffusion
Inosmosis,movementofmolecules
takesplacethroughasemi-permeable
membrane.
Indiffusion,thereisnoroleofsemi-
permeablemembrane.
Itinvolvesmovementofonlysolvent
moleculesfromonesidetotheother.
Itinvolvespassageofsolventaswell
assolutemoleculesfromoneregion
totheother.
Inosmosis,diffusionofonlysolvent
moleculesfromlowerconcentrationof
solutiontohigherconcentrationof
solutiontakeplace.
Indiffusion,anetdownward
movementofgivensubstancefrom
higherconc.tolesserconc.isfound.
Osmosisislimitedtosolutionsonly. Diffusioncantakeplaceinliquids,
gasesandsolutions.
Osmosiscanbestoppedorreversedby
applyingadditionalpressureonthe
solutionside.
Diffusioncanneitherbestoppednor
reversed
Differences Between Osmosis and Diffusion

39. Osmosisisaofdiffusionofliquids.Whentwosolutionsofdifferentconcentrations
areseparatedbyaselectivelypermeablemembrane,diffusionofwaterorsolvent
moleculestakesplacefromthesolutionoflowerconcentrationtothesolutionof
higherconcentrationiscalledOsmosis

40. Hypotonic–The solution on one side of a membrane where the solute
concentration is less than on the other side.
Hypertonic–The solution on one side of a membrane where the solute
concentration is greater than on the other side.

41. Green & Turgid Grapes
Shrunken & Dry Grapes
(A). HYPERTONIC SOLUTION: Higher conc. of solvent
(B). HYPOTONIC SOLUTION: Lower conc. of solvent
Watery & Turgid Grapes
Shrunken & Dry Grapes
Grapes soaked in
simple water

42. Osmosisisaofdiffusionofliquidandsolid.Whentwosolutionsofdifferent
concentrationsareseparatedbyaselectivelypermeablemembrane,diffusionof
waterorsolventmoleculestakesplacefromthesolutionoflowerconcentration(5%)
tothesolutionofhigherconcentration(10%)iscalledOsmosis.

43. Osmosis
•Osmosis is the movement of WATERacross a
semi-permeable membrane
•At first the concentration of solute is very high on
the left.
•But over time, the water moves across the semi-
permeable membrane and dilutes the particles.

44. Thecellsarerestrainedfrom
swellingbyinwardlyexerted
cellwallpressure.Thewater
pressureexertedbythecell
contentsagainstthecellwallis
calledturgorpressure.Turgor
pressureistheactualpressure
exertedbytheprotoplastof
theturgidcellagainstthecell
wall,whileosmoticpressure,
oftenusederroneouslyasa
synonymofturgorpressure,is
actually the maximum
pressure which can be
developedinthecellsap
solutionseparatedfrompure
waterbyarigidmembrane
whichispermeabletoonly
water(Fig.1.4).
Acell,theprotoplasmofwhichexhibitsturgorpressure,issaidtobeturgidorto
possessturgidity.Turgidityisresponsiblefortherigidityofmostsofttissuesof
plants,suchasleavesandyoungstems,andisessentialtotheirmechanical
support.

45. Flaccid cellPlasmolysis
Turgor Pressure
Fully Turgid cell
Decreased Increased
DPD (SP) NIL-0
DPD Increased
O P & T P
equilibrium
Diagram showing relationship of OP, TP & DPD.
As TP increased DPD (SP) decreased.

46. The>DPD(DiffusionPressureDeficit),thereisa>suction
pressure,hence>(greater)amountofwaterisabsorbedinthe
cells,resultinincreaseosmoticpressure.

Incellduringosmosistheincreasingturgorpressureforcesto
thecytoplasmoutagainstcellwall,therebycellwallpressure
isexertedtorestorenormalcyincellsize.
Turgorpressureisequal&oppositetowallpressureinfully
turgidcell.
DPD(SP,suctionpressure)=OP–TP(WP,WallPressure)

Endo-osmosis:Entranceofwaterstops.
Exo-osmosis:Loosingofwaterfromthecell

47. Molecules are always moving
Molecules move randomly and bump into
each other and other barriers

48. Concentration gradient
Concentration Gradient -change in the concentration of a
substance from one area to another.

49. Molecules in solution tend to slowly spread
apart over time. This is diffusion.T
1
T
2 T
3
Diffusion

50. Diffusion
•Movementofmoleculesfromanareaofhigh
concentrationtoanareaoflowerconcentration.
•Factorsthataffecttherateofdiffusion:sizeof
molecules,sizeofporesinmembrane,
temperature,pressure,andconcentration.

51. Diffusion
[High] [Low]
concentrated, high energy molecules
diffuse, low energy molecules

52. Diffusionwillcontinueuntilequilibriumisreached.
Thismeanstherewillbeanequaldistributionof
moleculesthroughoutthespace.Thisiswhyfood
coloringmovesthroughoutabeakerofwater;whyodors
smellstrongatfirstandthendisappearovertime.
Equilibrium,aresultofdiffusion,showstheuniformdistributionof
moleculesofdifferentsubstancesovertimeasindicatedinthe
abovediagram.

53. Which molecules will diffuse in
each of the figures below?
1
2
3
4
5 6

54. ANSWERS
1
2
3
4
5 6
No Movement
No Movement

55. Osmosis–A Special kind of Diffusion
Diffusion of water across a selectively permeable membrane (a
barrier that allows some substances to pass but not others).
The cell membrane is such a barrier.
Small molecules pass through –ex: water
Large molecules can’t pass through –ex: proteins and
complex carbohydrates

56. Over time molecules will move across the
membrane until the concentration of
solutes is equal on both sides. This type of
solution is called ISOTONIC.

57. 1. Due to osmosis, plant cells maintain their water content despite the loss of water to the air
that is constantly occurring.
2. It provides turgidity to the softer tissues which leads to mechanical support to the plant
and give definite shape to young plant organs.
3. It controls the absorption of water by root hairs from the soil and equal distributiobnof
water.
4. Diffusion pressure deficit is responsible for the movement of water across the cortical
cells of the roots.
5. Cell to cell diffusion of water is also affected by osmosis.
6. Conduction of water from xylem elements to the neighboringcells is controlled by
osmosis.
7. Growing tips of roots remain turgid because of osmosis and are, thus, able to penetrate
into the soil.
8. Higher osmotic pressure of the cells provides resistance to the plants against drought and
freezing injury.
9. It controls opening and closing of stomata during transpiration through its regulation of
the turgidity of guard cells.
10. Movement of plants and plant parts (e.g., movement of leaflets of the sensitive plant
Mimosa pudica) are controlled by cell turgor which is induced by osmosis.
11. It greatly influences the meristematicactivity of the cells and hence growth of the plant is
occurred.
12. Dehiscence of fruits and sporangia are also controlled by osmosis.

58. Lecture-6
(A)Imbibition
(B) Plasmolysisand
(C) Water potential

59. Imbibition:Q-1A(a)Seme.EndExam-June-2017
TheAbsorptionofwaterbyhydrophiccolloidalparticleswithoutformingsubstancesiscalledas
Imbibition.
Imbibant:Thesubstancewhichcanimbibeorabsorbaliquidwithoutformingasolutionis
calledImbibant.
ImbibitionalPressure:
Theimbibitionofwaterisincreasethevolumeoftheimbibantduetowhichpressureiscreated
isknownasImbibitionalPressure.
Imbibitionalpressureisthepotentialmaximumpressurethatanimbibantwilldevelopifitis
submergeinwater.
Differenttypesoforganicsubstanceshavedifferentimbibingcapacitysuchas
protein,starch,celluloseetc.
Proteinhashighamountofimbibingcapacitycomparetostarchandcellulose,
whereasstarchhaslowimbibingcapacitycomparetoprotein.
Cellulosehasleastimbibingcapacitythenproteinandstarch.That’swhy
proteinaceouspeaseedsswellmoreonimbibitionthanstarchywheatseeds.
Theamoutofwaterimbibedbyasubstanceisalsodeterminedbythedegreeof
cohesionofthemoleculesoftheimbibingsubstances.
Woodswellmorethangelationbecausethereismoreofcohesiveattraction
betweenwoodmoleculesthangelation.
Theimbibitionrateisaffectedbyincreaseintemperature,presenceofsoluteand
typesofsolution,pHofsolutionandpermeabilityofseedcoat.

60. Factorsassociatedwithimbibition:
Increaseinconcentrationofsolute,decreasetheimbibitionrate.
Someionsinhibitsimbibition
Imbibitionalsoaffectedbyacidityandalkalinity.
Duringimbibitionenergyisalsoreleaseasaheat.
Imbibitionalpressurehelpsinbreakingsoilprofilesbygerminating
seeds.
The relationship of DPD, IP and TP is as follow:
DPD= IP-TP

61. Whenplamolysedcellplacedagaininhypotonic
solutionhavinglessconc.Thancellsap,Water
fromoutsideentersinprotoplasm,Hence
endosmosisisoccur,itcomesbackinoriginal
positionandstretchesupwiththecellwall.This
processiscalleddeplasmolysis.Turgor
Pressurebuildsinthecellandcausesosmosis
tostopbecauseoftherigidcellwall.
Whencellisplacedinhigherconc.
Solution,exoosmosisisoccureandwater
comesoutfromprotoplasm,shrinksand
leavethecellwall,thisiscalled
plasmolysis.Plantswillwiltwhencells
losewaterthroughosmosis.
Hypotonic
Solution
Hypertonic
Solution

62. Protoplast
Cell wall
Vacuole
Vacuole
Protoplast
STAGES IN PLASMOLYSIS:

63. ELODEA CELLS
As viewed under the microscope

65. Wateristhemostabundantconstituentofallorganismsincluding
plants.Virtually,allphysiologicalandbiochemicalfunctionsofall
plantscellsandtissuestakeplaceduetowater.
Thelowerthewaterpotentialcellortissuemeansthiscellortissue
hasgreatertheabilitytoabsorbwaterfromthesurroundingcells.
Thehigherthewaterpotentialcellmeansthiscellhasthegreateris
theabilitytosupplywatertoothersurroundingcellsandtissues
whichhavinglowerwaterpotential.Inotherwords,waterloosefrom
theregionofhigherwaterpotentialtotheregionoflowerwater
potential.
ThemovementofH
2
Ostopswhendifferenceinwaterpotential
betweentworegionsiszeroandatthisstage,equilibriumissaidtobe
achieved.
Waterpotentialofpureliquidissetequaltozero.Thuswaterpotential
ofacellorplanttissueoranaqueoussolutionisalwayslessthan
zeroandhasnegativenumber.Itisneverinpositivenumberlike1,1.5,
2.0ormore.

66. •DEFINITION:WATERPOTENTIAL
Waterpotentialisdefinedasthedifferencebetween
freeenergyofwatermoleculesinpurewaterandenergyof
wateronanyothersystem(e.g.waterinsolutionorinaplant
cell).Itisrepresentedbygreekletterpsi(Ψ)andismeasuredin
bars/Mpa.(apressureunit=14.5lb/inch²,750mmHgor0.987atm)
•ForthesolutiontheWaterpotentialisdeterminedbythree
internalfactors.
•COMPONENT OFWATERPOTENTIAL:-
1.Solutepotential.(Ψs)=Osmoticpotential(OP)
2.Pressurepotential.(Ψp)=TPorWP
3.Matricpotential.(Ψm)
Waterpotentialincaseofsoil(Ψw)=Ψs+Ψp+Ψm
Waterpotentialincaseofplants=Ψs+Ψp
sIMILARLY,osmoticpressureisequivalenttoosmoticpotential
(ᴫ)butoppositeinsign,i.e.ᴫ=-OP(ᴫischaracteriedbynegative
valueasᴫforpurewateriszero)

67. •Solutepotential:-
Thechangeinfreeenergyofwatermolecules,producedby
theadditionofsoluteiscalledassolutepotential.Itisalso
knownasOsmoticpotential.Itisalwaysnegative.
•Matricpotential:-
Apotentialisexertedonthesurfacesoilparticlesoronthe
surfacecellwalltowhichwatermoleculesareabsorbedis
calledasmatricpotential.
•Pressurepotential:-
Generationofpressureduetoentryofwatermoleculesin
systemiscalledaspressurepotential.

68. Osmoticpotentialdependsupontheconcentrationofsoluteincell
sap.Highertheconcentration,higheristheosmoticpotential.
TheequationΨw=Ψs+Ψpshowsthathighertheosmoticpotentialof
acellsap,morenegativeisthewaterpotentialandgreatertheability
toabsorbwaterfromthesurrounding,whenaplantcellisplacedin
water,itwillabsorbwateruntilthepressurepotentialattainsthe
maximumvalueandnofurtherabsorptionofwaterispossible.Atthis
stage,thecellachievesfullturgidityanditswaterpotentialisequalto
zero.
Whenplanttissueisimmersedinsolution,aconcentrationofplant
tissuewillchange(increaseordecrease)dependinguponwater
potentialofthetissueandsolution.
(A).Ifsolutionishypertonic(withlowerΨw)thetissueslosewater
andsolutionbecomesdilute.
(B).Ifthesolutionishypotonic(withhigherΨw)thetissueabsorbs
waterandthesolutionbecomesconcentrated.
(C).Ifsolutionisisotonic(withΨw=tissuesap)thetissueneither
losesnorabsorbwaterandsolutionconcentrationdoesnotchange.

69. WaterpotentialofprotoplasmisequalbutoppositetoDPDorsuction
pressure(SP).
Ψw= -DPD
TheequationΨw=Ψs+Ψpshowsthathighertheosmoticpotentialof
acellsap,morenegativeisthewaterpotentialandgreatertheability
toabsorbwaterfromthesurrounding,whenaplantcellisplacedin
water,itwillabsorbwateruntilthepressurepotentialattainsthe
maximumvalueandnofurtherabsorptionofwaterispossible.Atthis
stage,thecellachievesfullturgidityanditswaterpotentialisequalto
zero.
Fullturgidcell,valueofDPDiszero.WP=OP
Nonturgidcell,DPD=OP–WPORΨ=ᴫ+WP
Infullyturgidcell,ΨsandΨpareequalbutoppositeinsign,
sothatΨwiszero.
Concentrationofsolutioninwhichaplanttissueisimmersed
changes(increaseordecrease)dependinguponwaterpotentialofthe
tissueandsolution.
(A).Ifsolutionishypertonic(withlowerΨw)thetissueslosewater
andsolutionorcellsapbecomesconcentrated.
(B).Ifthesolutionishypotonic(withhigherΨw)thetissueabsorbs
waterandthesolutionbecomesdilute.
(C).Ifsolutionisisotonic(withΨw=tissuesap)thetissueneither
losesnorabsorbwaterandsolutionconcentrationdoesnotchange.

70. Ψsis-10barsandΨpis10bars,Ψwillbezero
Ψ=Ψs+Ψp
Ψ=-10bars+10bars
Ψ=0bars
Andincaseofflaccidcell,Ψpwillzero…
Ψ=Ψs+Ψp
Ψ=-10bars+0bars
Ψ=-10bars(itislesscomparetopurewateri.e.zero)
Incaseofplasmolysedcell,suppose,Ψs=-10barsandΨp=-2bars
Ψ=Ψs+Ψp
Ψ=-10bars+-2bars
Ψ=-12bars,thenvalueofΨwillbemorenegative
AdjecentcellsareA&B,
AcellΨs=-16andΨp=8;BcellΨs=-12andΨp=2;
Hence,
ΨincellAwillbe-8(-16–8)andΨincellBwillbe-10(-12–2).
Since,watermovesfromhigherwaterpotentialtolowertowater
potentiali.e.flowofwaterfromcellA(-8)toCellB(-10).

72. Rootpressure:Q-1A(2)Seme.EndExam-June-2016&Q-1A(d)
Seme.EndExam-June-2017
Definition:
Inplants,osmoticpressureforcetodrivefluidsupwardintothe
xylemfromtherootsandexudationoffluidwhenthestemiscut
offjustaboveground,thispressureiscalledasrootpressure.

74. Lecture-7
Absorptionofwater

75. Life processes are driven by energy
•Plants are dynamic & metabolic systems
–1000s of reactions occur every second.
•Processes can be ……
1.Energy consuming or utilizing Reactions OR
EndergonicReactions OR
Anabolic Reactions (synthesis of food materials) .
2. Energy releasing Reactions OR
ExergonicReactions OR
Catabolic Reactions (breakdown of molecules).

76. Thelifeisoriginatedinanaqueousenvironmentinthe
courseofevolution…,hencewaterisessentialforlife…
 Thesubstances,necessarytoplantlife,waterisrequiredin
thelargestamount.
 Mostcellsandtissues: ≥80%
 Growingcells: ≥90%
 Dormantseedsandbuds:≤10%
GENERAL INFORMATION RELATED TO CROP WATER RELATIONS

77. (A) Importance/ Functions / Role of
Water in Plants:
Waterisamajorconstituentofprotoplasm.
Wateristhesolventinwhichmineralnutriententeraplantfromthe
soilsolution.
Mineralnutrientsaretransportationfromonepartofcelltoanother
andfromcelltocell,fromtissuetotissueandorgantoorganwith
thehelpofwater.
Wateristhemedium/reactantofmetabolicaswellasbiochemical
reactions.
Inphotosynthesis,thehydrogenatominwatermoleculeis
associatedtoorganiccompoundandoxygenatomwasreleasedas
gas.
Waterpresentinvacuolesimpartsturgiditytocells,thusmaintain
theirformandstructure.
Q-3 d) Seme. End Exam-June -2015 & Q-3A (a) Seme. End Exam-June -2017

78. (Conti…)
Gainandlossofwaterfromthecellsandtissuesis
responsibleforvarietyofmovementsofplantparts.E.g.
Mimosapudica
Theelongationphaseofcellgrowthdependsonabsorptionof
water.
Waterisametabolicproductofrespiration.
Morewaterisabsorbedbyplantandgreateramountofwater
arelostbytranspiration.
Watermaintainsthetemperatureinplanttissues.
Waterhelpsinenergytransferandstorage.
Waterprovidessupporttoaquaticplants.
Waterhelpsinmobilityofgamates/pollengrains.
Waterplayanimportantroleindessiminationofspores,fruits
andseeds.
Itaffectsmorphological,anatomicalandphysiological
processesdirectlyorindirectly.

79. Natureofcellularwater:
Alargefractionofwaterinplantcellsisfreeandmobile.
Muchofthiswaterispresentinvacuoles.
Thevacuolarwaterissimilartoadilutesaltsolution.
Thisadsorbedwaterisespeciallygreaterinthevicinityofcellmembranes
namely,themembranepresentinendoplasmicreticulum,chloroplast,
mitochondria,tonoplastandplasmamembrane.
Further,moretheinterspaceswithintheproteinandlipidlayersofcell
membranesareoccupiedbywatermolecules.Thiswaterhasaveryhigh
density,thanliquidwaterduetosemi-crystallineinstructure.
Wood(1925)reportedthatKochiabiosiaandRhagoidaabsorbedwaterfrom
atmosphere.
Uptakeofwaterbyleavesisinfluencedby:
(i)Structureandpermeabilityofcuticleandepidermis
(ii)Hairinessandwettingofleafsurface
(iii)Deficiencyofwaterinparenchymacellsclosetoepidermis.

80. Types:
Gravitationalwater:-Q-1A(f)Seme.EndExam-June-2017.
Thewaterwhichreachesdeepbeyondrootzoneintothesoilafterrainsdueto
gravitationiscalledasgravitationalwater.Theplantscannotabsorbthiswater
throughtheirroots.
Capillarywater:-Thewaterwhichremainspresentininterspaces(capillary
poresormicropores)ofparticlesiscalledcapillarywater.Itisheldsostrongly
thatgravitycannotremoveitfromthesoilparticles.Itistheonlyavailablewater
isabsorbedbyplantroots.
Hygroscopicwater:-Thewaterthatheldtightlyonthesurfaceofsoilcolloidal
particle(heldsotenaciously-31to-10000atmospheresduetoadhesionforces)
andpresentaroundthesoilparticlesintheformofthinvapourlayeriscalledas
hygroscopicwater.Itcannotbeseparatedfromthesoilunlessitisheated.Itis
alsonotabsorbedbytheplantroots.Microbesuseitforbiologicalactivities.
Crystallinewaterorchemicallycombinedwater:-thewaterwhichremains
chemicallyboundtothesoilparticleiscalledcrystallinewater.Itisalsonon-
availablewater.E.g.CuSO
4
5H
2
O;FeSO
4
,7H
2
Oetc.
Runningwater:-aftertherains,apartofwaterdrainsaway.Itisknownasrun
awaywaterandisnotavailabletoplants.

81. from-0.1to-0.5barallgravitationalwaterleachintosoil
from-0.5to-31barscapillarywaterisavailabletoplant
from>-31baronwehavehygroscopicwater

82. 1.Gravitationalwater
2.Capillarywater
3.Moisturearoundparticlescontains
solublesaltsavailableforroot.
4.Hygroscopicwater
5.SoilParticle
6.Airpocket

83. Field capacity is depend on size
of soil particles ….
5% in sandy soil
35% in loamy soil
45% in clay soil
Negligible in gravel and rocks

84. DEFINITIONS:-
The following are the technical terms must be understood while the
availability of water from soil.
1. Field capacity,
2. Permanent wilting percentage (PWP)
3. Total soil moisture stress (TSMS)
4. Soil moisture tension (SMT).
1. Field Capacity:
Itmaybeconsideredaswatersaturationpointofthesoil.Field
capacityofthesoilwatercontentholdbyasoilafterthoroughlywetting.
Thisisthewaterinthesoilafterallowingthesurpluswatertodrainofftill
thecapillarymovementofafterwaterstops.

87. 2. Permanent Wilting Percentage (PWP) :-
Thisisalsocalledwiltingpercentage,wiltingpointorwilting
coefficient.
Permanentwiltingpercentageisdefinesasthepercentageofsoil
waterleftwhenleavesofplantgrowinginthesoilfirstexhibitthe
symptomsofpermanentwiltingi.e.theleaveswillnotrecovertheir
turgiditywhenplacedinasaruratedatmosphere.Itmaybe1%in
somecoarsetoapproximately24%inheavyclaysoil.
Permanentwiltingpercentageisthepercentageofthesoilmoisture
belowwhichnogrowthofaplantoccurs.Wiltedplantscannot
restoretheirturgidityastherateofwaterabsorption.

88. 3. Total Soil-moisture Stress (TSMS) :-
TSMSisdefinesasthesumofthesolute
potentialofthesolutionandthesoilmoisture
tension(TSMS).
4. Soil moisture tension :-
Itmeanstotalsumofhydrostaticforce,
adsorptiveforceandgravitationalforce,which
areresponsibleforholdingthewaterinthe
soil.

89. (C) ROOT STRUCTURE
Meristematiczone
Cell Elongation zone
Maturation
zone
Tracheid/ vessel

90. Root absorb water mainly from the apical region.
ROOT HAVING A FOUR ZONES:
1.Meristematiczone
2.Elongation zone
3.Differentiation zone: consist of dermal (Epidermal cells), cortical (Parenchyma
cells) & stellar tissue ((Pericycle, Phloem 7 Xylem cells)
4.Maturation zone
ROOT HAIR :
Roothairisthespecialmodifiedcellofepidermismeantforabsorptionofwater.
Roothairwallconsistscelluloseandpectinsubstancesbotharehydrophillicin
nature.
Cell membrainenclosing cytoplasm, nucleus & vacuole (water controller)
ENDODERMIS:
It is a bounding layer of stele and cell are thickening by suberianor cutinor some
time lignin is called Casparianstrips .
Certain cells of endodermis , opposite to protoxylemhave no such thickness, they
are thin wallwhichprovide passage to the water.
XYLEM:
Xylem consist of tracheids, vessels and xylem parenchyma cells of which first two
are thick walled due to deposition of lignin.
Thickening areas facilitate movement of water because of lignin is a hydrophilic
substance.
Transverse walls are perforated and continuous channel is maintained in the plant.

91. (D) PATHWAY OF WATER IN ROOT
Sutcliffe(1969)proposedtwopathwaysofradialmovementofwater.
1.celltocellacrosstheroot 2.Acrossthecortex
Thewaterisabsorbedfromthesoilbytheroothaircells.
Fromtheroothaircell,thewaterreachestheleavesbypassingthroughanumberofcell
fromtheroothairtostemxylem.
Waterandionsenterroothairs.Waterismovethroughcortexcellsandenterinto
endodermis.
Theendodermalcellslyingoppositetoroothairarespeciallymodifiedtotransportthe
absorbedwater.
Theseendodermalcellsarecalledpassagecells.
Thepassagecellsarepermeabletowaterbecausetheylackcasparianthickeningintheir
walls.

92. Otherendodermalcellsareprovidedwithcasparianthickeningandare
impermeabletowater.(Thickeningbysuberianorcutinorsometimelignin)block
watermovementhence,forcewaterisariseandwatergetentryintopericycle
(yellowcolor)andfinallygoesintoXylem(Pinkpart).Greencellsindicates
phloem.
Endodermalcellsandpericycleselectsnutrientsthatenterintothephloem
(Greenpart).
Thewaterfromthepassagecellpassintothepericyclecellsandgoesintothe
xylemcells.
Throughthexylemtubes,thewatermovesupthroughstemxylemtoleafxylem.
Themovementofwaterfromonecelltoanotherisbroughtaboutbyturgor
pressure.

93. Phloem Cells
Xylem Cells
http://www.botany.hawaii.edu/faculty/webb/BOT41
0/Xylem/Xylem-1.htm

94. PART-1

96. Lecture-8
Absorption of water

97. SITEOFWATERABSORPTION:
Majorportionofwaterrequiredbyplantsis
absorbedbyroots.Waterisabsorbedthroughrootshairs.
Therootshairarelocatedinagroupjustabovetherootcap.Thisareaoftheroot
iscalledasroothairzone.
Roothairsaretubularhairlikeprojectionoftheepidermalcells.Soroothairisin
theformofasinglecell.
Theepidermisbearingroothairisalsoknownaspiliferouslayeroftheroots.
Thewallofroothairsispermeable.Itconsistsofcelluloseandpecticsubstances
whicharestronglyhydrophilic(waterloving)innature.Nexttocellwallthereis
plasmamembraneenclosingcytoplasm,nucleusandvacuole.Vacuoleisfilled
withcellsap.

98. Lack casparian
thickening

100. (A) Mechanism of water absorption:
Theuptakeofwaterbyplantsiscalledwaterabsorption.
Waterisabsorbedfromthesoilmainlythroughroothairs.Kramer
(1949)proposedthewaterisabsorbedbytwomechanismsthey
are
1.Activeabsorptionand
2.Passiveabsorption
1. ACTIVE ABSORPTION:
Whentheroothairsabsorbedwaterbytheirownefforts,itisknown
asactiveabsorption.Inthisprocesstherootcellsplayactiverolein
absorptionofwater.Metabolicenergyreleasedthroughrespirationis
consumedinwaterabsorption.
THE ACTIVE ABSORPTION IS TWO TYPES:
(I).ActiveOsmoticAbsorption
(II).ActiveNonosmoticAbsorption

101. (I). Active Osmotic Absorption:
Thewaterisabsorbedbytheroothairsbytheoperationofosmoticforces.Its
calledActiveOsmoticAbsorption.Atkins(1916)andpriestly(1922)first
postulatedtheActiveOsmoticAbsorption.
Osmoticpressure(o.p)ofthecellsapoftheroothairisusuallyhigher(2atm)
thantheo.pofsoilwater(1atm).
Astheroothaircell-containslesswater,ithaslessturgorpressure(T.P.)and
lessT.P.ofroothaircellresultinincreaseddiffusionpressuredeficit(D.P.D)
thisleadstotheincreaseinthesuctionpressure(S.P.)ofroothairs.Hence,
soilwaterentersintotheroothaircellthroughitssemi-permeableplasma
membranebyendosmosis.
Thewatermovesgraduallybycelltocellandreachestheinnermostcortical
cellsandtheendodermis.
Osmoticdiffusionofwaterintoendodermistakeplacethroughspecialthin
walledpassagecellwhichlackcasparianthickenings.Waterfromendodermal
cellsisdrawnintothecellofpericyclebyosmoticdiffusionwhichnow
becomesturgid.
Inthelaststep,waterisdrawnintoxylemfromturgidpericyclecells.

102. (II). Active Non-osmotic Absorption of water:
Thimann(1951)andBogenandPeru(1953)suggestedthatabsorptionof
waterisanactiveprocessbutoccuresduetonon-osmoticreasonsevenagainst
DPG(DiffusionPressureGradient)thatrequiresextraenergysuppliedbycellular
respiration.
Theroothairabsorbswaterwithouttheinvolvementofosmoticforces.
SometimesabsorptionofwatertakeplaceevenwhentheO.P.ofthesoilwateris
higherthantheO.P.ofthecellsap.Thistypeofabsorption,whichisnon-osmotic
andagainsttheosmoticgradientiscalledactivenon-osmoticabsorptionofwater.
Followingaresupportingpointsofthistheory-
•Wiltingofrootsoccursinnon-aeratedsoilssuchasfloodedareas.
•Thefactorwhichinhibitsrespirationalsodecreasedwaterabsorption.
•Poisonswhichretardmetabolicactivitiesoftherootcellsalsoretardwater
absorption.
•Auxinswhichincreasemetabolicactivitiesofthecellsstimulateabsorptionof
water.

103. 2. Passive Absorption:
*Ittakesplacemainlyduetotranspiration.
*Movementofwateragainstosmoticgradient.
*Rateofabsorptionisequaltorateoftranspiration
*Itispurelyaphysicalprocess.
*Fastermovementofwaterthanosmoticdiffusion.
Passiveabsorptiontherootsremaininactive.
Thewaterabsorptionforcesarefirstproduceinthecelloftheleavesthus
absorptionofwatergovernedbyothercellsthanrootitself.
DPDofleafcellsincreases,resultedinmovementofwaterfromxylemtoleaf.
Passiveabsorptionofthewatertakesplace,whentherateoftranspirationis
usuallyhigh.
Rapidevaporationofwaterfromtheleavesduringtranspirationcreateatension
inwaterinthexylemoftheleaves,thistensionistransmittedtowaterinthe
xylemoftherootthroughthexylemofthestemandthewaterrisesupwardto
reachthetranspiringsurfaces.
Asaresult,soilwaterentersintothecorticalcellsthroughroothairtoreachthe
xylemoftherootstomaintainthesupplyofthewater.Sotherootcellsremain
passiveduringtheseprocesses.
------------------------------------------------------------------------------------------------------------
*5-SupportingpointsforPassiveabsorptionofthewater

104. Sr. Active water absorption Passive water absorption
1.Active absorption of water occurs due
to the activity of root and particularly
root hairs.
The passive water absorption occurs due to
the activity of upper part of plant, such as
shoot and leaves.
2.It requires energy or ATP. It does not require energy.
3.Active absorption creates root
pressure.
Root pressure is not created due to passive
absorption.
4.The movement of water takes place
from the solution of lower
concentration i.e. against the
concentration of gradient.
The movement of water takes place from the
solution of lower concentration to the higher
concentration solution i.e. according to
osmotic gradient.
5.The absorption of water occurs by the
osmotic and non osmotic processes.
The water is absorbed due to the active
transpiration in aerial parts.
6.
The rate of absorption of water depend
upon the DPD.
The rate of absorption of water depend upon
the transpiration.
7.In the movement of water, living part of
protoplast is involved. Show symplast
pathway.
The movement of water is through free
spaces or apoplastof root and it may
include cell wall and inter cellular spaces.
8.
Evidences in support of active water
absorption are root pressure, bleeding
and guttation.
Evidence in support of passive absorption
can be given by cutting the roots under
water. The absorption of water will occur if
all the roots are removed.
Q-2A (iii) Seme. End Exam-June -2015& Q-2A (5) Seme. End Exam-June -2016
Differences between Active and Passive water absorption

105. Sr. Osmotic theory: Non Osmotic theory:
1.It is proposed by Atkins (1916) and
priestly (1922)
Thimann(1951) and Kramer (1959).
2.Water is absorbed due to osmotic
difference between soil water and that of
tonoplasm.
Water absorption is an active process occurs
due to non osmotic reason against the DPD.
3.D.P.D. of root hair is increased due to
high O.P and low TP of root water is
absorbed by endosmosis .
Occurs against the D.P.D. gradient and
requires the expenditure of energy released
from respiration.
4.TP of root hair increase and D.P.D.
decreases water moves from root hair to
inner cells and finally reaches into the
xylem.
There may be some carrier substances in the
wall of root cells, which bind with water and
carry, it to the inner tissue, (certain bacteria in
higher plants).
5.Process require no energy (ATP). Process require energy (ATP) comes from
respiration.
6.Operate in fast transpiring plants.Operate in very slowly transpiring plants.
Q-2A (a) Seme. End Exam-June -2017
DIFFERENCES BETWEEN OSMOTIC THEORY NON -OSMOTIC THEORY:

106. Q-1A (g) Seme. End Exam-June -2015

107. FACTOR AFFECTING WATER ABSORPTION RATE
A.EXTERNAL ENVIRONMENTAL FACTOR:
1.Availablesoilwater:
Capillarywaterisreadilyavailableforabsorption.
Iftheamountofwaterinthesoilthatincreasedthefieldcapacity,itcreatea
badeffectonsoilaerationandalsoreducetherateofabsorption.
Similarly,onshortageofsoilwatercausepermanentwiltingpercentageand
plantdieoff.
2.ConcentrationofsoilSolution:
Ifthesoilsolutionishighlyconcentrated,highosmoticpressurethancellsap,
waterisnotabsorbed.
Itisonereasonthattheplantsfailtogrowinhighlysalinefields.Thisis
popularlyknownasphysiologicaldryness.
Q-2B (c) Seme. End Exam-June -2017

108. 3.SoilTemperature:
20
0
to30
0
Ctemperaturesismostsuitableforabsorption.
Thelowtemperaturereducestherateofabsorption.
Averyhightemperaturekillsthecells.
Lowtemp.causenegativeinfluenceonabsorption….
Slowerrateofrootelongation
Slowerrateofmetabolicactivities
Reducedrateofsoilwaterdiffusion
Decreasepermeabilityofcellmembrane
Increasedviscosityofwaterandprotoplasmaswellas
colloidalgelsincellwall.
4.Soilaeration:
Oxygendeficiencyretardsthegrowthanddevelopmentofplant
rootsanddisturbedtheirmetabolicactivities.
HighCO2increasestheviscosityoftheprotoplasmandreducethe
rateofabsorptionofwaterunderwater-loggingsoil.Thisisalso
knownasphysiologicaldryness.

109. B. INTERNAL ENVIRONMENTAL FACTORS:
1)Transpiration:
Ahigherrateoftranspirationincreasestherateofabsorptionofwater.
Transpirationproducesatensionorpull,transmissionofwaterfromroots
xylemtostemxylemthroughhydrostaticsystemofplants.
2)Rootsystemofplant:
Hairy,abundentandwelldevelopedroothairsystemshowhigherratesof
waterabsorptionthanverysmallrootsandlessnumberofroothairs.
Inmoistcondition,roothairsarewelldevelopedandinlargequantity.
Coniferplantsbearfewrootsbutabsorblargeamountofwaterwiththehelp
ofmycorrhizalhaphae.
Maizeplantdoesnotproducedroothairinculturesolutionbut,produce
abundentrootsinfieldcondition.
3)Metabolism:
Pooraeration,applicationofpesticides/anesthetic(chloroform)andKCN
(Potassiumcynide)reducestheabsorptionrateduetohindranceinmetabolic
activities.

111. Lecture-9
StomatalPhysiology

112. StomatawasdiscoveredbyPfeffer&name‘stomata’wasgivenbyMalphigii.
Stomatacover1-2%ofleafarea.
Itistinyandminuteporepresentinepidermislayerofleafandsoftaerialparts
oftheplant.Algae,fungiandsubmergedplantsdonotpossessstomata.
(a)Stomataareminuteporesofelipticalshape,consistsoftwospecialized
epidermalcellcalledguardcells.
(b)Theguardcellsarekidneyshapeindicotyledonanddumbellshapein
monocotyledonandtheyremainjoinedattheend.
(c)Thewalloftheguardcellsurroundingtheporeisthickenandinelasticdue
torestofthewallsarethin,elasticandsemi-permeable.
(d)Eachguardcellhasacytoplasmiclining&streaming,centralvacuole.It
cytoplasmcontainssinglenucleus,starchmoleculesfloatingundercytoplasmic
fluidandnumberofchloroplast.Thechloroplastofguardcellarecapableof
verypoorphotosynthesis,becausetheabsenceofRUBISCOenzyme.
(e)Stomatagenerallyoccurhigherinnumberuponthelowersurfacethan
uppersurfaceoftheleaf.
(A)STOMATA

115. STOMATAL SIZE
♠TheSizeandshapeofstomaandguardcellvaryfromplanttoplant.
Whenfullyopen,thestomatalporemeasures10-40µinlengthand3-12µ
inwidth.
♠Sizemayberangedfrom7X3µ(Phaseolusvulgris)and38×8µ(inAvena
sativa)and4X26(ZeamaysL.).
♠Guardcellsarealsoknownasmodifiedepidermalcells,subsidiarycells
oraccessorycells.
♠Eachstomaisnormallysurroundedbytwospecializedepidermalcells
knownasGuardcells.
♠Thewalloftheguardcellssurroundingtheporeisthinandelastic(outer
layer)andinsidethelayeristhickandinelasticduetothepresenceofa
secondarylayerofcellulose.
♠Inmanygymnospermsandxerophyticplants{plantsgrowingindesert),
thestomataarepresentembeddeddeeplyintheleaves,sothattheyare
notexposedtosunlightdirectly.Suchdeeplyembeddedstomataare
calledsunkenstomata.Thisisanadaptationtocheckexcessive
transpirationintheseplants.

116. Number of Stomata (StomatalFrequency):
Thenumberofstomatainadefiniteareaofleafvariesfromplant
toplant.Xerophytespossesslargernumberofstomatathan
mesophytes.
Numberofstomata/sqcm.is1000—60,000indifferentplant
species.Thenumberofstomtaperunitareaofleafiscalled
StomatalFrequency.
Stomatafrequencyoftreesandshrubsishigherthanherbs.
Inisobilateralleaves(inmonocots),approximatelythesame
numberofstomataarefoundonuppersurface(adaxial)and
lower(abaxial)surface.
 Insomeothersespeciallywoodyspeciestheyareconfinedto
thelowerepidermis.
 Infloatingleaves,suchaswaterlilies,lotus,stomataare
occurredonlyintheupperepidermis.

117. (B) TYPES OFSTOMATA BASIS ON
DISTRIBUTION :
Dependinguponthedistributionandarrangementofstomataintheleavesfive
categoriesofstomataldistributionhavebeenrecognizedinplants.
1.Appleormulberry(hypostomatic)type:
Stomataarefounddistributedonlyonthelowersurfaceofleaves,e.g.,apple,
peach,mulberry,walnut,etc.
2.Potatotype:
Stomataarefounddistributedmoreonthelowersurfaceandlessonitsupper
surface,e.g.,potato,cabbage,bean,tomato,pea,etc.
3.Oat(amphistomatic)type:
Stomataarefounddistributedequallyuponthetwosurfaces,e.g.maize,oats,
grasses,etc.
4.Waterlily(epistomatic)type:
Stomataarefounddistributedonlyontheuppersurfaceofleaf,e.g.,waterlily,
Nymphaeaandmanyaquaticplants.
5.Potamogeton(astomatic)type:
Stomataarealtogetherabsentorifpresenttheyarevestigeal.e.g.,Potamogeton
andsubmergedaquatics.
MetacalfandChalkrecognizedfourtypesofstomataonthebasisoftheir
structure-

118. Sr.
No.
Name of the plant No. of stomata
per sq. cm. upon
the upper
surface
No. of stomata
per sq. cm. upon
the upper
surface
1Helianthus annus(Sunflower) 58 156
2Lycopersicumesculentum
(Tomato)
12 130
3Phaseolusvulgaris(Mung) 40 281
4Solanumtuberosum(Potato) 51 161
5Zeamays(Maize) 52 68
6Avenasativa (Jav) 40 43
DISTRIBUTION OF STOMATA IN DIFFERENT PLANTS

119. a.Anomocytictype:
Inthesestomata,accessorycellsareabsent.Theguardcellsaresurroundedby
ordinaryepidermalcells,e.g.,familiesRanunculaceae,Cucurbitaceae,
PapaveraceaeandMalvaceae.
b.Anisocytictype:
Inthesestomatatheguardcellsaresurroundedbythreeaccessorycells.Of
thesetwoarelargerwhereasoneissmallerinsize.g.,familyBrassicaceae.
c.Diacytictype:
Inthesestomatatheguardcellsaresurroundedbytwoaccessorycells.Their
common wallsareatrightangletothewallsofguardcells,families
Caryophyllaceae,Acanthaceae.
d.Paracytictype:
Inthesestomatatheguardcellsarealsosurroundedbytwoaccessorycells,but
theircommon wallsareparalleltoguardcells,e.g.,familiesRubiaceae,
Fabaceaeetc.
X-TYPES OFSTOMATA BASIS ON ARRANGMENT:

120. X-TYPES OF STOMATA ON THE BASIS OF DEVELOPMENT
(PANT, 1965):
Therearethreetypesofstomata:
1.Mesogynoustype:
InthistypeofstomataguardcellsaswellassubsidiaryorAccessory
cellsbotharedevelopedfromonemothercell.e.g.Rubiaceace&.
Brassicaceaefamily.
2.Perigynoustype:
Inthistypeguardcellsareformedfrommothercellwhilesubsidiary
cellsfromnearbymothercells,eg.:Cucurbitaceaefamily.
3.Mesoperigynoustype:
Inthistypeguardcells&onesubsidiarycellsisformedfrommother
cellwhileothersubsidiarycellsdevelopIndependently.e.g.:
Ranunculaceae,Caryophyllaceaefamily.

121. (3) STOMATAL MOVMENTS WITH EXAMPLES:
Consideringthebehaviorofstomatalmovements,fivecategorieshave
beenrecogniosed.
(1)Photoactivemovements:
Lightdirectlyandindirectlycontrolsstomatalmovement.Suchstomata
remainopenduringdaytimeandclosedatnight(dark).
(2)Skotoactivemovements:
Stomataremainclosedduringdaytimeandopenatnight(dark).E.g.
succculentplants.
(3)Hydroactivemovements:
Incertaincases,stomataopenduetoexcessivelossofwaterfrom
epidermalcellsandcloisedduetoturgorconditionsofepidermalcells.
(4)Autonomous movements:
Insomecases,Suchstomataopenandcloseatarateof10-15minutes
showingdiurnalrhyhmicpulsation.
(5)Passiveandactivemovements:
Openingofstomataisconsideredasactiveprocesswhileclosingisthe
passiveprocessandthisiscausebytheturgorchangesintheguardcells.

123. ♠Whenturgidityincreases,theouterthinwallsofguardcells
stretchoutwardtherebyinnerwallisalsostretchingoutward.
♠Theinnerwallbecomesconcave(Antargol)andresultisthe
spaceisoccur,pourwidensandporeopens.StomatalTurgor
Mechanismisinvolvedinopeningandclosingofstomata.
♠K+(Potassiumions)playcrucialrole.
♠TheopeningofstomataaretheresultofactivetransportofK+
fromepidermaladjacentcellsintotheguardcells.
♠Malicacidissynthesizedinsubsidiarycellsfromstarchand
goesintocytoplasmofguardcellsinthepresenceoflight.
Dissociation
♠Malicacid-R(COOH)2 MalateR(COO-)2+2H+(Hydrogenions)
Exchange
♠H+ K+(adjacentcells)
♠InfluxofK+andeffluxofH+thatincreaseconcentrationofK+
inguardcell(Vacuoles)therebyOsmoticpressureis
developed;waterisenterintotheguardcells;increaseturgor
pressure;guardcellsbecomesturgidandfinallyopenthe
stomata.

124. Subsidiary
cells
Nucleus of
Sub. cells
Nucleus of
Guard cells
Vacuoles
K
K
K
K
H
H
H
H
K+ ions +
MalicAcid

125. Fig. 39.12b
Guard cell
become turgid
Guard cell
become flaccid

126. ♠ABAplayimportantroleinclosingofstomata.
♠ABAinhibitsK+uptakebychangingdiffusionandpermiability
ofguardcells.TheK+movesouttothesubsidiarycells.
♠ABAinducestheprocessofacidificationthatloweringthepH.
AtthelowpH,starchissynthesizedandosmoticpressureof
guardcellsfallsandwatermovesoutofguardcellsto
subsidiarycells.
♠Guardcellsthenbecomeflaccidandstomatalporeisthus
closed.

127. Mechanism of Stomatalopening and closing: (Discussedin Pl. Phy. 3.1)
Enzymaticconversionofstarchintosolublesugarincreasestheosmoticconcentration
ofcellsapofguardcells.
Withtheresultthatthesecellsabsorbmorewaterfromtheiradjoiningcellsandtheir
turgorpressureincreases,thisresultsintheopeningofstomata.
Innightthesugarisformedagainintostarchandtheirturgiditydecreasesleadsto
closingofstomata.
Thisconversionofstarchintosugaroccursinpresenceofip(inorganicphosphate)andthe
reactioniscatalysedbyenzymephosphorylase.
Starch + ip(insoluble)
Light, high pH 7.0
Glucose-1-phosphate
Dark, Low pH 5.0
phosphorylase
HydrogenionconcentrationandCO2concentrationarealsoresponsiblefortheopeningand
closingofstomata.IftheCO2concentrationislow,stomataopenmorewidely.Starchis
convertedintosolublesugar.IftheHionconcentrationdecreasesi.e.ifitislessthan7
thenGlucose-1-phosphateisconvertedintostarchandifthepHis7thenthestarchis
convertedinGlucose-1-phosphate.

128. Very little CO2 Fixation in Guard Cells Reduced CO2 in Guard Cells
ATP Synthesis
Respiration occurs
Possible Photosynthesis
ATP Synthesis
ATP-MediatedH+/K+pump
H+outofandK+intoGuard
cellsofcl-anionsfollow
IncreaseK+/Cl-andmalate
concentrationintoGuard
cells
Decreased osmotic potential
in Guard cells
WaterpotentialofGuardcells
morenegativerelativeto
surroundingcells
Osmotic entry of water
into Guard cells
AN INTEGRATED SCHEME OF THE PROBABLE MECHANISMS OF STOMATAL OPENING
Increase pH in Guard cells
Starch phosphorylase
activated
Hydrolysis of starch
Concentration of soluble
sugar increased
Sugar concentration may be
insufficient to affect water
potential
ATP Synthesis
HCO3+ increases combines
with PEP to form malicacid
Turgorpressure increased
Stomata open
LIGHT

130. HugovonMohl(1856)AGermanbotanistfromStuttgurt-
preparedastomatalclockandobservedthechangesoccurin
dayandnighttimes.

133. Q-1Selectappropriateanswerandtickmarkonit.
1.Itistheprocessbywhichmovementofcarbohydrates
throughvascularsystem(Phloem)iscalled
(a)Translocation(b)Transformation(c)Transpiration(d)Transduction
Objective Questions

134. 2.Thetheoryofplanttransportwater&mineralsthrough
vascularsystemisknownas
(a)Munch’sMass-
Flow of
Assimilate
(b)SpecificMass
Transfer
(c)Pressure-
Flow
Hypothesis
(d)Allofthese

135. 3.Sievetubecellisthememberof
(a)Vessel (b)Xylem (c)Tracheid (d)Phloem

136. 4.Energyconsumingduringvariousmetabolicreactionsin
thecellsforsynthesisoffoodmaterialsiscalled
(a)Endergonic
Reactions
(b)Anabolic
Reactions
(c)Utilizing
Reactions
(d)Allofthese

137. 5.Waterandionsenterintoroothairsandmovebetweenthe
membranesof
(a)Endodermiscells(b)Epidermalcells(c)Cortexcells(d)Pericycle

138. 6.Thenarrowslipthatblockthewatermovementandforce
thewaterthroughcellmembranesofendodermisreferas
(a)Casparianstrips(b)Corticalstrips(c)Pericycle
strips
(d)Noneofthese

139. 7.Thehollow&tubularshape,smallindiameterandsideto
sideoverlapstructurefoundinXylemiscalled
(a)Tracheid (b)Vessel (c)Cortex (d)Vesicle

140. 8.Watermoleculesstickstocellwallsofxylemthrough
specificforceiscalled
(a)Cohesion (b)Adhesion (c)Cohesionand
Adhesionboth
(d)Noneofthese

141. 9.Thelocationwhereallplantpartsaremeettheirown
nutritionalneeds(roots,stems,fruits)isreferas
(a)Growingregions(b)Sink (c)Storage
organs
(d)Source

142. 10
.
Phloemconsists
(a)vascular
parenchymacells
(b)sievetubecells(c)companion
cells
(d)Allofthese

143. 11.Energyreleasingduringvariousmetabolicreactionsinthe
cellsiscalled
(a)Exergonic
Reactions
(b)Catabolic
Reactions
(c)Breakdownof
molecules
(d)Allofthese

144. 12.Osmoticpotentialisalsocalledas
(a)Solutepotential(b)pressure
potential
(c)Both (d)Noneofthese

145. 13
.
Theleafsynthesissugarthattransferintophloemsieve
tubescellsisknownas
(a)Phloemunloading(b)Phloemloading(c)Both (d)Noneofthese

146. 14
.
Pitsareobservedinfollowingpartofthexylem
(a)Cortex (b)Vessel (c)Tracheid (d)Vesicle

147. 15.Duringphotosynthesis,sourcesareplaceswheresugarsare
being
(a)Consumed (b)Inhibited (c)Reduced (d)Produced

148. 16.Insymplastictransport,neighboringcellsofcytoplasmsare
interconnectby
(a)Primarycellwall(b)Plasma
membrane
(c)Plasmodesmata (d)Noneofthese

149. 17.Whichpartoftherootthatselectsnutrientsandthenthey
enterintothephloem?
(a)Casparianstrips(b)Epidermalcells(c)Cortexcells(d)Pericycle

150. 18.Thehollow&tubularshape,largeindiameterandcells
stackedstructurefoundinXylemofangiosperms
(floweringplants)isknownas
(a)Tracheid (b)Vessel (c)Cortex (d)Vesicle

151. 19.Themesophyllcells(symplast)ofleafsynthesissugarthat
moveintocompanioncellsandfinallytransferintophloem
sievetubescellsthrough
(a)Plasmalemma (b)Plasma
membrane
(c)Plasmodesmat
a
(d)Plasmodia

152. 20.Thesugar(photosynthates)aretransferfromphloemsieve
tubeelementstothecellsofasinkiscalled
(a)Phloemunloading(b)Phloemloading(c)Both (d)Noneofthese

153. 21.Watermoleculesaretightlybindswitheachotherthrough
hydrogenbondsthatprovideunbrokencolumniscalled
(a)Cohesion (b)Adhesion (c)Cohesionand
Adhesionboth
(d)Noneofthese

154. 22
.
Duringtheevaporationofwaterintoairfromthe
surfacesofleafthatcausepullingofwaterfrom
downwardtoupwardandcreatinga‘pull’onthewater
columniscalled
(a)Transpirational
pull
(b)Transcription
alpull
(c)Transductio
nalpull
(d)Allofthese

155. 23
.
Fromwhichpartoftheleaf,watervaporisreleaseinthe
atmosphereduringtranspiration
(a)Mesophyllcell(b)Stoma (c)Xylemvessel(d)Allofthese

156. 24
.
Photo-assimilatesimporteris
(a)Source (b)Sink (c)Both (d)None of
these

157. 25
.
Limitationofsinkisnotfoundin
(a)Maize (b)Pulses (c)Bajra (d)Ragi

158. 26
.
Followingisnotanexampleofsource
(a)Fruit (b)Youngstem(c)Peduncle (d)Leaves

159. 27
.
Poresareobservedinfollowingpartofthexylem
(a)Cortex (b)Vessel (c)Tracheid (d)Vesicle

160. 28
.
Thelocationwherefoodisproducedby
photosynthesizingleavesiscalled
(a)Growing
regions
(b)Sink (c)Storage
organs
(d)Source

161. 29
.
Duringphotosynthesis,sinkareplaceswheresugarsare
being
(a)Consumed (b)Inhibited (c)Reduced (d)Produced

162. 30
.
Companioncellisattachedwith
(a)Sieveplate (b)Vessel (c)Tracheid (d)Sievetube
cell

163. 31
.
LowcanopyphotosynthesisandlowoptimumLAIisa
limitation
(a)Source (b)Sink (c)Both (d)Noneofthese

164. 32
.
Photo-assimilatesexporteris
(a)Source (b)Sink (c)Both (d)Noneofthese

165. 33.
Transportofassimilates/Photosynthates/foodmaterials
fromonecelltoanothercellthroughcellwallisknown
as
(a)Symplast (b)Cytoplast (c)Chloroplast(d)Apoplast

166. 34
.
Limitationofsourceisnotfoundin
(a)Wheat (b)Sorghum (c)Oilseeds (d)Rice

167. 35
.
Followingisnotanexampleofsink
(a)Fruits (b)Seeds (c)Nuts (d)Stipules

168. 36
.
Transportofassimilates/Photosynthates/foodmaterials
fromonecelltoanothercellthroughplasmodesmatain
cytoplasmisknownas
(a)Symplast (b)Cytoplast (c)Chloroplast(d)Apoplast

169. 37
.
Hormonalimbalanceissignof
(a)Source (b)Sink (c)Both (d)Noneofthese

170. 38
.
VegetativegrowthatReproductivephase,thereis
limitationof
(a)Source (b)Sink (c)Both (d)Noneofthese

171. 39
.
Earlyleafsenescencefromtheplantislimitationof
(a)Source (b)Sink (c)Both (d)Noneofthese

172. 40
.
Lateanthesisinplantduetolongvegetativephaseisan
exampleof
(a)Sinklimitation(b)Source
limitation
(c)Both (d)Noneofthese

173. Lecture-10
Under Chapter: Mineral Nutrition of Plants, Functions and
Deficiency symptoms of nutrients

174. 1.Nutrients:
Asubstance/chemicalrequiretosurviveofplantornecessaryforthesynthesisoforganic
compoundsinplants.
2.Mineral:Aninorganicelement.
3.PlantNutrition/Mineralnutrition:
Thesupplyandabsorptionofchemicalcompoundsneededforgrowthandmetabolismof
plantsmaybedefinedasPlantNutrition.
4.Nutriophysiology:
Itdealswithmetabolicandbiochemicalfunctionsoftheelementsandtheirinteractionwith
aspectsofplantphysiologyandplantbiochemistry.
5.Heterotrphic:
Thebothorganicandinorganicsubstancesaresupplyneededtoanorganismtocompletethe
lifecycleiscalledHeterotrphic.
6.Autotrophic:
TheorganismswhichsynthesistheirownorganicrequirementaarecalledasAutotrophic.
(A)INTRODUCTION

175. Plant Ash -40 Elements
Essential elements Non-essential elements
Necessary for normal growth &
Development
Not Necessary for normal growth &
Development
17 Elements

176. (B) CRITERIA FOR ESSENTIALITY OF ELEMENTS
(ARNON and STOUT)
An element to be considered essential, It must fulfill following criteria
1.Plantunabletocompleteitslifecycle
intheabsenceofthatelement.
2.Thefunctionofelementmustnotreplaceable
byanotherelement.
3.Theelementmustbedirectlyinvolvedinplantmetabolism

177. (C) Classification of Nutrient

178. (A) Mengeland Kirkby-Classification
a.Group 1 -Part of C compounds -N & S
b.Group 2 -Energy storage -P & B
c.Group 3 -Remain Ionic form -Ca, K, Mg, Mn& Cl
d.Group 4 -Redoxreactions -Fe, Cu, Zn, Mo & Ni

179. (A)MacronutrientsorMajorelements:
Theelementsthatrequiredbyplantsinconcentrationgreater
than0.5mmol/larecalledtoasmacronutrientsormajor
elements.
(B)MicronutrientsorMinorelements:
Theelementsthatrequiredbyplantsinconcentration
lessthan0.5mmol/larecalledasmicronutrientsorminor
elementsortraceelements.
Micronutrientsarerequiredinextremelysmall
quantityforthehealthygrowthofplants.Theyarethe
componentsofplantcellproteinsofmetabolicand
physiologicalimportance.

180. (B) ESSENTIAL ELEMENTS (17)
MACRO NUTRIENTS
or
MAJOR ELEMENTS
MICRO NUTRIENTS
or
MINOR ELEMENTS
or
TRACE ELEMENTS
C, H, O, N, P, K, Ca, Mg and S
Fe, ZN, B, Cu, Mn, Mo, Cland Ni
9 ELEMENTS
8ELEMENTS
Theelementsareessentialfor
plantgrowth&completelife
cycleiscalledE.E.
Thevariablemicro-elementsTi,Br,Li,
Rb,Ag,Be,Si,Sr,Cd,Pb,As,Cr,Ni,Al,
Co,Ba,Cs,Ge,Sn,andVarefoundin
someplants.

181. (C) Classification of Plant Nutrients according to
Dry weight Basis (%)

182. Macro Nutrients
Frame Work Nutrients
(High quantity-
>6.0%)
--------------
Carbon Hydrogen
Oxygen
Primary Nutrients
(Medium quantity-
0.2-1.5%)
-------------
Nitrogen
Phosphorus
Potassium
Secondary Nutrients
(Micro quantity-
<0.2%)
--------------
Calcium Magnesium
Sulphur

183. (D) Classification based on structural and
functional role of elements:
1.Structural elements
Frame work elements + Protoplasmic elements
(C, H & O) (N, P & S)
2.Balancing Elements -K, Ca & Mg
3.Catalytic Elements -Fe, Cu, Zn, Mo, Mn& Cl
4.Chlorophyll Element -Mg
5.Cell wall Element –Ca
6.Osmotic Balance Element -K

184. (E) Classification based on
mobility of elements
Mobile Elements:
Nitrogen, Phosphorus, Potassium and Magnesium
Immobile Elements:
Calcium, Boron, Iron, Copper and Sulphur
MobileandImmobileElements:
Zinc,Molybdenum,Manganese

185. Beneficial Elements
Definition:Elementswhicharenotrequiredforallplants
buttheycanpromoteplantgrowthandessentialfor
particularplantspp.
Elementswhichpromoteplantgrowthinparticular/many
plantspeciesbutarenotabsolutelynecessaryfor
completionoftheplantlifecycle,orfailtomeetArnon
andStout'scriteria.
1.Silicon, 2. Sodium, 3. Selenium, & 4. Cobalt

186. 1. Silicon –Rice
↑the availability of P, Ca & Mg
PreventsMn& Fe toxicity
Keeps the leaves to erect and uncurved–Stiffness
Prevents lodging –Mechanical strength
Pest & disease resistance
2. Sodium--Regeneration of PEP in C4 &
CAM plants:
Replace Kto some extent
Essential for Atriplexvesicaria(Halophyte)
Essential for Glycolysisprocess

187. 3. Selenium
Analogof Sulphur –Compete with SO
4uptake
Benefit by reverse the P toxicity.
Composition of Cysteineand methioninein the place
of S.
4. Cobalt
Component of Vitamin B12
Involved in Carbohydrate metabolism
Required for bacteria–N fixation in root nodules

188. (F) CLASSIFICATION OF PLANT NUTRIENTS BASED ON
THEIR UPTAKE & BIOCHEMICAL FUNCTION:
Nutrient
elements
Uptake Biochemicalfunction
1st group
C,
H,
O,
N,
S,
Intheformof
CO2,
HCO3,H2O,
O2,
NO3,NH4+,N2(SO4)2”
SO2.
Theionsfromthesoil
solutionandthegases
fromtheatmosphere.
Majorconstituentsofthe
organiccompounds ofthe
plant.
Essentialelementsofatomic
groupswhichareinvolvedin
enzymaticprocesses.
Assimilationby oxidation
reductionreactions.

189. 2nd
Group
P,
B,
Si
Intheformof
phosphates,
boricacidorborate,
silicatefromthesoil
solution.
Theyareimportantinenergystorage
reactionsorinmaintainingstructural
integrity.
Borateandsilicateesterswhichbound
tothehydroxylgroupofanorganic
molecule (i.e.sugar-phosphates)
(Esterification)
Thephosphateestersareinvolvedin
energytransferreactions.

190. 3rdGroup
K,Na,Mg,
Ca,Mn,Cl
Intheformofcations
fromthesoilsolution
exceptchlorine.
Presentinplanttissuesaseither
freeionsorboundionssuchas
thepecticacidspresentinthe
plantcellwall.
Actasenzymecofactorsin
regulationofosmoticpotentials.
4thGroup
Fe,Cu,Zn,
Mo
Intheformofionsor
chelatesfromthesoil
solution.
Presentinachelatedform
Incorporatedinprostheticgroups.
Enableinelectrontransportby
valencychange.

191. Mobile Intermediate Immobile
Nitrogen Iron Calcium
Phosphorus Manganese Boron
Potassium Zinc
Magnesium Copper
Chlorine Molybdenum
Rubidium
Sodium
Sulphur
(G) CLASSIFICATIONACCORDING TO MOBILITY OF ELEMENTS
(PHLOEM TRANSPORT) OF INORGANIC SOLUTES
The mineral nutrients initially acquired by the roots move upward in
xylem. Many of them are then subjected to redistribution via the phloem but
a few are not. Immobility in the phloem presumably is caused by failure of
these elements to enter the sieve tube.
Bukovacand Wittwer(1957) studied the mobility of many radio actively
labeled mineral elements applied to leaves of bean plants and classified
them into three groups based on the mobility in phloem.

192. Lecture -11

193. FUNCTIONS OF PLANT
MACRO NUTRIENTS

194. Nitrogen
NitrogenisthefourthmostabundantelementinplantsfollowingC,OandH.
Nisamajorstructuralconstituentofthecell.Thecytoplasmandthecell
organellescontainsvaryingamountofnitrogenlargelyincombination
withC,H,O,PandS.
Itisanessentialconstituentofthedifferenttypesofmetabolicallyactive
compounds,likeaminoacids,proteins,nucleicacids,prophyrins,flavins,
enzymesandco-enzymes.
Beingessentialfortheformationofprotoplasm,thedeficiencyofN
inhibitscellenlargement
Asmuchas70PercentofthetotalleafNmaybeinchloroplast.Thus
theearlysymptomsofNdeficiencyaregeneralyellowingorchlorosis.
Plantscontainabout1to3percentofNondryweightbasis.

195. Phosphorus
Itisastructuralcomponentofthemembranesystemsofthecellandthe
mitochondria.
Itisanessentialconstituentofnucleoproteins,organicmolecules(ATP,
ADPetc)whichplayanimportantroleintheenergytransferreactionsof
cellmetabolism,nucleicacids,andcoenzymeslikeNADP.
Phosphorusinthephytinofseedsisregardedasareserve.
Theuniquefunctionsofphosphateinmetabolismareitsformationof
pyrophosphatebondswhichallowenergytransfer.Uridinetriphosphate
(UTP)Cytidinetriphosphate(CTP)andguanosinetriphosphate(GTP)are
involvedinthesynthesisofribonucleicacids(RNA).
BeingaconstituentofADP,Phosphoglyceradehydeandribulose
phosphate,Pisinvolvedinthebasicreactionsofphotosynthesis.
Phosphorusisrelativelymoreabundantinthegrowing&storageorgans.

196. Potassium:
Kplaysasignificantroleinstomatalopeningandclosing.Themechanismof
stomatalclosureandopeningdependsentirelyontheKflux.
K
+
enhancesthetranslocationofassimilatesandpromotesrateofCO2
assimilation.
Kactivatesthenumberofenzymesinvolvedinincorporationofaminoacidsinto
proteinsandthesynthesisofpeptidebonds.
Potassiumregulatesthemembranepermeabilityandkeepstheprotoplasmin
properdegreeofhydration.
Potassiumisknowntoincreasetheresistanceofplantstomoisturestress,toheat
andtodiseasescausedbypathogenicfungiandothermicroorganisms.
InadequateKrestrictstheformationofxylemandphloemtissue.Lignificationof
thevascularbundlesisgenerallyimpairedbyK
+
deficiency.Thiseffectprobably
makesKdeficientcropsmorepronetolodging.

197. Calcium
Calciumisrequiredforcellelongationandcelldivision
Calciumplaysanessentialroleinbiologicalmembranes.Calciumisdepositedin
thecellwallascalciumpectate.Cadeficiencyobviouslyimpairsmembrane
permeabilityandmembranesbecomemoreleaky.
Germinationandgrowthofpollenaswellasthegrowthofrhizobiumroot
nodulesisaffectedunderlowlevelsofCa
2
+supply.
Caappearstoplayaroleintheinhibitionofabscissionanddelaysleaf
senescence.
Calciumisanessentialco-factororanactivatorofanumberofenzymes
concernedwithhydrolysislikelipaseanda-amylase
Caisastructuralcomponentofthechromosomes.Whereinitpossiblybindsthe
DNAtoprotein.Cadeficiencyisknowntoresultinchromosomalabnormality.
Calciumplaysanimportantroleinneutralizingacids.Particularlycitricacid,malic
acid,oxalicacidwhichmaybecomeinjurioustoplants.

198. Magnesium
Themostwellknownroleofmagnesiumisitsoccurrenceatthecentre
ofthechlorophyllmolecule.Itisthereforeessentialforphotosynthesis.
Mgisaconstituentpartofthechromosomesandalsoessential
constituentofpolyribosomes,thekeyorganelleconcernedinprotein
synthesis.
Magnesiumisknowntoplayacatalyticroleasanactivatorofanumberof
enzymes,mostofwhichareconcernedincarbohydratemetabolism,
phosphatetransferanddecarboxylations.Theenzymeinorganic
pyrophosphatase,assuchisinactive.Itbecomesfunctionalonlyinthe
presenceofMg.
ItisalsorequiredfortheactivationoftheenzymeRuBPcarboxylase.
NitrogenmetabolismisalsoinfluencedbyMgnutrition.

199. Sulphur(PlantsmainlyabsorbSintheformofSO
4
2-
)
Sulphusrisaconstituentofaminoacids,cystine,cysteine,and
Methionine.
Thecharacteristicodourofcuciferousplants,onionandgarlicisduetothe
presenceofsulphurasaconstituentofvolatileoils.
Severalotherbiologicalactivecompoundslikevitamins(Thiamineand
biotin),lipoicacid,acetylco-enzymeA,ferredoxinandglutathionecontain
sulphurasanessentialpart.
Theactiveadenosine-5-phosphosulphate(APS)isanimportantsulphate
donorwhichisinvolvedinthesynthesisofglycosidesinmustardoil.Being
involvedintheactivationofnumberofenzymes,participatinginthedark
reactionsofphotosynthesis,sulphurisinvolvedincarbohydratemetabolism
oftheplants.
ThetotalScontentinplanttissuesisintheorderof0.2to0.5percentinthe
drymatter.

200. FUNCTIONS OF PLANT
MICRO NUTRIENTS

201. IRON
Ironisaconstituentofcytochromes,ferredoxin,catalaseandperoxidase.The
cytochromes(cytb6andcyt-f)playanimportantroleinelectrontransport
processofoxidativephosphorylation(respiration)andphotophosphorylation
(photosynthesis).Theironcontainingproteinferedoxinplaysanimportantrole
inthereductionofCO2,atmosphericnitrogenandofsulphate.
Theleghaemoglobinpresentintherootnodulesofleguminouscropscontains
ironasanessentialconstituent.
Althoughironisnotacomponentofthechlorophyllmolecule,itisessentialfor
itssynthesis.Ithassomeroleinthesynthesisofthechlorophyllprecursor
protoporphyrin-IX.Mostoftheiron(60-80%oftheironcontentoftheleaves)is
foundinthechloroplasts.
Theimportantironcontainingenzymesofhigherplantsissuccinic
dehydrogenase,cytochromeoxidase,catalase,peroxidaseandaconitase.

202. MANGANESE
Manganeseisbelievedtobespecificactivatorofsomeenzymelike
oxidases,peroxidases,dehydrogenasesandkinases.
Manganeseisknowntobeaconstituentofnitritereductaseand
hydroxylaminereductase,bothofwhichareconcernedinnitrogen
assimilation.Intheabsenceofmanganese,nitriteaccumulatesand
leavesshowsymptomsofnitrogendeficiency.
Manganeseplaysakeyroleincarbohydratemetabolismandalso
affectstheabsorptionofcalciumandpotassiumions.
Manganeseisinvolvedintheoxygenevolvingstepinphotosynthesis-
ofPSII(wateroxidizingenzymecomplex)

203. COPPER
Thecoppercontainingcompoundsplastoquinonesandplastocyanins
areinvolvedintheelectrontransportfromchlorophylltoNADPduringthe
primaryreactionsinphotosynthesis.Thuscopperstressinplantshas
beenshowntoresultinadecreasedrateofphotosynthesis.
Copperisaconstituentpartofseveralenzymeslikenitritereductase,
cytochromeoxidaseandascorbicoxidase.
Relatively,highconcentrationsofCuoccurinchlorophasts.About70
percentofthetotalCuintheleafisfoundintheseorganelles.

204. BORON
Boronisassociatedwiththereproductivephaseinplantsandits
deficiencyisoftenfoundtoassociatewithsterilityandmalformationof
reproductiveorgans.Boronisthusrequiredforthegerminationofpollen
andgrowthofpollentube.
Boronplaysanimportantroleincarbohydratemetabolism,particularlyin
thetranslocationofphotosynthates.
Boronwasconsideredtobeinvolvedinthetranslocationofsugarsinthe
formofsugarboratecomplexes.Thesecomplexespassmorerapidly
throughcellmembranesthanthefreesugars.
Boronisrequiredfortheproperdevelopmentanddifferentiationof
vascularelements.

205. ZINC
Zincisametalcomponentofanumberofmetalloenzymeslikealcohol
dehygenaseandlacticdehydrogenase.
Zincisessentialforthesynthesisoftheaminoacidtryptophan,a
precursorofanimportantplantgrowthhormoneindoleaceticacid(IAA).
ZinciscloselyinvolvedinN-metabolismoftheplant.
Zincplaysaroleinplantmetabolisminvolvedinstarchformation.Zinc
alongwithCuhasbeenshowntobeaconstituentoftheenzymesuper
oxidedismutase.

206. MOLYBDENUM
Moisanessentialcomponentoftwomajorenzymesinplantsviz.,nitrate
reductaseandnitrogenase.Nitratereductaseconcernedwiththe
reductionofnitratetonitriteinbothmicroorganismandhigherplants.
Byvirtueofbeingaconstituentofnitratereductase,Moplaysdirectrole
innitrogenmetabolismofplants.
Moisknowntobeaspecificinhibitorofacidphosphatase.

207. CHLORINE
Chlorinehasbeenshowntobeinvolvedintheoxygen
evolutioninphotosystemIIinphotosynthesis(ClandMn
areimportantforthisreaction)
Itraisesthecellosmoticpressure.
Chlorineacceleratestheactivationofamylasewhich
convertsstarchintosolublesugars.

208. FUNCTIONS OF BENEFICIAL NUTRIENTS
a)COBALT
Cobalt is required by rhizobiafor the fixation of elemental nitrogen both by
leguminous and non-leguminous symbionts.
It is a structural component of vitamin Bi
2(cyanocobalamine).
B
12
is essential for the formation of hemoglobin concerned in nitrogen
fixation.
b)SODIUM
In higher plants, sodium has so far been shown to be essential only for
two halophytic species Atriplexvasicariaand Hologetonglomeratus.
The best known role of sodium is in the maintenance of osmotic relations
of the cell.
Sodium has beneficial effect on growth and water relations of sugar beet.

209. c)SILICON
The effect of Si is especially important in the yield and quantity of the
rice crop.
Recent studies have shown that, Silicon imparts disease resistance
and lodging resistance in paddy
The grain yield of the plants with Si is twice more than the plants
without Si.
The concentration of Si in rice will be around 100 mg g
-1
.

210. Lecture -12

212. Nitrogenbeingamobileelementwithinaplant,it'sdeficiencyresultsin
movementofNfromoldertoyounger(upper)leaves.Asaresulttheolderleavesturn
yellowincolour.
Inyoungplants,growthisstuntedwithyellowishgreenleaves.Yellowingof
leavesisduetothecollapseofchloroplastsresultingindecreaseofchlorophyll
content.
(A) NITROGEN

213. Yellowingalwaysstartsfromtheolderleavesandspreadstoyoung
ones.

214. SevereNdeficiencyaffectstheleaftissuetobecomedryandnecrotic.
Olderleavesareshedprematurely.
Rootgrowthisaffectedandbranchingisrestricted.

215. Shootbecomeshort,thinwithuprightgrowthandspindlyappearance.
Floweringisreduced.
Incereals,tilleringispoor,numberofearsperunitareaandnumberof
grainsperearheadisreduced.

216. GenerallythesymptomsofPdeficiencyappearintheolderleaves.
Youngplantsarestuntedwithdarkbluegreenleaves.
Stemsbecomeslender
Rootsystemislimited.Primaryandsecondaryrootselongateinlengthwithshort
tertiaryroots.
(B) PHOSPHORUS

217. InmanyplantspeciesPdeficiencyinducestheformationofanthocyanin
pigmentandtheleavesacquirepurplecolorprimarilyalongmarginsandonthe
lowerstalk(eg.Maize)

218. Theformationoffruitsandseedsisdepressedandripen
slowly.

219. Plantoftendwarfedatmaturity.
Inpotato,tubersmaydeveloprustylesionsintheflesh.

220. The most characteristic symptom of K deficiency is tip and marginal
scorching of most recently matured leaves.
Maize Tomato
(C) POTASSIUM

221. In barley which is the most susceptible of the cereals, numerous small
brown areas develop in the areas between the veins.
Roots are slender and poorly developed in sugar beet.
In certain temperate fruit trees, K deficiency may result in severe "die-
back“
Resistance of plants to infection by bacterial and fungal pathogens is
reduced.
Putriscine(foul-smellingorganic chemical compound) accumulates under
K+ deficiency.

222. SymptomsofCadeficiencyappearearliestandseverelyinmeristametic
regionsandyoungleavesbecauseitisimmobileone.
Breakdownofmeristemetictissuesinstemsandrootsoccur.
Rootspoorlydeveloped,lackfiberandmayappeargelatinous.
Littleornofruiting.
(D) CALCIUM

223. Theapicalbud"diesoff"andthussmallbranchesarisefromlowerleaf
axilsgivingtheplantbushyappearance.

224. Calciumdeficiencycauses"bitterpit"diseaseinappleand"blossom
endrot"intomatoandwatermelon.
"BITTER PIT" DISEASE IN APPLE

225. "BLOSSOM END
ROT" IN TOMATO

226. "Blossom End Rot" in Watermelon.

227. Interveinalyellowingorchlorosisoccursinolderleavesandunderseveredeficiency
theareasbecomenecrotic.
(E) MAGNESIUM

229. Incotton,Mgdeficiencyinducesformationofanthocyanin
pigmentsandareddishcolorationofleavesduringwinter.

230. Incitrus,thechlorosiscommencesatthetipsandmarginsoftheleafand
spreadinwardtowardsmidribbyleavinginvertedVshapeatthebottomofthe
leaf.

231. IngeneralfruittreesaresusceptibletoMgdeficiencyandshowvariedpatterns
ofchlorosis,necrosisandpigmentationofoldleaveswhichshedprematurely.

232. Due to sulphurdeficiency Chloroticsymptoms first appear in younger most
recently formed leaves.
(F) SULPHUR

233. Sulphurdeficiency: Shoot growth is more affected than
root growth.

234. Sulphurdeficiency: stems often become slender.

235. Sulphurdeficiency: Leaves become narrow and
chloroticin cruciferae.

236. Beingrelativelyimmobile,Fedeficiencyappearsfirstontheyoungerleavesof
theplant.
(G) IRON

237. Irondeficiency:Inmostspecieschlorosisisinterveinalandafine
reticulatepatterncanbeobservedinthenewlyformedleaves,thedarker
greenveinscontrastingmarkedlyagainstalightergreenoryellow
background.Theyoungestleavesmayoftenbecompletelywhiteand
totallydevoidofchlorophyll.

238. Sulphurdeficiency:Intheleavesofcerealsthedeficiencyisshownby
alternateyellowandgreenstripsalongthelengthoftheleaf.
 Infruittrees,irondeficiencyisassociatedwithhighleavesofCaCo3inthe
soil,whereitiscalled"limeinducedironchlorosis"

240. Mottled(Spottedorblotchy)chlorosiswithveinsgreenwhichappearsfirston
youngerleaves.
Stembecomesyellowishgreen,oftenhardandwoody.
(H) MANGANESE

241. ManganeseDeficiency:Ingroundnutleaves,theveinsaresurroundedbya
definitezoneofnonchloroticinterveinaltissue.
CharacteristicsymptomsofManganesedeficiencyincertaincropshavebeen
givenspecificnames.Theyare
greyspeckofoats,
speckledyellowofsugarbeet,
marshyspotofpeas,
pahalablightofsugarcaneetc.

242. Bisimmobileinmostplantspeciesandsymptomsappearfirstattopsandroots.
Theyoungestleavesaremisshaped,wrinkledandarethickerandofadark
bluishgreencolor,shedprematurely.
(I) BORON

243. BoronDeficiency:Plantsdwarfed,stunted,flowerdevelopmentandseed
productionusuallyimpaired.

244. BoronDeficiency:Rootsexhibitsswollenroottips.
CharacteristicsymptomofBdeficiencyincertaincropsare
Heart rot in sugar beetHollow stem in cauliflower
Brown heart of turnip Corky pith of apples
Hard fruit of citrus
Brown heart of turnip

245. Boron Deficiency: Hollow stem in cauliflower

246. Youngleavesshowchlorosis
Terminalleaves,shootsarewiltedanddistorted,frequentlyfollowedbydeath
resultingindevelopmentofseveralauxillarybuds.
(J) COPPER

247. Copper Deficiency: Cereals show bushy growth with
white twisted tips and reduced panicle formation

248. CopperDeficiency:Poorornoheadingincabbageand
lettuce.
In citrus, Cu deficiency leads to exanthema or die-back.

249. LittleleafandrosettearethecommonsymptomsofZndeficiency.
Leaveschloroticandnecrotic,younggrowthfirstaffected,resulting,
prematureshedding.
(K) ZINC

250. Zinc Deficiency:

251. ZincDeficiency:Inmaize,resultsinwhiteoryellowemergingleaves,a
conditioncalledwhitebud.

252. ZincDeficiency:Inmonocotsandparticularlyinmaize,chloroticbandsform
oneithersideofthemidriboftheleaf.

253. InRiceZndeficiencycauses'khairadisease'

254. Symptoms of Mo deficiency are similar to those of N deficiency because in the
absence of Mo, nitrate is not metabolized.
Leaves show marginal scorching and rolling or cupping.
(L) MOLYBDENUM

255. MOLYBDENUM Deficiency: In extreme deficiency, the leaf lamina is not formed
and only the rib is present in cauliflower which is called whiptail disorder.

256. Chlorosisofyoungerleavesandanoverallwiltingoftheplant.
Insomeplantspecies,liketomato,leavesshowchloroticmottling,bronzingand
tissuenecrosis.
Withering of leaves and wilting of plants, which are called weeping willow habit of growth.
In cereals and grasses, necrotic spots develop on leaves.
(M) CHLORINE
(N) SILICON

257. NUTRIENT DEFICIENCIES AND SOME SPECIFIC NAMES
Specific names have been given to symptoms of certain nutrient deficiencies. They are:
Calcium
Bitter pit in apple, Blossom end rot in tomato
Manganese
Grey speck of oats, speckled yellow of sugar beat, Marsh spot of
pea pahalablight of sugarcane, Frenchingof tungtree.
Boron
Heat rot in sugar beat, Browning or hollow stem in cauliflower,
Top sickness of tobacco, Brown heart of turnip, Cracked stem of
celery, Corky pith of apple, hard fruit of citrus.
Copper
Exanthema or dieback in citrus
Zinc
White bud in maize, khairadisease in Rice.
Molybdenum
Whiptail in cauliflower

258. TOXICITY SYMPTOMS OF
PLANT NUTRIENTS

259. TOXICITYSYMPTOMSOFPLANTNUTRIENTS
Definition:Asexcesssupplyofoneormoreoftheessentialelements,
particularlytheheavymetalsbringsaboutareductioningrowthand
oftenleadstotheproductionofvisualsymptomsattimesiscalled
toxicityinplant.
Thevisualeffectsofexcesssupplyofelementsmaybeduetoadirect
effectoftoxicityofelementsorbyinducingdeficiencyofanother
element.
Eg.ExcessPhosphorussupplymayretardtheuptakeandtranslocation
ofCuandZn,thusshowsCuandZndeficiencysymptoms.
UnderfieldconditionsN,SandAltoxicitiesarecommon.Mntoxicityis
observedinacidsoils.

260. A)NITROGEN
AsaNutrient-excessivenitrogencommonlyproducesplantsthatvegetativeso
thatyieldisreduced.
Insugarcanebothjuicequalityandsugarrecoveryisreduced.Fruitqualityis
impaired.
CerealsreceivingexcessNhavebeenshowntoexhibitlodgingasaresultofthe
decreasedthicknessofthecellwallsorduetothepoordevelopmentofthe
mechanicaltissuesofthestemorduetoboth.
Intomato,plantsarehighlyvegetativeandfruitproductionisreduced.
AsasaltahighlevelofNapplicationincreasesthesalinityofthesoil.
Alsotheformofnitrogen(NH
4
+orNO
3
--
)andassociatedions(SO
4
-
,NA+Ca++)
maymarkedlyaffectsoilstructureandplantresponse.

261. B)SULFUR

Excesssulfurcausesinterveinalyellowinginsorghumandlemonleaves.
Growthandleafsizewasconsiderablyreducedinallthecrops.

Excessiveconcentrationsofsulfurdioxideintheatmospherealsocause
toxicityintheplants.ThesymptomsproducedbyexcessiveSO
2wasdivided
into(a)acuteinjury(b)Chloroticinjury.

Theacuteinjuryconsistsofcollapsed(distortedormalformed)marginalor
interveinalareaswhichatfirsthaveadull,watersoakedappearance,later
dryingandbleachingtoanivorycolorinmostspecies.

Chloroticinjuryisayellowingoftheleafwhichmayprogressslowlyand
bleachescompletely,bleachingmostofthechlorophyllandcarotenoids.

262. AnothertypeofStoxicityisHydrogensulfidetoxicity(sulfideinjury).In
poorlydrainedricesoils,theH2Stoxicityiscommon.Thisdisorder
iscommonlycalledas"akagare"or"akiochi".
Thisanaerobicdisorderischaracterizedbyinhibitedroot
developmentandbrowning(orblackened)anddeathofrootswhich
precedethestuntingofshoots.
TheH2StoxicityalsodepressestheuptakeandtranslocationofPand
othernutrients.

263. C)ALUMINUM
Aluminumtoxicityiswidespreadinmostoftheacidicsoils.
Ingeneral,rootsareaffectedfirst,moreseverelythanthetopsunderaluminum
excess.
Inmostspecies,rootsappearthickandbrownandthetipsoftherootlets
oftenappearenlarged.
Inbarely,thegeneralgrowthoftheplantsandtilleringareseverelyrestricted.
Leaftipsoftenturnbrownandwither.
Thestembecomesdarkbrown,noearsareformedandplantsoftendie
prematurely.
Therootgrowthisseverelyrestrictedandtheroottipsappeardarkbrownand
enlarged.

264. Lecture-13
Under Chapter: Nutrient Uptake Mechanism

265. SoilserveasamainsourceofMineralsaltsinwhichclay
crystalswithacentralnucleuscalledmicellearepresentin
colloidalform.
Micellearenegativelychargedinordertomaintainabalance,
byattractingandholdpositivelychargedionsonthesurfaceof
colloidalclaycrystals.
Mineralnutrientsincomplexcombinedformsbecomeavailable
toplantrootonlywhentheyarebrokendownphysicallyor
chemically.
Theavailablemineralsofsoiloccurinionicform.
Thecommoncatonic(+)formsareK,Mg,Ca,Fe,Mn,Cu,Zn,Co.
Thecommonanionic(-)formsareP,Cl,SandCl.
Thelooselyabsorbedionscanbeeasilydisplacedfromthe
colloidondecreasingtheirownconcentrationinsoilsolution.
While,firmlyabsorbedionscanbereplacedbyotherions
whichhavemoreaffinityforthecolloids.
IntroductionofMineralsSaltAbsorption

266. Theorderforcationretentivecapacityofcolloidsisasbelow:
H+>Ca++>Mg++>K+>NH4+>Na+
Inplantselectrolytesarepenetrateinformofionsisaccompaniesbyentryof
anotherionsofequalelectrostaticcharge.
Themono-valentcationssuchasKandNaareabsorbedmorerapidlyas
comparetobi-valentorpolyvalentcationssuchasCaandMg.
Example:whencationuptakeismore,thecellproducesorganicacids
resultinginmoreanionstobalancetheexcesscations.Thehydrogenions(H+)
oftheorganicacids,however,passoutintoexternalmedium(soilsolution)to
compensateforthecations(K+)whichhavebeenremoved.
Thereadilyavailableionicformofwater,H+andOH-alsocompensateforthe
shortageofcationandanaionswhereeverrequired.
Conti……IntroductionofMineralsSaltAbsorption

268. Mineralionsarefoundinsoilsolutionorasionsonthesurfaceofcolloidal
particles.
Twotheoriesforionicexchange:
(i)Carbondioxidehypothesis(ii)Cationexchangehypothesis
(i)Carbondioxidehypothesis:
Accordingtothistheory,CO2producedbyrootsduringrespiration,reacts
withwatertoproducedcarbonicacidwhichdissociatesintohydrogenions
andbicarbonateions.
Thehydrogenionschangeplaceswithcationabsorbedonthecolloidal
particlesandbicarbonateionsreleasetheadsorbedanionstomakecation
andanionsavailabletorootsofplantscloseby.
Thishypothesisisthemovementofionsbetweenadsorptionsitesinthesoil
particleandroots.
(A)AvailabilityofMinerals
K+ HCO¯3
CO2 + H2O
H+ HCO¯3
K+
Root Clay micelle

269. (ii)Cationexchangehypothesis(Contactexchangetheory):
Thistheoryeliminatingtheshortcomingsofionicmovementbetween
adsorptionsitesinthesoilandroots,postulatethationsarenotcompletely
static.
ionsarealwaysoscillatingaroundtheiradsorptionsurfaceandoverlapeach
other,henceionexchangeoccurs.
Anequilibriumisalwaysmaintainedbetweenthedissolvedfractionsasany
depletioninthesoilsolutionisimmediatelycoveredbymovementofions.
Thoughthetheseboththeoriesarenotuniversallyaccepted.
(A)AvailabilityofMinerals
K+
Root
Clay micelle
H+
K+
H+
Clay micelle
Root

270. The availability of soil water and minerals
Long-distance transport of water from roots to
leaves

272. (B)MechanismofNutrientuptake
MechanismofNutrient/Mineralsalt/ionsuptake/absorptionplacedundertwo
broadcategories.
I.PassiveAbsorption:
ItincludesthetheoriesofMassflow,ionexchange,Donnanequilibriumand
diffusion.
II.ActiveAbsorption:
Itincludesthetheoriesrelatedtocarrierconceptstheory,Proteinlecithintheory,
cytochromepumphypothesis,andATPtheories.
I.PASSIVE ABSORPTION:
BriggsandRoberston(1957)demonstratedPassiveAbsorptionofionsbyroot
systemincontactwithsoilcolloidsandrootsolution.
1.MASSFLOWTHEORY(BULKFLOW):
Accordingtothistheory,ionsaretakenupbytherootsalongwithmassflowof
waterundertheinfluenceoftranspiration.
Lopushiinsky(1964)foundthathighhydrostaticpressureofwater,increaseion
uptakeintherootsusingradioactiveisotopesP32andCa45.
Researchersfailtoexplainthistheorywhenthereishighamountsalt
accumulationinthesoil(insuchconditionwaterisnotenterintheroot)against
osmoticgradient.

273. (B)MechanismofNutrientuptake
2.IONSEXCHANGE:
Ionsmaybeexchangewith
theionsabsorbedonthe
surfaceofcellwalloftissue
immersed in external
solution.
Ashydogenions(H+)and
hydroxylions(OH+)bothare
readyavailableonthe
surfaceofcellmembrane,the
cationsandanaionsare
exchange freelywithout
involveofmetabolicenergy.
Experimentcarriedoutwith
excisedbarleyrootstreated
withtheuseofradioactive
K+. After sometimes,
radioactiveK+ ions
exchangeplacewithnon-
radioactiveK+ionspresent
inthesolution.
Cl-
Br-
Figureexplainingionexchangetheory.NegativelyCl-
andBr-exchangewithoutdisturbingelectricneutrality
3 Br, 3Cl 6 Br, 0Cl
Left
column
0Br, 6CL3 Br, 3Cl
A -PART B -PART
Right
column
Right
column
Left
column

274. Donnanequilibrium showing ion
pair diffusion:
3.DONNANEQUILIBRIUM:
Thistheoryaccountsfornon-
diffusibleionsforcontrolof
electrochemicalequilibrium.
Inordertomaintainaninternal
balanceofcellortissue,suchions
wouldrequireionsofothercharge.
Infigure,ionexchange is
preventedduetonon-diffusible
ions(R-)insidecell.
Fixedanaions(Cl-)arepresenton
theinnersideofthemembrane,
cations(K+)inadditiontonormal
exchangewouldbeabsorbedto
maintaintheequilibrium.
Thusincreasingthecations
concentrationoftheinternal
solutionincomparisontoexternal
solution.
External
solution
Internal
solution
Internal
solutionExternal
solution

275. II. ACTIVE ABSORPTION:
Activeabsorptionissupportedby
metabolicenergy.
1.THECARRIERCONCEPTTHEORY:
ThistheoryproposedbyHonert(1937),
iontransportiscarriedoutbyorganic
moleculesorvesiclesasacarrierwhich
arepresentinplasmamembrane.
Ionsundergoesreversiblebindingwith
constituentofouterspacedesignatedas
acarrierandpassthroughthe
impermeableboundaryofouterand
innerspaceintheformofionand
carriercomplex.Onreachingitseparate
fromthecarrier.
Thisistheoryofselectivity,abundantof
selectedionsinmembraneandtheir
chemicalaffinitywiththecarrier
molecules.Carrierarealsoknownas
translocatorswhentranslocatesspecific
largeproteinmolecules.

276. 2.PROTEIN–LECITHINASCARRIER:
Accordingtothetheory
proposedbyBennetClark
(1956),carriercanbe
proteinassociatedwith
phosphatidei.e.lecithin,
synthesizedandhydrolyzed
incyclicmanner.
Ionsk+andcl-arepicked
upbylecithinfromouter
spacetoproducelecithin-
ioncomplexwhichmovein
innerspaceandreleasethe
ions(k+andcl-) on
hydrolysisofcomplex.
ATP isrequirefor
resynthesisoflecithin.

277. 3. CYTOCHROME_PUMP
HYPOTHESIS:
According tothetheory
proposed by Lundegardh
(1950),statedthatanion
absorptionisindependentof
cationabsorption.
Proton(H+)andelectron(e-)
areproducedoninnersurface
asaresultofDehydrogenase
reaction.
Viacytochromechain,electron
movesoutwardtoberelease
andunitedwithprotons(H+)
andoxygen(O)toformwater.
ReductionofIron(FromFe++
toFe+++)ofcytochromeonthe
outersurfacegetoxidizedby
losingtheelectron.
Theanionpickedupby
oxidizedironofcytochromeon
outersurface.

278. 4. ATP THEORIES:
According tothetheory
proposedbyLaties(1957)and
Sutcliffe(1959),statedthation
absorptioninthecellis
energizedbyATP.
Theenergyfromhydrolysisof
ATPmoleculescanbemade
availabletoenergizedionpump
throughactionofenzymes
presentinthecellmembrane.
Infirstcase,organiccompound
(adenine)firstphosphorylased
(addition of inorganic
phosphorus) on
dephosphorylased organic
compound.
Thecationisreleasedwhen
phosphorylationisoccur(cation
uptakerequiresATP)andanion
uptakeislinkedtoelectron
transfer.

279. (C)FactorsaffectingNutrientsuptakeORSaltAbsorption
(i)Temperature:
Increaseintemperatureincreasebothactiveandpassiveabsorption.
Beyondmaximumlimitoftemperature,absorptiongetinhibited
becauseofdenaturationofenzymesintheprocesses.
(ii)pH:
pHaffecttheavailabilityofionsinthemedium.
ThepHvaluesoutsidethephysiologicalrangedamagetoplant
tissueandinhibitsaltabsorption.
(iii)Light:
Lightindirectlyaffectthesaltabsorptionbyaffectingtheopening
andclosingofstomataduringtheprocessoftranspirationand
photosynthesis.
(iv)Oxygentension:
Thedeficiencyofoxygendecreasesaltabsorption.
(v)Interactionofions:
Absorptionofoneionmaybeinfluenceofanotherion.Interaction
isappearinprimarystagewhenlessavailabilityofionandspecific
bindingsiteoncarrier.However,ifenoughbindingsiteoncarrierare
present,Interactiondoesnotappear.

280. Lecture-14
(A)Photosynthesis & its Importance
(B) Chloroplast Structure
(C) Pigments
(D) Evidence in Support of Light &
Dark Reaction

282. Light Energy Harvested by Plants & Other
Photosynthetic Autotrophs
6 CO
2+ 6 H
2O + light energy →C
6H
12O
6+ 6 O
2
(A) Photosynthesis

283. •Photosynthesisisthevitalphysiologicalprocessoccurinthe
chloroplastofgreenplants(autotrophicorganisms)uselight
energytosynthesizessugarandoxygengasfromcarbondioxide
andwater.
•2500chlorophyllmoleculesarerequirefixingonemoleculeof
CO2inphotosynthesis.
OVERVIEW OF PHOTOSYNTHESIS
Carbon
dioxide
Water Glucose Oxygen
gas
PHOTOSYNTHESIS
+ 686 K Calories energy

284. 1.Photosynthesishelpstopurifyairandalsomaintainbalanceofoxygenand
carbondioxideintheecosystem.
2.Itprovidefoodeitherdirectlyasavegetables&fruits,cerealsandpulses
tovegetarianpeoplesorindirectlyprovidemeatormilkofanimalswhich
arefeedonplantstonon-vegetarianpeoples.
3.Itprovidevastreservoirofenergytomankindintheformfuel,suchas
coal,petroleum(oil),wood,naturalgases,ligniteetc.allenergy-rich
materialsofanorganicoriginthatalsoprovidepowertoindustries.
4.Oxygenicphotosynthesiswasresponsibleforconvertingthetotally
anaerobicconditiononearthintoaerobicatmosphere.
5.Excesssugarsproducedinphotosynthesisareeitherstoredintheformof
carbohydratesorusedinthebiosynthesisofotherorganiccompounds.

285. Life on Earth
depends on
flow of energy
from sun

287. Definition:Chloroplastisadoublemembranestructure,greenincolor&
ellipsoidalinshapethatcontainchlorophyllmoleculesinsidethequantasomes
whichareidentifiedasasiteofphotosynthesis,areofagreatbiological
importance.
Leeuwenhock(1679)hasisolatedseparatestructureofchloroplast.
Chloroplastsinhigherplants,mainlyfoundinpalisadeandspongytissueof
leaves.
Haberlandt(1882)foundanaverageof36Chloroplastsineachpalisadecell
and20ineachspongyparnchymacell.
palisademesophyll(sometimescalledpalisadeparenchyma,thecellsare
intactmeansnospaceamongthecells,containshugeamountofchloroplasts)
andOtherisspongymesophyll(spongyparenchyma,thecellsareloosely
arrangedandlargerspaceamongthecells,containslesschloroplasts).
Theleafisarrangedlikeadifferentlayersofcake.
Chemicalcompositionofchloroplast:
Content Per cent Content Per cent
Proteins 35-55 % Carotenoids4-5%
Lipids 20-30% RNA 3-4%
Chlorophyll a 75%
Chlorophyll b 25%
least DNA <0.02-0.1%

289. STRUCTURE OF CHLOROPLAST
Soluble proteins &
RUBISCO enzyme
in stroma

290. Envelop:Madeofdoublemembraneacrossmolecularinterchange.
Stroma:Internally,thechloroplastisfilledwithahydrophilicmatrixcalled
asstroma(fillsmoregelfluidvolumeofchloroplast)embeddedwith
grana.Itcontain50%ofsolubleproteinsofchloroplast,DNA,70Stype
ribosomes&RUBISCOenzyme.
Thylakoids:Aflattenedvesiclesarrangedlikestackedpilesofcoins
forminggrana.Eachgranamconsistsof5-25discshapedgranalamellae
(thylakoid)placedoneabovetheother.Itcontains50%ofproteins.
Itcontain5super-molecularcomplexes:
1.Photosystem-I(PSI)2.Photosystem-II(PSII)
3.Cytochromeb/f 4.ATPsynthase
5.LightHarvestingComplex(LHC):Chlorophylla&b
Eachgranalamellaofthylakoidenclosesaspacecalledloculusandthe
thylakoidmembraneconsistsofalternatinglayeroflipidsandproteins.
Someofthegranalamellaofthylakoidofisconnectedonegranato
anothergranabysomewhatthinnerstromalamellamembrane.
Chlorophyllandotherphotosyntheticpigmentsareconfinedtograna.
Thechlorophyllsarethesiteofphotochemicalreactions.

291. (Inner side of
Membrane is made up
of D1 & D2 sub-units)
(Outer side of
Membrane-Core is made
up of psaA& psaBsub-
units)

293. Plant Physiology III Edition
By
S.N. Pandye& B. K. Sinha

294. Thylakoidsin prokaryotes :
Inprokaryoteslikecyanobacteria,
purplebacteria,etc.,thylakoids
arepresentbuttheylienakedin
thecytoplasm.Chloroplastsare
absent.Inprokaryotes,pigments
aredistributeduniformlyonorin
thelamellae.

295. WHYAREPLANTS GREEN?
Plant Cells
have Green
Chloroplasts
Thethylakoidmembrane
ofthechloroplastis
impregnated(saturated)
with photosynthetic
pigments (i.e.,
chlorophylls,carotenoids).

296. Chemical Structure Chlorophyll a & b
Chlorophyll a: C
55H
72O
5N
4Mg and
Chlorophyll b: C
55H
70O
6N
4 Mg.
Mg porphyrinhead which is hydrophilic and a phytoltail -lipophilic
Twochlorophylls
differbecausein
chlorophyllb
thereisa–CHO
groupinsteadof
CH3groupatthe
3rdCatomin
pyrrolringII.

297. FracturesurfaceA:containsrare&smallsizeofquantasomes;
SurfaceB&D:containsthelargesizeofquantasomesseenonadjacentthylakoidmembranes;
FracturefaceC:containstightlypackedsmallquantasomes.
Twomajorsizesofparticlesareseenwhenmature
plantchloroplasts:
Large particles: 17.5 nm and small particles: 11 nm.
Ultra Microscopic
Structure of Thylakoid

298. No.Types of Molecules Numbers / quantasome
1.Chlorophyll a 160
2.Chlorophyll b 70
3.Carotenoids 48
4.Quinones 46
5.Phospholipids 116
6.Mono-galactosyl-di-Glyceride 346
7.Di-galactosyl-di-Glyceride 144
8. Sulpholipid 48
9.Phosphatidylcholine 58
10.Phosphatidylglycerol 47
11.Phosphatidylinositol 27
12.Some sterols & Osmiophilicgranules -
Total ≈1110

299. •Chloroplasts
absorb light
energy and
convert it to
chemical energy
Light
Reflected
light
Absorbed
light
Transmitted
light
Chloroplast
THE COLOR OF LIGHT SEEN IS THE COLOR NOT
ABSORBED

300. The various portions of E.S. are Gy, U.V. rays, visible rays and infrared rays, the
wavelength of these rays ranges from 280 nm to 1000 nm.

301. No.WavelengthsElectromagnetic
radiation
1.Below280nmX rays, Gamma rays and
Cosmic rays
2.280-390nmUltra violet radiation
3.430-470nmBlue light
Visible light (PAR)4.470-500nmBlue green light
5.500-560nmGreen light
6.560–600nmYellow light
7.600–650nmOrange light
8.650 -760 nm Redlight (VIBGYOR)
9.760 -1000 nm Farredlight(IR)
Different Electromagnetic radiations of various Wavelengths (nm)

302. Different pigments absorb light differently
Theabsorptionofdifferentwavelengthsoflightbyaparticularpigmentiscalled
absorptionspectrum.
Chlorophyllsabsorbmaximumlightinthevioletblueandredpartofthespectrum.
Theabsorptionpeaksofchlorophyllaare435violetblueand662redpartSkyblue
line);forchlorophyllb453and642(Palegreenline)respectively.Chlorophyllchas
absorptionpeakinblueregionat447;Chlorophylldhasabsorptionpeakinredregion
at688andin435violetblueregion.
Carotenoidsabsorblightenergyinblue(449)andbluegreenpart(478)ofspectrum.
(Orangeline).
435
violet
blue
662
red part
453
blue
642
Red
part

303. Water-splitting
photosystem
NADPH-producing
photosystem
ATP
mill
•Two types of photosystemscooperate in the light reactions
Thenormalstateofthechlorophyllmoleculeoratomiscalledas
groundstateorsingletstate.Whenanelectronofamoleculeoranatom
absorbsaquantumoflight,itisraisedtoahigherenergylevelwhichiscalled
asexcitedsecondsingletstate.Thisstateisunstableandhasalifetimeof10-
12seconds.
Theelectroncomestothenexthigher
energylevelbythelossofsomeofits
extraenergybyfollowingways:
i)Bylosingitsremainingextra
energyintheformofheat.
(ii)Bylosingextraenergyintheform
of radiant energy
(phosphorescence)andafterthe
incidentradiantlightiscutoff,
thechlorophyllmoleculesemit
phosphorescentlight.
(iii)Electronscarryingtheextraenergy
maybeexpelledfromthe
moleculeandisconsumedin
somefurtherphotochemical
reaction
Ground state or
singlet state
Exited state or
second singlet state

305. (C) Chloroplast Pigments
Figure 7.7
PHOTOSYNTHETIC PIGMENTS ARE OF THREE TYPES WHICH ARE
DISTRIBUTEDIN PLANT KINGDOM
(A) CHLOROPHYLLS:
Chlorophyll a : All photosynthesizing plants & only in Green-sulphurbacteria
Chlorophyll b : Higher plants and green algae
Chlorophyll c : Diatoms and brown algae
Chlorophyll d : Red algae
Bacteria chlorophylls: Purple and green bacteria
a, b, c, d & e
Chlorobium,Chlorophyll 650,Chlorophyll 660 are
distinguished
(B) CAROTENOIDS:
B-Carotenes: Higher plants and algae (Orange)
Xanthophylls: Higher plants and algae (Yellow)
Lutein: Green leaves and Green and Red algae
Fucoxanthin: Brown algae
Neoxanthin: Higher plants-Green leaves
Violaxanthin: Higher plants-Green leaves
(C) PHYCOBILLINS:
Phycocyanins: Blue green algae and red algae
Phycoerythrins: Blue green algae and Red algae
Allophycocyanin: Blue –green and Red algae

306. (A)BIOSYNTHESIS OF
CHLOROPHYLLS:
ALA–isaprimaryprecursorof
chlorophyll.
Itiscatalysedbyenzyme
Coproporphyrinogen oxidative
decarboxylaseconvertedinto
protoporphyrinIX.
DV=Divinyl
MV=Monovinyl
Catalysedby enzyme
Co-pro-porphyrinogen
oxidative decarboxylase

307. (B) BIOSYNTHESIS OF
CAROTENOIDS:
Acetateisaprimary
precursor.Firstacetyle
CoAissynthesized.
Roleofcarotenoids:
1.Itprotect the
chlorophyll against
photodynamic
destruction.
2.Itabsorbandtransfer
light energy to
chlorophylla.
MEP= Methyl Eno
Phosphate
DMAPP = Di-MethyleAmino
Pyro-Phosphate

308. (C)BIOSYNTHESIS OF
PHYCOBILLINS
Occuingonly algal divisions,
Rhodophyta, Cyanophyta
and Cryptophyta.
Red and blue
phycobiliproteinscalled
phycoerithrinsand
phycocyanins, respectively.
It also act as photosynthetic
pigments.
Light harvested is not
utilized but transferred to
chlorophyll a, that’s why
they are called as accessory
pigments.

309. (D) Evidences in support of light and Dark reaction
(i)Evidencefromtemperaturecoefficient:
TemperaturecoefficientisalwaysrepresentedassymbolQ10.
Forthephotochemicalreaction,Q10isalmostunityi.e.Q10=1;asitshowno
increaseintheratewiththeriseintemperature.
Forthedarkreaction,Q10isalwaysequalto2or3(Q10=2or3).Thelightand
darkreactionsareindependentbutinterlinked.
(ii)Evidencefromintermittentlight:
Warburg(1920)observedthatwhenintermittentlightabout1/16secondsweregiven
togreenalgaephotosyntheticyieldpersecondwashigherthancontinuoussupply
ofsameintensityoflight.
Explanation:
Inphotochemicalreaction,AisconvertintoBandbychemicalreactionBisconvert
intoC.Undercontinuouslight,ConversionAintoBproceedwithfasterratethan
ConversionBintoC.Asaresult,Bshowstendencyofaccumulation.Whilein
intermittentlight,thedarkphaseenablesBtoconvertintoCandtherateof
photosynthesisincreases.
(III)Evidencefromcarbondioxidereductionindark:
Tracertechniquewasusedinwhichusedheavycarbonincarbondioxide(C
14O2).
Theleaveswereputfirstinlight,butwhentheytransferredintothedark,are
foundtoreducedCO
2,purelyachemicalphase.

310. Lecture-15

311. 1.Lightreaction/Primaryphotochemical
reaction/Hill’sreaction/Arnon’scycle
(Activitiesfoundinthylakoidsorgrana)
2.Darkreaction/Blackman’sreaction/Path
ofcarboninphotosynthesis.
(ActivitiesfoundinStroma)
The whole mechanism of photosynthesis
consists of two parts.

313. Thelightreactionphaseofphotosynthesisiscomplicated
processwithseveraleventscanbestudiedunderthe
followingheadings.
(I)(a)ReddropandEmersoneffect
(b)Twopigmentsystem
(II)(a)productionofassimilatorypowers
(b)Photophosphorylation
(i)NoncyclicPhotophosphorylation
(ii)CyclicPhotophosphorylation
(iii)PseudocyclicPhotophosphorylation
(III)Energyrelationshipsandefficiencyofphotosynthesis
(IV)InterrelationshipofLight&DarkReaction

315. Photosynthesisisconsideredasatwoquantaprocess,i.e.takes
twolightquantaenergytodriveeachelectron.Since4electronsare
requiredforreductionofonemoleculesofCO2,8quantalightwillbe
requiredtoreduceitortoevolveonemoleculeofoxygen.
O2+4H+ CH2O+H2O
RadiantEnergy
4H2O 4(H++e-)+2H2O+O2
Lightraysconsistoftinyparticlescalledphotons.
Theenergycarriedbyaphotoniscalledquantum.
Thenumberofphotons(quanta)requiredtoreleaseonemoleculeof
oxygeninphotosynthesisiscalledquantumrequirement.
Thenumberofoxygenmoleculesreleasedperphoton(lightquanta)of
lightinphotosynthesisiscalledasquantumyield.
Thequantumyieldisalwaysinfractionofone.
Intheprocess,onemol.OfO2isevolvedutilizing8quantaenergy,
i.e.quantumyieldis1/8=0.12X100=12%quantumyield.

316. REDDROP:
RobertEmersonChalmersnoticedthatthereisasharpdecreasein
quantumyieldatwavelengthgreaterthan680nminphotosynthesis
(chlorellaplant)intheredpartofthespectrum,thephenomenon
wascalledasreddrop.
X-Later,theyfoundthattheinefficientfar-redlightbeyond
680nmcouldbemadefullyefficientifsupplementedwithlightof
shorterwavelength(bluelight).
EMERSON’SENHANCEMENTEFFECT:
Thequantumyieldfromthetwocombinedbeamsoflight
wasfoundtobegreaterthanthesumeffectsofbothbeamsused
separately.Thisenhancementorincreasingofphotosynthesis
processiscalledasEmerson’sEnhancement.

317. PIGMENT system I PIGMENTsystem II
Chlorophyll a 670 Chlorophyll a 660
Chlorophyll a 680 200 mole. Chlorophyll a 670 200 mole.
Chlorophyll a 695 Xanthophylls
1 cyt. f,1 plastocynin, 2 cyt. b563, FRS
(FerredoxinReducing Substance, iron &
copper
4 plastoquinone, 4 Mnmolecules,2 cyt. b
559, 1 cyt. b6, Chloride
Carotenoids -50 molecules carotenes Xanthophylls, violaxanthin, r-neoxanthin
Phycobillins
Chlorophyll a absorbing light 700 nm wave
length or called P700 form
Chlorophyll a absorbing light is 680 nm
wave length or P680 form
P700 form of Chlorophyll ais the active
reaction centre
P680 form of Chlorophyll ais the active
reaction centre
ThetwopigmentsystemsI(PSI)andpigmentsystemsII(PSII)areinterconnectedbya
proteincomplexcalledcytochromeb6–fcomplex.
Twosystemsarebasedonchloroplastfragmentationprocesswhichshowedtwotypes
ofparticleswithinchloroplastmembrane,smallerandlighterparticlesofPSIandlarger
andheavierparticlesofPSII.
SalisburyandRoss(1986)proposedthatgranamainlycontainPSIIwhilestroma
lamellaePSI.
InPSII,primaryelectronacceptoriscolorlesschl.athatlacksMghencecalled
pheophytin.

318. (Inner side of
Membrane is made up
of D1 & D2 sub-units)
(Outer side of
Membrane-Core is made
up of psaA& psaBsub-
units)
Cyto-b6f connect
PS I & PS II

319. Arnon(1956)usedthetermassimilatorypowerstoreferto
ATPandNADPH2(ReducedNicotinamideadenine
dinucleotidephosphate).
TheprocessofreductionofNADPintoNADPH+H+maybe
denotedasElectrontransportsysteminphotosynthesis.
WhiletheprocessofformationofATPfromADPand
inorganicphosphate(Pi)utilizinglightenergyiscalled
photophosphorylation.
Production of assimilatory powers in photosynthesis

322. In1937,RobertHilldemonstratedthatisolatedchloroplastsevolvedoxygen
(photolysisofwater)whentheywereilluminatedinthepresenceofa
suitableelectronacceptor,suchasacceptorferricyanide.
Theferricyanidereducedtoisferrocyanidebyphotolysisofwater.This
reactioniscalledHillReactionanditexplainthatwaterisusedasasource
ofelectronsforCO2fixationandoxygenisevolvedasaby-product.
LightreactionisalsocalledasHill’sreaction.ItisalsocalledasArnon’scycle
becauseArnonshowedthattheH+ionsreleasedbythebreakdownof
waterareusedtoreducethecoenzymeNADPtoNADPH.
LightreactionincludesphotophosphorylationasATPissynthesizedinthe
presenceoflightingranaportionofthechloroplastanditisfasterthan
darkreaction.
HILL REACTION:

323. Difference between
PhotosystemI and II

325. Plastoquinone(PQ) and Plastocyanin(PC) act as mobile electron
carriers between the two pigment systems.
NON CYCLIC ELECTRON TRANSPORT OR NON CYCLIC
PHOTOPHOSPHORYLATION
(Occur in all green plants in Z shape Model (Up-Down) Reaction
2e-
2e-
2e-
2e-
Pheophytin-
First Electron
Accepter
ExitedP700giveselectrontoFe3+inoneofthe
Fe-SproteincalledFRS-FerredoxinReducingSubs.
NADP
NADPH +H
Fd
2e-
NADPH2=ReducedNicotinamideAdenineDinucleotidePhosphate)
Mn-protein
Act as Mediator
683nm
673nm
2OH + 2H
+
↔ 2H
2O
Mg ++ & Cl-
O2 + H2O
Lossofelectron
fromP680thenit
attractelectronfrom
adjacentMn-protein
2ADP + 2Pi + 2NADP + 2H20 
2ATP + 2NADPH + H
+
+ O2
b6 (0.03 V
–f (0.36 V)
=0.33 V
Enter in to stromafor
synthesis of carbohydrate
-2e Drain out from
thylakoidgranam
PQH₂
-2e

326. NON CYCLIC PHOTOPHOSPHORYLATION

327. Electron from Pheois used in reduction of Plastoquinone(PQ to PQH₂) .
This steps require two electrons and two protons (2H+).
Four Types of Plastoquinonesreported from chloroplast:
3 are tocopherolquinones+ 1 is vit. K ( 1,4-naphtho –quinoneacetate)
REDUCTION OF PLASTOQUINONE
+2e, + 2H+
PQ PQH2
+2e, + 2H+
From PQH₂ electron move to cytochromb6.

329. Arnonandhisassociates(1954)showedisolatedchloroplastcan
producedATPwhenexposedtolightfromADP+PiiscalledPhoto-
phosphorylation.
Butwhichisdifferentfromoxidativephosphorylationoccurin
mitochondria.
THEROLEOFATPINPHOTOSYNTHESISISINTWOSTEPS:
1.ReductionofCO2
2.Phosphorylationofribulose5-phosphateintoribulose5-diphosphate
whichisCO2acceptorofC3plants
THREETYPESOFPHOSPHORYLATIONHAVEBEENRECOGNISED:
(i)CYCLICPHOTOPHOSPHORYLATION
(ii)NON-CYCLICPHOTOPHOSPHORYLATION
(iii)PSEUDOCYCLICPHOTOPHOSPHORYLATION
PHOTOPHOSPHORYLATION

330. (i) Cyclic electron transport and cyclic photophosphorylation
(Photosynthetic Bacterium-Rhodospirillumrubrum.)
P700 (PI)
P700 (PI)
Photon
683 mµ light
Cyt-b6
Cyt-f
2 Molecules of
ATP are formed
1Molecule
1Molecule

331. Differences betweenPhotosynthesis found in Bacteria and green plants
No. Photosynthesis in BacteriaNo. Photosynthesis in Plant
1Bacteriahavenodistinctchloroplast. 1Chloroplastiswelldeveloped
2Bacteriaabsorblightoflongerwave
length(800-900nmorinfrared)
2Theseabsorblightofshorterwavelength
(450-700nm)
3P
890isthereactioncentre. 3P
680andP
700aretworeactioncentre.
4Chlorophyll a isabsent and
bacteriochlorophyllandcarotenoidstakes
itsfunction.
4Chlorophyllaispresentwhichconverts
radiantintochemicalenergy.
5TheCarotenoidsareopenchainaliphatic
type.
5TheCarotenoidsarebicyclic.
6Oxygenisnotevolved(anoxygenic
Photosynthesis)
6Oxygen is evolved (oxygenic
Photosynthesis)
7Waterdoesnotserveasasourceof
reducingpower.
7Waterisserveasasourceofreducing
power.
8BacteriacanuseCO
2aswellasorganic
compoundssuchashydrogensulfideand
sulfurcompoundsasasourceofcarbon.
8OnlyCO
2isasourceofcarbon.
9Thephoto-reductantisNAD 9Thephoto-reductantisNADH
2
10Theprocessoccursinthepresenceof
lightbutintheabsenceofO
2.
10Bothpresentduringtheprocess.
11Emersoneffectisnotfound. 11Emersoneffectisfound.
12Cyclicphotophosphorylationisdominant.12Non-Cyclicphotophosphorylation is
dominant.
13Lycopeneisnotfound 13Lycopeneisfound

332. (1)Anoxygenicphototrophicbacteria:
(2)Oxygenicphototrophicbacteria:
(1)Anoxygenicphototrophicbacteriaarethegram-negative
bacteriathatcanuselightasanenergysourceandthey
areanaerobicastheydonotevolveoxygenduring
photosynthesis.Aerobicanoxygenicphototrophicbacteria
areanothergroup,whichareobligateaerobesthatcapture
energyfromlightbyanoxygenicphotosynthesis.
(2)Oxygenicphototrophicbacteriacanalsouselightasan
energysourcebuttheyareaerobicastheyevolveoxygen
inamannersimilartoasthatofgreenplants.

333. Aerobicanoxygenicphototrophicbacteriaaretheobligateaerobes
thatcapturelightenergybyanoxygenicphotosynthesis.
Anoxygenicphotosynthesisisthephototrophicprocesswherelight
energyiscapturedandstoredasATP.
Theproductionofoxygenisnon-existentand,therefore,waterisnot
usedasanelectrondonor.Aerobicanoxygenicphototrophicbacteria
arephotoheterotrophic(phototroph)microbesthatexistinavariety
ofaquaticenvironments.
Photoheterotrophsuselighttoproduceenergybutareunableto
utilizecarbondioxideastheirprimarycarbonsource.
Thisgroupofbacteriaareunabletoutilizethephotosynthetic
pigmentbacteriochlorophillforanaerobicgrowth.
Aerobicanoxygenicphototrophicbacteria(AAPB)areclassifiedin
twomarine(ErythrobacterandRoseobacter)andsixfreshwater
(Acidiphilium,Erythromicrobium,Erythromonas,Porphyrobacter,
Roseococcus,andSandaracinobacter)genera.
AAPBareusuallypinkororangeincolourwhenisolatedfromwater.
AAPBareobligatelyaerobicbacteriaexceptforRoseobacter
dentrifiicanswhichcanusenitriteortrimethylamineN-oxideasan
electronacceptorforphotosynthesisunderanaerobicconditions.

334. Unlikeanaerobicphototrophicbacteriathathaveseveralspeciesof
photosyntheticpigments,suchasbacteriochlorophylla,b,c,d,e,f,
etc.,AAPBcontainonlybacteriochlorophylla.
ThecontentofphotosyntheticpigmentsinAAPBislow,whilethe
accessorialpigmentscarotenoidsinAAPBareabundantin
concentrationanddiverseinspecies.
AAPBhavelightharvestingcomplexI(LHI)butusuallylackoflight
harvestingcomplexII(LHII).
AAPBcannotgrowonphotosynthesisindependently.
Thekeyenzymeofcalvincycleribulosebisphophatecarboxylase
(Rubp)hasnotbeenfoundinanyAAPBspecies.Butlightenergycan
enhancethetransportationandassimilationofsubstratefor
biosynthesis.
AAPBalsohavegreatpotentialsinbioremediationofpolluted
environments,suchasdecompositionoftoxicorganicsand
reduction,adsorption,precipitationandtransformationoftoxicheavy
metalstolesstoxicforms.
Thesespecificfunctionscanbeappliedtobioremediationofindustrial
wastewithheavymetalpollutionaswellasbioleachingofmetals
fromoresorminingtailingswithmetallevelstoolowforsmelting.

335. TheseareGram-negativebacteriathatcontainbacteriochlorophyll
andcanuselightasanenergysource.
TheseorganismsareanaerobicandtheydonotevolveO
2
during
photosynthesis.
Theanoxygenicbacteriagrowphototrophicallyonlyunderanaerobic
conditionsandareincapableofformingO
2
.
Anaerobicanoxygenicphototrophicbacteriaoccurinanaerobic
freshwaterormarineenvironments.
Theymayoccurbeneaththesurfaceofshallowaquatic
environmentsrichinorganicmatter,suchasstagnantponds,
ditchesandsaltmarshpools,orinsometimestheyhaveamuch
deeperhabitat,asatthebottomofalake.
Thesebacteriacontainvariouswater-insolublecarotenoidpigments,
whichcanabsorblightenergyandtransmitittothe
bacteriochlorophyll.
Thebacteriochlorophyllabsorbslightmorestronglywhenthelightis
oflongwavelength,i.e.,about725to745nmlongwavelength.

336. Thelightisoflongerwavelengththanthat
absorbedbythechlorophyllofoxygenicbacteria.The
bacteriochlorophyllandthecarotenoidpigmentsof
anoxygenicbacteriacanalsoabsorblightenergyin
thebluetoblue-greenrange.Thisisimportantwhen
anoxygenicbacteriaoccurinthedepthsofalake,
becausebluelightcanpenetratewateramoregreat
distancethanredlight.
Thecolourofanoxygenicphtotrophicbacteriais
determinedbythecarotenoids.Theanaerobic
anoxygenicphototrophicbacteriacanbedividedinto
twomajorgroupsonthebasisoftheirpigmentation,
i.e.,(A)Purplebacteriaand(B)greenbacteria.

337. (A) PURPLE PHOTOTROPHIC BACTERIA :
Purplebacteriaareproteobacteriathatarephototrophicin
nature.Theyarepigmentedwithbacteriochlorophyllaorb,
togetherwithvariouscarotenoids,whichgivethemcolours
rangingbetweenpurple,red,brown,andorange.
Photosynthesistakesplaceatreactioncentersonthecell
membrane,whichisfoldedintothecelltoformsacs,tubes,or
sheets,increasingtheavailablesurfacearea.
Likemostotherphotosyntheticbacteria,purplebacteriadonot
produceoxygen,becausethereducingagent(electrondonor)
involvedinphotosynthesisisnotwater.Insome,calledpurple
sulfurbacteria,itiseithersulfideorelementalsulfur.
Purplebacteriaorpurplephotosyntheticbacteriaare
proteobacteriathatarephototrophic,thatis,capableof
producingtheirownfoodviaphotosynthesis.
Theyarepigmentedwithbacteriochlorophyllaorb,together
withvariouscarotenoids,whichgivethemcoloursranging
betweenpurple,red,brown,andorange.

338. ThefamilyRhodospirillaceaecontainsthepurplenon-sulphurbacteria.The
purplenon-sulfurPhotosyntheticBacteriaconstituteanon-taxonomicgroupof
versatileorganismsinwhichmostcangrowasphotoheterotrophs,
photoautotrophsorchemoheterotrophs–switchingfromonemodetoanother
dependingonconditionsavailable,especiallythefollowing:degreeof
anaerobiosis,availabilityofcarbonsource(CO
2
forautotrophicgrowth,organic
compoundsforheterotrophicgrowth),andavailabilityoflight(neededfor
phototrophicgrowth).
Underaerobicconditions,culturesappearsorange-browntopurple-red.Under
anaerobicconditions,culturesmayappearsameasunderaerobicconditions
otherwisesomeappeargreenish-yellow.
Thehabitatoftheseorganismsincludeanaerobicaquaticenvironments,such
asmudandstagnantwater,althoughtheyareabletosurviveinair.
Thepurplenon-sulphurbacteriaexhibitadiversityofshapes,i.e.,helical,
nonprosthecaterod-shaped,ovoidorsphericalcells.
Thepurplenon-sulphurbacteriaarephotoorganotrophs,i.e.,organic
substancesservebothascarbonsourcesandaselectrondonorsforthe
reductionofcarbondioxide.
Somespeciescangrowautotrophicallybyusinghydrogensulphideasthe
electrondonor.Photosynthesisoccursonlyunderanaerobicconditionsinthe
light.
Chemotrophicgrowthforthepurplenon-sulfurbacteriaisachievedby
respiration,althoughtherearesomeexceptionalstrainsandspecieswhichcan
obtainenergybyfermentationoranaerobicrespiration.

339. ThefamilyChromatiaceaecontainsthepurple-sulphurbacteria.
Thepurplesulfurbacteriaareagroupofanaerobicproteobacteria
capableofphotosynthesis,andareoftenfoundinhotspringsor
stagnantwater.
Unlikeplants,algae,andcyanobacteria,theydonotusewateras
theirreducingagent,andsodonotproduceoxygen.Insteadtheyuse
hydrogensulfide,whichisoxidizedtoproducegranulesofelemental
sulfur.
Thisinturnmaybeoxidizedtoformsulfuricacid.
Culturesappearorange-browntopurple-violet.
Purplesulfurbacteriaaregenerallyfoundinilluminatedanoxiczones
oflakesandotheraquatichabitatswherehydrogensulfide
accumulatesandalsoin"sulfursprings"wheregeochemicallyor
biologicallyproducedhydrogensulfidecantriggertheformationof
bloomsofpurplesulfurbacteria.Anoxicconditionsarerequiredfor
photosynthesis;thesebacteriacannotthriveinoxygenated
environments.
Purple-sulphurbacteriamaybeovoidtorod-shaped,coccoid,or
helical.Allthegeneraofthisbacteriaarecapableofphotolithotrophic
growth,usingH
2
Sorelementalsulphurastheelectrondonorfor
CO
2
fixation.
Mostspeciesareanaerobicandcannotgrowinthedark.

340. (B) GREEN BACTERIA
Greenphototrophicbacteriacontainbacteriochlorophylltypescordand
minoramountsofbacteriochlorophylla.
Thepigmentsinvolvedinphotosynthesisarelocatedinmembrane-bound
vesicleswithinthecell.Culturesaregenerallygreenorbrownincolour.
ThefamilyChlorobiaceaecontainsthegreen-sulphurbacteria.Theseare
obligatoryanaerobicphotoautotrophicbacteria.
Theorganismscan'tgrowinthedarkevenundermicroaerophilic
conditions.
Thecellsareovoid,bean-shapedorrod-shaped.Multiplicationtakesplace
onlybybinaryfission.Photosynthesisisachievedusing
bacteriochlorophyll(BChl)c,d,ore,inadditiontoBChlaandchlorophyll
a.Green-sulphurbacterialiveasphotolithotrophs,usingH
2
Sasthe
electrondonorforCO
2
fixation.
Granulesofelementalsulphuraredepositedonlyoutsidethecellsandthe
sulphurcaneventuallybeoxidizedtoSO
4
2-
.Chlorobiumtepidumhas
emergedasamodelorganismforthegroup,andalthoughonlyten
genomeshavebeensequenced,thesearequitecomprehensiveofthe
family'sbiodiversity.
Theorganismscan'tgrowinthedarkevenundermicroaerophilic
conditions.Theirsmalldependenceonorganicmoleculetransportersand
transcriptionfactorsalsoindicatethattheseorganismsareadaptedtoa
narrowrangeofenergy-limitedconditions.

341. ThefamilyChloroflexaceaecontainsthegreennon-sulphurbacteria.
Inthisgroupofbacteriaflexiblefilamentsareformedandsothese
arealsocalledasthegreenflexibacteria.
Theypossessglidingmobility.Mostofthemdonothavegas
vesicles.Theorganismsaremainlyphotoorganotrophic,asthe
purplenon-sulphurbacteria,buttheycanalsogrowas
photolithotrophsasthepurplenon-sulphurbacteria,buttheycan
alsogrowasphotolithotrophswithH
2
Sastheelectrondonor.
Inthedarktheycangrowaerobicallyaschemoheterotrophs.
Themaingenus,Chloroflexus,isthermophilicandoccursinhot
springswhereitformsgreenororangemats.
Inhotsprings,withH
2
S,Chloroflexuswillformmatwithout
cyanobacteriaandmaybegreenincolour.Intheseconditions,these
arephotoautotrophic,withsulphideastheelectrondonor.
Thesestrainsareobligatelyanaerobicandthoghphtoautotrophicbut
growbestasphotoheterotrophs.Chloroflexusauranticusisfoundin
alcalinehotsprings(pH5.5-10),whereitoccursinanorangemat
belowalayerofcyanobacteria.Undertheseconditions,Chloroflexus
isprobablylivingphotoheterotrophically,dependentuponthe
cyanobacteriaforfixedcarbon.
Thesestrainsarefacultativelyaerobic.Chloroflexuscellsoccuras
filamentsortrichomesandexhibitglidingmotility.

342. Chromatophorescontainbacteriochlorophyllpigmentsandcarotenoids.Inpurplebacteria,such
asRhodospirillumrubrum,thelight-harvestingproteinsareintrinsictothechromatophore
membranes.However,ingreensulfurbacteria,theyarearrangedinspecialisedantenna
complexescalledchlorosomes.
Chromatophores

343. Photosyntheticbacteriaarecurrentlybeing
usedinvariousapplicationswhichinclude
waterpurification,
bio-fertilizers,
animalfeedand
bioremediationofchemicalsamong
manyothers.
Theyareusedinthetreatmentof
pollutedwatersincetheycangrowand
utilizetoxicsubstancessuchasH₂Sor
H₂S₂03.
Useful Applications for Photosynthetic Bacteria

344. Greenphototrophicbacteriacontainbacteriochlorophylltypescordand
minoramountsofbacteriochlorophylla.Thepigmentsinvolvedinphotosynthesis
arelocatedinmembrane-boundvesicleswithinthecell.Culturesaregenerallygreen
orbrownincolour.
ThefamilyChlorobiaceaecontainsthegreen-sulphurbacteria.Clorobium
sp.,Chloropseudomonassp.
Theseareobligatoryanaerobicphotoautotrophicbacteria.
Theorganismscan'tgrowinthedarkevenundermicro-aerophilic
conditions.
Thecellsareovoid,bean-shapedorrod-shaped.
Multiplicationtakesplaceonlybybinaryfission.
Photosynthesisisachievedusingbacteriochlorophyll(BChl)c,d,ore,in
additiontoBChlaandchlorophylla.
Green-sulphurbacterialiveasphotolithotrophs,usingH
2
Sastheelectron
donorforCO
2
fixation.Granulesofelementalsulphuraredepositedonly
outsidethecellsandthesulphurcaneventuallybeoxidizedtoSO
4
2-
.
Chlorobiumtepidumhasemergedasamodelorganismforthegroup,and
althoughonlytengenomeshavebeensequenced,thesearequite
comprehensiveofthefamily'sbiodiversity.

345. ThefamilyChloroflexaceaecontainsthegreennon-sulphurbacteria.
Inthisgroupofbacteriaflexiblefilamentsareformedandsothesearealso
calledasthegreenflexibacteria.
Theypossessglidingmobility.Mostofthemdonothavegasvesicles.
Theorganismsaremainlyphotoorganotrophic,asthepurplenon-sulphur
bacteria,buttheycanalsogrowasphotolithotrophsasthepurplenon-sulphur
bacteria,buttheycanalsogrowasphotolithotrophswithH
2
Sastheelectron
donor.
Inthedarktheycangrowaerobicallyaschemoheterotroph.
Themaingenus,Chloroflexus,isthermophilicandoccursinhotspringswhere
itformsgreenororangemats.
Inhotsprings,withH
2
S,Chloroflexuswillformmatwithoutcyanobacteriaand
maybegreenincolour.Intheseconditions,thesearephotoautotrophic,with
sulphideastheelectrondonor.Thesestrainsareobligatelyanaerobicand
thoghphotoautotrophicbutgrowbestasphotoheterotrophs.
Chloroflexusauranticusisfoundinalcalinehotsprings(pH5.5-10),whereit
occursinanorangematbelowalayerofcyanobacteria.Underthese
conditions,Chloroflexusisprobablylivingphotoheterotrophically,dependent
uponthecyanobacteriaforfixedcarbon.Thesestrainsarefacultatively
aerobic.
Chloroflexuscellsoccurasfilamentsortrichomesandexhibitglidingmotility.

346. Cyanobacteriaareaquaticandphotosyntheticgrampositiveprokaryotes,
liveinthewater,andcanmanufacturetheirownfood.Becausetheyare
bacteria,theyarequitesmallandusuallyunicellular.
Cyanobacteriahaveanelaborateandhighlyorganizedsystemofinternal
membraneswhichfunctioninphotosynthesis.Cyanobacteriagettheir
colourfromthebluishpigmentphycocyanin,whichtheyusetocapture
lightforphotosynthesis.
Bluephycocyaninoccurinallcyanobacteriaandabsorblightatwavelength
between500and650nm.
Cyanobacteriapossessingphycoerythrinhavearedorbrowncolour
insteadoftheusualbluish-greencolour.
Cyanobacteriacontainchlorophyllaratherthanbacteriochlorophyll;
becauseofthischlorophyllthecellsabsorbredlightof680to683nm.
Otherpigmentsincludewater-insolublecarotenoidsandalsowater-
insolublephycobilins,whicharethemajorlightabsorbingpigmentsin
cyanobacteriaandwhichcantransmittheenergyofabsorbedlighttothe
chlorophyll.

347. Photosynthesisincyanobacteriagenerallyuseswaterasanelectrondonor
andproducesoxygenasaby-product,thoughsomemayalsousehydrogen
sulfideasoccursamongotherphotosyntheticbacteria.
CarbondioxideisreducedtoformcarbohydratesviatheCalvincycle.In
mostformsthephotosyntheticmachinery(chlorophylla,carotenoid
pigments,photochemicalreactioncenters,andthephotosynthetic
electrontransportchain)isembeddedintofoldsofthecellmembrane,
calledthylakoids.Thylakoidsaretheflattenedmembranoussacslocated
withinthecell.Thesurfaceofthethylakoidsisstuddedwithgranules
calledphycobilisomes,whichcontainthephycobilinpigments.
Thephycobilisomecomponents(phycobiliproteins)areresponsibleforthe
blue-greenpigmentationofmostcyanobacteria.

348. Prochlorophytesareunicellular,sphericalorganisms, photosynthetic
Prokaryotemember ofthephytoplanktongroupPicoplankton.
Prochlorophytesareverysmallmicrobesgenerallybetween0.2and2µm.
TheymorphologicallyresembleCyanobacteria,butunlikecyanobacteria,
theseunicellularorganismscontainchlorophyllbinadditiontochlorophylla.
Theyalsopossessstakedthylakoidsandcanbedistinguishedfrom
cyanobacteria.
Theyalsolackphycobillinpigmentsandthecellsappeargrass-greenrather
thanblue-green.
MembersofProchlorophytahavebeenfoundascoccoid(spherical,coccus)
shaped,asinProchlorococcus,andasfilaments,asinProchlorothrix.
Theseoligotrophicorganismsareabundantinnutrientpoortropicalwaters
anduseauniquephotosyntheticpigment,divinyl-chlorophyll,toabsorblight
andacquireenergy.
Thestructureofthelight-harvestingcomplexes(LHC)fromprochlorophytes
isverydifferentfromthoseofchloroplastsystems,andisevolutionarilyvery
ancient.Thefunctionalassociationofthelight-harvestingapparatuswith
photosystemI(PSI)inbothProchlorothrixandProchloron,aswellasa
demonstratedcapacityforPSI-dependentanoxygenicphotosynthesisin
Prochlorothrix,mayindicatethatthereisanincreaseddependenceoncyclic
photophosphorylationintheseorganisms.

349. Photosynthesis occursinplantsandsomebacteria,wherever
thereissufficientsunlight–onland,inshallowwater,even
insideandbelowclearice.
Allphotosyntheticorganismsusesolarenergytoturncarbon
dioxideandwaterintosugarandoxygen.
Thereisonlyonephotosyntheticformula:
CO2+6H2O->C6H12O6+6O2.
Chemosynthesis istheuseofenergyreleasedbyinorganic
chemicalreactionstoproducefood.Chemosynthesis isatthe
heartofdeep-seacommunities, sustaininglifeinabsolute
darkness,wheresunlightdoesnotpenetrate.
Allchemosynthetic organisms usetheenergyreleasedby
chemicalreactionstomakeasugar,butdifferentspeciesuse
differentpathways.
Forexample, themostextensiveecosystem basedon
chemosynthesis livesaroundunderseahotsprings.Atthese
hydrothermal vents,ventbacteriaoxidizehydrogensulfide,
addcarbondioxideandoxygen,andproducesugar,sulfur,
andwater:CO2+4H2S+O2->CH20+4S+3H2O.

350. (i) Cyclic Photophosphorylation
•Process for ATP generation associated with some
Photosynthetic Bacteria
•Reaction Center => 700 nm

351. The cyclic electron transport involves only pigment
system I.(Bacterium-Rhodospirillumrubrum.) (Activity of
pigment system II is blocked)
Under this condition,
1. Only pigment system I remain active
2. Photolysis of water does not take place
3. Blockage of non-cyclic ATP formation and this
causes a drop in CO2 assimilation in dark
reaction
4. There is a consequent shortage of oxidized NADP

352. 1.Photolysisofwater,O2evolutionandreductionof
NADPdonottakeplace.
2.Theelectronreturnsorcyclesbacktooriginal
positionintheP700formofchlorophylla.Here,
chlorophyllmoleculeservesbothasdonorand
acceptoroftheelectron.
3.ItgeneratesenergyrichATPmoleculesattwosites
andwhichisnotoccurindarkreactionsof
photosynthesis.

353. Plastoquinone(PQ) and Plastocyanin(PC) act as mobile
electron carriers between the two pigment systems.
(II) NON CYCLIC ELECTRON TRANSPORT OR NON CYCLIC
PHOTOPHOSPHORYLATION
(Occur in all green plants in Z shape (Up-Down) Reaction
2e-
2e-
2e-
2e-
Pheophytin-
First Electron
Accepter
ExitedP700giveselectrontoFe3+inoneofthe
Fe-SproteincalledFRS-FerredoxinReducingSubs.
NADP
NADPH +H
Fd
2e-
NADPH2=ReducedNicotinamideAdenineDinucleotidePhosphate)
Mnprotein

354. Electron from Pheois used in reduction of Plastoquinone(PQ to PQH₂) .
This steps require two electrons and two protons (2H+).
Four Types of Plastoquinonesreported from chloroplast:
3 are tocopherolquinones+ 1 is vit. K ( 1,4-naphtho –quinoneacetate)
REDUCTION OF PLASTOQUINONE
+2e, + 2H+
PQ PQH2
+2e, + 2H+
From PQH₂ electron move to cytochromb6.

356. Role of ATP in photosynthesis is essential at two steps:
Firstly,itsupplementsenergyforthereductionofCO2
utilizingNADPH+H+.NADPH+H+istheend-productoflight
reaction.
NADPH+H+movetheelectronstophosphoglycericacid
(PGA)andintothecarboncycle.
Secondly,ATPisusedinthephosphorylation:
Ribulose-5-phosphate Ribulose-1,-5-diphosphate
incalvincycle.
Ribulose-1,-5-diphosphateistheCO2acceptorofC3plants.
1Glucosemoleculesynthesized18ofATPisnecessaryinC3
plants.

357. 2 H

+
1
/
2
Water-splitting
photosystem
Reaction-
center
chlorophyll
Light
Primary
electron
acceptor
Energy
to make
Primary
electron
acceptor
Primary
electron
acceptor
NADPH-producing
photosystem
Light
NADP

1
2
3
How the Light Reactions Generate ATP and NADPH

358. •The production of ATP by chemiosmosis in
photosynthesis
Thylakoid
compartment
(high H
+
)
Thylakoid
membrane
Stroma
(low H
+
)
Light
Antenna
molecules
Light
ELECTRON TRANSPORT
CHAIN
PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE

360. 1.ItinvolvesPSIandPSII
2.TheelectronexpelledfromP680ofPSIIistransferredtoPSIandhence
itisanoncyclicelectrontransport.
3.Innoncyclicelectrontransport,photolysisofwater(Hill’sreactionand
evolutionofO2)takesplace.
4.Phosphorylation(synthesisofATPmolecules)takesplaceatonlyone
place.
5.TheelectronreleasedduringphotolysisofwateristransferredtoPSII.
6.Thehydrogenions(H+)releasedfromwaterareacceptedbyNADPand
itbecomesNADPH2
7.Attheendofnoncyclicelectrontransport,energyrichATP,
assimilatorypowerNADPH2andoxygenfromphotolysisofwaterare
observed.
8.TheATPandNADPH2areessentialforthedarkreactionwherein,
reductionofCO2tocarbohydratetakesplace.

361. Comparison of cyclic and non cyclic electron transport and
photophosphorylationin Chloroplasts
Cyclic electron transport and
photo phosphorylation
Non cyclic electron transport and
photo phosphorylation
1.Associatedwithpigmentsystem
I
1.AssociatedwithpigmentsystemI
andII
2.Theelectronexpelledfrom
chlorophyllmoleculeiscycled
back.
2.The electronexpelledfrom
chlorophyllmoleculeisnotcycled
back.But,itslossiscompensated
byelectroncomingfromphotolysis
ofwater.
3.Photolysisofwaterand
evolutionofO2donottake
place
3.Photolysisofwaterandevolution
ofO2takeplace
4.Phosphorylationtakesplaceat
twoplaces(FD-PQ+Cyto.b-f)
4.Phosphorylationtakesplaceatonly
oneplace(Cyto.b-f)
5.NADP+isnotreduced 5.NADP+isreducedtoNADPH++H+

362. Illuminated
chloroplast
FMN + H2O FMNH2 + 1/2O2
ADP + Pi ATP
Arnonandhiscoworkers(1954)demonstratedanotherkindof
photophosphorylationinwhichevenabsenceofCO2andNADP,if
chlorophyllmoleculesareilluminated,theycanproducedATPfrom
ADP+PiinpresenceofFMNorVit.Kandoxygen.
Hence,ArnoncalleditFMNcatalysedphotophosphorylationwhich
involvesthereductionofFMNintoFMNH2andyieldATP.
TheFMNwiththehelpoflightandchlorophyllthatbreaksand
rejoinedthewatermolecules.
AsinglewatermoleculeissufficienttooperatePseudocyclic
photophosphorylation.
FlavinMono
Nucleotide

364. Energyrelationshiphasbeencalculatedintermsofelectrochemical
potential(eV).
Theoxygenwaterpotentialisabout-0.8eV(E’ₒ=-0.8V)andCO2
potentialis-0.4eV(E’ₒ=-0.4V).Thussingleelectrontransferrequires-
1.2eVenergy(=-0.8eVplus-0.4eV).
Duringreductionof1moleculeofCO2intocarbohydratefourelectrons
mustbetransferred.
Therefore,thetotalenergyneededinthereductionofamoleculeofCO2
wouldbe4.8eV.(1.2X4electrons)whichworksouttobe1,12,000
cal/mole.
Themaximumquantumyieldofphotosynthesisis1/8=12%.Sinceforthe
reductionof1moleculeofCO2intocarbohydratethetransferof4
electronsarerequired.
Itwassuggestedthatitmakestwolightquantatomoveeachelectron.As
energyofeachlightquantumis1.9eV,itwouldbesufficientforthese
steps.
CO2isreducedtocarbohydrateat-0.4eV(E’ₒ=-0.4V)andreducedNADP
alonehas–0.33eV(E’ₒ=-0.33V),henceNADPcannotprovidesufficient
energytoreduceCO2complex.Atthisstage,NADPH+H+issupported
bysupplyofadditionalenergyintheformofhighenergycompoundATP.

365. ATPmoleculeatthetimeofremovalofterminalphosphate
provides7,600cal.EnergywhichissufficienttoboosttheNADPH
+H+.
Duringthesynthesisof1glucosemolecule,18ATPand12NADPH
+H+arerequired.Fortheformationof1ATPmoleculefromADP,
7.6kcal(7600cal)energyisrequiredandforreductionofNADP
52.60kcal(52,600cal/mole)energyisrequired.
Totalenergyrequiredforsynthesisof1glucosemoleculewillbe–
1,36,800(18X7600)+6,31,200(52,600X12)=7,68,000cal
Whereasfreeenergyrequiredforthesynthesisof1hexose
moleculefromCO2is6,73,000cal;thatmeanstheutilizationof18
ATPand12NADPH+H+aremorethansufficientforthepurpose.
12H2O+12NADP+18ADP+18Pi 12NADPH+H++18ATP+6O2

366. 1
st
MethodofcalculationEfficiencyofphotosynthesisonthebasisof
energystoredbyATP&NADPH+H+:
ATPstoresenergynearly7.6kcal+NADPH+H+about52kcal(Total
59.6kcalisutilized).
Lightenergysynthesizedis4quanta(twoperphotosystem),eachof
quantais40kcaloflightenergy(4X40=160kcalissynthesized).
Now,ifwemeasuretheefficiency(alwaysexpressedin%)of
photosyntheticconversionoflightenergyintermofATPand12
NADPH+H+,itwillbe,
=37.25%
Efficiencyofphotosynthesisis100%-37.25%=62.75%.Thusmajority
portionofabsorptionoflightenergyiswasted.
59.2
(Stores energy utilized)
Efficiency (%) =---------------------------------X100
160
(Light energy synthesized)

367. 2
nd
MethodofcalculationforEfficiencyofphotosynthesisonthe
basisofCO2assimilation:
Efficiencyofphotosynthesis,calculationintermsofCO2assimilated
oroxygenevolvedismade.
ForeverymoleculeofCO2assimilatedoroxygenevolvednearly112
kcaloflightenergyisstored,hence6moleculesofCO2assimilation
i.e.673kcalisutilized(112X6=673kcal).
1moleculeofCO2consume8quanta,hence6moleculesofCO2(Each
moleculeofcarbohydratereducedin6moleculesofCO2)required48
quanta(6X8=48)perhexosemoleculeformed.
Now,ifweassuming40kcalenergypresentinmostefficientredlight,
hencetotal48X40=1920kcalissynthesisedtheefficiencyof
photosyntheticwillbe,
=35.052%
Efficiencyofphotosynthesisis100%-35%=65%.Thusmajorityportion
ofabsorptionoflightenergyiswasted.
673 (Stores energy utilized)
Efficiency (%) = -----------------------------------X100
1920 (Light energy synthesized)

369. Interrelationships between light & Dark Reaction
Lightreactioniscommonlycalledphoto-stageorhydrogentransfer
phaseanddarkreactionisknownassynthesisstageorcarbon
assimilationphase.
Levitt(1969)showedInterrelationshipsbetweenlight&Dark
Reaction.
ReductionofeachmoleculeofCO2,3ATP&2NADPH+H+
moleculesarerequired.
12ATPmoleculesarerequiredforuplifting12NADPH2,becausethe
redoxpotentialofNADPH2ismuchlower(E’0=-0.33V)than
required(E’0=-0.4V)toactashydrogendonorduringtheprocess.
Another6moleculesofATPareutilizedduringphosphorylationof
ribulose-5phosphatetoregenerateribulose-1,5diphosphate.
Similarly,12moleculesofNADPH2areutilizedbecauseforthe
reductionofeachmoleculesofCO2,4electrons(Hydrogenatoms)
arerequired.

370. SchemeticRepresentationofInterrelationshipsbetweenlight&DarkReaction

371. 1.Lightreactiontakesplaceinchlorophyllinthepresenceof
light.
2.Duringlightreaction,theassimilatorypowersATPand
NADPH2aresynthesized.
3.Theassimilatorypowersareusedindarkreactionforthe
conversionofCO2intoSugarsmolecules.
4.Photolysisofwateroccursinlightreaction.TheH+ions
releasedfromwaterareusedforthesynthesisofNADPH2
5.PlantsreleaseO2duringlightreaction

372. Lecture-16

373. Thefactthatnon-photochemicalprocess(onlychemicalprocesses)is
involvedinphotosynthesisoccurringindependentoflightwas
establishedbyBlackman(1905)iscalleddarkreaction.Thisreactionis
alsocalledasBlackman’sreaction.
Ittakesplaceinthestromaofchloroplast.
Thedarkreactionispurelyenzymaticanditisslowerthanthelight
reaction.
Indarkreaction,thesugarsaresynthesizedfromCO
2.
Theenergyrichcompound,ATPandtheassimilatorypower,NADPH
2of
lightreactionusedinit.
Lateron,Calvin&Coworkersadvancedstudyonunicellulargreenalga
Chlorellapyrenoidosa–Classicmaterialforstudystatedfollowingpoints:
Itgrowluxuriantly(rapidlydividing),avoidscontamination,and
synchronousculture.
Theentireplantbehaveasasingleprotoplastandcontainsall
photosynthesispigments.
Indarkreactiontwotypesofcyclicreactionsoccur
1.CalvincycleorC3cycle
2.HatchandSlackpathwayorC4cycle

375. Why it is called C3 cycle?
1.Inthiscycle,thefirstformedstablecompoundisa3carbon
compoundviz.,phosphoglycericacid(PGA).
Why it is called Basshamcalvincycle?
2.Thepathofcarboninphotosynthesiswasfirstdemonstrated
byJ.A.BasshamandM.Calvinin1957atEnglewoodCliffs,N.J.Prentice
Hall,Steinberg,Howard.
Why it is called calvincycle?
3.ItwasfirstobservedbyMelvinCalvininchlorella,unicellular
greenalgae.CalvinwasawardedNobelPrizeforthisworkin1961.
Why it is called Carbon assimilation cycle?
4.SynthesisofCarbohydratesbylongchainchemicalreactions
usingcarbondioxide.
Why it is called Reductive pentose phosphate cycle?
5.TheATPproducedinphotophosphorylationisusedtoconvert
Ribulose5-(pentose)phosphate[C
5H
11O
8P] Ribulose1,5-bisphosphate(RuBP)[C
5H
12O
11P
2.]
Why it is called path of carbon in photosynthesis?
6. Carbon compound CO
2is used for Synthesis of Carbohydrates.

376. C3 -Calvin Cycle
•C
3plants(80% of plants on earth).
•Occurs in the stroma.
•Uses ATPand NADPHfrom light rxn& atmospheric CO
2.
•To produce glucose: it takes 6 turnsand uses 18 ATP and 12 NADPH.
♠Wheat (TriticumaestivumL. )
♠Rice (Oryzasativa L.)
♠Barley (HordiumvulgareL.)
♠Oat (Avenasativa L.)
♠Rye (SecalecerealeL.)
♠Pigionpea(CajanuscajanL.)
♠Chick pea (CicerarietinumL. )
♠Sweet pea (PisumsativusL. )
♠Black gram (PhaseolusmungoL.)
♠Groundnut (ArechishypogeaL.)
♠Sasame(SesamumindicumL.)
♠Cotton (Gossypiumspp.)

377. STRUCTURAL PECULIARITIES OF C
4
PLANTS:
The most distinguishable anatomical feature of the leaves of C
4
plants is the presence bundle sheath
cells containing chloroplasts.
These cells are radially arranged around a vascular bundle.
The bundle sheath cells lack granain chloroplasts, while mesophyllcells have well-developed grana
in sugarcane. However, in Bermuda grass, the chloroplasts of bundle sheath cells possess grana. So
dimorphic chloroplasts by no means occur in all C
4
plants.
The arrangement of chloroplast containing cells (bundle sheath cells) around vascular bundle is also
a characteristic feature of C
4
plants.
These are arranged one or more wreath like layers consisting of large thick-walled cylindrical cells.
Bundle cells remain surrounded by one or more wreath like layers of mesophyll.
This anatomical arrangement is called Kranztype (Kranz=wreath, a German term).
Themesophyllcellsalmostthree
timesmoreactiveinnon-cyclic
electrontransportsystem(Green
plants)thanbundlesheathcells.
But,Forcyclicelectrontransport
systembothcellswereequally
efficient.
Besides, PEP carboxylase
(PEPCO)occursinmesophyll
cells.
Whilemostofribulose-1,5-
diphosphate carboxylase
(RUBISCO)andmalicenzymesare
remaininbundlesheathcells.

378. •The location and structure of chloroplasts
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Chloroplast
Mesophyll
CHLOROPLAST Intermembrane space
Outer
membrane
Inner
membrane
Thylakoid
compartmentThylakoid
Stroma
Granum
StromaGrana

381. ThereactionsofCalvin’s
cycleoccurinthreephases.
1.Carboxylativephase
2.Reductivephase
3.Regenerativephase

382. Review: Photosynthesis uses light energy to
make food molecules
Light
Chloroplast
Photosystem II
Electron transport
chains
Photosystem I
CALVIN
CYCLE Stroma
LIGHT REACTIONS CALVIN CYCLE
Cellular
respiration
Cellulose
Starch
Other organic
compounds
•A summary of
the chemical
processes of
photosynthesis

383. Light Independent Reactions
Calvin Cycle
♠CO2isaddedtothe5-CsugarRuBPbythe
enzymerubisco.
♠Thisunstable6-Ccompoundsplitstotwo
moleculesofPGAor3-phosphoglycericacid.
♠PGAisconvertedtoGlyceraldehyde3-phosphate
(G3P),twoofwhichbondtoformglucose.
♠G3Pisthe3-Csugarformedbythreeturnsofthe
cycle.

384. 1.3CO2+3Ribulose Carboxydismutase 3-unstableintermediate
biphosphate 6carboncompound
2.3unstable +3H2O Carboxymutase 3phosphoglycericacid
Intermediate
6-Ccompound
1.Carboxylativephase
1. 3 Phospho + ATP
glycericacid
2. Reductive phase
Kinase
1,3 diphospho
glycericacid
+ ADP
2. 1,3 diphospho
glycericacid
+ NADPH2
Triosephosphate
Dehydrogenase
3 phospho
glyceraldehyde
+NADP +H3PO4
1. 3 phospho Triosephosphate isomerase
glyceraldehyde
Dihydroxyacetone PO4
(DHAP)
3. Regenerative phase
2. 3 phospho+ DHAP Aldolase
glyceraldehyde
Fructose 1,6 diphosphate

385. 3. Fructose 1,6 diphosphate Fructose 6 phosphate
Phosphorylase
4. 3 phosphoglyceraldehyde Ribulose1,5 biphosphate
5.3 phospho +
glyceraldehyde
Fructose 6
phosphate
Transketolase Xylulose5
phosphate
Erythrose4 +
phosphate
6. Erythrose4 phosphate + DHAP Aldolase Sedoheptulose1 ,7
diphosphate
7. Sedoheptulose1 ,7
Diphosphate
+ ADP
Phosphatase
Sedoheptulose7
phosphate
+ ATP
8.Sedoheptulose+ 3 phospho Transketolase
7 phosphate glyceraldehyde
Xylulose
5 phosphate
Ribose 5
phosphate
+
9. Ribose + ATP Phophopentokinase
5 phosphate
Ribulose1,5
diphosphate
+ ADP

387. 2-turn = 6X2
=12 ATP used
2-turn = 3X2
=6 ATP used
2-turn = 6X2
=12 NADPH used

388. IMP

389. Calvin Cycle
•Remember:C3 = Calvin Cycle operates only
in mesophyllcells.
C
3
Glucose

390. SynthesisofcarbohydratesfromCO
2(assimilationof
carbon).
Usesoftheassimiatorypower(ATPandNADPH
2)
requiredforcarbonassimilation.
ItstorestheATPenergyformedduringlightreactionin
thecarbohydratemoleculesasthefoodenergy.
Itistheprimarysourceoforganicfoodandfoodenergy
foralltheorganisms.
CalvinCycle(C-3cycle)reactionoccurinall
photosyntheticplantsi.e.C-3,C-4andCAMplants,
duringthedarkphaseofphotosynthesis.

391. LIGHT REGULATING ENZYMES
1. RuBPcarboxylase(Rubiscoor RuDPcarboxylase)
2. NADP –linked Glyceraldehyde-3-phosphate-dehydrogenase(GAPDH)
3. Fructose-1,6-bisphophate phosphatase(FBPase)
4. Sedoheptulose-1,7-bisphosphate phosphatase(SBPase)
5. Phosphofructokinase
INHIBITORS OF PHOTOSYNTHETIC PROCESS
1.Urea derivatives: Herbicide CMU 3-(p-Chlorophenyl)-1,1-Dimethylurea,
Simazine, atrazine, bromaciland isocilblock ETC between Q and PQ.
2.Azideand Cyanide CN
−
or N
3
−
, accumulation of H
2O
2is observed, parallel to
inhibition of photosynthesis.
3.Diquatand paraquatherbicides are referred as viologendyes accept electron
from PS I and produce toxic forms of oxygen (superoxide and hydroxy) common
inhibitors of photosynthetic process.

392. Lecture-17

394. Why it is called C4 cycle?
1.Inthiscycle,thefirstformedstablecompoundisa4carbon
compoundviz.,oxaloaceticacid(OAA).
Why it is called Hatch and Slack cycle?
2.AustralianscientistsM.D.HatchandC.R.Slackhadworked
outthepathwayin1966.
Why it is called dicarboxylicacid cycle?
3.Kortschakandhiscoworkers(1954)reportedtheformationof
twocarboxylicacidsasprimaryproductsofphotosynthesisinsugarcane
withtheactionoftwocarboxylaseenzymesareused–(i)PEPcarboxylase
(ii)RuBPcarboxylase.
Why it is called cooperative photosynthesis?
4.Photosynthesisistakeplaceinboththecells:InMesophyll&
Bundlesheathcells.

395. C4 Plants
•Hot,moistenvironments.
•15%ofplants(grasses,corn,sugarcane).
•Dividesphotosynthesisspatially.
•Lightrxn-mesophyllcells.
•Calvincycleoperatesonlyinbundlesheathcells.
•About8,100plantspeciesuseC4carbonfixation.
•C4carbonfixationismorecommoninmonocotscompared
withdicots,with40%ofmonocotsusingtheC4pathway,
comparedwithonly4.5%ofdicots.
•C4photosyntheticpathwaymost.46%ofgrassesareC4.

396. C4 Plants
♠Bajra(PennisetumglaucumL.)
♠Maize (ZeamaysL.)
♠Sorghum (Sorghum bicolor L.)
♠Sugarcane (SachharumofficinarumL. )
♠Bermundagrass (Panicummaximum L.)
♠Chidhograss (CyperusrotandusL.)
♠Crabgrass (DigitariasamguinalisL. )
♠Pigweed grass(Amaranthusspp. L.)
♠Rhodes grass (ChlorisgayanaL.)
♠Salt bush ( AtriplexspongiosaL.)
♠Guard cells of Tulip (TulipagesnarianaL. )
♠Dayflower (CommelinacommunisL.)

397. FOUR STEPS IN HATCH AND SLACK
CYCLE:
1.Carboxylation
2.BreakdownofOxaloacetate
3.Splittingmalateandaspartate
4.Phosphorylation

398. 1.Carboxylation:
Ittakesplaceinthechloroplastsofmesophyllcells.
Phosphoenolpyruvate(PEP),a3carboncompoundpicks
upCO2andchangesinto4carbonoxaloacetateinthe
presenceofwater.Thisreactioniscatalysedbythe
enzyme,phosphoenolpyruvatecarboxylase(PEPC).
2.Breakdown:
Oxaloacetatebreaksdownreadilyinto4carbonmalate
andaspartateinthepresenceoftheenzyme,
transaminase(TS)andmalatedehydrogenase(MD).
Thesecompoundsdiffusefromthemesophyllcellsinto
bundlesheathcells.
3.Splitting:
Inthesheathcells,malateandaspartatesplit
enzymaticallytoyieldfreeCO2and3-carbonpyruvate.
TheCO2isusedinCalvin’scycleinthesheathcell.
Decarboxylation
Malate CO2+Pyruvate(Pyruvicacid)
ThesecondCarboxylationoccursinthechloroplastofbundlesheathcells(C
3cycle).TheCO2isacceptedby
5carboncompoundribulosediphosphateinthepresenceoftheenzyme,carboxydismutaseandultimatelyyields3
phosphoglycericacid.Someofthe3phosphoglycericacidisutilizedintheformationofsugarsandtherestregenerate
ribulosediphosphate.
4.Phosphorylation:
Thepyruvatemoleculeistransferredtochloroplastsofmesophyllcellswhere,itisphosphorylatedto
regeneratephosphoenolpyruvateinthepresenceofATP.Thisreactioniscatalysedbypyruvatephosphokinase(PPK)and
thephophoenolpyruvateisregenerated.
InHatchandSlackpathway,theC3andC4cyclesofcarboxylationarelinkedandthisisduetotheKranz
anatomyoftheleaves.TheC4plantsaremoreefficientinphotosynthesisthantheC3plants.
Theenzyme,phosphoenolpyruvatecarboxylaseoftheC4cycleisfoundtohavemoreaffinityforCO2than
theribulosediphosphatecarboxylaseoftheC3cycle.
Mesophyll cell of chloroplast
Bundle sheath cell
of chloroplast
PEPC
1
2
4
3
MD
TS
PPK

399. (i)Thefirstgroupincludesmaizeand
sugarcanewhereCO
2isinitiallyfixedto
phosphoenolpyruvateandoxaloacetateis
formed.Themalateproducedfromitis
transportedtobundlesheathcells.Thisplants
haveNADPdependentmalicenzyme(NADP-
ME).
(ii)Thesecondgroupincludesplantssuchas
PanicummaximumandChlorisgayana,in
whichcase,itisaspartate,ratherthanmalate,
transportedtobundlesheathcells.Thereitis
transaminated(RemovalofNH2molecule)to
oxaloacetatewhichbecomesconvertedinto
pyruvateandCO
2,byPEPcarboxykinase.
Theseareaspartateformertype1.
(iii)ThethirdgroupincludesAtriplex
spongiosa.Inthiscase,theaspartate
producedinmesophyllcellsistransportedto
bundlesheathcellswhereitistransaminated
andreducedtomalate.Themalateis
decarboxylatedtoformpyruvateandCO
2.
Theseareaspartateformertype2.
Mesophyll cell of chloroplast
Bundle sheath cell
of chloroplast
CholletandOgren(1975)recognisedthreecategoriesofC4plants:
3
2
1
Trans-
amination
NADP-ME
enzyme

400. TheCO2,releasedisre-fixedbyRubiscoinbundlesheathchloroplastbutpyruvateistransportedto
cytosol.Now,pyruvatetransaminatedtoalanineandtransportedbacktomesophyllcellof
chloroplast.
PyruvateisconvertedintoPhosphoenolpyruvatebytheenzymepyruvatephosphodia-kinase
(PPDK)anditisenterintothecytosolandsynthesisofaspartateviaOAbytheactionofPEPC.OA
isproducedaspartatewiththeenzymeAspAT(AsparticacidTranslocator).
Thebundlesheathmitochondriaarefunctionallycontainingdifferentenzymesthanchloroplast.
IthasbeenassumedthatanAsp/Glutaratetranslocator/oxoglutaratetranslocator/malate
translocator/pyruvatetranslocatorarefunctioninbundlesheathmitochondria.
ThesediscoveriesprovidenewinspirationforeffortstoconvertC
3cropsintoplantsbecausethe
anatomicalchangesrequiredforC
4photosynthesismightbelessstringentthanpreviouslythought.
Recent studies: Some plants
have NAD-dependent malic
enzyme (NAD-ME):
Aspartateistransportedfrom
mesophyllcelltobundlesheath
mitochondria,whereitistrans-
aminatedtooxaloacetateby
mitochondrial aspartate
aminotransferase.
Oxaloacetateisfurtherreduced
tomalate,whichisthen
decarboxylatedtopyruvateby
NAD-MEinthebundlesheath
mitochondria.
Mesophyll cell
Cytosol
Bundle sheath
mitochondria
Cytosol
Bundle
sheath
Chloroplast

401. C4 Plants
Mesophyll Cell
CO
2
C-C-C
PEP
C-C-C-C
Malate
ATP
Bundle Sheath Cell
C-C-C
PyruvicAcid
C-C-C-C
CO
2
C
3
Malate
Transported
glucose
Vascular
Tissue
pyruvatephosphokinase

402. Fig. 10.21

403. KranzAnatomy Is Not Essential For C4 Plants:
AnimportantadaptationtoCO2-limitedphotosynthesisincyanobacteria,algaeandsomeplants,inwhich
CO2-concentratingmechanism(CCM)wasdevelopedduringdevelopmentalera.
EvolutionofaCCMoccurredfromthebeginningatleast15-20millionyearsago.
Duringdevelopmentalera,theyresponsedtoatmosphericCO2reduction,climatechange,geologicaltrends,
andevolutionarydiversificationofspecies,underhightemperature,droughtandsalineconditions.
Inplants,thisisachievedthroughabiochemicalinorganiccarbonpumpcalledC4photosynthesis,discovered
35yearsago.
RecentstudiesonBorszczowiaaralocaspicaandBienertiacyclopteraofthefamilyChenopodiaceae(dicot)
haveshowntoC4–photosynthesiswithasinglechlorenchymacellwithoutpresenceofKranzanatomyby
intra-celluarpartitioningofenzymesanddimorphicchloroplastsintwocytoplasmiccompartmentswithin
singlecell.
Dimorphicchloroplastsarelocatedbetweentheirtwocytoplasmiccompartments.
TheatmosphericCO
2enterthechlorenchymacellatthedistalendandconvertintoC4acids(Oxaloacetic
acidandmalicacid).TheC4aciddiffusetotheproximalpartthroughthicytoplasmicspaceattheperiphery
ofthemiddleofthecell.
Now,inproximalside,C4acidsisdecarboxylatedbyNAD-MEinmitochondriaandreleasedCO2whichis
capturedbyRubiscoenzymewhichispresentoutofsurroundingthemitochondria.
ThussufficientamountofCO
2assimilationistakeplace.

404. Figure1Lightmicroscopyofleaves(transversesections).a,Borszczowiaaralocaspica;b,Salsolalaricina;andc,Suaedaheterophylla.ch,
chlorenchymacell;h,hypodermalcell;k,Kranzcell;p,palisadecell;v,vasculartissue;w,waterstoragecell.Scalebars,50mm.
Figure2Immunolocalizationofphotosynthetic
enzymesinleavesofBorszczowiaaralocaspica
byconfocallaserscanningmicroscopy.
ImmunolocalizationofRubisco(a),PEP
carboxylase(b),highermagnificationshowing
Rubiscoinchloroplastsinproximalendofcell
(c),highermagnificationshowingPEP
carboxylaseincytosol(d),pyruvate,Pidikinase
(PPDK)(e)andNAD-malicenzyme(f).Reddots
indicatewheretheenzymeispresent.cp,
chloroplast;ch,chlorenchymacell;h,
hypodermalcell;n,nucleus;v,vasculartissue;
w,waterstoragecell.Scalebars,50mm.
proximal end
Borszczowia
aralocaspica
Distal end -few chloroplasts, few mitochondria, large central vacuole,
lack of grana,nostarch, and air space between distal parts.
Proximal end-High density of cytoplasm with numerous chloroplasts and
large mitochondria at cell periphery, presence of Rubisco, grana, starch,
and no air space between proximal parts.
chlorenchymacells
Rubisco
Rubisco
PPDK-Distal end
Proximal end-
NAD-ME
C4 acid diffuse from
cytoplasmicspace at
the periphery of the
middle of the cell
CO
2Enter
OAA & MA
Diffusion

405. Biological significance / Advantages of C4 cycle
ResistancetoWaterstress:
InhotanddryenvironmentsC4photosynthesisismoreefficientthanC3photosynthesis.
Thisisduetotworeasons.
1.Systemdoesnotundergophotorespiration
2.Plantscanabletoshut(close)theirporesforlongerperiodsoftime,thusavoidingwater
loss.
Photorespiration:
ThisisaprocessaddingofCO
2tothegrowingsugar,atthattimeRubiscoalsoaddsoxygen.
Insituations,photosynthesisisoccurveryfast(athightemperature,highlevelsoflightor
both),thereissomuchO
2availableotherwisereactionbecomesasignificantproblem(Asin
C
3).C
4plantssolvethisproblembymaintainingahighconcentrationofCO2intherelevant
portionoftheleaf(thebundlesheathcells).
WaterLoss:
Plantsexchangegases,CO
2andO
2,withtheirenvironmentthroughporesknownasstomata.
WhenthestomataareopenCO2candiffuseintobeusedinphotosynthesisandO2,a
productofphotosynthesiscandiffuseout.However,whenthestomataareopentheplant
alsoloseswaterduetotranspiration,andthisproblemisenhancedinhotanddryclimates.
PlantsthatperformC4photosynthesiscankeeptheirstomataclosedmoretimethantheir
C3equivalentsbecausetheyaremoreefficientinincorporationCO2.Thisminimizestheir
waterloss.

407. CAM Plants:
•Hot, dry environments.
•5% of plants (cactus and ice plants).
•Stomatesclosed during day.
•Stomatesopen during the night.
•Light rxn-occurs during the day.
•Calvin Cycle -occurs when CO2 is present.

408. CAM Cycle:
Definition:CAMplants(CrassulaceanAcidMetabolismplants)-
Incertainplants,CAMCycleisoperatediscalledCAMplants.
ThefamiliesofCAMplantsare
1.Crassulaceae 2.Cactaceae 3.Euphobiaceae
4.Liliaceae 5.Orchidaceae6.Vitaceae
Theyshowsdiurnalpattern(Day&Night)oforganicacid
formation(Malicacid).
MostoftheCAMplantsaresucculentse.g.,
Pineapple,Bryophyllum,Cactus,Crassula,Kalanchoe,Kleinia,
Opuntia,Orchid,,Sedium.
InCAMplantspossesstwocycles(CAMcycle-Dark&Calvin
cycle-Day)occurinthemesophyllcells,whileInC4plants,
calvincycleoccursonlyinbundlesheathcells(notin
mesophyllcells).

409. 1.Crassulaceae
48plantGenerainCrassulaceae:
Adromischus,Aeonium,Afrovivella,Aichryson,Altamiranoa,Amerosedum,Bryophyllum
Chiastophyllum,Cotyledon,Crassula,Cremnophila,Dudleveria,Dudleya,Echeveria
Graptopetalum,Graptoveria,Hylotelephium,Jovibarba,Kalanchoe,Kungia,Lenophyllum
Meterostachys,Monanthes,Ohbaea,Orostachys,Pachyphytum,Pachyveria,Parvisedum
Perrierosedum,Phedimus,Pistorinia,Poenosedum,Pseudosedum,Rhodiola,Rosularia,
Sedastrum,Sedum,Sempervivum,Sinocrassula,Stylophyllum,Tacitus,Tetraphyle,
Thompsonella,Tillaea,Tolmachevia,Tylecodon,Umbilicus,Villadia.
ThePlantListincludes5,399speciesrankforthefamilyCrassulaceae.Ofthese
1,312areacceptedspeciesnames.
2.Cactaceae
Thecactusfamilyconsistsofabout131generaand1,866speciesoffloweringplants.
3.Euphobiaceae:
Itcomprisessome7,500speciesand275generaoffloweringplantsdistributedprimarilyin
thetropics.
SomeImportantplantsarrangedalphabeticallybycommonname.
cassava (Manihot esculenta),castor-oilplant(Ricinuscommunis),
copperleaf(genusAcalypha),croton(Codiaeumvariegatum),jatropha(genusJatropha),
manchineel(Hippomanemancinella),mercury(genusMercurialis),purgingcroton(Croton
tiglium),rubbertree(Heveabrasiliensis),sandboxtree(HuracrepitansandH.polyandra),
spurge(genusEuphorbia),crownofthorns(E.milii),poinsettia(E.pulcherrima),slipper
spurge(E.tithymaloides),snow-on-the-mountain(E.marginata),tallowtree(Triadica
sebifera),tungtree(Verniciafordii)

410. 4.Liliaceae
LiliaceaeisinthemajorgroupAngiosperms(Floweringplants).
16plantGenerainLiliaceae
•Amana,Calochortus,Cardiocrinum,Erythronium,Fritillaria,Gagea,Lilium,Lloydia,
Medeola,Nectaroscordum,Nomocharis,Notholirion,Prosartes,Scoliopus,Tulipa,
Zygadenus
ThePlantListincludes1,991scientificplantnamesofspeciesrankforthefamilyLiliaceae.
Ofthese712areacceptedspeciesnames.
5.Orchidaceae:
925plantgenera.ThePlantListincludes69,900scientificplantnamesofspeciesrankfor
thefamilyOrchidaceae.Ofthese27,135areacceptedspeciesnames.
6.Vitaceae
14 plant Genera inVitaceae
Acareosperma,Ampelocissus,Ampelopsis,Cayratia,Cissus,Clematicissus,Cyphostemma,
Leea,Parthenocissus,Psedera,Rhoicissus,Tetrastigma,Vitis,Yua
ThePlantListincludes3,038scientificplantnamesofspeciesrankforthefamilyVitaceae.
Ofthese950areacceptedspeciesnames.

412. Duringnight(Dark
period)whenstomata
areopen;
Inthe1
st
step,CO
2
is
fixedbyPEPthroughthe
carboxylationactionof
enzymePEPcarboxylase
intoOxaloaceticacid.
Inthe2
nd
step,this
Oxyloaceticacidis
subsequentlyconverted
intomalicacid(malate)
by enzyme malic
dihydrogenase.
Night (StomatesOpen) Day (StomatesClosed)
Vacuole
C-C-C-C
Malate
Malate Malate
C-C-C-C
CO
2
CO
2
C
3
C-C-C
Pyruvic acid
ATP
C-C-C
PEP
glucose
Oxalo
Acetic acid
CAM Plants
1.Acidification:
PEP
Carboxylase
MalicAcid
Malic
dihydrogenase
Themalicacidproducedindarkisstoredinthe
vacuole.Themalicacidincreasestheacidityofthe
tissueshenceitiscalledasacidification.

413. DuringDay(Lightperiod)when
stomataareclosed;
Malicacidisformedinthenight,is
convertedintopyruvicacidinday
timehence,acidityduetoMalic
aciddecreasesinthecells.Thisis
calleddeacidification;+one
moleculeofCO
2
isproduceddueto
theactionofmalateenzyme.
ThereleasedCO
2
isusedin
carboxylationofRuDPinthe
presence of enzyme
carboxydismutasetoproducePGA
(1
st
stableproductofcalvincycle).
PGAacidisreducedtophospho-
glyceraldehydebyNADPH+H
+
in
thepresenceofTriosephosphate
dehydrogenase(TPD).
Night (StomatesOpen)Day (Stomates Closed)
Vacuole
C-C-C-C
Malate
C-C-C-C
Malate Malate
C-C-C-C
CO
2
CO
2
C
3
C-C-C
Pyruvicacid
ATP
C-C-C
PEP
glucose
CAM Plants
2.Deacidification:

414. Day(Lightperiod)whenstomata
areopen;
Phospho-glyceraldehyde-(a)
convertedintoDihydroxy-
acetone-phosphate(DAP)-(b)in
thepresenceoftriose
phosphateisomerase.
Now,onemoleculeofboth(a
&b)unitedtoformfructose-
1,6-diphosphateinthe
presenceofaldolaseenzyme.
From fructose-1,6-
diphosphatesdifferenttypesof
compoundformedsuchas
glucoseorstarch.
RemainingPyruvicacidis
convertedintoPEPby
reductionofATPintoADP.PEP
latersynthesisstarch.This
starchisusedfordarkreaction
cycle.
Night (StomatesOpen)Day (StomatesClosed)
Vacuole
C-C-C-C
Malate
C-C-C-C
Malate Malate
C-C-C-C
CO
2
CO
2
C
3
C-C-C
Pyruvic acid
ATP
C-C-C
PEP
glucose
CAM Plants
Conti…

415. MAIZE
PINEAPPLE

416. No. C3 cycle No. C4 cycle
1.OnlyC3cycleisfoundinC3plants.1.BothC4andC3cyclesarefoundin
C4plants.
2.TheefficiencyofC3plantforCO2
absorptionatlowconcentrationisfarless
andhence,theyarelessefficient.
2.TheefficiencyofC4plantforCO2
absorptionatlowconcentrationisquite
highandhence,theyaremoreefficient
plants.
3.TheCO2acceptorisRibulose-1,5-
diphosphate.
3.TheCO2acceptorisphospho
enolpyruvate(PEP).
4.Thefirststableproductisphospho
glycericacid(PGA).
4.Oxaloacetate(OAA)isthefirststable
product.
5.Plantsshowonetypeofchloroplast
(monomorphictype).
5.Plantsshowdimorphic(Kranz)typeof
chloroplast.Thechloroplastsinbundle
sheathcellarecentripetallyarranged.
6.Ineachchloroplast,hastwopigment
systems(PSIandII)arepresent.
6.Inthechloroplastsofbundlesheathcells
PSIispresentbutPSIIisabsent.
7.TheCalvincycleenzymesarepresentin
mesophyllchloroplast.Thus,theCalvin
cycleoccurs.
7.Calvincycleenzymesareabsentin
mesophyllchloroplasts.Thecycleoccurs
onlyinthechloroplastsofbundlesheath
cells.

417. No. C3 cycle No. C4 cycle
8.TheCO2compensationpointis50-150
ppmCO2.
8.TheCO2compensationpointis0-10
ppmCO2.
9.Photorespirationispresent 9.Photorespirationisabsentorslight
degree.
10.TheCO2concentrationinsideleaf
remainshigh(about200ppm).
10.TheCO2concentrationinsidetheleaf
remainslow(about100ppm).
11.Duringphotosynthesis,infullsunlight
(10,000–12,000ft.c.)15-25mg.of
CO2isproduced/cm2leafarea/hour.
11.Duringphotosynthesis,40-80mg.of
CO2isproduced/cm2leafarea/hour.
12.Thelightsaturationintensityreaches
in1000-4000ft.c.
12.Itisdifficulttoreachsaturationevenin
fullsunlight.
13.Bundlesheathcellsarenotfound.If
foundtheyareundeveloped&non-
functional.
13.Thebundlesheathcellsarehighly
developed.
14.Maximumphotosynthesisisoccurat
optimumtemperaturerangeis10-
25°C.
14.Photosynthesisisoccurevenathigh
temperaturerangeis30-45°C.Atthis
temperature,therateofphotosynthesis
isdoublethanthatisinC3plants.

418. No. Features C3 C4 CAM
1.Leaf structure Bundle sheath cells
lacking chloroplast
Bundle sheath cells
having chloroplast
Bundle sheath cells lacking
chloroplast,Large vacuoles
in MS cells
2.Enzyme utilized to fix CO2Rubisco PEP Carboxylase PEP Carboxylase
3.Optimum photosynthesis10-25°C 30-45°C 35°C
4.Environment/ Adapted
Climate
Efficient at Cool &
Moist
Efficient at Hot &
Moist-Dry
Environment
Efficient at Hot, Dry (in arid
and stressful)
5.CO2 fixation in Mesophyll cell fix CO2
and produce Glucose
Mesophyll cell fix CO2
and Bundle sheath
cells produce Glucose
Mesophyll cell fix CO2 and
Bundle sheath cells
produce Glucose
6.Product G3P Day and NightMalateDay and NightMalateNight only
7.No. of stomata 2000-31000 10000-16000 100-800
8.Photorespiration Up to 40% Not Detectable Not Detectable
9.Stomataopen during day
time
Yes Yes No (Openingin Night)
10.Inhibition of
photosynthesis by oxygen
Yes No Yes during the day and no
in night
11.Separation of
photosyntheticprocess
None Spetial Temporal
12.Taxonomy diversity Very wide Many grasses & very
few trees
Very few species

419. No. Features C3 C4 CAM
13.Light saturation point (lux)65000 >80000 Like C3
14.Maximum Photosynthates
(mg/dm/h)
30 60 3
15.Max. growth rate
(g/dm/day)
1 4 0.02
16.WUE 600 300 50
17.The CO2 compensation
point (ppm)
50 5 2 (in dark)
18.The first stable productC3Compound
(Phosphoglycerate)
C4Compound
(Aspartate& Malate)
C4 & C3Compound
(Night & Day respectively)
19.Leaf Chlorophyll a to b
ratio
2.8 ±0.4 3.9 ±0.6 2.5 ±3.0
20.Theoreticalenergy
required for net CO2
fixation
1 : 3 : 2
( CO2: ATP: NADPH)
1 : 5 : 2
( CO2: ATP: NADPH)
1 : 6.5 : 1
(CO2: ATP: NADPH)
21.Type of Chloroplast Monomorphic Dimorphic Monomorphic
22.Leaf Isotopic ratio (δ13 C)-22 % to -34 % -11% to -19 % -13% to -34%
23.Examples Cool season grasses
(Monocot: wheat,
oat, rye
Dicot: Legumes,
tobacco, potato)
Worm season grasses
(Monocot: Maize,
Sugarcane
Dicot: No major crops
but some weeds)
About 6 families
(Pineapple, Orchids, Agave,
Opuntiaetc.)

420. SYNTHESIS OF POLYSACCHARIDES
1.SUCROSE:
Thecombinationoftwomoleculesi.e.fructose-6-phosphateandUridinediphosphate
glucose(UDP-glucose)inthepresenceofenzymesucrosephosphatesynthetase,
producesucrose-6-phosphatewhichonhydrolysisyieldssucrose.
Intheformofsucrose,carbohydrateistranslocationsfromoneregiontoother.
In certain Bacteria,
Sucrose
Glucose -1-phosphate + Fructose Sucrose + Pi
Phosphorylase
2. STARCH:
Hexosanpolysaccharidemadeupoflargenos.ofglucoseunits
Twocomponents:Ingeneral,starchcontainAmylose20-30%andrestisamylopectin.
Starchsynthesesinamyloplastsofchloroplasts.Itcanbeformedfromthe
condensationofα-D-glucose.
Starchgrainsarestrongresistancetoactionofhydrolysingenzymes.
3. CELLULOSE:
Itischiefconstituentofcellwallofautotrophicplants.
Itismadeupofglucosanof500-20000β-D-glucoseunitsconnectedwithoxygen
bridge.
Itisoccureinmicrofibrilconsistingof2parts-
Crystallinecore-purecellulose&Non-Crystallinecore-hemicellulose(withmany
substances).

421. POTATO
RICE
PEA
MAIZE
BANANA
WHEAT
OAT

423. I. INTERNAL FACTORS
1. Breakdown of Chlorophyll Molecules:
Thebreakdownofchlorophyllpigmentorchlorophyll-proteinstructure
duringmetabolismexhibitinefficientphotosynthesis.
2.Hydrationofprotoplasm:
someunknownfactorsprobablyenzymaticinnatureaffect
photosynthesis.Photosynthesisisyetnotstartintheprotoplasmofyoung
seedling.ThedecreaseinHydration(Water)ofprotoplasmreducetherateof
photosynthesis.
3.Protosyntheticenzymesystems:
TheamountandnatureofenzymesplayadirectroleasMullerandZiegler(1969)
demonstratedthatNADP-linkedglyceraldehyde-3-phosphatedehydrogenase
showedlightresponsecurvedsimilartophotosyntheticactivity.SimilarlyPEP
carboxylaseactivitiesofCO2fixationinC4plants.Greatertheenzymeactivityat
higherlightintensityincreasethecapasityofaleaftoabsorbmorelight.

424. 4.Leafstructure/anatomyandleafresistance:
Theleafcharacterssuchasleafsize,chlorophyllcontent,number
ofstomata,andLeaforientationaresomeofthefactorsthatare
responsibleforphotosynthesis.
Kreidemann(1975)statedthatinC4plants,leafresistance
controlledbystomatalaperaturewhichregulatephotosynthesis.ButinC3
plants,internalfactorsincludecarboxylationeffeciencyplayroleforleaf
resistancethanstomatalresistance.
5.Demandforphotosynthetes:
Rapidlygrowingplantsshowincreaserateofphotosynthesisthan
matureplants.Neales&Incoll(1968)observedthatiftheareaofleaf
surfaceisreduced,CO2assimilationperleafincreases.Thedemandof
photosynthetesisloweredbyremovalofmeristem.
6.RoleofPhytohormones:
Treharneandhiscoworkers(1970)reportedfirstthat
photosynthesismayberegulatedbyplanthormonesystem.Hefoundthat
gibberellicacidandcytokininincreasethecarboxylatingactivityand
photosyntheticrates.Meidner(1967)alsoreportedthatkinetin@3μm
(micromoles)causes12percentincreaseinphotosynthesiswithinone
hourofthetreatment.

425. 7.Geneticcontrol:
ThefixationofCO2iscontrolledbythechloroplast’sowngenes.
Elmore(1967)workedoutphotosyntheticactivityofhybridandinbred
linesofcornandfoundconsistencedifferenceduetogeneticalterationin
both.
8.LeafAge:
Thenewlyexpandedleavesshowasigmoidcurve(Maximum
photosyntheticactivity)andchloroplastfunctiondeclinesasleavesage.
Kriedmann(1970)explainedthatitnotonlytheconsequencesof
increasedchlorophyllcontentbutalsoanalterationininternalanatomy
anddiffusiveresistancetoenhanceCO2uptake.
9.TranslocationofCarbohydratesinleaf:
Iftheaccumulatedcarbohydratesarenottranslocated,the
photosyntheticrateisreducedandrespirationisincreased.Sugaris
convertedintostarchandgetsaccumulatedinthechloroplasts,hencerate
ofphotosynthesisisdecreased.

426. I.EXTERNAL FACTORS
ExternalEnvironmentalfactorsaffectingtherateofphotosynthesisas
conceptsoflimitingfactors.
Undertheprincipleoflimitingfactors,themagnitudeofphotosynthesisis
limitedonlybyoneofasetoffactorsatatime.
Theriseofphotosynthesisisstopsabruptlywhenanotherfactorbecoming
limiting.
Example:
Suppose,leafisexposedtoperticularlightintensitytoutilize5mgofCO2
/hrbutonly1mgisavailable,hereCO2islimitingfactor.Incaseofsupplyof
CO2itincreased2mg/hr.
ButiftheCO2supplyisraisedto6mg/hr,theconditionischangedandnow
lightisbecomesthelimitingfactor.

427. A) LIEBIG LAW OF MINIMUM:
ThisconceptwasformulatedbyGermanchemistJustinvonLiebig,
oftencalledthe“fatherofthefertilizerindustry”.ThisisanexampleofLiebig’s
LawoftheMinimum,whichstatesthatplantgrowthwillcontinueaslongasall
requiredfactorsarepresent(e.g.light,water,nitrogen,phosphorus,potassium
etc.).
Whenoneofthosefactorsisdepleted,growthstops.Increasingthe
amountofthe“limiting”componentwillallowgrowthtocontinueuntilthat
component(oranother)isdepleted.
Thenutrientmosttypically“limiting”algaegrowthinlakesis
phosphorus.Ifphosphorusconcentrationscanbemaintained,thenalgalgrowth
wouldbecontrolled.
InMarkTwainLake,(thelargestreservoirinnorthernMissouri),lightis
thefactorthatmostoftenlimitsalgae.(http://www.lmvp.org)
Adeficiencyorabsenceofanyonenecessarycomponent,whenall
othersarepresent,rendersthesoilbarrenforcropsforwhichthatnutrientor
factorisneeded.Itisalsocalledas"barrenconcept".

428. B) BLACKMAN'S LAW OF LIMITING FACTORS (1905)
Thelawstatesthat“Whenaprocessisconditionedastoitsrapiditybya
numberofseparatefactors,therateofprocessislimitedbythepaceofthe
slowestfactor”.Toexplaintheprincipleoflimitingfactor,Blackmangavethe
followingillustrationwhichisalsoshowngraphicallyinbelowFig.
AB=increaseinamountofCO2(upto5mg)
BC=CO2becomesthelimitingfactor
BD=increaseCO2withmediumlight
intensitythatincreasesrateof
photosynthesis.
DE=Lightintensitybecomesthelimiting
factor
DF=increaseinlightintensityfromthe
mediumtohighwithCO2,therateof
photosynthesisismaximumatF.
FG=further,increaseinCO2willnot
increasetherateofphotosynthesis,
whichbecomesconstantalongtheline
FG.Itindicatesthatsunlightagain
becomesthelimitingfactor.

429. Supposealeafisexposedtoacertainlightintensitywhichallowstheleaftoutilize5
mgofCO2perhourinphotosynthesis.ThephotosynthesiswillnotoccuriftheCO2
istotallyabsentintheatmosphere.
IfonemgofCO2isavailable,therateofphotosynthesisislimitedduetoCO2factor.
IftheCO2concentrationisincreasedintheatmospherefrom1mgto5mg/hour,
therateofphotosynthesisincreasesalongthelineAB.
Thus,theincreaseinphotosyntheticratewillbeproportionatewiththeincreasein
CO2concentrationupto5mg.AnyfurtherincreaseinamountofCO2,willnot
increasetherateofphotosynthesisandtheratebecomesconstantalongtheline
BC.Thisisbecausethelightfactor(lowintensity)hasnowbecomethelimiting
factor.AdditionofCO2withincreaseinlightintensityincreasestherateof
photosynthesisalongthelineBD.UndertheseconditionsincreaseofCO2willnot
increasetherateofphotosynthesis.
TheratebecomesconstantalongthelineDE.Herealsothelightintensitybecomes
thelimitingfactor.Further,increaseinlightintensityfromthemediumtohigh,
increasestherateofphotosynthesisalongthelineDFbyaddingCO2.Whentherate
attainsmaximumatF,further,increaseinCO2willnotincreasetherateof
photosynthesis,whichbecomesconstantalongthelineFG.Itindicatesthatsunlight
againbecomesthelimitingfactor.
Besides,lightandCO2,otherfactorssuchastemperature,water,etcmayalso
becomelimitingundercertainconditions.

430. I.EXTERNAL FACTORS
1.Light:
a.Lightintensity:
Therateofphotosynthesisisgreaterinintense(Bright-full)lightthanin
diffused(Dimed-muted)light.Theplantsaregroupedintotwotypesonthebasisof
lightrequirement.
i.Heliophytes(Sunplants,plantrequirehighlightintensityforoptimum
photosynthesis&growinfullsunlight)
ii.Sciophytes(Shadeplants,plantrequirelesslightintensityforoptimum
photosynthesis&growinshadyplaces)
b.Lightquality(wavelength):
Photosynthesisoccursonlyinthevisiblepartofthelightspectrumi.e.,
between400and700nm.Themaximumrateofphotosynthesisoccursatredlight
followedbybluelight.Thegreenlighthasminimumeffectandphotosynthesis
cannottakeplaceeitherintheinfrared(IR)orintheultraviolet(UV)light.
c. Light duration:
In general tropical plants get 10-12 hours of light per day and this longer
period of light favoursphotosynthesis.

431. 2.Carbondioxide:TheincresesinCO2concentrationupto1%increasedtherateof
photosynthesisincreases.But,veryhighconcentrationofCO2istoxictoplantsinhibiting
photosynthesis.
3.Temperature:Therateofphotosynthesisincreasesbyincreaseintemperatureupto
40ºCandafterthis,thereisreductioninphotosynthesis.Hightemperatureresultsinthe
proteinscoagulationanddenaturationofenzymes.Thetemperaturerequirementfor
optimumphotosynthesisvarieswiththeplantspecies.Forexample,photosynthesis
stopsinmanyplantsat0ºCbutinsomeconifers,photosynthesiscanoccurevenat-35
ºC.
4.Water:Theamountofwaterutilizedinphotosynthesisisquitesmallandevenless
than1percentofthewaterabsorbedbyaplant.Waterrarelyactsasalimitingfactor
forphotosynthesis.Duringwaterscarcity,thecellsbecomeflaccidandtherateof
photosynthesismightgodown.
5.Oxygen:Oxygenisaby-productofphotosynthesisandanincreaseintheO2
concentrationresultsinadecreaseintherateofphotosynthesis.Thephenomenonof
inhibitionofphotosynthesisbyO2wasfirstdiscoveredbyWarburg(1920)ingreenalga
ChlorellaandthiseffectisknownasWarburg’seffect.InplantsthatshowWarburg’s
effect,increasedO2concentrationresultindiversionofhigherrateofphotorespiration
andlowerphotosyntheticproductivity.
6.Mineralnutrientelements:Theabsenceofelementcopperiscomponentof
photosyntheticenzymes&Mgiscomponentofchlorophyllareaffectsphotosynthesis.
7.Osmoticrelationsofplant:ItisIndirectlyaffectedasaffecttheavailabilityofwater.

434. Respiration
• Thecellularoxidationor
breakdownofcarbohydratesinto
CO2andH2O,andreleaseof
Kineticenergywhichisutilizedin
variousvitalprocessesiscalledas
respiration.

435. Respiration
The plant breathing
At all times day and night
Done for energy purposes

436. What is ATP?
•AdenosineTriphosphate.
•Itisanenergyrichcompound
•Asourceofenergyforthecell
•ATPistheenergycurrencyofthecellasit
isspentduringcellularwork.
•EnergyismainlyreleasedasheatandATP
duringrespirationincellshowever,during
respiration,someATPshouldbeconsumed
firstbeforeotherATPcanbeformed.
•Glucoseisbrokendownduringcellular
respiration.Itisstoredwhenenergyisnot
neededstraightaway.

437. What is ATP?
•Adenosine Triphosphateis a molecule
composed of:
•1 xAdenosine
•3x phosphate
Phosphate
Adenosine
High
energy
bond

438. How is it formed?
When ADP and Pi combine together…
(Pi = inorganic phosphate)

439. How is it formed ?
energy
ADP + Pi ATP
release of energy
ADP = adenosine
diphosphate

440. Uses of ATP in cells are:
•Driving chemical reactions in cells.
•Active transportation of substances
in phloem & xylem.
•Synthesis of protein.
•Transmission of messages from
cytoplasm to nucleus and vice-versa.

441. The most common and important forms of
cellular energy.
•Chemical bonds (e.g., ATP, CH2O)
•Electrons (redoxreactions)
•Electrochemical gradients
Anelectrochemicalgradient:Anionthatcanmoveacrossa
membrane.
Thegradientconsistsoftwoparts,thechemicalgradient,or
differenceinsoluteconcentrationacrossamembrane,andthe
electricalgradient,ordifferenceinchargeacrossamembrane.

442. Fig. 8.14

444. Cellular respiration
•Chemical-bond energy in sugars is
converted to energy-rich compound ATP
which can then be used for other
metabolic reactions

445. Differences between
Respiration and Photosynthesis
aerobic
respiration
photosynthesis
2. energy is
released
2. energy (light) is
absorbed
1. produces carbon
dioxide and water
1. requires carbon
dioxide and water
3. an oxidative
process
3. a reductive
process

446. aerobic
respiration
photosynthesis
5. occurs in all
living cells at
all times
5. occurs in green
plants only when
light is available
4. Catabolic/ breaking
down process
4. Anabolic /a synthetic
process
6. occurs in
mitochondria
6. occurs in
chloroplasts

447. aerobic
respiration
photosynthesis
8. Light is not
essential
8. Light is essential
7. Include dehydrolysis
& decarboxylation
7. Include hydrolysis &
carboxylation
9. 38 ATP molecules
are formed from 1 G
9. To form 1 G, 18 ATP
molecules are used

448. Importance / Significance of Respiration:
•1. It release energy which is used in metabolic
processes (Cell division).
•2. Formation of compounds for cell constituents.
•3. It converts insoluble food into soluble form.
•4. It liberate CO2 to maintain carbon cycle in
nature.
•5. It converts store (potential) energy to kinetic
energy.
•6. It forms intermediate products, Fats & Proteins

450. (1)Mitochondriaisprovideenergyhenceitiscalled“Power
Houseofcell”.
(2)Theyarepresentineukaryoticcellwhichrespireaerobically
butabsentinprocaryoticcelllikebacteriarespire
anaerobically.
(3)Itisrodshape,size-1-3mminlength&0.5-1mmin
width.
(4)Itcoverstwomembraneoflipoprotein–outermembraneis
smoothwhileinnermembraneisfoldedtoformmanyfinger
likeprojectioniscalled“Cristae”.Theplacebetweentwo
membranesiscalled“IntermembranespaceorOuter
Chamber”whichisfilledwithwateryfluid.
(5)Innermembraneenclosescavitywhichisfilledwithgranular
substanceisknownasMatrix.
(6)“Cristae”containsF1particlesthatconsistofBase,Stalk
andHead.Cristae&F1particleshaveavariouscytochromes
viz.,Cyt.b,c,a,a3thatformingETSchain.
(7)ATPandTerminaloxidationistakeplaceoncristae.
(8)MatrixcontainenzymesrequiredforKreb’scycle.

452. Matrix contain enzymes required for Kreb’scycle

455. (1)Mitochondriaisprovideenergytovariousorganalleshenceit
iscalled“PowerHouseofcell”.
(2)2ATPmoleculesperglucosemoleculeoxidationareformedin
GTPmills.
(3)MitochondriareleaseCO2duringrespirationwhichisuseful
forplants.
(4)Biogenesisofribosomes(70Stype)takeplaceinmatrixof
mitochondria.
(5)StructuralProteinsynthesistakeplaceinmitochondria.
(6)Nucleicacidmetabolism(FormationofnewDNAs)and
transcription(FormationofRNAs)isfoundinmitochondria.
(7)Mitochondriumiscapabletochangetheshapeandreplicate
itselfbybuddingorbyconstriction.

457. RespirationQuotient:
Itisaratiobetweenthevolumeof
CO2Givenoutandoxygentakenby
specificweightoftissueingivenperiodof
timeatstandard temperatureand
pressure.
RespirationQuotient:_____________
volumeofO2absorbed
volume of CO2 evolved

458. 1.RQOFCARBOHYDRATE :
For carbohydrate oxidation glucose yields 6 CO2 for 6 O2 consumed.
C6H12O6 + 6 O2 →6 CO2 + 6 H2O
RQ or RER = 6 CO2 / 6 O2 = 1.00
Theratioofhydrogentooxygenincarbohydratesisequaltothatofwater.
Alloftheoxygenconsumedbycellsisusedtooxidizethecarboninthecarbohydrate
tocarbondioxide.
Inturn,theresultantproductionofcarbondioxideisequaltooxygenconsumedand
theratiois1.00.
2.RQOFFATS:
Lipidscontainconsiderablyfeweroxygenatomsinproportiontoatomsofhydrogenand
carbon.
Thus,whenfatisdegradedrelativelymoreoxygenisneededtooxidizefattocarbon
dioxideandwater.
Intheexampleofpalmiticacid,23O2moleculesareconsumedfortheoxidationof16
CO2molecules:
C16H32O2 + 23 O2 →16 CO2 + 16 H2O RQ or
RER = 16 CO2 / 23 O2 = 0.696 or 0.7
(Means RQ is less than Unity i. e. 1.0)
Incaseofaceticacid,liberateequalamountofCO2molecules,henceRQisunity.
CH3COOH (Acetic acid) + 2O2 →2CO2 + 2H2O
RQ = 2CO2/2O2 =1

459. 3.RQOFPROTEINS&DERIVATIVES:
Thenormalcellsconsumeproteinonlyduringstarvingconditions,hence
seldomrespired.
Likefats,proteinsarecompoundswithlesseroxygenascomparedto
carbohydreate,O(oxygen)/C(carbon)ratioisverylow.
Thehydrolysisproductsofproteinsrequiremoreoxygenfortheir
completeoxidation.
Thus,RQvalueofproteinfluctuatesaround0.79ex.Ammonia,Amides.
Ifcompleteoxidationofproteinistakeplace,RQvalueis1.0.
Theproteinisdeaminatedandthenitrogenandsulphurareexcreted.
Theresultingketo-fragmentsarethenoxidized.
4.RQOFSUCCULENTS:
IntheseplantssuchasOpuntiaormembersofCrassulaceaehaving
anthocyaninrichinleaves,nocompleteoxidationofcarbohydrateistake
place.Atnight,whenstomataopen,oxygenisabsorbedandintermediate
compoundsareformedduetopartialoxidation.RQismostly0(zero).
2C6H12O6 + 3O2 →3C4H6O5+ 3H2O (Malicacid)
2C6H12O6 + 3O2 →2C6H8O7+ 4H2O (citric acid)
RQ =CO2/O2 = 0/3 =Zero

460. 5.RQOFORGANICACID:
TheyarerichinoxygenO/Cisvryhigh.Hence,lesseroxygenisneededtobe
absorbedandmoreCO2isevolved.RQis>1.0
2C4H6O6 (Tartaric acid) + 5O2 →8CO2+ 6H2O
8CO2/5O2= 1.6
2(COOH)2 (Oxalic acid) + O2 →4CO2+ 2H2O
4CO2/1O2= 4.0
6.RQOFWHENOXYGENISUTILISEDFOROTHERMETABOLIC PROCESSES:
Synthesisofanthcyanineandconvertionoffatstocarbohydratealsorequire
oxygenandCO2isnotevolvedmore,thereforeRQisfallbelowunity(<1.0).
7.RQOFMATURING FATTYSEEDS:
Duringmaturationofseeds,simplecarbohydrateisconvertedintofats.Inthis
processoxygenisreleasedbutitusedupinrespiration.ThereforeRQismore
thanunity(>1.0).
Butingerminatingfattyseeds,seedsusingfatforrespirationandcarbohydrate
isalsosynthesizingfromfat,henceRQisfallbelowunity(<1.0).
8.RQOFTISSUERESPIRINGINABSCENCEOFOXYGEN:
InanaerobicrespirationinwhichCO2isevolvedwithoutabsorptionofO2,
thereforeRQismorethanunity(>1.0).
C6H12O6 →2C4H5OH+ 2CO2
2 CO2/0 O2= 2/0 = infinity

463. Energy yield depends on
oxygen
Two types of Respiration
•Aerobic (with oxygen)
–38 ATP molecules per glucose molecule
•Anaerobic (without oxygen)
–2 ATP molecules per glucose molecule

464. Aerobic respiration
•Release of energy from glucose
involves oxygen.

465. Breakdown of Pyruvic
Acid
•Pyruvicacid is broken down to carbon
dioxide and water
•Needs oxygen
•Lots of energy is produced (enough
to make 38 ATP’s)
•Controlled by enzymes

466. Anaerobic respiration
•In plants and yeast
–Two stages
–No lactic acid produced
–Not reversible
–Little ATP produced

467. Anaerobic respiration
•In plant and yeastcells:
•Release of energy from glucose in the absence of oxygen.
Glucose
•Thisreactionisirreversiblesincethereisalossof
carbons(asCO
2).Thisprocessisalsocalled
fermentation.
pyruvicacid
ethanol + CO
2
2ADP+2Pi --->2ATP

468. Differences
aerobic
respiration
anaerobic
respiration
complete
oxidation
incomplete
oxidation
2. oxidation
of sugar
essential
1. oxygen
requirement
nil
3. energy
released
large
amount -38
ATP
small
amount –2
ATP

469. aerobic
respiration
anaerobic
respiration
in most
living cells
in lower organisms
(e.g. bacteria and
yeast)
5. occurrence
inorganic:
CO
2and H
2O
4. end
products
organic: ethanol
or lactic acid +
CO2

470. aerobic
respiration
anaerobic
respiration
Long time Short time7. Continue For
Glycolysis,
ETS, Kreb
cycle
6. Involves Glycolysis,
Fermentation
8. Toxic ProductNot Formed Formed

472. Respiratorysubstrate:
Arespiratorysubstrateisanorganicsubstancewhichcanbe
degradedtoproduceenergywhichisrequiredforvariousactivitiesof
thecell.Therespiratorysubstratesincludecarbohydrates,fats,organic
acids,proteinetc.
Respirationinwhichcarbohydrateisusediscalledasfloating
respirationandifproteinsareused,protoplasmicrespiration.
Duringrespiration,complexsubstratesarebrokenintosimple
onesandfinallyCO2isliberatedandwaterisformed.
1.Carbohydrates:
Theallcomplexcarbohydratesarefirsthydrolyzedtosimple
hexosesugars(glucoseandfructose)andthentheyareutilized.
Starch →Disaccharides →Hexosessugars
2.Fats:
Fatsarefirstbrokendowntoglycerolandfattyacids.The
fattyacidsarebrokendowntoacetylcoenzymebyoxidation.Itenters
Kreb’scycleforfurtherdegradationandreleasesenergy.
Glycerolcandirectlyentertherespiratorychannelvia
glyceraldehyde.

473. 3.organicacids:
Organicacidsnormallydonotaccumulatein
plantstoanyappreciableextentexceptinthemembers
ofthefamily,Crassulaceae.Organicacidsareoxidized
underaerobicconditionstocarbondioxideandwater.
4.Proteins:
Proteinsareusedupasrespiratorysubstrate
onlyinseedsrichinstorageproteins.Theproteinsare
hydrolyzedtoformaminoacids.Later,theaminoacids
undergodeamination(Removalofaminogroup–NH4)
formingorganicacidsandtheorganicacidscanenter
Kreb’scycledirectly.

476. Glycolysis Kreb’scycle ETS Chain
Glucose + PyruvicAcid NADH2 +FADH2 ATP (Energy)
In cytoplasm In Mitochondria
NADH =
FADH =

478. 1. Glycolysis
• Breakdown ofglucosetopyruvicacid
ControlledbyvariousenzymesthatProducesalittle
energy(enoughtomake2ATP’s)iscalledGlycolysis.
• Gycolysis,fermentation,anaerobicrespiration
andlacticacidformationprocessesoccurfreelyinthe
cytoplasmwhile,Krebscycleoccursinthematrixof
mitochondriaintheeukaryoticcellsandonthe
surfaceofmesosomesinprokaryoticcells.Enzymesof
glycolysisarefoundinthesolubleportionof
cytoplasm,calledcytosol.Theseenzymesareremain
activelifetimeandrequiredagainandagaincalled
constitutiveenzymes.

479. Step -1
Step -2
Step -5
Step -4
Step -3

480. Step -6
Step -7 Step -8
Step -9
Step -10

481. Phosphorylationin Glycolysis
(Trans-Phosphorylation)
• Withtheproductionofpyruvicacidthe
Gycolysiscomesthanend.NowifATP
moleculesusedupandproducedduringGycolysis
arecalculatedasfollow:
•Itisfoundthatduringthewholesequenceof
reactions,TwomoleculesofATPareusedup:
•OnewhenGlucoseisphosphorylated and
convertedintoGlucose-6-phophateand
•Other when Fructose-6-phophate is
phosphorylatedandconvertedintoFructose-1-
6-diphophate.

482. Phosphorylationin Glycolysis(Trans-Phosphorylation)
•ItisfoundthatFourmoleculesofATPareproduced:
•TwoATPmoleculesareproducedduringconversionof
1,3-Diphosphoglycericacidconvertedinto3-phosphoglycericacid.
•AnotherTwoATPmoleculesareproducedduringconversionof2-
phospho-enol-pyruvicacidintopyruvicacid.
•ThismeansthatinthesequenceofreactionsofGlycolysisthere
isanetgainofTwoATPmolecules.
•Stepsarefollows:(TwoATPsareusedup)
•Glucose+2ATP Fructose-1-6-diphophate+2ADP
(FourATPsareproduced)
•2(1,3-Diphosphoglyceric acid)+2ADP 2(1,3-phosphoglyceric acid)+2ATP
•2(2-phospho-enol-pyruvic acid)+ 2ADP 2Pyruvic acid + 2ATP

483. C6H12O6 + 2ATP + 2NAD + 4ADP+2H3PO4
Significance / Importance of Glycolysisin plants
The overall glycolyticprocess can be summarized as follows:
↓
2 CH3COCOOH + 2ADP + 2NADH2 + 4 ATP
Pyruvicacid
•Thusthereisagainof4-2=2ATPmoleculesper
hexosesugarmoleculeoxidizedduringthisprocess.
•Besidesthis,2moleculesofreducedcoenzymeNADH2
arealsoproducedpermoleculeofhexosesugarin
glycolysis.
•Duringaerobicrespiration,thesetwoNADH2
moleculesareoxidizedviatheelectrontransport
chaintoyield3ATPmoleculeseach.Thus6ATP
moleculesareformed.

484. •However,TwomoleculesofNADH2arealso
producedinthisprocessandfromitseachmolecule
3ATPmoleculesareproduced(ButoneATPisloss
totransferNADH2intoETSChain).
•Asaresults,4ATPmoleculesareformedinsteadof
6ATPineukaryotes,whileinprokaryotes6ATPare
produced.
•ThemoleculesofNADH2generatedduringglycolysis
remainsinthecytoplasmitcannotenterinto
mitochondriabutdirectlytransferredtoETSof
mitochondriathroughshuttlesystem(Translocation
ofsolutes).

485. Pyruvate
Kreb Cycle
AlanineAA &
α-Ketoglutarate
Ethanol
Lactate
NAD
CO2 +H2O +ATP +
Electrons + Protons
NADH+H
NAD
NADH+H
Break down of PyruvicAcid metabolised through four different paths
Glutamate
1
2
4
3
Lactic acid
dehydrogenase
Alcohol
dehydrogenase
Pyruvatedecarboxylase
Acetaldehyde and CO2

487. BreakdownofPyruvicacidtolacticacidisnotmuchfamiliarin
higherplantsbutiscommoninanimaltissuesandmusclein
gycolysis.
Lacticaciddehydrogenase
PyruvicAcid Lacticacid+NAD
Ingycolyticreaction,lacticacidareproduced,where3-
Phosphoglyceraldehydeisoxidisedto1,3-Diphosphoglycericacid.
LookonthebalancebalanceofATPmoleculesshowssamepath
wayasearlier.
1. Formation of lactic acid:
Stepsarefollows:(TwoATPsareusedup)
Glucose+2ATP Fructose-1-6-diphophate+2ADP
(FourATPsareproduced)
•2(1,3-Diphosphoglyceric acid)+2ADP 2(1,3-phosphoglyceric acid)+2ATP
•2(2-phospho-enol-pyruvic acid)+ 2ADP 2Pyruvic acid + 2ATP

488. WhenneededPyruvicacidcanbeutilizedtosynthesise
Aminoacids.Nos.ofbiosynthetictransminationsreactionsare
involvedbutsimply,
2. Fate (out come) of Pyruvicacid to Alanine:
Pyruvicacid + Glutamate Alanine+ α-Ketoglutarate

489. FirstStep:Inalcoholicfermentation,pyruvicAcidisfirst
convertedintoAcetaldehydeandCO2(withtheactionof
pyruvatedecarboxylase).
pyruvatedecarboxylase
PyruvicAcid AcetaldehydeandCO2
SecondStep:AcetaldehydeisnowconvertedintoEthanol(with
actionofalcoholdehydrogenase)andNADHisreducedinNAD.
Alcoholdehydrogenase
Acetaldehyde+NADH2 Ethylealcohol+NAD
TheutilizationofPyruvatebyfermentationisverycommonin
yeastcellsandmanyplanttissues.Theprocessstopswhen
concentrationofalcoholexceeds15percent,thereafterit
becomestoxictogrowthofyeast.
3.Alcoholic fermentation (Anaerobic Respiration(without oxygen)

490. Anaerobic (without oxygen)

491. FateofPyruvateistodegradeuptoCO2andH2Olevel
throughKrebscycleandrespiratorychaininwhichenergyis
trappedintheformofATPmolecules.Alltheenzymesof
TCAcyclearefoundinmitochondrialmatrix.
(i)Pyruvate CO2+Electrons+Protons
(ii)Pi+ADP Water+ATP
4.Fate of Pyruvate to CO2 and H2O
(Aerobic Respiration(with oxygen)

492. TheoxidativedecarboxylationofPyruvateintoAcetylCoAinvolves
thepresenceofatleastfiveessentialcofactorsandacomplex
enzyme.
Thecofactorsinvolved:
(i)Mgions,
(ii)ThiaminePyro-Phosphate(TPP)
(iii)NAD+
(iv)CoenzymeA(CoA)
(v)Lipoicacid
Pyruvate+TPP TPP-complex+CO2
TPP-complex+Lipoicacid Acetyllipoicacidcomplex+TPP
Acetyllipoicacidcomplex+CoA AcetylCoA+lipoicacid
Lipoicacid+NAD Lipoicacid+NADH+H+(NADH2)
Fate
Reduced form Oxidisedform

493. Krebs cycle
3
4
2
1
Pyruvate+ TPP
TPP-complex +
Lipoicacid
Acetyl lipoic
acid complex
Acetyl CoA
Pyruvicacid
Release of
Lipoicacid

494. Acetyl lipoic
acid complex

497. PyruvicacidisconvertedintoAcetyl–CoA(with
theactionofpyruvatedehydrogenaseenzyme
andreleaseCO2+NADPH2.
AcetylCoAistheconnectinglinkbetween
Glycolysis(EMPpathway)andKrebcycle.
AcetylCoAisReactwithaOxalo-aceticacid
withtheuseof1moleculeofH2OandCitric
acidisformed.

498. Significance/ importance of Krebcycle:
(1)PerGlucoseofmolecule,24moleculesofATPareformed
inKrebcycle.
(2)Itprovidescommonpathwayforbreakdownof
carbohydratesandfats.
(3)Itformsanumberofintermediateproductswhichserveas
buildingblockstosynthesisothercomplexorganic
compounds(8)suchascitrate,Iso-citrate,α–kito-
glutarate,succinatylCoA,succinate,fumarate,malate,
oxyloacetateetc.
(4)ItformsanumberofreducedcoenzymeslikeNADH2and
FADH2whichreleaseelectronsthroughETS.
(5) ReleaseCO2isutilizedinfixationinchloroplast.

503. Goal:tobreakdownNADHand
FADH
2,pumpingH
+
intotheouter
compartmentofthemitochondria
Inthisreaction,theETScreatesa
gradientwhichisusedtoproduce
ATP, Electron Transport
Phosphorylationtypicallyproduces
32ATP's.

504. Krebcycle is occur in the
matrix of the mitochondria
1
2
3
4
5
6
7
8
Coenzyme A with Sulfhydryl

505. No. Substrates Products Enzyme Reaction type
1Oxaloacetate+
Acetyl CoA+ H
2O
Citrate+
CoA-SH
Citrate synthaseAldol
condensation
2Citrate Isocitrate+ H
2OAconitase Dehydration
3Isocitrate+ NAD
+
α-Ketoglutarate+
CO
2
Isocitrate
dehydrogenase
Oxidation
4α-Ketoglutarate+
NAD
+
+CoA-SH
Succinyl-CoA+
NADH + H
+
+
CO
2
α-Ketoglutarate
dehydrogenase
Oxidative
decarboxylation
5Succinyl-CoA+
GDP+ P
i
Succinate+
CoA-SH + GTP
Succinyl-CoA
synthetase
substrate-level
phosphorylation
6Succinate+
ubiquinone(Q)
Fumarate+
ubiquinol(QH
2)
Succinate
dehydrogenase
Oxidation
7Fumarate+H
2O L-Malate Fumarase H
2O addition
(hydration)
8L-Malate+
NAD
+
Oxaloacetate+
NADH + H
+
Malate
dehydrogenase
Oxidation
Steps of Krebcycle :

506. High Proton concentration + + + +
Low Proton concentration -----
F
0
particle
F
1
particle
4H+
Inner membrane
Oxysome
+

508. Electron Transport Chain (ETS):
Respirationisabiologicaloxidationandthisoxiativecatabolismcanbe
representedas
C6H12O6+6O2-----6H2O+6CO2+686K.cal.
Outoffourtypesofoxidations:
1.Bygainofmolecularoxygen
2.Byremovalofhydrogen(dehydrogenation)
3.Bychangeinvalency
4.Byhydrationfollowedbydehydrogenation
Themostcommontypeofoxidationfoundinrespirationisremovalof
pairofhydrogenfromoxidizingsubstrate,pairofhydrogenultimately
dissociatedintotwoprotonsandtwoelectrons2H=2H++2e.
Twoprotonsreleasedinmediumashydrogenions(H+)areavailable
forcombinationwithO2toformwater.
InactualreductionofO2towater,fourelectronsaretakenupby
oxygenfollowedbyadditionoffourprotons.
O2+4e(2e+2e)--2O2
2O2+4H+--2H2O

509. Thelinkingofenzymesoftherespiratorychainisintheformofaforkedchainconnectedwitha
communalchainofcytochromesleadingtomolecularoxygen.
Forchannelizingpairsofhydrogenfromsubstrates-Pyruvicacid,Iso-citricacid,α-Kitoglutaric
acidandMalicacidintoaonebranchhavingaseparateenzymesystemfunctions.
ThesehydrogenpairsendedultimatelyincombinationwiththeprostheticgroupNAD+.High
electronpressurereducedNAD+intoNADH2and2electrons&2protonsreleased(one
transferredtoPgroup&an.
otherreleasedinthemediumasH+ion.
2H ----2H+ + 2e
NAD + 2H+ +2e ---NADH + H+
Nowtwoelectrons&oneprotontransferredtoFADprostheticgroup.
Insecondbranch,HydrogenpairremovedfromSuccinicacidandtransferredtoFADwhichreduced
intoFADH2andreleased2H++2eandconvertedintoFumaricAcid.
Succinicacid + FAD ----FumaricAcid+ FADH2
Innextstep,electronsarestep-wisepassedthroughcytochromesb,c,aanda3withthehelpofiron
atomtooxygen.
1-Branch
2-Branch
Figureshowingtwobranches,oneelectroncomingfromPyruvicacid,Iso-citricacid,α-Kitoglutaric
acidandMalicacidandotherfromSuccinicacid.
2e-+ 2H+

510. Inhigherplants,Ubiquinoneisactedasreserviorofelectrons.
Prostheticgroupsarenon-peptide(non-protein)compoundsthat
mostlyattachtoproteinsandassistthemindifferentways.They
canbeinorganic(likemetals)ororganic(carbon-containing)and
bindtightlytotheirtarget.
Prostheticgroupscanbindviacovalent(electron-sharing)ornon-
covalentbonds.

511. Schematic diagram showed
oxidation-reductionpotentialin
wholeseriesofsteps.
Reductionalpotentialpushthe
electronsintothecytochromes
chainandoxygenpulltheelectron
fromcytochrome.
ThereforeitdevelopsaPush-Pull
systemduringelectrontransfer.
AtthreedifferentstepsATPis
released.
1.NADH--FAD
2.Cyt.b--Cyt.C
3.Cyt.a--Cyt.a3
Atcertainsteps,theenegry
releasedbyelectronisnot
sufficienttobindinorganic
phosphate(Pi)withADP,itwillbe
wastedinformofheator
fluorescencelight.
Infact,0.28eV(electricvolts)
ormoreenergyisrequiretoform
ATP.
Thusrespiratorychainfunctionas
chemical machinery of
mitochondria.
volts

512. ChemiosmoticTheory(Mitchell,1961):
1.NADH2reducedinNADand2H++2e-releasedinETS.
Conversionofchemicalenergy(NADH)intoosmoticenergy
(Differencesinconcentrationofprotonsontwosidesof
mitochondrialmembrane)iscalledchemiosmosis.
2.MitchellexplainprocessofATPformation,bothin
respiration&photosynthesis(i.e.Oxidativeandphoto-
phosphorylation).
3.ATPaseenzymeisbehavelikeareversibleenzyme.
4.AsaresultofaccumulationofH+ionstooutsideofthe
mitochondrialmembrane,aconcentrationgradientofH+
ionsbetweenoutsideandinsideofmitochondriais
established.
5.AccumulationofH+ionsserveaspotentialenergyforATP
formation.
6.WhentheseH+ionsre-enterinmitochondria,fromHigh
ProtonconcentrationthroughFoparticle(stalk)toF1
particlesofoxysomepotentialenergyisusedtodrivethe
ATPaseforATPformation.
ATPase(dehydrated)
ADPPi------------------- ATP+H2O
ATPase(hydrated)
ATP+H2O------------------- ADP+Pi
9.TheseH+ionscombinedwithoxygentoformwaterleadingtodehydrationandasaresultofATP
areformed.Thus,oxygenisthefinalelectronacceptorattheendoftheETS;asoxygen
acceptsapairofelectrons&twoprotons,sotheseprotonsarejoinwiththeelectronsto
producethetwohydrogenatoms,thusformingwater.
O+2e --½O2
½O2 + 2H+ --H2O
OR O2 +4e (2e +2e) --2O2
2O2 + 4H+ --2H2O

513. Cytosol-8 ATP
+
Mitochondria (Out of
krebcycle) –6 ATP
+
Mitochondria (in kreb
cycle) –24 ATP
=
Total 38 ATPs are
formed
-----------------
Glucose Glucose
Pyrophosphate=2 ATP
Glycolysis=4 ATP
NADH=28 ATP
FADH2 = 4 ATP

514. BecauseNADHgivesupitselectrontoComplexI,whichis
atahigherenergylevelthantheotherComplexes.WhenComplexI
transferstheelectrontoComplexIII,energyisgivenofftopump
protonsacrossthemembrane,creatingagradient.Theelectron
movesagaintoComplexIVandagainpumpsmoreelectronsacross
themembrane.BecauseNADHstartedwithComplexI,ithadmore
chancestopumpsmoreprotonsacrossthegradient,whichpowers
theATPsynthaseandgivesus3ATPpermoleculeofNADH.FADH2
produces2ATPduringtheETCbecauseitgivesupitselectronto
ComplexII,bypassingComplexI.BybypassingComplexI,wemissed
achancetopumpprotonsacrossthemembrane,solessprotonshave
beenpumpedbythetimewegettoComplexIV.Protonsstillhave
beenpumped,enoughtofuel2ATPcreatedbyATPsynthase.

515. (A)AEROBICRESPIRATION:
1Glucosemoleculecontainsabout6,86,000calories(686Kcal.)of
energyintheformofbond.
1ATPmolecule7600caloriesofenergyistrapped.
InoxydativephosphorylationviaGycolysisandKrebcycle36ATP
aregained.
Thismeans36X7600X100/6,86,000=39.8i.e.40%oftotal
energyistrappedintheformofATPmolecules,whileremaining
60%energylost/wasteasheatorflorescencelight.
(A)ANAEROBIC RESPIRATION:
2ATPmoleculesareformedperGlucosemolecule.Theefficiencyof
thisrespirationwillbe
C6H12O6----2C3H4O3+4H+52Kcal
2X7600X100/52,000=29.23%oftotalenergyistrappedinthe
formofATPmolecules,whileremaining70.77%energylost/wastage
insuchrespiration.

516. ElectronTransportChain(ETS):
Mitochondrialinnermembraneproteinsformatransportchainfor
electronsandprotons.
NADH+H+arrivesatthefirstcarrierandtransfers2e-
and1H+anotherH+ispickedupfromthematrixsolutionthe2e-
and2H+sarecarriedfromtheinnertoouterface,wherethe2
H+saredepositedintheintermembranespacethusprodues4H+;the
2e-sreturn,pickupanotherpairofH+andrepeatthetrip2more
times,foratotalof3roundtrips.
FAD(FlavinAdenineDinucleotide)isreducedtoFADH2that
entersintotheETSfurtheralong,andthuspumpsonly2pairsof
H+s(4H+)intotheintermembranespace.
Thealternatereductionandoxydationofubiquinone(a
componentofETSchain)isalsopumps2pairsofH+s(4H+)intothe
intermembranespace.
Whenelectronflowthroughcomplexes,I,II,III,IV,these
complexesactasaprotonpumps.Theypumpoutprotonsacrossthe
innermembranefrommatrix.

518. Cytoplasm
Mitochondria

519. No.OXIDATIVE PHOSPHORYLATION No. PHOTO -PHOSPHORYLATION
1.Itisoccurduringrespiration. 1.Itisoccurduringphotosynthesis.
2.Itisfoundinsidemitochondria
particularly,electrontransport
systeminvolvingcytochromes.
2.Itisfoundinsidechloroplast
particularly,pigmentsystemIand
II.
3.Theprocessesoccuroninner
membraneofcristae.
3.Theprocessesoccurinthylakoid
membrane.
4.Oxygenneededduringterminal
oxidation.
4.Oxygenisnotneeded.
5.ATPformationisduetoenergy
producefromelectrontransfer
5.ATPformationisduetolight
energy
6.TheATPmoleculesareutilizedin
variousmetabolicactivitiestake
placecytoplasm.
6.TheATPmoleculesareusedup
forCO
2assimilationindark
reaction.
Comparison between oxidative phosphorylation and
photo-phosphorylation

520. 5 –Types
(1)GrowthRespiration:
Itisdefinedastheamountofcarbohydraterespired
intheprocessthatresultsinanetgaininplantbiomass.
(2)MaintenanceRespiration:
Arespirationwhichprovidestheenergyforliving
organismstomaintaintheirbiochemicalandphysiological
processiscalledMaintenanceRespiration.
(3)SaltRespiration:
Itisdefinedasincreaseinoxygenuptakeand
emissionofCO2whensaltisaddedtotissuerespiringin
water.

521. (4)Alternaterespiration:
Inhigherplants,theactivitiesofcytochromeoxidaseare
inhibitedinpresenceofcyanide.Undersuchconditions,cyanide
resistanceoxidaseenzymebecomesfunctional.Electronfrom
Ubiquinonepassestoflavo-proteincomplextoalternateoxidase
(cytochromeoxidasetocyanideresistanceoxidase)andfinally,
electronisacceptedbyoxygen.Thisisknownas“alternative
respirationoralternativerespiratorypathway”.
Thispathwaydissipates(disperse)mostofthechemical
energyofrespiratorysubstratesasheat(burnexcess
metabolitesandenhancethesynthesisofsecondarymetabolites,
whichperformprotectivefunctions).
ComplexI
ATPflavo-proteincomplex
NADH
e-
Succinate
ComplexII
Fig:CyanideResistantRespirationoralternativepathway
Fe-S
Fe-S
Alternate oxidase
UQ
O2

522. (5)Woundrespiration:
WoundincreasetheRateofrespirationduetoincreases
concentrationofphosphatidylcholineintissues.
AccordingtoHopkins(1927)whenaportionofplantis
woulded,starchisconvertedintosugarsthatincreaserateof
respiration.Aftersometimes,respirationrestoresnormally.
FormationofActinomycinD,preventswoundrespiration
andcyanideresistanceonlywhengiveninthefirst10to12
hoursafterthecuttingofpotatotuberslices.The
phosphatidylcholineincreaseswithsliceaginganditisinhibited
byactinomycinD.Thesynthesisofthreecriticalenzymesof
phosphatidylcholine,namely,
(i) phosphorylcholine-glyceridetransferase,
(ii) phosphorylcholine-cytidyltransferase, and
(iii) phosphatidylphosphatase.
Neithersuccinicdehydrogenasenorcytochromeoxidaseactivity
increaseswithtimeinagingpotatoslices.

523. Summary
Aerobic
respiration
Anaerobic
respiration in
plants and
yeast
Glycolysis YES
(Cytoplasm)
YES
(Cytoplasm)
ATP Yield 38/1G 2/1G
Product(s) CO2 + H20 +
Energy (ATP)
CO2 + Ethyle
Alcohol

527. Inhigherplants,theactivitiesofcytochromeoxidaseareinhibitedinthepresence
ofcyanide.Undersuchconditions,cynideresistanceoxidaseoralternateoxidase
(AOX)becomesfunctionalfromubiquinoneofETSchain.
OnceAOXbecomesfunctional,itreducetheeffectofcyanideandithelpsin
respirationagainstcyanideandtorun/operatethekrebscyclebyprovide
intermediaryorganicacids.
KrebcyleisinhibitedwhenATPorelectron(NADH)fromitarenotsufficiently
takenout.
Cyanide-resistantrespirationwasdiscoveredatthebeginningofthe20thcentury.
Duringthestudyofanthesisinthermogenicplants,foundtobeatypicalfeature
ofplantrespiration.
Thephenomenonofrespirationresistanttocyanideisconnectedwiththepresence
intherespiratorychainofanadditionalterminaloxidase—alternativeoxidase
(AOX).
ThepresenceofAOXinhigherplantmitochondriaposestheroleinplant
metabolism.
AOXgenesexpressedinSauromatumguttatum,Arabidopsisthaliana,Glycinemax,
PisumsativumandNicotianatabacumthatalteredthephysiological,developmental
andenvironmentalconditions.
AOXwasfoundtobeencodedbyasmallfamilyofnucleargenes(subfamilies
AOX1,AOX2aandAOX2b,formerlynamedAOX3).
TheAOX1geneismostwidelyknownforitsexpressionbystressstimuliinmany
tissuesandispresentinbothmonocotyledonanddicotyledonplantspecies.
CYANIDE RESISTANCE RESPIRATION

528. Plantrespiratorychainbranchesatthelevelofubiquinonefromwherethe
electronsflowthroughthecytochromepathwayortoalternativeoxidase.
Transferofelectronsfromubiquinonetooxygenbyalternativeoxidaseand
hasanon-proton-motivecharacterand,bybypassingtwositesofH+
pumpingincomplexesIIIandIV,lowerstheenergyefficiencyof
respiration.
Thephysiologicalroleofalternativeoxidaseasa“survival”proteinthat
allowsplantstocopewiththestressfulenvironment.
Alternative oxidasein plant mitochondrial respiratory chain

529. AOX= alternative oxidase;
Cytc = cytochromec;
QH2 = ubiquinol(reduced ubiquinone);
ND ex/in = NAD(P)H dehydrogenases, respectively external/internal
I, NADH —
ubiquinone
oxidoreductase
II, succinate—
ubiquinone
oxidoreductase
V, ATP
synthase
IV, cytochromec
Oxidase
III, ubiquinol—
cytochromec
oxidoreductase
AOXbranchfromthemainrespiratorychainatthelevelofubiquinoneandcatalyses
thefour-electronreductionofoxygentowater)

531. Thedetailspathwaywereworkedoutby
Horecker(1951)andRacker(1954)with
radioactivecarbonC14.
InPantosePhosphatePathway,Glucose-
6-phosphateisfinallyconvertedintoFructose-
6-phosphateaftercompletionofcycle.
InPPP,completeoxidationofoneglucose
molecule,sixCO2moleculesareproduced,the
numberofNADPH2willbe6X2=12,so12
moleculesofNADPH2willproduced12X3ATP=
36moleculesofATPwhichisequaltoGycolysis
+Krebcycle.

533. 1
2
3
4
5
6
2
7
8

534. Significance/importanceofPantosePhosphatePathway:
(1)HaxosesugarisbreakdownintoCO2andH2Owithout
participationofglycolysisandKreb’scycle.
(2)OxygenisrequiredforsynthesisofH2O.
(3)Itissourceof5carbonsugarswhichareconstituteof
nucleotidesandnucleicacids.
(4)Oxidationofonemoleculeofglucose,12NADPHare
formedand36ATPmoleculesaresynthesised.
(5)Reactiontakeplaceincytoplasm.
(6)NADiselectronacceptorandNADPHisusedforfurther
reactions.

536. (I)InternalFactors:
(1)Protoplasmicfactors:
Youngcellshavemoreactiveprotoplasmrespiremore
rapidlythanOldercells(largevacuoleandthickcellwall).
Rateofrespirationisalsoaffectedbyqualityof
enzymespresentinprotoplasm.
(2)Concentrationofrespiratorymaterial:
Rateofrespirationincreasewiththeincrease
respiratorysubstractssuchasafterphotosynthesis
respiratoryrateishigher.

537. (II)ExternalFactors:
(1)Temperature:
Increaseintemperature,Rateofrespirationis
increased.Forevery10°Criseintemperature,Rateof
respirationisdoubled,ifnoanyfactorsarelimiting.
(2)Light:
Rateofrespirationincreasewiththeincreaselight
intensity,openingandclosingofstomatarapidlywhen
respiratoryrateishigher.
(3)Oxygen:
Whenoxygencontentisreducedto1%theRateof
respirationreachesitsminimumandevolutionofCO2is
raisedup.

538. (II)ExternalFactors:
(4)CarbonDioxide:
IncreaseinCO2concentrationinatmosphere,Rateof
respirationisfalldown.
(5)Water:
Storageofwaterreducetherateofrespirationbecause
itmaintainturgidityofthecells.Butsmallstorageofwater
increaserespiratoryratebecauseundersuchcondition,starch
isconvertedintosugarsthatincreaserateofrespiration.
(6)Injury:
InjuryincreasetheRateofrespiration.Accordingto
Hopkins(1927)whenaportionofplantisinjured,starchis
convertedintosugarsthatincreaserateofrespiration.After
sometimes,respirationrestoresnormally.

539. (II)ExternalFactors:
(7)Effectofcertainchemicalsubstances:
ChemicalssuchasAzides,Cyanides,Carbonmonoxide,
Ethanol,HydrogenParoxide,Iodo-acetate,andLacticacid;
someanaestheticsgroupchemicalssuchaschloroform,
ether,acetoneandformaldehyde;variousalkaloidsand
differentglycosidessynthesisedandpresentinthecells,are
increasedtherateofrespiration.
(8)MechanicalEffects:
Mechanicaltreatmentssuchasrubbingtheleavesby
handandevenslightbendingofleavesissufficientto
increasetherateofrespiration.

540. Lecture-21

542. INTRODUCTION
Inearlierliterature,growthregulatorswerereferredas
hormones.Hormoneisagreekwordderivedfromhormao
meanstostimulate.
Thimann(1948)suggestedthetermforhormonesoftheplants.
Philips(1971)definedgrowthhormoneassubstanceswhichare
synthesizedinparticularcells.
Definition:
Theyareorganiccompoundssynthesizedinverylow
concentration,translocationfromonepartofaplantandto
anotherpartresponsibleforphysiologicalresponsessuchas
growthpromotion,differentiationorinhibitionofgrowth.

543. COMMONPHYTOHORMONES:
Auxins,Gibberellins,Cytokinines,Ehtlene,DorminandFlorigen
Butnow,PHYTOHORMONESarebroadlyclassifiedintotwogroups:
growthpromotingsubstancesand
growthretardingsubstances
Vitaminsarealsogrowthregulator
whethertheyarenaturallyoccurringgrowth
substancesorsyntheticgrowthsubstances.

544. GROWTHREGULATINGHORMONESCANBECLASSIFIEDASUNDER:
NATURALGROWTHHORMONES:
-Auxins:IAA
-Gibberellins:GA3
-Cytokinines:Kinetin,Zeatin
-Ethylene:Ethylene
-Dormin:ABA,Phaseicacid,Xanthoxin
FloweringHormones:Florigen,Anthesin,Vernalin
Miscellaneousnaturalgrowthsubstances:Vitamins,Phytochrome,
Traumaticsubstances
Phenolicsubstances:Caumarin
SYNTHETICGROWTHHORMONES:
SyntheticgrowthPromoters:Syntheticauxins,Syntheticcytokinines
etc.
Syntheticgrowthretardants:CCC(ChloromequatChloride),AMO
1618(AmmoniumTri-methylChlorideCarboxylate),PhosphonD,
Morphactins,Malformins,MaleicHydrazide(MH).

545. THE RELATIVE CONCENTRATION OF SOME PLANT
HORMONES:
No.PlantPart AuxinsGibberellinsCytokininesABA
1Shoottip +++ +++ +++ +
2Youngleaves +++ +++ +++ +
3Elongatedstem ++ ++ +++ +
4Lateralbuds + ++ + ++
5Flowersandfruits + + ++ +
6Developingseeds + +++ ++ ++
7Matureleaves + + + +++
8Lateralshoot +++ ++ ++ +
9Maturestem + + + +
10Root + + + +
11Roottip +++ ++ +++ +
+++ = denotes high concentration, ++ = denotes medium concentration,
+ = denotes low concentration

546. THE RELATIVE CONCENTRATION OF SOME PLANT
HORMONES:
No.PlantPart AuxinsGibberellinsCytokininesABA
1Shoottip ? ? ? ?
2Youngleaves ? ? ? ?
3Elongatedstem ? ? ? ?
4Lateralbuds ? ? ? ?
5Flowersandfruits ? ? ? ?
6Developingseeds ? ? ? ?
7Matureleaves ? ? ? ?
8Lateralshoot ? ? ? ?
9Maturestem ? ? ? ?
10Root ? ? ? ?
11Roottip ? ? ? ?
+++ = denotes high concentration, ++ = denotes medium concentration,
+ = denotes low concentration

548. TheveryexistenceofgrowthsubstanceswasproposedbyCharlesDarwin
(1880)inhisbook“ThePowerofMovmentsinPlants”.Heworkedoncanary
grassandconceivedtheidea,whenseedingarefreelyexposedtolateral
lightsomeinfluenceistransmittedfromtheuppertolowerpartcausingthe
laterbend.
Auxinsareagroupofphytohormonesproducedintheshootandrootapices
andtheymigratefromtheapextothezoneofelongation.
Auxinspromotethegrowthalongthelongitudinalaxisoftheplantand
hencethename(auxeing:togrow).
Went(1928)isolatedauxinfromtheAvenacoleoptiletipsbyaparticular
methodcalledAvenacoleoptileorcurvaturetestandconcludedthatno
growthcanoccurwithoutauxin.
Theterm,auxin(DerivedfromGreekword‘Auxein=togrow)was
introducedbyKoglandHaagen-Smit(1931).
Thimann&Skoog(1933)notedthatauxininhibitedlateralbudformation
IndoleAceticAcid(IAA)istheonlynaturallyoccurringauxininplants.

549. AvenaCurvatureTestIBA:
Cut off the tip of Avenacoleoptile
Place on agar block
Auxindiffuses into agar block
Place the agar block asymmetrically
on cut coleoptilestump
Coleoptileshowed
typical curvature
Theauxincausecellwallloosening,
henceauxintreatedcellwallbecomemore
extensibletherebyhelpsincellelongation.
Why cell wall loosening is take place?
Auxincausereceptivenessinthe
cellsofcoleoptilethatsecreteH˖ionsthereby
pHisreduced.Increaseinaciditylooseningcell
wallandfinallyfastgrowthisoccur.ReducedpH
promotestheactivityofhydrolysisandbreaking
thepolysaccharidebondandallowtostretchcell
wallmorerapidly.
Auxindiffused /
treated cell wall
Stretch more rapidly
Auxinuntreated cell wall
Auxinsareabundantin
thegrowingtipssuch
ascoleoptiletip,buds,
roottipsandyoung
leaves.

550. Tropism
HigherconcentrationofAuxinisaccumulatedatdarksideand
causingmoregrowthascomparedtoilluminatedside.Thusdue
tounequalgrowthofthetwosides,causesbendingofthestem
towardslight.

551. They are characterized by the following features:
1.Polar translocation:
The transport of auxinis predominantly polar. In stems, polar transport of auxin
is basipetal i.e., it takes place from apex towards base.
1.Apical bud dominance
2.Variable behavior of root and shoot growth
3.Root initiation
4.Delay in abscission
5.Differentiation of xylem elements

552. KoglandSmit(1931)isolated40mgof
auxinafrom150litresofhuman
urine.
Kogl,ErxlebenandSmit(1934)
isolatedauxinbfromcorngermoil.
Latertheyalsoisolatedanotherauxin
fromhumanurinethatisheteroauxin,
whichwaslatelycalledIAA,theyare
naturallyinallhigherplantsandfungi.
Chemically,itwasrecognizedas
auxentriolicacid(C18H32O5).
Someotherauxinsviz,Indole-3-
acetaldehyde,Indole-3-acetonitrile,
Indole-3—ethanol,4-chloro-IAAare
alsofoundinplants.
Chemical Structure of Auxins

553. Inplants,auxin(IAA)issynthesizedingrowingtipsor
meristematicregionsfromwhere;itistransportedtoother
plantparts.
Inmonocotseedling,thehighestconcentrationof
auxinisfoundincoleoptiletipwhichdecreases
progressivelytowardsitsbase.
Indicotseedlings,thehighestconcentrationisfound
ingrowingregionsofshoot,youngleavesanddeveloping
auxiliaryshoots.

554. X-Destruction & Inactivation of Auxinin plant
₪DestructionofauxinsduetoOxidationbyO
2inthepresence
oftheenzymeIAA-oxidaseorperoxidase.
OxidationinvolvesremovalofCO
2fromthe
carboxylicgroupofauxin(IAA)andresultsintheformation
of3-methyl-oxindole.
₪Inactivationofauxinsinplantsbyitsconversionfreeform
intoboundformiscalledboundauxinorconjugatedauxin;
inwhichauxinisconjugatedtoavarietyofsubstancessuch
ascarbohydrates,aminoacids,proteinsetc.
₪RapidinactivationofauxinmayoccurbyirradiationwithX-
raysandgammaraysandUltravioletlight.

555. 1. IBA : IndoleButyric Acid
2. NAA : Naphthalene Acetic acid (αand β)
3. MENAA: Methyl ester of Naphthalene acetic acid
4. MCPA: 2 -Methyl -4 -chlorophenoxyacetic acid
5. TIBA : 2, 3, 5 -Tri iodobenzoic acid
6. 2, 4-D : 2, 4-dichlorophenoxyacetic acid
7. 2, 4, 5-T: 2, 4, 5 –Trichlorophenoxyacetic acid
8. Picloram: Tordon

556. 1.Apicalbuddominance–Inhibitionoflateralbuds
2.Cellenlargementandelongation-Strafford(1967)statedthatAmylaseactivity,
Permeability,ATPformation,cellwallplasticityisincreasedandviscocity&wall
pressureisdecreased
3.AcidgrowthHypothesis:AuxinissuggestedtoactivateH+/K+pump,soK+enterin
cellinexchangeofH+whichbreakacidlabilebondsandactivatewallhydrolysis
enzymeswhichrenderthecellwallsoft.
4.Cellwallsynthesis:Auxinincreasetheactivityofcellulosesynthetaseresponsiblefor
synthesisofwallmaterialsduringcellexpansionandsomeotherenzymesnamely,
catalase,invertase,amylase,cellulaseetc.ItalsopromotemRNAdirectedprotein
synthesis.
5.Vasculardifferentiation:Auxinhelpsinestablishingthecontactbetweenxylemand
callustissueforproducingnewshootafterbudgrafting.
6.Nucleicacidactivities:Setterfield(1963)reportedIAAincreasetotalRNAsynthesis
activitiesandsomespecificenzymes.IAAactsuponDNAtoinfluencethe
productionofmRNA.ThemRNAcodesforspecificenzymesresponsiblefor
expansionofcellwalls(Wlikins,1969).
7. Manifold activities: Listed in next slide

557. 1. Seed germination
2. Root initiation & Root growth
3. Uniform Flowering –Tobacco, Mango, Pineapple and lettuce -NAA
4. Parthenocarpy-Grapes, Cucumber, Watermelon, Brinjal-NAA, IBA
5. Control Fruit setting and quality, mechanical harvesting of fruits
6. Prevention of premature drop of fruits
7. Tissue and organ culture
8. Eradication of weed –Selective killers-2,4-D, 2-4,5-T, MCPA, Picloram
9. Auxinsas growth inhibitor: At high concentration
10. Development of fruits and seeds
11. Callus formation
12. Auxinpromote ethylene production
13. Sex expression –Promote female flowering -Cotton
14.Respiration-RapidlysupplyofATPAbscission
15.Defoliationofplants
16.Inhibitionofprolongeddormancy

558. Role of Auxins
Apical Dominance –Growth is like a Christmas Tree
1

559. Removal of
apical bud
Growth of
lateral buds
Apical bud
lateral
buds
Thimann&Skoog(1933)notedthatauxin
inhibitslateralbudformation.Ifapicalbud
isremoved,lateralbudssprout,this
phenomenonisreferredasapicalbud
dominance.
1

560. Controlling leaf Abscission
3

561. Vascular differentiation5

562. Parthenocarpy

563. Sex Expression:
In cucurbits (Monoecious)
applicationofAuxinreducemale
flowersandincreasefemaleflower.
InHemp (dioecious)auxin
induceproductionoffemaleflowers
onmaleplants.

564. Cell enlargement and Cell
Elongation:
AuxinstimulateCellenlargementand
CellElongationandintheapical
region.
Because Auxinincreases:
Cell permeability
Cell wall plasticity

565. Tissue Culture Propagation
Auxin:CytokininRatio
 High–LowRootformation
 Low–HighShootsformation
 EqualCallusformation

566. Actinomycin–D
Puromycin
Chloromphenicol
Transcinnamicacid
Naphthylthalamicacid(NTA)
CCC

567. 1.Auxincauselooseningcellwall.
2.IAAcauseorganbending.
3.Removalofapicalbudthelateralbudsstarttheir
growthanddevelopment.
4.Auxinsappliedinmonociousplants.
5.Nodulesareformedinleguminousplants.
6.Auxinscanbeusedasaherbicides.
7.Auxinmovementisbasipetal.
AUXIN

569. Itisasecondimportanthormonefoundinplants.
Konishi(1898)-AJapanesefarmerfirstknownGibberellin.
AJapanesescientistKurosawa(1926)foundthatthericeseedlingsinfectedby
theascomycetefungusGibberellafujikuroi(F.moniliforme).
Theinfectedseedlingsgrowverytall,thinandturnedpaleyellowincolor.Itis
alsoknownas“FoolishseedlingofRiceorBakanaediseaseofrice”.
Yabuta,HayashiandKahnbe(1935)firstisolatedactivesecretedprinciple
substance(GA)fromfungus.Anactivesubstancewasisolatedfromthe
infectedseedlingsandnamedasGibberellin.
YabutaandSumuki(1938)isolatedGibberellinsAandBincrystalformfrom
fungus.
WestandPhinney(1956)discoveredGAsasnaturalproductofplants
MacMillanandSuter(1958)isolatedGiberellicacidfirsttimefromimmature
seedsofPhaseoluscocineus.

570. Extremely
elongated
seedlings of rice
is called
“Foolish seedling
of Rice”

571. They are characterized by the following features:
1.Prevention of genetic and physiological dwarfism.
2.Breaking of domancy
3.Induce flowering in long day plants
4.Increase amylase activity
5.Substitute for chilling effect

572. Chemistry of Gibberellins
Giberellinarecyclicditerpenes.
Chemicallyrepresentedbymolecular
formulaesuchasC
19H
24O
6(GA
1),C
19H
26O
6
(GA
2),C
19H
22O
5(GA
3)etc.
Morethan110differentGibberellinsare
knownandarenamedasGA
1,GA
2,GA
3
uptoGA
76…

25typesarereportedfromGibberellafujikuroi

51Typesarefoundinhigherplants.
Chemical Structure of Giberellic acid-3
H
H

573. Siteofsynthesisofgibberellins:
Gibberellinsaresynthesizedbyyoungleaves(Majorsite),roottipsandimmature
seed(embryo).
Distributionofgibberellins:
Gibberellinsmovesreadilyinalldirectionandalltissuesincludingphloemand
xylem.
McComb(1964)reportedthatGAmovesthesametypeasthecarbohydrate
translocatesystemwithsimilarvelocity(5cm/hr).
Theyfoundinallpartsofhigherplantsincludingshoots,roots,leaves,flower,
petals,anthersandseeds.Ingeneral,reproductivepartscontainmuchhigher
concentrationsofgibberellinsthanthevegetativeparts.
Itispassive,no-polaranddiffusetype.
Immatureseedsareespeciallyrichingibberellins(10-100mgpergfreshweightof
theseeds).
Inplants,gibberellinsoccurintwoformsfreegibberellinsandboundgibberellins.
Boundgibberellinsusuallyoccurasgibberellin–glycosides.

574. 1.Apicalbuddormacy–Incertaincases,dormancyregulatedbyGibberellinsvia
counteractingeffectofendogeneousgrowthretardantdorminandceasemeiotic
activity.Coldtreatmentbreakthedormancy.
2.Roleofsub-apicalmeristem:Itregulatemitoticprocessesinthisregion.growth
retardantAMO1618ceasecelldivisionanddwerfingofstembutisrestoreby
Gibberellins.
3.Cellelongation–InteractionoflightandGibberellinsindicatethatredlightdwarfpea
was37mminht,ButwhentreatedwithGA1&GA3,itattained120cmhtthat
showedenhancementofcellelongation.
4.Fruitgrowth:Crane(1964)producednormallookingfruitsfromunfertilizedflowerof
tomato,appleandpeachesusingGibberellins.
5.Flowering:Lang(1960)demostratedthataddedgibberellinsatproperstageof
hyoscyamusniger(longdayfloweringplant)causedfloweringonshortdaysas
gibberellinsflorigensynthesisedthroughGA.
6.Seedgermination:GAsynthesisinscutellum(cotyledon)andstimulatetheenzymeα
–amylaseandotherhydrolyticenzymesaswellasgluconeogenicenzymes
(Meanssynthesisofsugarfromsubstancesotherthancarbohydrate).Infat-rich
seed,sourceofsugarislipid.
7.Metabolismoffoodinseedstoragecells:AkazawaandMiyata(1982)suggestedthat
GAstimulateconversionofstoragepolymersintosucroseandothers.

575. 1. Seed germination:
2. Root initiation & Root growth:
3. Leaf expansion :
4. Hyponasty of leaves: GA3 treated chrysanthemum leaves more erect.
5. Flowering: –Sex expression –Increase male flowers in Maize and other crops
6. Parthenocarpy-tomato, apple and peach
7. Increase Fruit setting: Krishnamurthiet al. (1959) increase Fruit setting in pusaseedless grapes.
Increase size of fruits, Increase sugar yield, control creaking in fruits
8. Decrease Fruit drop: Reduction in fruit drop in citrus reticulata.
9. Stem elongation: Elongation of internodes thereby increase plant height in sugarcane, tobacco,
pea, bean, tomato, sweet corn, lettuce. Role of leaf expansion.
10. Pollen germination: Ethirajanet al. (1963) stated that in sugarcane, normally pollens are not
germinate, but pollens treated with GA3 are germinated. similarly, pollen tube growth
accelerated in Vincaroseaand Eichhorniacrassipes.
11. Breaking Dormancy : GA application helps in breakingof bud and seed Dormancy in potato.
12. Commercial uses of GA:
Boltingandflowering
GA3useinbreweriestoincreaserateofmaltingandsugarcontentinsugarcane.
GA3Preventrinddisordersduringstorage(Barley).
Increaselatexproductioninrubbertrees.
Thompsonseedlessgrapeandlesssusceptibletofungalinfections.

576. 1.Seedgermination-Synthesisoftheenzymeα–amylase.
2.BreakingDormancyofbuds-Inhibitactivityofdormin.
3.Sexexpression–Increasemaleflowers
4.Boltingandflowering
5.GA3enhanceGluconeogenesis(synthesisofsugarfrom
substancesotherthancarbohydrate)
6.Parthenocarpy–tomato,appleandpeach
7.Elongationofinternodes&Increaseplantheight,leaf
expansion,sizeoffruits,Increasesugaryield,control
creakinginfruits
8.GA3useinbreweriestoincreaserateofmalting
9.GA3Preventrinddisordersduringstorage(Barley).
10. Hyponasty of leaves
11. Induces pollen germination in sugarcane
12. Increase latex production in rubber trees

577. Definition:
Bolting:Itisprocessinwhichstemelongates
rapidlyandisconvertedintofloralaxis
bearingflowerprimordiaduetoapplicationof
gibberellinsevenundernon-inductiveshort
daysiscalledbolting

578. Gibberellins and Fruit Size
•FruitFormation:
•"ThompsonSeedless"grapesgrownin
CaliforniaaretreatedwithGAtoincreasesize
anddecreasepacking.

579. Therearenumbersofsyntheticcompoundswhichprevent
thegibberellinsfromexhibitingtheirusualresponsesinplants
suchascellenlargementorstemelongation,hencetheyare
calledasantigibberellinsorgrowthretardants.
1. Phosphon-D 4. AMO –1618
2. CCC 5. Ancymidol
3. Peclobutrazol(Cultar) 6. B-9
•B-9 : N -dimethyle-amino succinicacid
•AMO –1618: Ammonium TrimethylChloride Carboxylate
•Phosphon-D: 2,4-Dichloro-benzyl TributylPhosphoniumChloride

580. GIBBERELLIN AND AUXIN INTER -RELATIONSHIP:
No.ResponseofPlant Auxins Gibberellins
1Polartranslocation ? ?
2Promoterootinitiation ? ?
3LateralbudsinhibitionorApical
dominance
? ?
4LeafAbscissiondelay ? ?
5PreventDwarfism
(Genetic&Physiological)
? ?
6Seedgermination&Breakingof
Dormancy
? ?
7Inductionoffloweringinlongday
plant
? ?
8Promoteelongationofcells ? ?

581. GIBBERELLIN
1.GA3playsanimportantroleinseedgermination.
2.GA3promotesfloweringinlongdayplants
3.GA3isappliedforsexexpressionincucurbites.
4.GA3isappliedongrapesanditsbranches…..
5.GA3isusedbybreweries.

583. Skoog(1955)demonstratedthatwhenpithtissuesofNicotianatabacumwere
separatedfromvasculartissuesandthesevasculartissuesgrewinauxin
containingmediumthatshowedonlyenlargementwithoutcelldivision.Butagain
pithtissuesplacedincontactwithvasculartissuesresumed/startedcelldivision.
Thisobservationprovedpithtissuecontaincytokininsresponsibleforcelldivision.
Thechemicalsubstancewasidentifiedas6-furfurylamino-purine.
Miller,Skoog,SaltzaandStrong(1955)isolatedsubstancefromherringspermDNA
andnameditKinetin.
Letham(1963)proposedtheterm,cytokinin.
FairleyandKingour(1966)usedtheterm,phytokininsforcytokininsbecauseof
theircrucialroleinplantorigin.
Varioustermshavebeenusedforkinetin-likesubstancesuchasKinetenoidand
phytocytonin.
NaturallyoccurringcytokininsareKinetin,Zeatin,Zeatin-riboside,Zeatinribotide,
Dihydro-ZeatinandIsopentyladenine
SyntheticcytokininsareBenzyladenine(BA)and6-BAP(6-Benzylaminopurine),
Thidiazuron.

584. They are characterized by the following features:
1.Initiation of cell division
2.Delay of senescence ( Richmand-Lang effect) –Working
with Xanthium
3.Use in tissue culture
4.Counteract apical bud dominance
5.Induces flowering in short day plants

585. Chemistry of Kinetin
KinetinisChemicallyrepresentedby
molecularformulaesuchasC
10H
9N
5O.
Strong(1956)suggestedthatkinetinwas
anadeninebearingafurfurylsubstituent
at6position.
Milleretal.(1965)proposedmethylon
furanringorasamethyleneradical
betweenfuranandpurinenuclei.
Chemical Structure of Kinetin

586. Chemical Structure of cytokinins

587. NATURALLY OCCURRING CYTOKININS FOUND IN PLANTS:
No.Short Name Chemical Name
12 ip 2-Isopentyl
22iPA 2-Isopentyl adenine
3Cis–ribosyl-zeatin9-B-D-ribo-furanosylpurine
4Zeatin 6-(4-Hydroxy-3-Methyl-2-trans-butenyl-aminopurine)
purine
5Ms 2iPA 6-(-3 Methl-2-butenylamino)-2-Methylthio-9-B-D-
ribofuranosylpurine
6Ms-ribosyl-zeatin6-(4-Hydroxy-3-Methyl-1-2-butenyl-amino)-2-Methylthio-
9-B-D-ribofuranosylpurine
7Dihydro-Zeatin6-(-3-Mehtyl-4 butenyl-aminopurine) purine
Severalsubstanceshavecytokinin-likeactivitiessuchaskinetin,6-aminopurine
(adenine),6-benzimadazole,6-benzyladenine(6-BAP),1-benzyladenine
consideredassyntheticcytokinins.
SYNTHETIC CYTOKININS :
Note: *kinetin is not generally accepted as natural occurring substance found in plants.
Some cytokinins reported in tRNAof wheat germ & yeast. Zeatinribosidefound in
coconut milk.

588. Extractedfromcoconutmilk&tomatojuice
FlowersandfruitsofPyrusmalusPear,plumandbhendi
CambialtissuesofPinusradiataPeach,Eucalyptus
regnansandTumourtissuesofNicotianatabacum
ImmaturefruitsofZeamays,Juglanssp.(Blackwalnut)
andMusasp.
FemalegametophytesofGinkgobiloba
Fruitlets,embryoandendospermsofPrunuspersica
SeedlingofPisumsativum
RootexudatesofHelianthusannuus

589. Siteofsynthe=sisofcytokinines:
cytokininesaresynthesizedbyroot,alsoreportsforbasipetal
movementinpetioleandisolatedstem(Osborne&Black,
1964).
Distributionofcytokinines:
Kende(1965)statedthatcytokininesmovesupwardperhaps
inxylemstream.
Sethandhiscoworkers(1966)reportedthatauxinsenhances
kinetinmovementinbeansstems.

590. 1.CelldivisionandDifferentiation:
IAAaloeproducesafewmitosesintobbacopithtissuebutkinetinincombinationwit
IAAinducedmanymitoses.
Cytokininsalmostneveractsalone.Inconjunctionwithauxins,itstimulatecelldivision
eveninnon-meristematictissues.
2.Cellenlargement:CellenlargementbyCytokinins,effectisdoubledincombinationwith
auxins.Similarresultswereobtainedintobaccopithandcorticalcellsoftobbacoroots
(Aroraetal.,1959).
3.Morphogenesis:Skoog&Miller(1957)observedmorphogenesisthatwhenbalanced
levelofIAA+KCallusinductiontobaccopithtissueandifbalanceisaltered;(Low
IAA/HighK)Regeneration,(LowK/HighIAA)Rootformationoccurinsomesp.
4.BreakingofDormancyofseeds:TheseedsofLactucasativarequiredredlightfor
breakingofDormancybutthiseffectisoverpoweredbytheapplicationofkinetin.
SimilarlyintheseedsofXanthiumpennsylvanicum,carpetgrass,tobaccoreportedby
Khan(1964)..
5.Removalofapicaldominance:WiksonandThimann(1958)foundthatcytokinins
counteract(Controversialeffect)theusualapicaldominanceofbudcontainhighauxins
andinducelateralbudformationwithvasculardifferentiation.
6.Initiationofinterfascicularcambium:Sorokinandhiscoworkers(1962)observed
kinetininduceinterfascicularcambiuminpeastemsections.

591. 7.Richmand-Langeffect(1957):ItisalsoreferredasDelayofsenescenceworkingwith
attachedleavesofXanthium,disappearanceofchlorophyllanddegradationofprotein
withagingyellowleaves.Buttreatedtheseleaveswithkinetinwerebecamegreenafter
theperiodof20days,thatindicateskinetindelayofsenescence.
8.Mobility:SachsandThimann(1964)statedthatcytokininsarepracticallyimmobilein
plantbutexogenousapplicationonbudtipvisualizeditsmovementpolar&basipetal
direction.
9.Nucleicacidmetabolism:Guttman(1957)foundquickresponseofincreaseamountof
RNAinnucleiofonionroot;similarly,DNAisrapidincreaseintobaccopithcellsafter
kinetintreatment.
10.Proteinsynthesis:Proteinsynthesistakeplaceinlargequantityinmeristematiccells
whentreatedwithkinetin.Thepresenceofseveralnucleotidesaspotentcytokininsin
tRNAprovidessupportinProteinsynthesis.
11.IncorporationofRNAfromnucleustocytoplasm:FordandSrivastava(1966)indicated
thatplanttissuerequiringcytokininsincorporatetheRNAfromnucleustocytoplasm.
12.Cytokininsandflorigines:Maheshwari(1982)shownthatcytokininisabundantin
floweringofshortdayplants(Duckweed,Spirodela,Lemna,Wolffia)whichappearsas
afloriginsinplant.
13.Commercialapplications:listedbelow

592. 13. COMMERCIAL APPLICATIONS:
1)Increaseselflifeoffruits&flowers
2)Quickeningofrootinductionandproducingefficientrootsystem.
3)Increasingyieldofcrops.
4)Increasingoilcontentinseedslikegroundnut.
5)SynthesisandAccumulationofaminoacids,phosphates&other
substancesandtranslocationofsolutes-Predominantlypolar
6)Cytokininsprovideresistancetoextremelyhightemperature,coldand
diseases;
7)Synthesisofseveralenzymesinvolvedinphotosynthesis.

594. Nelijubou(1901)statedthatethylenegasaltertheTropistic(negative
phototropism)responsesofroot.
Inblueorwhitelight,rootsexhibit,butredlightinducespositivephototropism.In
thefloweringplantArabidopsis,thephotosensitivepigmentsphytochromeA
(phyA)andphytochromeB(phyB)mediatethispositivered-light-based
photoresponseinrootssincesinglemutants(andthedoublephyABmutant)were
severelyimpairedinthisresponse.Whileblue-light-basednegativephototropismis
primarilymediatedbythephototropinfamilyofphotoreceptors,thephyAand
phyABmutants(butnotphyB)wereinhibitedinthisresponserelativetotheWT.
Denny(1924)suggestedthatehyleneishighlyeffectiveininducingfruitripening.
Gane(1934)establishedrelationshipbetweenethyleneandinductionofripening
offruits.
PrattandGoeschi(1969)hadfirstreportedthatripeninginclimactericfruitsis
duetoemissionofEthylene.

595. Chemistry of Ethylene
Ethylene(IUPACname:ethene)is
ahydrocarbonwhichhastheformulaC2H4or
H2C=CH2.Itisacolorlessflammablegaswitha
faint"sweetandmusky"odourwhen
pure.[4]Itisthesimplestalkene(a
hydrocarbonwithcarbon-carbondouble
bonds).
Chemical Structure of Ethylene

596. ♠Itisastageoffruitripeningassociatedwithethylene
productionandcellrespirationrise.
♠Maximumrespirationratejustbeforesenescenceinmanyfleshy
fruitsiscalledClimactericrise.
♠Climactericisthefinalphysiologicalprocessthatmarkstheend
offruitmaturationandthebeginningoffruitsenescence.
♠Itsdefiningpointisthesuddenriseinrespirationofthefruit
andnormallytakesplacewithoutanyexternalinfluences.After
theclimactericperiod,respirationrates(notedbycarbon
dioxideproduction)returntoorbelowthepointasbeforethe
event.
♠Theclimactericeventalsoleadstootherchangesinthefruit
includingpigmentchangesandsugarrelease.
♠Thefruitsareusedasfoodpurposewhentheclimactericevent
ispeakandtheiredibleripeness.Atthisstage,fruitshavingthe
besttasteandtextureforconsumption.
♠Aftertheeventfruitsaremoresusceptibletofungalinvasion
(diseases)andbegintodegradewithcelldeath.

597. No. Climacteric fruit No. Non-climacteric fruits
1.Climactericfruitsenteringin‘climacteric
phase’evenafterharvesti.e.theycontinueto
ripen.
1.Non-climactericfruitsonceharvesteddonot
ripenfurther.
2.InClimactericfruits,Duringtheripeningfruits
emitethylenewithincreasedrateofrespiration.
2.InNon-Climactericfruits,therateofrespiration
remainssteadyduringtheirripening.
3.InClimactericfruits,theperiodofoccurrence
ofclimactericpeakinfruitsshowsvariationin
differentfruitspecies.Bananaclimacteric
(ripening)rapidlythanappleandmango.
3.InNon-Climactericfruits,periodofoccurrence
ofclimactericpeakinfruitsissameinallfruit
species.
4.Thesefruitsareharvestedhardandgreenin
color,butharvestedfullymaturewhen
transportedtonearconsumptionareas.
4.Generally,Thesefruitsareharvestedinsoftand
inripenstage.But,Inordertoimproveexternal
skincolorandmarketacceptance;citrusfruits
likeorange,lemon,mousambiandkinnowcanbe
treatedwithethylene,asade-greeningagent.
5.Climactericfruitsproduceveryhighamountof
ethylenewithinafruits.
5.Non-climactericfruitsproduceverysmall
amountofethylenewithinafruits.
6.Smalldoseofethyleneisusedtoinduceripening
undercontrolledconditionsoftemp.&
humidity.
6.Highdoseofethyleneisrequiredtoinduce
ripeningprocess.
7.Climacteric fruits are:
*Mango*Banana*Papaya*Guava*Sapota
*Kiwi*Fig*Apple*Passionfruit*Apricot
*Plum*Pear.
7.Non-climactericfruitsare:
*Orange,*Lemon,*Mousambi *Kinnow
*Grapefruit*Grapes*Pomegranate*Litchi
*Watermelon*Cherry*Raspberry*Blackberry
*Strawberry*Carambola*Rambutan*Cashew.

598. Membranepermeability:Ethyleneincreasecell
permeability
Nucleicacidandproteinmetabolism:
Tissuestreatedwithehyleneenhancetheactivities
ofgenes,synthesisofmRNAandenzymessuchas
cellulase,chlorophyllase,protease,amylase,
catalase,peroxydase,invertaseandothers.
Reductioninauxinmetabolism:Itreduces
biosynthesisofauxinsandinhibitsitstransportfrom
siteofsynthesis.

599. Ethyleneisremainintheplantasagaseousformat
normaltemperaturesunderwhichaplantcanlive
hence,itisdifficulttovisualizedandvery
complicatedtodeterminethathowitisdistributed
intheplant.
Butnowdays,itiswellknownthatitisproduceby
flowers,leaves,stems,roots,tubersandseeds.

600. 1.Abscission:Ehyleneisaprincipalacceleratorofabscission.Itcauseabscissionby
promotingcellwalldestroyingenzymes.Hence,itiscalledasphytogerontological
hormone.
2.NaturalRipeningandclimactericrise:Ehyleneleadstocellpermeability
Degradationofphospholipidcausedbyanincreaseintheactivityof
phospholipase.
ClimactericriseSeenearlierslides.
3.Activationofmalicenzymeandpyruvatedecarboxylaseenzyme:Duringclimecteric
rise,CO2productionisincreasethusRQvaluealsoincreases.Thissystemshown
tobedecarboxylationofmalicandpyruvicacidscatalyzedbyboththeenzymes.
Climactericrespirationisinsensitivetocyanide.
4.Degreeningofcitrusandbananafruits:Greencitrusandbananafruitsarenot
acceptableinmarket,thereforeartificialDegreeningisrequired.InUSA,
degreeningisdonebyethylenetreatment(5-10ppm)inanair-conditioned
room,hencethismethodiscalled‘Tricle’method.
5.Chlorophyllaseactivity:EthyleneincreasetheChlorophyllaseactivitywhichleads
toDegreening.
6.Ripening:Ripeningandmaturityoffruitsaretwobasicpropertiesofthisgas
hormone.UniformRipeninginpineapple,fig;inducedfruitinginornamental
plantsandpre-harvestdefoliation.

601. 1.Hastenstheripeningoffleshyfruitsex.Banana,tomatoes,citrus,pearsetc.
2.Itisusedassugarcaneripener.
3.Itpromoteslatexproductioninrubberplant.
4.Sexexpression-↑numbers♀flowers
5.Itreleaseseeddormancyandimprovedseedgermination.
6.Itimprovenutqualityinwalnutfruits.
7.Itpromotesbulb,tubersandrhizomeformation.
8.Itusedasafruitthinner.
9.Itpromotesfemaletomaleratioincucurbites.
10.Breakingdormancyofseeds,tubersandbulbs
11.Preventionofsproutinginonion.
12.Itstimulatessenescenceandabscissionofleaves
13.Itiseffectiveininducingfloweringinpineapple
14.Itcausesinhibitionofrootgrowth
15.Itstimulatestheformationofadventitiousroots
16.Itstimulatesfadingofflowersandinhibitflowering
17.Itstimulatesepinastyofleaves

603. Abscissicacidisanaturallyoccurringgrowthinhibitorandacceleratorsof
abscission.
Hemberg(1949)observedthepresenceofsubstanceresponsibleforthe
growthinhibitoryactivitiesinplants.
Adicott(1963)isolatedAbscissinIfromtheburrsofmaturecottonfruits
andanotherasubstancestronglyantagonistictogrowthfromyoung
cottonfruitsandnamedAbscissinII.Laterontwonamesofsame
compoundwaschangedtoAbscissicacid.
Wareing(1965)identifiedthesubstanceinAcerpsuedoplantanusleaves
andbudsthatinducesdormancyinbudsthereforegavethenamedas
Dormin.
ABAissesqui-terpenoid,(Sesquiterpenes,areanimportantconstituent
ofessentialoilsinplants)itfoundinallplantsexceptalgae,bacteriaand
liverworts.

604. Chemistry of Abscissic acid
ABApossessasymmetricalcarbonatom
thereforeexistaseither(+)or(-)
enantiomers.
Naturally,occurringABAisalwaysin(+)
andactiveform(2-cis-ABA)than2-
trans-ABAisnotbiologicallyactivebutit
canbetransformedintocisforminthe
presenceofultravioletrays.
Chemical Structure of
Abscissic acid

605. Wareingandhisco-workers(1965)observedthat
inAcerpsuedoplantanusandRibesnigrumABAis
manufacturedinmaturedleavesandmoveup/
transportedtoshootapexthroughxylemandphloem
andalsoinparenchymacellsoutsidethevascular
bundles.
Inleaves,itissynthesizedfromdegradationof
carotenoidspigmentpresentinchloroplast.
ItisNopolarityintransports.

606. 1.Inducebuddormancy:Wareingandhisco-workers(1965)observedthatinbirch,sycamore
(Acerpsuedoplantanus)andblackcurrent(Woodytrees)ABAinducedormancy.Theendogenous
levelofabscissicacidisinfluencebydaylengthandchillingeffect
2.Senescence:WareingandHillman(1967reportedthat)Senescenceofisolatedexcisedleafdiscs
ofAcerpsuedoplantanusispromotedbyABA.NaturalleafSenescencedeterminedbyABA.
3.Abscession:Adicottandhiscoworkers(1964)observeduniversalroleofABAaccelerateleaf
abscissionincottonplants.
4.Flowerinitiation:Incertainshortdayplantssuchasribesnigrum,PharbitisnilandFragaria,
ABAinducesfloweringduringshortdaysandinhibitsfloweringinlongdayplants.
5.Stomatalphysiology:ABAalterplasmamembranebyaffectingchangesinbioelectrical
potentialacrossthemandeffluxofK+ions.
6.Releaseofethylene:ABAstimulatereleaseofethylene.
7.CounteractGA:Suchasinductionofhydrolases,amylaseactivitiesinbarleyseedlings,these
effectmaybeduetoDNAdependentRNAsynthesiswhichmayacceleratedbyGA.
8.StressHormone:ABAisalsoactasstresshormonehelpingtheplantstocopewiththeadverse
environmentalconditionssuchasmoisturestress,flooding,injury,mineraldeficiencyetc.

607. 1. Geotropism in roots
2. Stomatalclosing: Defense against moisture, salinity,
chilling and freezing stress
3. Besides other effects:
i. Induce bud dormancy and seed dormancy
ii. Induce flowers & tuberisation
iii.Induces senescence of leaves, fruit ripening, abscission of
leaves, flowers and fruits
iv.Increasing the resistance of temperate zone plants to frost
injury
iv.ABA stimulates and release of ethylene
v.Induction of red coloration in tomato

609. Brassinosteroids(BRs)areaclassof
polyhydroxysteroidsthathavebeenrecognizedasa
sixthclassofplanthormones.
Brssinswerefirstexplorednearlyfortyyearsago
whenMitchelletal.reportedpromotioninstem
elongationandcelldivisionbythetreatmentof
organicextractsofrapeseed(Brassicanapus)pollen.
Andnowfoundintea,beanandrice.
Brassinolidewasthefirstcompoundisolated
brassinosteroidin1979.
10mgyieldofbrassinosteriodsrequired230kgof
Brassicanapuspollengrains.
Sincetheirdiscovery,>70BRcompoundshavebeen
isolatedfromplants.
HISTORYOFBRASSINOSTEROIDS

610. Chemistry of brassinosteroids
Brassinosteroidsarehydroxylated
derivativesofcholestaneandtheir
structuralvariationscomprisethe
substitutionpatternatringsAandBas
wellastheC-17sidechain.Theycanbe
classifiedasC
27,C
28,and
C
29compounds,dependingonthealkyl-
substitutionpatternofsidechain.Upto
now65freebrassinosteroidsand5
brassinosteroidconjugateshavebeen
characterized.
Chemical Structure of
brassinosteroids

611. •Promotecellexpansion(cellelongation),Celldivisionand
cellwallregeneration.
•Promotevasculardifferentiation.
•Promotepollenelongationforpollentubeformation.
•Protectiontoplantsduringchillinganddroughtstress.
•Delayedsenescence
IMPORTANCE OF BRS IN NUMEROUS PLANT PROCESSES:

612. PHYSIOLOGICAL EFFECTS OF BRASSINOSTEROIDS IN
PLANTS:
No. Cell level Whole plant level
1Stimulationofelongation
andfission
Growthpromotion
2Effectonhormonalbalance Increaseinthesuccessoffertilization
3Effectonenzymeactivity;H.-
pumpactivation
Shorteningtheperiodofvegetative
growth
4Activationofproteinand
nucleicacidsynthesis
Sizeandquantityoffruitsincrease
5Effectontheproteinspectrum
andontheaminoacid
compositionofproteins
Effectonthecontentofnutritive
components
andfruitqualityimprovement
6Enhancement of the
photosyntheticcapacityand
oftranslocationofproducts
Cropyieldincrease

614. 1.Triacontanol:ItsaturatedalccholIsolatedfromshootsofalfalfa.20%growthis
enhancedinfoliageofseedingofmaizeandrice.
2.Salicilicacid(2-hydroxybenzoicacid):Responsibleforproductionofaromainleaf
&inflorescenceforattractpollinators.Italsoconferdiseaseresistanceintobacco–
TMVandnecrosisvirus.
3.Turgorines:Responsiblefornyctinasticmovement(sleepingindaylikenight)eg.
Mimosa,acasialeavescontrolledbyactivationofpulvinibyturgorinessubstance.
4.Traumaticacid:WoundHormone:Itisextractedduringwoundorinjuryinplant
whichstimulatemeristematicactivitiesofcorkcambiumtocoverthewound.
5.Florigen:Itisreponsibleforinitiationoffloweringinplants.Itsynthesisinolder
leavesandtransferredtoflowerbudgrowingregions.Florigen=GA3+A
(Anthesin).SynthesisofFlorigendependsondurationoflight.
6.Anthesins:Newlydiscoveredgroupanditisresponsibleforflowerformation.
7.Vernalin:Asubstanceisformedduringvernalisation.
(A)NaturalGrowthPromoters:

616. (A)NaturalGrowthInhibitors:
(A)Batasins:Itispresentinyam(Discoreabbatatus)plants.Itcausedormancyof
bulbils.i.e.continuevegetativegrowthandswellingofaeriallateralbuds.
1.Jasmonicacid:Itispresentinoilofjasmine,promotesleafsenescence.
2.Lunularicacid:Presentinliverworts(non-vascularssuchasmosses,Bryophytes)
whereitpreventgerminationofgemmebeforefallfrommotherplant.
3.Xanthoxin:PotentgrowthinhibitorthatconvertviolaxanthinintoABA.
4.Uniconazole:Retardsboltinginradish
5.Paclobutrazol:Suppressionofgrowthofleavesandstemse.g.rice.
6.Dormin:Growthinhibitorderivedfromsycamore(figsp.ofAfrica)leaves.
7.AbscisinII:Isolatedfromcottonfruits(Ohkumaetal.,1963)
9.Phaseicacid:Presentinseedsofbean(Phaseollusmultiflorus)
10.Theospirone:Naturalinhibitorintealeaves.
11.Juglone:Alactonepresentinrootsofblackwalnut&hennaleaf.
12.Unidentifiedtoxin:Buffalogourd(Cucurbitafoetidissima)weedyvineinsemiarid
causeallelopathyinrhizosphere.
13.Chlorogenicacid:FoundinGreencoffeebeans-anantiseptictobacteriainplant
wounds.
14.Terpenoid,suchasABA
15.PhenolicandBenzoicacidderivativesandlactonesfoundinmostofplants.

617. Buffalogourd (Cucurbita
foetidissima)weedyvinein
semiaridcauseallelopathyin
rhizosphere.

618. (B)Artificial/SyntheticGrowthInhibitors:
1.Cycocel:(2-chloroethyltrimethylammoniumchloride(CCC)reduceplantheightin
cotton.
2.Phosphon-D:(2,4–dichlorobenzyl–tributylphosphoniumchloride):Shortenthe
lengthofinternodesinflax.
3.AMO–1618:Reducethestemlengthinmanycerealgraincrops.
4.Morphactins:Chloroflurenol,Chlorflurun,Flurenol,Methylbenzilate,
Dichloroflurenol.Allareresponsibleforinhibitseedgermination,seedlinggrowth
andstemelongation;DemorphogenesisinBegonia;induceflowering;Breakdown
ofapicaldominance.
5.Maleichydrazide(MH):Useasadefoliantsincottonthataidinmechanicalharvest
andcontrolsuckersintobacco.
6.TIBA:Regim-8,aninhibitortoIAAtransportcausemoreuprightleavesinsoybean
(Plantlikeachristmastree)thatharvestmorelightandpodandseedyieldis
increased.
7.SADH/Diaminozide(marketedasKylar):usedinrunnertypeofpeanutvar.Dixiein
USonlargescalethatreducelodging,curtaillatevegetativegrowthofvine
therebyincreaseyield.

619. 1.Reduceheightandinternodeselongationtoprevent
lodging.
2.TIBAinhibitsIAAtransportresultsinuprightleavesfor
betterlightpenetration.
3.Defoliantsfacilitatesmechanicalharvestingofcotton.
4.CCCenhancetillerformationandpreventlodgingin
wheatandbarley.
5.MHisusedforsuckerscontrolintobbaco
Peclobutrazol(Cultar)usedinsuckerscontrolin
banana.

621. 3
2
1
4

622. Thimann(1935) found that an amino acid, tryptophan is converted
into Indole3 acetic acid. Tryptophan is the primary precursor of IAA in plants.
Decarboxylationof tryptophan
Tryptamine
Indole-3-acetaldehyde
Deamination
Tryptophan decarboxylase
Tryptamineoxidase
Indole3-acetic acid (IAA)
Indole3-acetaldehyde dehydrogenase

624. Theprimaryprecursorfortheformationofgibberellinsis
acetate.(14stepsBiosynthesis)
→Acetate+COA→AcetylCOA
→Mevalonate5-phosphate(Mevalonicacid)→Mevalonatepyrophosphate
→Isopentanylpyrophosphate→Dimethylallylpyrophosphate
→Geranylgeranylpyrophosphatemonoterpene(GGPP)→Farnesyl
pyrophosphate(sesquiterpene)
→trans-Geranylgeranylpyrophosphate,diterpene(T-GGPP)→Copalyl
pyrophosphate
→Kaurene→Kaurenoicacid
→HydroxyKaurenoicacid→Aldehyde
→Gibberellins.(GA1toAllotherGAs–at19-20Centigrade)

625. Itisassumedthatcytokininsaresynthesisedasin
thecaseofpurinesinplants(nucleicacidsynthesis).
Roottipisanimportantsiteofitssynthesis.
However,developingseedsandcambialtissuesarealso
thesiteofcytokininbiosynthesis.
Kende(1965)reportedthatcytokininsmove
upwardsperhapsinthexylemstream.Theroot-produced
cytokininsaretransportedacropetallytotheshoottip.
However,basipetalmovementinpetiole.
Theprecursorfortheside-chainsofadeninein
cytokininsisgenerallyisoprene,sotheterpenoid
biosynthesispathwaysarepartiallysharedwith
gibberellins.Thematerialmadeinthiscaseisisopentenyl
pyrophosphate.

626. Di-methyl-allyl
pyro-phosphate

628. The immediate precursor of ethylene is Methionine. Chemically ethylene is called as 2-
Chloro-ethyl-phosphonic acid. The compound which liberate ethylene is called ethrel.
CH3 –S -CH2 –CH2 –CH (NH2) –COOH ---Methionine
Methional
FMN (Flavinmononucleotide) + Light
CH2 =CH2 Ethylene
Transminase
Butyric Acid
Peroxidase+
H2O2
Peroxidase+
H2O2
Flavin
EthylenemaybeformedfromMethionineeitherinthepresenceofTransminaseand
PeroxidaseorinthepresenceofFMNandPeroxidase.Boththeprocesses,hydrogen
peroxideisutilized.

629. AdamandYang(1977)haveworkedoutthepathwayforthebiosynthesisofethylene
fromaminoacidmethionine.
MethionineisactivatedbyATPtogiverisetoS-adenosyl-methionine(SAM)inthe
presenceofanenzymemethionineadenosyltransferase.
ThecompoundSAMinpresenceofenzymeACCsynthetasebreakintoS-Methyl-Thio-
Adenosine(MTA)andAmino-Cyclo-propaneCarboxylicacid(ACC).
ACCisfinelyconvertedintoethylene.
(SAM)

630. Arabidopsis thaliana.
TheformationofS-AdoMet (S-adenosyl
methionine)frommethionineiscatalysedbySAM
synthetaseattheexpenseofonemoleculeofATP
permoleculeofS-AdoMetsynthesized
(i).Arate-limitingstepofethylenesynthesisisthe
conversionofS-AdoMettoACCbyACCsynthase
(ii).MTA(methylthioadenosine)istheby-product
generated,alongwithACC,byACCsynthase.
RecyclingofMTAbacktomethionineconserves
themethylthiogroupandisabletomaintaina
constantconcentrationofmethionineincellseven
whenethyleneisrapidlysynthesizedandthe
methioninepoolissmall.MalonylationofACCto
malonyl-ACC(MACC)depletestheACCpooland
reducesethyleneproduction.
(iii)ACCassubstrateconvertintoethylene
catalysesbyACCoxidaseandgeneratescarbon
dioxide(CO2)andhydrogencyanide(HCN)
(iv).Cyanideismetabolizedbyβ-cyanoalanine
synthase enzyme toproduce non-toxic
substances.Transcriptionalregulationofboth
ACCsynthaseandACCoxidasebyhomeotic
proteinsindicatedbydashedarrows.
(ACC)
(MTA)
Thisreactionispresumedtobetriggeredbyethylene
formingenzyme(EFE)presentincellmembrane.
Aerobicprocessrequiringoxygenwhichislateron
convertedintowater.

631. Lightenhancestheoccurrenceofthemost
effectiveactivatedform,thecisformofABA
thatsuppress/inhibitthegrowth.
DeactivationofABAisoccurwhencisform
convertedintotransformofABA.
SynthesisofABArequirespresenceoflight.
However,wheatleaves,Avacadofruitshow
synthesisofABAindark.
ZEP=zeaxanthinepoxidase
VDE=violaxanthinde-epoxidase
Farnesylpyro-phosphate
Xanthoxinis precursor of ABA
(ii) Carotenoidpathway for
biosynthesis of abscissic acid
(i) Isoprenoidpathway for
biosynthesis of abscissic acid
Geranylpyro-phosphate
(Isopentylpyro-phosphate)
1
4
3
2
mutant in the tobacco gene (N.
plumbaginifoliaABA2)
ABA1(AT5G67030) locus of Arabidopsis
carotenoidand chloroplast regulation
ABA4locus (AT1G67080), a highly conserved
unique plastid membrane
DPA (Dihydrophasicacid
AAO3(ArabidopsisAldehydeOxidase-3), and
MCSU (LOS5/ABA3 and molybdenum cofactor
sulfurase).
DXP (1-Deoxy-D-Xylulose

632. ABA-GE = ABA Glucose Ester
NCED = 9-cis-epoxycarotenoid dioxygenase
ABA1= AT5G67030 locus of Arabidopsis
ABA2 = Mutant in the tobacco gene (N. plumbaginifolia)
ABA4 = Locus (AT1G67080), a highly conserved unique plastid
AAO3 = ArabidopsisAldehydeOxidase-3
MCSU = Molybdenum Cofactor Sulfurasemembrane-localized protein
DXP = 1-Deoxy-D-Xylulose-5-Phosphate
CCR-2 = Carotenoidand chloroplast regulation-2
DPA = Dihydrophasicacid
SDR = Short-chain alcohol dehydrogenase/reductaseencoded by
theAt ABA2gene

634. ABA is derived from
C
40epoxycarotenoidprecursors
throughanoxidativecleavagereaction
inplastids.
TheC
15intermediatexanthoxinis
convertedtoABAbyatwo-step
reactionviaABA-aldehydeincytosol.
Abioticstressessuchasdroughtand
saltactivatethebiosyntheticgenes
(italicized),probablythroughaCa
2+
-
dependentphospho-proteincascade
asshownontheleft.ABAfeedback
stimulatestheexpressionofthe
biosyntheticgenes,whichisalsolikely
through a Ca
2+
-dependent
phosphoproteincascade.
Among the biosynthetic
genes,NCEDisstronglyupregulated
bystress(indicatedwithathick
arrow),whereasSDRisregulatedby
sugar.
ABAbiosyntheticenzymesareshowninsmallovals.
TheNCEDstepprobablylimitsABAbiosynthesisinleaves(indicatedwithadashedarrow).
ZEP,zeaxanthinepoxidase;NCED,9-cis-epoxycarotenoiddioxygenase;AAO,ABA-aldehyde
oxidase;MCSU,MoCosulfurasearetransfactors,allareinducedbysugarstovariousextents.

635. Pro-plastidcanbetransmitted
intoEtioplastorLeucoplastor
Chloroplast.
Etioplastconvertedinto
Chloroplast.
Chloroplastchangeinto
Chromoplast.
Leucoplastisconvertedinto
AmyloplastorElaioplastor
proteinoplast.

636. Chloroplasts:
Theyareprobablythemostknownoftheplastids.Theseareresponsible
forphotosynthesis.Thechloroplastisfilledwiththylakoidscontaing
chlorophyll,whichiswherephotosynthesisoccurs.
Chromoplasts:
Thechloroplastsactuallyconvertovertochromoplasts.Thereare
carotenoidpigmentsallowforthedifferentcolorsyouseeinfruitsandthe
fallleaves.Oneofthemainreasonsistoattractpollinators.
Leucoplasts:
Theyarethenon-pigmented,colorlessorganelles.Theyarefoundinthe
non-photosyntheticpartsoftheplant,suchastheroots.Dependingon
whattheplantneeds,theymaybecomeessentiallyjuststorageshedsfor
starches,lipids,andproteins.
Leucoplastsarefurthersubdividedintothreedifferentplastids:
Amyloplastsarethelargestofthethreeandarechargedwithstoring
starch.
Proteinoplaststhathelptostoretheproteinsthataplantneedsandare
typicallyfoundinseeds.
Elaioplastsareusedtostorefatsandoilsthatareneededbytheplant,
specificallyinseeds.

638. Lecture -23

640. Itisdefinedas“avitalprocesswhichbringsaboutanincreasethatisanirreversibleor
permanentchangeinsizeform,weightandvolumeofcell,organorwholeorganism”.
OR
Plantgrowthdefinedasitisacombinationofprocessesofcelldivision,elongationand
differentiation.
GrowthRegions:
FirstKindofGrowthregionsinplantsaretheapicesofshootandroots.
Itisalsoknownasapicalmeristems,primarymeristemsorregionsofprimarygrowth.
Apicalmeristemsisresponsibleforincreasethelength,differentiationofvarious
appendagesandformationofplanttissues.
SecondkindofGrowthregions,Incaseofbambooandmint,increaseinlengthisoccurs
duetointercalarymeristemswhichareseparatedbypermanenttissue.
ThirdkindofGrowthregions,isregionoflateralmeristemwhichbringsaboutsecondary
growthtoincreasethethicknessofplantingirth(secondarygrowth).
Additional:
Growthisrestrictedonlytolivingcellsandisaccomplishedbymetabolicprocesses
involvingsynthesizeofmacromolecules,suchasnucleicacids,proteins,lipidsand
polysaccharidesattheexpenseofmetabolicenergy.
Growthatcellularlevelisalsoaccompaniedbytheorganizationofmacromoleculesinto
assemblagesofmembranes,plastids,mitochondria,ribosomesandothercellorganelles.
Cellsdonotdefinitelyincreaseinsizebutdivide,givingrisetodaughtercells.
AnimportantprocessduringcelldivisionissynthesisandreplicationofnuclearDNAin
thechromosomes,whichisthenpassedintothedaughtercells.Therefore,thetermgrowth
isusedtodenoteanincreaseinsizebycelldivisionandcellenlargement,togetherwiththe
synthesisofnewcellulosematerialsandtheorganizationofcelluloseorganelles.

641. PATTERNS & FEATURES OF PLANT GROWTH:
Growthinplantsisrestrictedtocertainzones,recentlyproducedby
celldivisioninameristem.Celldivisionalonedoesnotcauseincreased
size,butthedivisionofcellularproductsalsoincreaseinvolumeand
causegrowth.Rootandshoottips(apices)aremeristematicinnature.
Shoot system with apical meristem Root system with apical meristem

642. ADDITIONAL: EXAMPLES OF GROWTH IN PLANTS:
1. Germination: increase in length of radicleand plumule
2. Leaf growth: increase in size and number of leaf
3. Flower: increase flower number in inflorescence
4. Seed growth: increase seed size, weight after fertilization
MEASUREMENT OF GROWTH:
Growth can be measure by a variety of parameters as follows:
A. Fresh Weight:
Determinationoffreshweightisaneasyandconvenientmethodofmeasuring
growth.Formeasuringfreshweight,theentireplantisharvested,cleanedfordirtparticlesif
anyandthenweighted.
B. Dry Weight:
Theweightoftheplantorganisusuallyobtainedbydryingthematerialsfor21to48
hat70
o
Cto80
o
Candthenweighingit.Themeasurementsofdryweightmaygiveamorevalid
andmeaningfulestimationofgrowththanfreshweight.However,itmeasuringthegrowthof
darkgrownseedingitisdesirabletotakefreshweight.
C. Length:
Themeasurementoflengthisasuitableindicationofgrowthforthoseorganswhich
growinonedirectionwithalmostuniformdiametersuchasrootsandshoots.Thelengthcanbe
measuredbyascale.Theadvantageofmeasuringlengthisthatitcanbedonethesameorgan
overaperiodoftimewithoutdestroyingit.
D.Area:
Itisusedformeasuringgrowthofplantorganslikeleaf.Theareacanbemeasured
byagraphpaperorbyasuitablemechanicaldevice.Nowadaysmodernlaboratoriesusea
digitalleafareameter(photoelectricdevice)whichreadsleafareadirectlyastheindividualare
fedintoit.

643. PHASES OF GROWTH:
Growthisnotasimpleprocess.Itoccursinmeristematicregionswherebeforecompletion
ofgrowth,ameristematiccellhastopassthroughthefollowingphases:
(A)CellFormationPhase:
(B)Thedividingmeristematiccellsarethinwallediso-diametric(havingdiametersofthe
samelength)anddenseprotoplasmwithlargenucleuswithoutvacuolesandinterspaces.
Thenewlyformedcellsafterthefirstphaseofcelldivisiontopassthroughsecondphase
i.e.cellenlargement.
(B)CellElongationPhase:
Inthisphase,largequantityofsolutesinsidegrowingcells,waterentersthecellsdueto
osmoticeffect,increaseturgidityandexpansionofcellsanddilationofthethinandelastic
cellwall.DuringcellelongationofcellwallCellulosemoleculesdepositioninprimarycell
wallhenceincreaseinvolumeofcellwhichabsorbedmorewaterandincreaseturgidity.
(C)CellDifferentiation(CellMaturation)Phase:
Inthislastphaseofresults,appearanceoflargevacuolesandcellmaturationsecondary
cellsformationarelaiddownandcellmaturesandgetdifferentiatedintopermanentcell.
Germinating seeds showing
phases of growth

644. Figure growth and differentiation regions and representative cell types of
maize root tip (From Baldovinos, 1953)

645. KINETICS OF GROWTH AND SIGMOID (S ’SHAPED) GROWTH
CURVETURE:
Definition:
Ifthegrowthrateofacell,organ,wholeplantorwholeplantor
wholelifecycleofplantmeasuredintermsoflength,size,area,volume
dryweight,ithasbeenfoundthatdifferentgrowthphasesresultsin‘S’
shapedcurvature(Sigmoidcurvature).Inastandardgrowthcurve3well
markedregionscanbeobserved,
1.Logarithmicphase
2.Linearphase/
ExponentialPhase
3.Steadyphase/
Stationaryphase/
Staticphase/
Maturityphase/
Senescencephase:
Theoverallgrowthmaybeaffectedbyexternalorinternal
factorsbut‘S”shapecurvedneverinfluenced

646. Three stage of growth :
1.
Thisgrowthcurvesuitwelltoentirelifeofannualplantswhenmeasured
intermsofdryweightagainsttime.
Insenescenceplant,thereisafallinthegrowthratebecauseofincreased
catabolicprocessesagainstanabolicprocesseswhileincaseofearlystage
ofseedgerminationandsproutingtubersadecreaseindryweightisdue
toutilizationofstoredfood.
Logarithmicphase:
Itisanadjustmentphaseinwhichthecellsadjusttothenewenvironment
andstartsgettingthenutrients.
Itisthephasegrowthofcells(inlognumbers)areslowbutcontinuous.
2.Linearphase:
Itisaphaseinwhichmaximumgrowthisoccurinanyorganism.Itis
exponentialphaseasthenumberofcellsincreased.Growthisincreaseas
moneyinvestedtodrawcompoundinterest.
3.Stationaryphase/Staticphase/Steadyphase/Maturityphase/Senescence
phase:
Thecellgrowth&celldensitybecomesstatic(Nofurthergrowthistook
place)becauseof…
1.exhaustionofnutrients2.depletionofoxygenand
3.increaseintheconcentrationoftoxiccompounds.
Inthisphase,decreasesgrowth,organismbeginstosenesceandfinally,
deathoforganismtakeplace.

649. AGR = dw
dt
W
2-W
1
AGR =
T
2-T
1
1.ABSOLUTE GROWTH RATE (AGR): -
AGR is the total growth per unit area and determined when the field of
the plant or organ is to be calculated.
RGR is growth of each per unit time expressed per unit of the critical
weight or volume.
RGR is measured when growth rates of two plants are compared.
Example is given.
Where,W
2
andW
1
aredryweightsatthetime
intervalT
1
andT
2.
Itsunitisgram/day.

650. 2.RELATIVEGROWTHRATE:-(RGR)
Itisanincreaseinplantmaterialperunitplantmaterialper
unittime.Itrepresentstheefficiencyofaplantasaproducerofa
newplantmaterial.Itmeansefficiencyindexofdryweight
production.Itisbasedoncompoundinterestlawderivedby
Blackman(1919).
TheconceptofRGRisgivenbyWest,Kidd,DrigesandFisher
in1921.
RGR = L ×dw
W dt
RGR = loge W
2-log W
1
T
2-T
1
Where, log W
1
= dry weight of plant at time interval T
1
loge W
2
= dry weight of plant at time interval T
2
Its unit is gram/gram/ day.

651. 3. BIOMASS DURATIONS:-
It expresses dry matter production efficiency of
the crop during growing period.
BMD = dw×dt
2
BMD = W
1
+ W
2
×T
2
-T
1
2
Its unit is gram/day.

652. 4. LEAF AREA INDEX (LAI):-
It describes size of assimilatory apparatus (Leaf) of
a plant in relation to land area occupied. It is ratio of
leaf area to land area occupied.
It means how much leaf area to unit area of land
can be measured by 1. graphic method 2. Planimeter
method and 3. leaf area meter devices.
LAI = LA
P
P
Leaf area
LAI =
Land area

653. 5. Net ASSIMILATION RATE (NAR) OR Unit Leaf Rate (ULR)
It is an index of productive efficiency of the plant. It is
an increase in dry weight per unit leaf area or photosynthetic
area. Unit is gm/M
2
NAR = L ×dw
A dt
W
2
-W
1×loge LA
2
-loge LA
1
Where, W
2
-W1 is change in dry weight at time interval T
2
and T
1
. A
2
and A
1
is change in leaf area at time interval T
1
and T
2
LA
2
-LA
1 T
2
-T
1
=

654. 6. LEAF AREA DURATION (LAD):-
Wetakeintoaccountboththemagnitudeofleafarea
anditspersistenceintime.Thus,itrepresentstheleafinessof
thecropduringgrowingperiod.Inotherwords,itgivesan
estimateforthewholeopportunityforphotosynthesisthatthe
croppossessesduringtheperiodunderconsideration.
LAD = LA
2
-LA
1
×T
2
-T
1
Where,LA
1
andLA
2
areleafareaattimeintervalT
1
andT
2
.
2

655. 7. LEAF AREA RATIO (LAR):-
LAR characterized the relative size of assimilatory
apparatus. It is product of two simple ratio.
LAR = SLW ×LWR
Where, SLW = Specific leaf weight
It is defined as mean area of leaf displayed per unit
leaf weight.
It is measure of leaf density or relative thickness.

656. SLW = Leaf area
Leaf dry weight
LWR: It is ratio of leaf dry weight to total dry weight.
LWR = Leaf dry weight
Total plant dry weight
LAR = SLW ×LWR
Leaf area ×Leaf dry weight
Leaf area
LAR =
Total plant dry weight
Leaf dry weight X Total plant dry weight
=

657. 8.CROPGROWTH RATE(CGR):-
Itcanbedefinedasincreaseindryweightperunittimeper
unitarea.Itcanbeexpressedasgram/m2/day.Itisbasedon
simpleinterestlaw.
CGRismeasuredbyharvestingplantatfrequentintervals
andcalculatingincreaseindryweightfromoneharvesttonext.
W
2-W
1
CGR = -----------------
(T
2-T
1) ×GA
1 ×dw
= ----------------
P dt
Where, W
1and W
2are dry weight at time interval T
1and T
2
and GA is Ground area occupied by plant at each sampling.

658. 9. HARVEST INDEX (HI):
Itisalsoknownascoefficientofeffectivenessfor
formationofeconomicpartofthetotaldrymatter
produce.
TheratioofEconomicalyieldtoBiologicalyieldis
knownasHarvestIndex.
Economicalyield×100
HI(%)=
Biologicalyield

659. ♠Themeasurementofgrowthispossibleinterms
ofincreaseofweightorincreaseinheight
(length),volume,areaetc.
♠Thesimplestmethodformeasurementofgrowth
isusingscaleandmeasurethegrowthatregular
intervalsfrombeginningtoend.
♠Someothermethodareusedformeasurementof
growthsuchasHorizontalmicroscope,
Auxanometers,Bose’sCrescograph,Space
markerdiscetc.
THE MEASUREMENT OF GROWTH

660. (1)HORIZONTAL
MICROSCOPE FOR
GROWTH
MEASUREMENT:
Itcanmeasurethe
increaseinlengthwiththe
helpofmicroscopewhich
slidesonaverticalscale.
Apointismarkedonthe
growingobjectbyIndiaink
andfocusedagainandagain
intheslidingmicroscopeat
regularintervals.
Thedistancetravelledby
themicroscope(onvertical
scale)givesthemeasureof
growth(Fig.1).
Figure: 1

661. (2) AUXANOMETER
(A)Arc Auxanometer:
Itconsistsofverticalstand
withapulleyconnectedtoa
pointeronanarcscaleasshownin
theFig.2.
Athreadcanbepassedover
thepulleywithoneendtiedtothe
growingpointoftheplantand
otherendcarryingaweighttokeep
thethreadstretched.Withthe
growth,pulleymovesresultingin
movementofthepointertoindicate
therateofgrowthonthearcscale.
Therateofgrowthcanbe
easilycalculated.Ifauxanometer
pulleyisof4”sizeandpointeris
20”longfromthecenter,the
growthwillbeindicatedtentimes
magnified.
Figure: 2
Stand
Weight
Top of Plant
Arc scale
Pully
Pointer
Potted
Plant

662. (B) Pfeffer’sautomatic auxanometer:
Itconsistsofaverticalstandholdingto
twopulleys(Oneissmalldiameterpulley
insidethewheel+Oneisoutsidewheel).On
wheel,passesathreadcarryingtheweightsat
twoendstokeepitstretched.
Thethread(cord)ononesideofthe
wheelisalsoconnectedwithafinescratching
pointerwhichtouchesasmokedpaperdrum
rotatingautomatically(seeFig.3).
Overtheothersmallpulleyalsopasses
athreadoneendofwhichisconnectedtothe
growingpointoftheplantandtheotherend
tiedwithaweighttokeepitstretched.
Whenthegrowthtakesplacethe
smallpulleyismoving,thewheelisalsomoves
thepointertocontinuouslymakeascratching
markontherotatingsmokeddrumtorecord
growthonpaper.Withthehelpofradiiof
boththepulleysandrateofrotationofthe
drumtheactualrateofgrowthcanbe
calculated.
Figure: 3

663. (B) Pfeffer’sautomatic auxanometer:

664. (3) CRESCOGRAPH:
(A) Bose Crescograph:
Indian Scientist,
Sir Dr. JagadishChandra Bose
Nov. 30, 1858 –Nov. 23, 1937
India, in 1958 issued a
commemorative postage stamp in
honor of the centennial of his birth.

665. Bose invented the
Crescograph an electrical
instrumentthatcouldmeasurethe
growthofaplant.Heworkedasa
physicist,biologist,botanist,
archaeologistandwasawriter.
Heisrecognizedasthe
inventorofthefirstwireless
detectiondeviceandforhis
discoveryofmillimeterlength
electromagneticwaves.
IntheFig.4,Crescograph
monitoringaMimosapudica
(SensitivePlant).Itisvery
sensitiveapparatusbasedona
systemofcompoundlevers.
Itcanmagnifygrowthone
thousandtotenthousandtimes
andcanrecorditsprogressby
minutesandevenbysecondsona
platewhichoscillates(swing)to
andfroatregularintervals.
(A) Bose Crescograph:
Figure: 4

666. (B)Modernelectroniccrescograph
designedbyRandallFontesto
measureplantmovement:
However,itsnormaloperating
rangeisfrom1/1000to1/10,000of
aninch.Thecomponentwhich
actuallymeasuresthemovementis
adifferentialtransformer(A).
Itsmovablecoreishinged
betweenpoints(B)and(C).
Twoleverarmshingedat
points(D),(B)and(E),(C),forma
parallelo-gramthatholdsthecore
centeredwithintheopeningofthe
differentialtransformerasitmoves
upanddown.
Amicrometer(F)isusedto
adjustandcalibratethesystem(see
inbelowFig.5A).
Figure: 5A

667. DetectthemovementofMimosapudica:
Theelectrodesshownwithincircle(c)
andintheblow-uptotheright,were
developedtomonitorelectricalpotentials
forlongperiodsoftimedependably
withoutdamagingtheplant(usedforto
Waterflowsdownfromtheupper
beakersalongpolyesterwicks(D),overthe
electrodes(F),ontoasecondsetofwicks
(E),andfinallyintothelowersetof
beakers(seeinFig.5B).Thisprocesskeeps
theelectrodesconstantlywetandin
electricalcontactwiththeplantstem.In
thepreviouspicture,thephilodendronleaf
wasshownsupportingthechainwhichwas
attachedtothemovementdetectordirectly,
whileinthisfigurethechainissupported
bytheleverarm(A).Thishasbeendone,
inordertokeeptheweightofthechain
frompullingdownonthedelicateleaf.The
MimosaPudicamovessuchrelativelylarge
distances(1ormoreinches)insuchshort
periodsoftimethata20to1reduction
leverarm(A)mustbeusedjusttokeepits
movementswithintherangeofthe
movementdetector.
The plant movement detector above is capable of
measurements as small as 1/1,000,000 of an inch
Figure: 5B

668. (4)SPACEMARKERDISC:
BySpacemarkerdisctheareaofleaf
ismeasuredandmarkedatregularintervals
anditisrecordedtocalculatetherateof
growth.

670. DEVELOPMENT:
Definition:Itmaybeisdefinedas“anorderlychangeor
progress,oftentowardsahigher,moreordered/complex
stage.Changesmaybegradualorveryabrupt”.
Examples of development in plants are:
1. Development during germination
2. Change from vegetative to a flowering condition
3. Development during senescence
4. Development during leaf: From single leaf primordium
to a complex mature leaf.

671. The developmental phases in plants are:
(1) Juvenile phase
(2) Vegetative phase
(3) Reproductive phase
(4) Senescence phase
Thusgrowthreferstoquantitativechangesand
developmentrefersqualitativechangesareknownas
DIFFERENTIATION .

672. 1.Initiationofflowerprimordial
2.Buddevelopment
3.Developmentandmaturationofsepal,petal,stamen,pistilandnectoryetc.
4.Developmentofembryosacwithenclosedegg,synergid,antipodalcell/polar
nuclei
5.Developmentofpollengrainwithinanthers
6.Anthesis(Openingofflower)
7.Pollination
8.Transferofpollengrainfromanthertostigmaandthenpollentubereachin
toembryosacthroughstyle
9.Formationoftwomalegamatesfromgenerativenucleusinthepollentube
10.Formationofzygotethroughfertilizationbetweeneggnucleiandsperm(male
gamete)calledfertilization.Anothermalegameteisfusedwiththepolarnulei
(2n)andformtheprimaryendosperm(3n)iscalleddoublefertilization.
11.Developmentofembryofromzygote
12.Developmentofendospermfromtheprimaryendospermnuclei
13.Developmentofseedfromtheovule
14.Developmentoffruitfromthetissuesthatsupporttotheovule(ovary)
15.Fruitripening
PRINCIPALEVENTSOFREPRODUCTIVE GROWTH ANDDIFFERENCIATION OR
MICROSCOPIC /SUBMICROSCOPIC EVENTSAREASUNDER:

674. No.Determinate Plant Species No.Indeterminate Plant Species
1Inthisspecies,theshootapex
ofmainshootandtillersget
transformedintoflowering
apex.Meansreproductive
phasewillstartafter
completionofvegetativephase.
1Evenonsetofreproductive
differentiation,thevegetative
growthofapicalmeristems
(vegetative)isremaincontinue
toproducevegetativeorgans.
2Wheat,maize,bajara,riceetc. 2Groundnut,cotton,pulses,okra,
soybeanetc.Thisisalsotruefor
perennialcrops.
No. MonoeciousPlant SpeciesNo. DioeciousPlant Species
1Inthisspeices,maleandfemale
flowerarebornonsameplant
atdifferentpositiononplant.
1Inthisspeices,containimperfect
staminate(male)andpistilate
(female)flowersondifferent
plants.
2Wheat,Maize,Bajara,Riceetc.2Papaya,Datepalm,Parwaretc.

675. No. Determinate Tomato Plant Species No. Indeterminate Tomato Plant Species
1 Sometimesreferredtoas"bush"tomatoes. 1 Italsoknownas"vining"tomatoes.
2 Plantcompletingmostofitsgrowingbefore
thefruitareset.
2 Itwillgrowaslargeasyouallowthemtoo.
3 Fruitgenerallyripenatonceoveraperiodof
acoupleofweeks
3 Fruitwillripencontinuousonnumberof
branchesthroughoutlifespan.
4 Afterwhich,fruitproductionislimited. 4 Itwillproducefruitallseasonlong.
5 Theplantwillgenerallydieatthispoint. 5 Itwillliveforlongtime,usuallykilledbyfrost.
6 Tendtogrowonlyafewfeettall 6 Generallyneedsupportorstructureonwhich
togrowverytall.
7 Theyarebesttobeplantedascontainer
plantsandnorequirepruning.
7 Theyarebesttobeplantedinfieldand
requirepruning.

677. GROWTH FACTORS AND GROWTH CORRELATION:
(A)INTERNAL FACTORS:
1. Resistance to biotic and abiotic stresses
2. Photosynthetic rate
3. Respiration
4. Partitioning of assimilate and nitrogen
5. Chlorophyll, carotene and other pigment contents
6. Types and location of meristems
7. Capacity to store food resources
8. Enzyme activity
9. Direct gene effects (e.g. Heterosis).
10.Differentiation
11. The rate at which plants show resistance towards biotic and abiotic stresses
Geneticfactors:
Nucleus,cytoplasm,chloroplastandmitochondriaarecontrollingcentersof
cellresponsibleforprovidinginformationandmanagealltheactivitiesof
cell.

678. 1) Environmental / Climatic factors:
i. Light –intensity, quality and duration
ii.Temperature
iii. Water
iv. Photoperiod
v. Gases –Co2, O2, N, SO2, Fe, Cl, O3
vi. Wind
vii. Gravity
viii. Nearness to sea
ix. Elevation from sea level
x. Others-sound, music, magnetic field, electromagnetic radiation.
2) Edaphic(soil factors):
i. Soil Texture
ii. Soil Structure
iii. Organic matter
iv. CEC
v. Soil pH, base saturation
vi. Nutrient availability (Fertility status): 16 elements
vii. Soil moisture
viii. Soil temperature
ix. Soil aeration
x. Drainage
3) Biological factors:
i. Weeds
ii. Insects
iii. Diseases
iv. Nematodes
v. Soil microorganisms –N2 fixation, Bacteria, Fungi, Algae
vi. Man & Grazing animals
vii.Other Plant Species: Some plants of species that release chemicals which cause toxic effect to the main
crop plants, this phenomenon is called as allelopathyand species are known as allelopathicplants.
viii.Various types of herbivorous, mycorrhiza(symbiotic fungal association with plant roots)

679. Lecture -24
PhysiologyofcropplantsbyGardner,Pearce&Mitchell

682. Definition:
Growthanalysis:
Theanalysisofyieldinfluencingfactorsandplantdevelopmentasnet
photosynthateaccumulationintegratedovertimeisknownasgrowthanalysis.
Growthanalysiscanbemadeatindividualplantlevelorplantcommunities.
TheanalysesmadeatindividualplantlevelareRGR,AGR,NAR,LAR,SLA,SLW
andallometry(shoot/rootratio).
TheanalysesmadeatplantcommunitylevelareLAI,LAD,CGRandDMA.
Thetechniqueofgrowthanalysisisadvantageoustocropscientistasithelps
tofindouttherelationshipbetweenphotosyntheticproductionandrateof
increaseindrymatter.

683. GROWTH ANALYSIS -CALCULATION OFGROWTH
PARAMETERS:
PlantGrowthAnalysisisastandardmethodofestimating
netphotosyntheticproductionofindividualplantandplant
population.
Basedondifferencesbetweentheprimary/initialvalueof
dryweightofwholeplantorplantparts(leaf,stem,root)
andfinallydryweightoffullygrownplantaftersynthesisof
assimilatory/photosyntheticproductsatcertaintime
intervals.
Variousindicesandcharacteristicscalculatedtodescribe
growthrateofvariousplantsorplantpopulation.
Relationshipbetweentheassimilatoryapparatusanddry
matterproductionbyfollowingtwomethods:
1.NondestructiveplantgrowthAnalysis.
2.DestructiveplantgrowthAnalysis.

684. 1.)NonDestructivePlantGrowthAnalysis:-
Withoutanydestruction/injure/damageofplantparts
observationsaretoberecordedfromminimumfiveplantsper
treatmentandreplicationwhicharetobeselectedandtagged
randomly.Allobservationstoberecordedofspecifictime
intervalrightfromcropgrowingperiodtoharvestingand
superiorityisdesired.
Followingareobservation/charactersforNon
destructiveplantgrowthanalysis:-
1.Plantheight 7.Lengthofearhead
2.Numberofbranches 8.Numberofearheadperplant
3.Numberofleaves 9.Numberofspikeletsperearhead(in
cereals),ballsperplant(incotton),
podsperplant(Pegionpea)
4.Numberoftilering 10.Numberandlengthofinternode
(Sugarcane)
5.Numberofflowering 11.Lengthanddiameteroffruits
6.Numberoffruits

685. Whencropismaturedthenharvestitattimeof
harvesting,followingobservationsaretobe
recorded:-
1.Numberofgrainsperearhead.
2.Testweight.
3.Numberofpodsperplants
4.Numberofgrainsperpod
e.g.incaseofgroundnut
i)Numberofflowers.
ii)Numberofpegs.
iii)Numberofpods.
iv)Numberofkernelperplant.
v)Numberofindividualkernel.

686. 2.) Destructive Plant Growth Analysis:-
Inthismethods,plantpopulationcanbedestructedonbasis
ofseparationofroot,straw,leaves,reproductiveorgans(fruits
andgrains).Inthismethod,plantperunitareaandfreshdry
weighttobeconsideredandrecordedinthelaboratory.
Destructiveplantgrowthanalysisisastandardmethodof
estimatingnetphotosyntheticproductionofindividualplantand
plantpopulation.
Basedonprimaryvalueofdryweight(DW)ofawholeplant
orplantparts(leaf,stem,rootetc)anddimensionofassimilatory
/photosyntheticapparatus(leafarea)assessedingrowingplant
materialatcertaintimeintervals.
Variousindicesandcharacteristicscalculatedtodescribe
growthrateofvariousplants/plantpartsandrelationship
betweentheassimilatoryapparatusanddrymatterproduction.

687. PhysiologyofcropplantsbyGardner,Pearce&Mitchell

688. LIMITATION OF GROWTH FACTORS
Theplantresponsetonutrientlimitationwastheearliestsubjectsofscientificplant
investigatorswhicharetooextensiveandcomplextopredict.
However,knowledgeofthetheoriesleadtobetterunderstandingofplantresponseand
canaidinplanningandmanagementstrategies(seeinfigure)
TheclassicworkswasdonebyLiebig,Sachs,BlackmanandMitscherlich
onthisaspect.
Figure:
Some limiting factors in
crop production

689. LIMITATION OF GROWTH FACTORS
(1) LIEBIG LAW OF MINIMUM:
ThisconceptwasformulatedbyGermanchemist,JustisvonLiebig,
oftencalledthe“fatherofthefertilizerindustry”.
ThisLawoftheMinimum,whichstatesthatplantgrowthwill
continueaslongasallrequiredfactorsarepresent(e.g.light,water,
nitrogen,phosphorus,potassiumetc.).
Whenoneofthosefactorsisdepleted,growthstops.
Increasingtheamountofthe“limiting”componentwillallowgrowth
tocontinueuntilthatcomponent(oranother)isdepleted.
Ex.Thenutrientmosttypically“limiting”algaegrowthinlakesis
phosphorus.Ifphosphorusconcentrationscanbemaintained,then
algalgrowthwouldbecontrolled.
InMarkTwainLakecoveredbyforestarea,(thelargestreservoirin
northernUnitedstateMissouri),lightisthefactorthatmostoften
limitsalgae.

690. MARK TWAIN LAKE
COVERED BY FOREST
AREA
THE LARGEST
RESERVOIR IN
NORTHERN UNITED
STATE MISSOURI

691. Liebig(1862)stated“Adeficiencyorabsenceofonenecessaryconstituent,allother
beingpresent,rendersthesoilbarren(thinsoil,sand,orrocks,⅓areahasvegetation)
forcropforwhichnutrientisneeded”.Itisreferredasthe“Barrelconcept”.
Ifbarrelhasstaves(narrowstripsofwoodorironplatesthatformthesides&covering)
ofdifferentheights,thelowestoneetablishesthecapacityofthebarrel(Fig.).
Accordingly,thegrowthinlowsupply(whether,itisclimatic,biologicalorgenetic
components)thatsetthecapacityofyield).

692. Frederick Frost
Blackman, 1866-1947(2) BLACKMAN: OPTIMA AND LIMITING FACTORS
F.F.Blackman‘stheoryofoptimaandlimitingfactors(1905)wasstatedas
follow:
“Whenaprocessisconditioned(outcome)astoitsrapidlybyanumberof
separatefactors,therateofprocessislimitedbypaceoftheslowestfactor.”
LightandCO2arerequiredforphotosynthesis.
Blackman‘stheorysuggeststhatthereisanabruptcessationoftheprocess,
the“BlackmanResponse,”ifonefactorbecominglimiting(Fig.1).However,
natureseemstoabhorangle(adversecondition)andthistypeofresponseis
seldomfound.
Responselinestofactorslimitingphotosynthesisarecurvilinearand
approachamaximumlimitasymptoticallyi.e.distancebetweenthe
curvelineapproacheszero(Fig.2).
Fig.1.AssimilationofCO2and
itsinteractionwithlight
intensity
Fig.2.Photosynthesisofacucumberleafinrelationto
lightintensity,temperatureandCO2concentration
(Gaastra,1963)
Fig.2
Fig.1

693. (3) MITSCHERLICH: LAW OF DIMINISHING RETURNS
AGermansoilscientistE.A.Mitscherlich(1909),developedanequationrelatedto
growthtosupplyofgrowthfactors.
Heobservedthatwhenplantshadadequateamountsofallbutonelimitingelement
thegrowthresponsewasproportionaltothelimitationelement.
TheMitscherlich“lawofdiminishingreturns”states,“Theincreaseinanycrop
producedbyaunitincrementofadeficientfactorisproportionaltothedecrementof
thatfactorfromaximum”.Theresponseiscurvilinearinsteadoflinear,asBlackman
hadsuggested.
Fig.GrowthresponsecurveDescribedbyMitscherlichequation
Amountofnutrientorfactorrequiredtogiveone-halfyield
(Bauleunit)asappliedintheMitscherlichequation
BauleUnit Added
(x)
Predicted Yield % of
Maximum (y)
0 0.00
1 50.00
2 75.00
3 87.50
4 93.75
α 100.00
Mitscherlichequationisasfollows:
Dy/dx=C(A-Y)
Where,disincrementofchange,
dyistheamountofincreaseinyield(y)resultingfroman
incrementofthegrowthfactor(dx),
Aismaximumpossibleyieldobtainedwithanygiven
quantityofthefactorx,and
Cisaproportionalityconstantthatdependsonthenature
ofthegrowthfactor
Thegrowthincreaseinyield(y)isthegreatestforthefirst
incrementofX.
Theamountofincreasedyield(y)becomesprogressively
smallerwitheachaddedincrementofx,theoretically
about½theresponsefromthepreviousincrementcalled
BauleUnit.
When,yieldA=100,C=0.301.IfAis100%,
theequationis…Log(100–Y)=Log100-0.301x

694. PhysiologyofcropplantsbyGardner,Pearce&Mitchell

695. Locationofgrowth:Inhigherplantsgrowthisrestrictedtocertain
embryoniczones/regionscalledMERISTEMS.
TYPES OF MERISTEMS:
(A)BASEONDURATION:
1.Indeterminatemeristems:Apicalmeristemsofaxilorganssuchasstemandroot
apexthatgrowforlongertime.
2.Determinatemeristems:Leaves,flowersandfruitswhichgrowforlimitedperiod
time.
(B)BASEONLOCATION:
1.Apicalmeristems:Growthislocatedatthetipstemandrootwhichareresponsible
forthegrowthintermsofincreaseinlengthorheight.
2.Lateralmeristems:Growthislocatedincambiumandcorkcambium,responsible
forincreaseingirth/thickness.
3.Intercalarymeristems:Growthlocatedbetweenregionsofmaturedifferentiated
tissues(node&internodehelpsinstemregainuprightposition;leafblade&sheath
helpsinextendleaflength)e.g.inmint,bamboo,grassesinternodesandleafsheath
continuesgrowthatbasalregionsafterthatupperpartisdifferentiated.
Meristemmaybediffuse(lesscellnumber,cellactivity,self-generating
hormonecapacityascomparedtomassedmeristem(apicalbud).Maize&wheat
shootfrommainapicalmassedmeristemdevelopedproductive&vigouroustillers
thantillersdevelopedfrompseudostems.

696. Sugarcane stem NeemTree stem

697. TYPES OF GROWTH:
1. PRIMARY GROWTH:
Itisresultedintoincreaseinlengthorheightofplantaxis.Itis
responsibleforformationoflateralappendageslikebranches,roots,
leaves,floralpartsetc.
2. SECONDARY GROWTH:
Itisresponsibleforgrowthdiameter/girthofrootandstem.The
activityinlateralmeristemsislocatedincambiumandcorkcambium.
Thisconsistsofuniseriatedlayerofcellslocatedbetweenregionsof
maturedifferentiatedtissuesi.e.xylemandphloem.

698. PhysiologyofcropplantsbyGardner,Pearce&Mitchell

699. Plantgrowthisacombinationofacomplexprocessesofgrowthanddifferentiation
thatleadstoaccumulationofdrymatter.
Differentiationprocesseshave3-requisite:
(1)Favorabletemperature
(2)Availableassimilatesinexcessofmostmetabolicuses
(3)Properenzymesystemtomediatedifferentiation
If,3–requisitearemeet,3-differentiationresponsesoccurred:
(1)Cellwallthicking
(2)Depositofcellinclusions
(3)Hardeningofprotoplasm(Loomis1953)preventingfromnaturalstressessuchascold,
heatordrought
Firstessentialtodifferentiationprocessesisavailabilityofcarbohydrate&enzymeswhile
growthrequiredfactorsforsynthesissuchaswater,Nandsomeotherelements.
ThelimitofphotosynthesiswhenthereiswaterorNdeficienciesresultincellwallthickening,
alkaloidsaccumulation,protoplasmhardeningthatcauseschemicalanatomyandmorphology
changes.
Theproductionofqualityofcropproductsoftenrequirebalancebetweengrowthand
differentiation.
Cerealcropsgrownunderhigh-waterandhighNregimes,havethinwallinstemandtendto
lodge.Limitingthesefactorscausereverse.While,thinwallsaredesirableinthepetiolesof
celeryfortenderness.
GROWTH AND DIFFERENTIATION

700. Sugarinsugarbeet&sweetmelonsaccumulatepoorlyifN&waterareexcessive.
Npromotebiomassoftops&rootwhichisnegativelycorrelatewithsucrose.
Productionofgoodassimilatoryandsugar-storagesysteminvegetativegrowthrequirehigh
radiationcooltemperature,sandyloamsoil,lessthanoptimumN&water.
Alfalfaaccumulatesstarchesinfleshytaprootsinsunnydays,coolnights.Thephotosynthesisoutput
isexceedsgrowthandmaintenancerespirationrequirements.Thisresultwasaccumulationof
carbohydratefoodreserveintaprootsandhardeningoftheprotoplasmforoverwintering(Escalada
andSmith,1972)
48
250
44
80

701. Lecture-25

703. INTRODUCTION (pp. No. 90).
……
Thewaterisabsorbedbyroothairsofplantfromwhereitreachesxylemviacortical
cellsandpassagecellsanditreachestopofplantwhereitistranspiredbyleaves
andusedforothermetabolicactivities.
Thexylemismainwaterconductingtissue.
Theupwardmovementofwaterfromstembasetotreetopoftheplantthrough
xylemiscalled“ASCENTOFSAP.”
Sometimesitcoversaheightofmorethan90mt.againstgravitationalpullin
AustralianEucalyptusandCalifornianSequoia.
10metersheightofwatercolumnliftthewaterrequiredpressureofone
atmosphere.
Toraiseofwaterupthatrequiredsomespecialmechanism.
BeforediscussionofTHREETHEORIES,GiveyouGeneralinformation.
Q-4A (2) Seme. End Exam-June -2016

704. –Xylem is hollow& tubular. Xylem are of 2 types:
–Vessel : slightly large diameter; cells stacked.
Vessel members only occur in angiosperms (flowering plants)
–Tracheid: smaller diameter; side to side overlap
–

705. coast redwood
(Sequoiadendrongiganteum)
Lift of water column over
10 mt. require pressure of
1 (one) atmosphere

706. How water goes up to the
top of the tree?

707. How water goes up to the
top of the tree?
coast redwood
(Sequoiadendrongiganteum)

708. Thecoastredwood(Sequoiadendrongiganteum),the
world'stallesttree.AnotheristhecoastDawnredwood
(Metasequoiaglyptostroboides).
Thetallestlivingtree,namedHyperion,is115.55mor
379.1ft(measuredin2006)atcoastalareaofPacificOceanin
theNorthwestoftheUS(California).
Inviewoffactthatitisnotpossibletoliftofwater
columnover10mt.becausethisistheheightofwatercolumn
thatcanbemadetostandatpressureof1(one)atmosphere,
henceriseofwateruptosuchheight(115.55m)needssome
specialmechanism.

710. (pp. No. 90).
THEORIESFORASCENTOFSAP/TRANSLOCATION OFWATER/TRANSPORT OF
WATER
Varioustheorieshavebeenproposedtoexplainthe
mechanisminvolvedinascentofsap.
Theriseofwatertosuchagreatheightbecomesa
problemtoexplain.
Thesecanbegroupedunderthreeheading:
1.VitalTheories
2.RootPressureTheory
3.PhysicalForceTheories
Q-4A (2) Seme. End Exam-June -2016

711. 1)VITAL THEORIES: (pp. No. 90).
In1880,GermanScientists-Westermeir,GodlewskiandJansestatedthatthe
livingcellsofastemplayanessentialroleintheascentofsap.
In1883,Westermeirstatedthattheupwardpassageofwaterinthestemwas
affectedinwoodparenchymaandthattracheidsandvesselsactedaswater
reserviorsratherthanconductingelements.
Godlewski(1884)proposedclambering(orrelaypump)theory.Heproposedthat
xylembringwaterbypumpingactionofwaterinanupwarddirection.
Ascentofsaptakesplaceduetothepumpingactivityofthecellsofxylem
parenchymawhichareliving.Thecellsofthemedullaryrayswhicharealsoliving,
insomewaychangetheirO.P.WhentheirO.P.becomeshightheydrawwater
fromthelowervesselandtheirO.P.becomeslow.NowduetothelowO.P.,water
fromthecellsofxylemparenchymaispumpedintotheabovevessel.Thisprocess
isrepeatedagainandagainandwaterrisesupwardinthexylem.
Janse(1887)supportedthetheoryofGodlewskiandshowedthatifthelower
portionofabranchiskilled,theleavesofabovethebranchareaffectedwithina
fewdays.
Q-4A (2) Seme. End Exam-June -2016

712. According to J. C. Bose Theory (1923) : (pp. No. 91).
AnIndianScientist,proposed“Pulsationtheoryofascentofsap.’’
Theupwardtranslocationofwatertakesplaceduetothepulsatoryactivityofliving
cellsofinnermostcorticalcellslayerjustoutsidetheendodermisthatabsorbed
waterfromoutsideandpumpthesameintothevessels.Thistheorywasalso
rejectedbecausemanyworkerscouldnotrepeathisexperimentandmanyothers
foundnocorrelationbetweenpulsatoryactivityandtheascentofsap.
(Bose,inhisexperimentusedanelectricprobewhichwasconnectedtoa
galvanometer.Whentheneedleoftheelectricprobewasinsertedintothestem
slowlyandslowly,thepointerofthegalvanometershowedsomeoscillationsbut
whentheelectricprobeneedlereachedtheinnermostlayerofcortex,thepointerof
galvanometershowedviolentoscillations.Heattributedthistothepulsatingactivity
ofthesecells.)
ObjectionstoVitalTheories:
Strasburger(1891)andOverton(1911)whodemonstratedthatascentof
sapwascontinuesin75yearsoldoaktree,eveninthestemsinwhichlivingcells
havebeenkilledbytheuptakeofpoisonslikepicricacidandcarbolicacid.The
ascentofsapdoesnotaffected.Theseabovevitaltheoriesseemedonly
hypothetical,andwasfurtherdiscardedbytheexperiments.
Q-4A (2) Seme. End Exam-June -2016

713. 2) ROOT PRESSURE THEORY: (pp. No. 91).
Ifplantstemiscutafewinchesabovefromitsbasewithasharpknife,
thexylemsapisseenflowingoutthroughthecutend.Thisphenomenon
iscalled“exudationorbleeding”.
PriesteyStocking(1956)firsttimeexplainedthattheprocessofupward
flowofwater(exudation)isduetoahydrostaticpressuredevelopedin
therootsystem.Intheroot,thepressureisdevelopeddueto
accumulationofabsorbedwater,thisisknownasrootpressure.
Theterm rootpressurewasgivenbyStephanHalesin1727.
SheproposedthatRootpressuredevelopedlargelyduetoosmotic
phenomenon.
Rootpressureusuallyinarangeof+1to+2bars.
RootpressureisaffectedbyrespiratorypoisonsandevenO
2supply.
Thisindicatesthatitrequiresexpenditureofmetabolicenergyanditis
anactiveprocess.
Itisbelievedbysomescientiststhatrootpressureisresponsibletodrive
watertoanyheightoftheplant.

714. 2) ROOT PRESSURE THEORY:
ObjectionstoVitalTheories:(pp.No.91-92).
Kramers,Unger,Renner,DixanandJolly,Stewardetc.haveobjectedthistheory.
Although,rootpressurewhichisdevelopedinthexylemoftherootscanraisewaterto
acertainheightbutitdoesnotseemtobeaneffectiveforceinascentofsapduetothe
followingreasons:
(i)Rootpressurehasnotbeenobservedinallplants.Ingymnosperms(nakedseed
withoutovaryorinfruit)rootpressurehasrarelybeenobserved.
(ii)Wateriscontinuestoriseupwardevenabsenceofroots.Magnitudeofroot
pressureisverylow(about2atms).
(iii)Inactivelytranspiringplants,rootpressureisnotobserved.
(iv)Rootpressureiscommonlyobservedduringfavourableperiodofgrowthwhen
transpirationrateislow.Evenintheabsenceofrootpressure,ascentofsap
continues.Forexample,whenaleafytwigiscutunderwaterandplacedinabeaker
fullofwateritremainsfreshandgreenforsufficientlongtime.
(v)Theamountofwaterexudedbyrootpressureisverylow.Only5%oftotalwater
lossduringexcessivetranspiration.
(vi)Therateofrisewaterisbyrootpressureistooslowtoexplaintherateofascentof
waterinaplant.
(vii)Inplants,rootpressure,isalwaysbelow2atmosphereandthereforewaterdueto
rootpressurecanriseupto21mts.If,favourableconditionsareavailable.Itmay
haveinyoungplantsbeforeleavesaredevelopedandbeforetranspiration
becomesadominantfeature.

715. 3) PHYSICAL FORCE THEORIES: (pp. No. 92).
Profounderofphysicalforcetheoriesbelievedthatlivingcellsarenotinvolvedinascentofsap
andItispurelyaphysicalphenomenon.
(1)Capillarity Theory OR Capillary Force:
In plants the xylem vessels are placed one above the other forming a sort of continuous channel
which can be compared with long capillary tubes.
Boehm(1809)proposedthistheoryandstatedthatwaterrisesinnarrowtubesduetoforce
ofsurfacetension.
Hestatedthatwaterrisesupthroughtheorinthewallsofxylemchannelsduetocapillary
action.Butsomeinvestigatorsdidnotsupportedthistheoryoflumenofthetracheids.
Thetheorysaysthatascentofsaptakesplaceduetoatmosphericpressure.But,itisnot
acceptedbecausetheatmosphericpressurecannotraisewaterbeyond34feet.
ObjectionstoTheoryofCapillarity:
(i) The value of capillarity is very small. It can raise water to a height of about 150 cm in vessels
of normal diameter (0.032mm) where as large vessels with diameter 0.5 mm, it will rise up to
6.0 cm. Therefore, Only the capillaries of 1µm can rise up to 29.95 mts.
(ii) Capillarity occurs only when base of the tube dips in container having water. Xylem vessels
are not directly connected with soil water, hence this theory cannot be function.
(iii) Rise due to capillarity will increase when the lumen of vessels is less. Tall plants should,
therefore, have narrow vessels as compared to smaller plants. The truth is, however, reverse.
(iv) Capillarity cannot operate in plants having tracheids due to the presence of end walls.
(v)InGymnosperms,usuallythevesselsareabsent.Otherxylemelementsdonotform
continuouschannels.

716. Conti…..3) PHYSICAL FORCE THEORIES: (pp. No. 93).
(2)Imbibitional Theory :
PropoundedbyUnger(1868)andadvancedSachs(1878)supportedtheviewthatascentof
sap/watermovesupwardinstementirelythroughthewallsofxylemelementsdueto
processofimbibition.
Thoughthemovmentofwaterthroughbycolloidsisextremelyslow.
Theimbibitiontheorywasdiscardedbecause,atpresentevidentthatxylemwalldonotcarry
water,itmovesthroughthelumenofthexylem.
Objections to Theory of Capillarity Imbibition :
Nowitiswellknownthatimbibitionalforceisinsignificantintheascentofsapbecauseittakes
placethroughthelumenofxylemelementsandnotthroughwalls.
(Aleafytwigiscutunderwaterandthecutendisdippedinmeltedparaffinwaxforsometime.
Athinsectionofstemnearcutendisremovedtoexposethecellwalls.Thetwigistransferredto
abeakercontainingwater.Thetwigsoonwiltsbecausethelumensofxylemelementshavebeen
pluggedbywax).
TheImbibitionalmovementofwaterhasbeennotfoundonlyslowbutalsonegligible.

717. Conti…..3) PHYSICAL FORCE THEORIES:
(3) Atmospheric Pressure Theory : (pp. No. 93).
ThistheorystatedthatAtmosphericPressureisresponsibleforascentofsap.Watermovesup
wardtofillupthegapinthefallofatmosphericPressureatthetranspiringsurfaceduetoloss
ofwaterduringtranspiration.
Two Main Objections to Theory of Capillarity Imbibition :
(i)Fortheoperationofatmosphericpressure,thepresenceoffreesurfaceatlowerendofthe
plantisessentialwhichcannotfoundinplant.
(ii)Itisnotapplicablebecauseevenifcompletevacuumiscreatedatthetranspiringsurface,
themaximumriseofwatercanbe10mts.Whereas,novacuumisobservedintheplants
andcertainplantsarefarmoretaller.
(4) Transpiration Pull / Cohesion Theory of Water / Cohesion-Tension Theory : (pp. No. 93).
ThistheorywasoriginallyproposedbyDixonandJolly(1894)andgreatlysupportedbyCurtis
andClerk(1951),Milburn&Johnson(1966)andLevitt(1969).Thistheoryisveryconvincingand
universallyaccepted.
Itisbasedonthefollowingfeatures/characteristics:
(i)CohesiveandAdhesivepropertiesofwatermoleculestoformacontinuouswatercolumnin
thexylemfrombasetothetopoftheplant.
(ii)Waterislossfrommesophyllcellsduetotranspirationhence,pullingforcedevelopsand
thatputthecellsundertension.
(iii)Tensionmaycauseabreakinthewatercolumnbutduetothetensilestrength(cohesive
propertyofwatermolecules-StrongHydrogenBonds),continuescolumnisnotbroken.
(iv)Thetensionoftranspirationpullistransmittedtowaterincolumnfromrootregion.

718. •How do plants get nutrients and water up xylem?
1.Transpiration:Processofevaporation/lossofwaterfromthe
aerialpartsofplantsintheformofvaporiscalledtranspiration.
2.Adhesion:Watermoleculessticksoradheretocellwallsofxylem
throughadhesionforceiscalled“Adhesion”.
3.Cohesion:Watermoleculesaretightlybindswitheachother
throughhydrogenbondsiscalled“Cohesion”.Watermovesthrough
xylemwithunbrokencolumn(Nogapbetweenwatermolecules)
4.Transpirationalpull:DuringtheevaporationofwaterintoAir
fromthesurfacesofleafthatcausepullingofwaterfromdownward
toupwardandcreatinga‘pull’onthewatercolumniscalled
Transpirationalpull.
Essentially,osmoticpressureofairisgreaterthanosmoticpressure
withinleaves.
: (pp. No. 93).

719. •Transpiration:
Transpirationalpull
•flow from greater to lower water
concentration
•relies on cohesion &
adhesion of water
–cavitations breaks chain of water
molecules
Ascent of sap (xylem)

720. Xylem vessel
surface

721. •How do plants get nutrients and water into roots?
Thelossofwaterfromleafsurfaceofmesophyllcellsduetotranspiration,reduces
thewateramountandcauseanincreaseintheosmoticpressureofthesecells.
ThusareducedwaterpotentialisincreasesDPD.
Waterfromtheadjacentcellsispulledtomeetthislossofwaterandasaresult,a
pullisdevelopedinmesophyllcellsandxylemcellsofleaves.Thistension
ultimatelytransmittedtorootthroughthestemtracheids.
Roothairsgreatlyincreasesurfaceareaoverwhichto‘absorb’water.Roothairs
havegreaterosmoticpotentialthansoil.
Why ? Because …..
Highconcentrationofionscreatesagreaterosmoticpressureinplantthan
surroundingsoilwater;hence,Rootcellsactivelypumpingionsinsideorinto
cells(byusingATP)fromthesoilandwatermovesintocellsbyosmosis.
•OsmoticorSolutepotential=pressure
Mechanism of Ascent of Sap
(pp. No. 94).

722. Mechanism of Ascent of Sap
(pp. No. 94).
Fig. V.S. of a Leaf showing
stomataltranspiration
generating a transpiration pull

723. EVIDENCE (8 Nos.) IN SUPPORT OF THE THEORY OF COHESION –TENSION:
(pp. No. 94 -95).
Whenthereisacomparisonbetweentwoidenticalconditions:
A.Transpirationthroughporouspotand
B.Transpirationthroughlivingplant
Inporouspotexperiment,i.e.atthetopofacontinuouswatercolumnaporous
potisplacedanditswaterissubjectedtoevaporation,thewatercolumnisputunder
pressure/tension.
Thiscolumnisnotbrokenduetothecohesivepropertyofwatermoleculeswhile
evaporationcontinues.Thus,itisbelievedthatasimilarkindofmechanismmayoperatein
plant.
Fig.:Demonstration
ofcohesion–tension
theorybyphysical
system
(Evaporation of
waterfromporous
potpullsupthe
columnofmercury
duetotension)

724. Themagnitudeofthisforceisveryhigh(sometimesupto350
atmos.),thereforethecontinuouswatercolumninthexylemcannot
bebrokeneasilyduetotheforceofgravityorotherobstructions
offeredbytheinternaltissuesintheupwardmovementofwater.
Theadhesivepropertiesofwateri.e.theattractionbetweenthe
watermoleculesandthecontainer’swalls(herethewallsofxylem)
furtherensurethecontinuityofwatercolumninxylem.
Accordingtosomeworkers,themainobjectionagainstthistheoryis
thatcertainair/gasbubblespresentintheconductingchannelswill
breakthecontinuityofthewatercolumn.Iscalledas“cavitation.”
Thishasbeencounteractedbyotherswhosaythattherearenoair
bubblesandifatallarepresent,theywillnotbreakthewater
columnwhichwillremaincontinuousthroughotherelementsofthe
xylemparallelcolumnofvesselssidebysidehence,temporarilyc
cavitationiseliminated.Whentensionisrelivedbyrainorsimplyat
nightthegasesaredissolvedinsolutionandcolumnbecame
continuous.(Fig.).
Incaseofwater,theelec-
tropositiveH-atomsof
onewatermoleculeare
connected with
electronegativeO-atoms
ofotherwatermolecules
byH-bonds).
AlthoughH-bondisvery
weak(containingabout
5k.cal.energy)butwhen
theyarepresentin
enormousnumbersasin
caseofwater,avery
strongmutualforceof
attractionorcohesive
forcedevelopsbetween
watermolecules and
hencetheyremaininthe
formofacontinuous
watercolumn inthe
xylem.
Objection to cohesion
–tension theory
Explanations
PP. No. 96
Fig. L.S. of a portion of stem showing the pathway of water
when disrturbeddue to air vacuole

725. Lecture-26

727. Definition:Thelossofwaterfromaerialpartsof
plantsintheformofvaporisknownastranspiration
andinformofliquidisknownasguttation.
Themicroscopicporesinagreatnumberspresent
ontheepidermalsurfaceoftheleafiscalled
stomata.

728. It is regulated by vapourpressure, diffusion pressure, osmotic pressure
PP. No. 98

729. SubgenusEquisetum:
•Equisetum arvenseL. –field horsetail, common horsetail or mare's tail; circumborealdown through temperate
zones.
•Equisetum bogotenseL. –Andean horsetail; upland South America up to Costa Rica; includesE. rinihuense,
sometimes treated as a separate species.
•Equisetum diffusumL.–Himalayan horsetail; Himalayan India and China and adjacent nations above about 1500
feet (450 m).
•Equisetum fluviatileL.–water horsetail; circumborealdown through temperate zones.
Strawberryleaf

730. NO. TRANSPIRATION NO. GUTTATION
1 Itoccursmostlyduringthedaytimewhen
temperatureiscomparativelyhigher.
1Itoccursduringthecoldhoursofnightand
earlymorning.
2 Waterisgivenout/lostintheformof
vapours.
2Waterisgivenout/lostintheformofliquid
droplets.
3 Waterlostispurewater. 3Waterlostcontainsdissolvedsalts,sugars
andaminoacids.
4 Itoccursthroughstomatalenticelorcuticle
areopen.Itoccursthroughallaerialplant
parts.
4Itoccursatvein-endsonthemarginortipsof
theleaveswherehydathodesarepresent.
5 Transpirationisacontrolledandregulated
phenomenon.
5Guttationisanuncontrolledphenomenon.
6 Transpirationmaintainthetemperatureof
plant.
6Ithasnorelationwithtemperature.
7 Ittakesplaceunderdryconditionswhichdo
notfavourwaterlossthroughdiffusion.
7Ittakesplaceunderhumidconditionswhich
favourwaterlossthroughdiffusion.
8 Itisregulatedbyanumberoffactors,the
chiefbeingtheopening&closingof
stomata.
8Itcontinuesaslongasadequatesupplyof
waterismaintainedandtheenvironmentis
coldandhumid.
9 Excessivetranspirationunderdeficitwater
(stress)supplycancausewiltingofplant.
9 Itdoesnottakeplaceunderdeficitwater
(stress)andneverresultsinwiltingofplant.
DIFFERENCES BETWEEN TRANSPIRATION AND GUTTATION
PP. No. 98

731. AMOUNT OF WATER TRANSPIRED:
Huge amount of water transpired by plants
In Zeamays(corn plant)
Water occuringas constituent = 1872 g
Water Used in matabolicactivities = 250 g
Water Transpired = 2,02,106 g
Total water used in growing season = 2,04228 g
Crotolariajuncea= 27 kg in 140 days
Helienthusannus56 Kg in 120 days
Birch tree (with 2,00, 000 nos. of leaves) = 300-400 kg of water per hot day
Birch forest of 400-600 trees evaporates some 20,000 barrels of water per day
PP. No. 99

732. Transpiration is Unavoidableand Dangerous but necessary evil
Itisevilbecause…
Transpirationispurelyincidentalduetostructuralarrangementsofplantsfor
exitandentryofgases.
Lossofwaterdoesnotserveanygoodpurposeintheplantlifewhichresultsin
wilting,seriousdesiccationandoftendeathofaplantifaconditionofdroughtis
experienced.
Aloosesoilandexposedsituation,suddenextremeevaporationduetohighlight
intensity,hotwinds,hightemperature,blazingsunprolongeddrought,depleted
soilmoistureandpoorwaterretentivecapacityofsoiletc.aretherelativecauses
ofsuchdeaths.
Italsoconsumedenergyandcausesunnecessaryabsorptionofexcesswaterby
roots.
TranspirationisUnavoidable.Aslongasthereisneedofingressandegressof
CO2andO2duringmetabolicprocessesphotosynthesisandrespiration,living
cellshavetobeexposed,thetranspirationofwaterlosswillbeunavoidable.
Evenmildwaterstressduetotranspirationresultsinreducedgrowthrateand
reductionofyield.
Injuryinplant,dehydrationtakeplaceandheavytranspirationlosswhenthe
atmosphericconditionsareaggressive.
PP. No. 99

733. Transpiration is Advantageous / great significance /
Transpiration is necessary for the plant
because…
Itcreatesuctionforceandhelpsinascentofsap.
Itaffectsthediffusionpressuredeficit,therebyindirectlyhelpingdiffusion
throughthecells.
Itaffectstheabsorptionofwaterandmineralsbyroots.
IthelpsinEvaporationofexcesswaterfromtheexposedsurfaceofcells
TranslocationofFood/Mineralsdissolvedinwateraredistributedthroughout
plantbodybytranspirationstream.
Maintaintem.ofleaveshascoolingeffectonplant.
ItbringabouttheOpening&closingofstomata
Wetsurfaceofleafcellsallowgaseousexchange.
Waterisconductedinmosttallplantsduetotranspirationpull.
Transpirationaffectsindirectlytheprocessesofrespirationandphotosynthesis.
PP. No. 99

734. PP. No. 100
Twostages:
1.Evaporationofwaterfromthecellwallsintotheintercellularspaces.
2.Intercellularspacesintooutsidetheatmosphere.
Thelossofwaterfromleafsurfaceofmesophyllcellsdueto
transpiration,reducesthewateramountandcauseanincreaseinthe
osmoticpressureofthesecells.Thusareducedwaterpotentialis
increasesDPD.

735. Watervaporlostdirectlythroughcuticularlayer(water-impervious
protectiveouterlayercoveringtheepidermalcellsofleaves,consists
ofcutin,waxy,water-repellentsubstancealliedtosuberin,foundinthe
cellwallsofcorkytissue)presentonepidermalcellsofleavesis
refferedcuticulartranspiration….
Waterislostasvapordirectlythroughlenticels(smallopeninginthe
corkytissuecoveringstemsandtwigs)iscalledaslenticular
transpiration…
Thethinwalledlooselyarrangedmesophyllcells,haveanabundance
ofintercellularspace,providesanidealconditionfortheevaporation
ofwaterfrominternalleafsurface,Watervapordiffuseintothe
atmospherethroughtheopenstomatatermedasstomatal
transpiration....

736. CuticularTranspiration
Thecuticulartranspirationaccountsto2to20%ofthetotal
transpirationlossfromplant(xerophytestomesophytes).Thecuticle
althoughretardswaterloss,issomewhatpermeabletowatervapor.In
plantswiththickcuticles,thisformoftranspirationisinsignificant.
LenticularTranspiration
Thelenticulartranspirationamountto0.1to1%ofthetotal
transpirationlossfromplantswhichisinsignificantwhencomparedto
stomataltranspiration.However,lenticulartranspirationmaycause
somedesiccationinthosetreesthatshedtheirleavesattheonsetof
thewinter.Duringcoldwinterwaterabsorptionbyrootsisata
minimum,thustheimportanceoflenticulartranspirationisincreased.
StomatalTranspiration:
Thestomataltranspirationaccountsto80to98%ofthetotal
transpirationlossfromplants(treetoherbaceousplants).Undervery
dryconditions,stomataareclosedandwaterlossoccursthroughthe
cuticleandlenticels.

738. StomatawasdiscoveredbyPfeffer&name‘stomata’wasgiven
byMalphigii.Stomatacover1-2%ofleafarea.
Itisminuteporepresentinsoftaerialpartsoftheplant.Algae,
fungiandsubmergedplantsdonotpossessstomata.
(a)Stomataareminuteporesofelipticalshape,consistsoftwo
specializedepidermalcellcalledguardcells.
(b)Theguardcellsarekidneyshapeindicotyledonanddumbell
shapeinmonocotyledon.
(c)Thewalloftheguardcellsurroundingtheporeisthicken
andinelasticduetorestofthewallsarethin,elasticandsemi-
permeable.
(d)Eachguardcellhasacytoplasmiclining,centralvacuole.It
cytoplasmcontainssinglenucleusandnumberofchloroplast.
Thechloroplastofguardcellarecapableofverypoor
photosynthesis,becausetheabsenceofRUBISCOenzyme.
STOMATA

739. (e)Guardcellsaresurroundedbymodifiedepidermalcells,
knownassubsidiarycellsoraccessorycells,whichsupportsin
themovementofguardcells.
(f)TheSizeandshapeofstomaandguardcellvaryfromplantto
plant.Whenfullyopen,thestomatalporemeasures3-12inwidth
and10-40inlength.
(g)Inmanygymnosperms andxerophyticplants{plantsgrowing
indesert),thestomataarepresentembeddeddeeplyinthe
leaves,sothattheyarenotexposedtosunlightdirectly.Such
deeplyembeddedstomataarecalledsunkenstomata.Thisisan
adaptationtocheckexcessivetranspirationintheseplants.
Inmanygymnosperms andxerophyticplants(plantsgrowingin
desert),thestomataarepresentembeddeddeeplyintheleaves,
sothattheyarenotexposedtosunlightdirectly.Suchdeeply
embedded stomataarecalledsunkenstomata.Thisisan
adaptationtocheckexcessivetranspirationintheseplants.

740. Number of Stomata (StomatalFrequency):
Thenumberofstomatainadefiniteareaofleafvariesfromplant
toplant.Xerophytespossesslargernumberofstomatathan
mesophytes.
Numberofstomata/sqcm.is1000—60,000indifferentplant
species.Thenumberofstomtaperunitareaofleafiscalled
StomatalFrequency.
Stomatafrequencyoftreesandshrubsishigherthanherbs.
Stomatanearlyoccupyonetotwopercentoftotalleafareawhen
fullyopen.
Inisobilateralleaves(inmonocots),approximatelythesame
numberofstomataarefoundonuppersurface(adaxial)and
lower(abaxial)surface.
Indorsiventralleaves(indicots)thenumberofstomataonthe
uppersurfaceismuchlessincomparisontothosefoundonthe
lowersurface.

742. Sr.
No.
Name of the plant No. of stomata
per sq. cm. upon
the upper
surface
No. of stomata
per sq. cm. upon
the upper
surface
1Helianthus annus(Sunflower) 58 156
2Lycopersicumesculentum
(Tomato)
12 130
3Phaseolusvulgaris(Mung) 40 281
4Solanumtuberosum(Potato) 51 161
5Zeamays(Maize) 52 68
6Avenasativa (Jav) 40 43
DISTRIBUTION OF STOMATA IN DIFFERENT PLANTS

743. DISTRIBUTION OF STOMATA
1. Only on the lower surface –Oak, apple, orange
2. More on lower surface and less on upper surface –
Bean, sunflower
3. Equally on both surfaces -maize, oats
4. Only on upper surface –water lily
5. Absent or functionless –hydrophytes (Hydrilla)

744. DISTRIBUTION AND TYPES OF STOMATA:
Dependinguponthedistributionandarrangementofstomataintheleaves
Fivecategoriesofstomataldistributionhavebeenrecognizedinplants.
1.Appleormulberry(hypostomatic)type:
Stomataarefounddistributedonlyonthelowersurfaceofleaves,e.g.,apple,
peach,mulberry,walnut,etc.
2.Potatotype:
Stomataarefounddistributedmoreonthelowersurfaceandlessonitsupper
surface,e.g.,potato,cabbage,bean,tomato,pea,etc.
3.Oat(amphistomatic)type:
Stomataarefounddistributedequallyuponthetwosurfaces,e.g.maize,oats,
grasses,etc.
4.Waterlily(epistomatic)type:
Stomataarefounddistributedonlyontheuppersurfaceofleaf,e.g.,waterlily,
Nymphaeaandmanyaquaticplants.
5.Potamogeton(astomatic)type:
Stomataarealtogetherabsentorifpresenttheyarevestigeal.e.g.,
Potamogetonandsubmergedaquatics.
MetacalfandChalkrecognizedfourtypesofstomataonthebasisoftheir
structure-

745. Fig. Stomatalclock as observed in the
lower epidermis of a leaf
Hugo von Mohl(8 April 1805 –1 April 1872)
He was a German botanist from stuttgart

746. Hugo von Mohl(8 April 1805 –1 April 1872)
He was a German botanist from stuttgart

748. STOMATALFREQUENCY ANDINDEX:
♠Stomataaretinyorminuteporesofellipticalshape
surroundedbytwosubsidiarycellsfoundintheepidermis
ofleaf.
♠Sizemayberangedfrom7X3µ(Phaseolusvulgris)and
38×8µ(inAvenasativa)and4X26(ZeamaysL.).
♠Eachstomaisnormallysurroundedbytwospecialized
epidermalcellsknownasGuardcells.
♠Theguardcellsarekidney-shapedindicotyledonous
plantsanddumble-shapedinthemembersofgraminceae
family(monocotyledonousplants)andtheyremainjoined
attheend.
♠Thewalloftheguardcellssurroundingtheporeisthinand
elastic(outerlayer)andinsidethelayeristhickand
inelasticduetothepresenceofasecondarylayerof
cellulose.

749. ♠Whenturgidityincreases,theouterthinwallsofguardcells
stretchoutwardtherebyinnerwallisalsostretchingoutward.
♠Theinnerwallbecomesconcave(Antargol)andresultisthe
spaceisoccur,pourwidensandporeopens.StomatalTurgor
Mechanismisinvolvedinopeningandclosingofstomata.
♠K+(Potassiumions)playcrucialrole.
♠TheopeningofstomataaretheresultofactivetransportofK+
fromepidermaladjacentcellsintotheguardcells.
♠Malicacidissynthesizedinsubsidiarycellsfromstarchand
goesintocytoplasmofguardcellsinthepresenceoflight.
Dissociation
♠Malicacid-R(COOH)2 MalateR(COO-)2+2H+(Hydrogenions)
Exchange
♠H+ K+(adjacentcells)
♠InfluxofK+andeffluxofH+thatincreaseconcentrationofK+
inguardcell(Vacuoles)therebyOsmoticpressureis
developed;waterisenterintotheguardcells;increaseturgor
pressure;guardcellsbecomesturgidandfinallyopenthe
stomata.

751. Fig. 39.12b
Guard cell
become turgid
Guard cell
become flaccid

752. ♠ABAplayimportantroleinclosingofstomata.
♠ABAinhibitsK+uptakebychangingdiffusionandpermiability
ofguardcells.TheK+movesouttothesubsidiarycells.
♠ABAinducestheprocessofacidificationthatloweringthepH.
AtthelowpH,starchissynthesizedandosmoticpressureof
guardcellsfallsandwatermovesoutofguardcellsto
subsidiarycells.
♠Guardcellsthenbecomeflaccidandstomatalporeisthus
closed.

754. Very little CO2 Fixation in Guard Cells Reduced CO2 in Guard Cells
ATP Synthesis
Respiration occurs
Possible Photosynthesis
ATP Synthesis
ATP-MediatedH+/K+pump
H+outofandK+intoGuard
cellsofcl-anionsfollow
IncreaseK+/Cl-andmalate
concentrationintoGuard
cells
Decreased osmotic potential
in Guard cells
WaterpotentialofGuardcells
morenegativerelativeto
surroundingcells
Osmotic entry of water
into Guard cells
AN INTEGRATED SCHEME OF THE PROBABLE MECHANISMS OF STOMATAL OPENING
Increase pH in Guard cells
Starch phosphorylase
activated
Hydrolysis of starch
Concentration of soluble
sugar increased
Sugar concentration may be
insufficient to affect water
potential
ATP Synthesis
HCO3+ increases combines
with PEP to form malicacid
Turgorpressure increased
Stomata open
LIGHT

756. Antitranspirants:
Intranspiration,almost98%ofwaterlostwhichisabsorbedby
plantsandonlyinsignificantamount(2%)isutilizedbyplants.
Inthisview,Antitranspirantsareassettoagriculturistandalso
tonaturetosavewater,butitcausenegativeeffectonplant
processes.
Definition:
AnyChemicalsorsubstanceswhenappliedtoplantsfor
thepurposeoftoretard/reducetranspirationisknownas
Antitranspirants.
THREE TYPES OF ANTITRANSPIRANTS:
1. StomatalClosing Type
2. Film Forming Type
3. Reflective Type

757. (1) STOMATAL CLOSING TYPE
Whenantitranspirantsareappliedinlowconcentration(10-4M),itexerted
verylittletoxiceffectuponleavesandresultedinpartialclosureofstomatalpores
fortwoweeks.
1.PhenylMercuricAcetate(PMA)
2.AbscisicAcid(ABA)
3.Carbon-di-Oxide(CO2)
4.CCC
5.Salicylicacid
6.M8-hydroxy-quinolinesulfate(8-HQS)
7.Mono-methyl
8.Mono-glyceryl
9.Estersofn-decenyl-succinicacid
10.Thiodan
CO
2isaneffectiveantitranspirant.Alittleriseinitsconcentrationfrom
natural0.03-0.05%inducedclosureofstomata.ThehigherrateofCO
2diffusioninto
theleafisalsoreducedtranspirationandadverslyaffectonphotosynthesisand
respiration.However,usageofCO2hasoneadvantagethatitinhibits
photorespiration.Butoverallitisnoteconomicalandpracticallyfeasibleinfield
(Onlyfeasibleinglasshouses).

758. 2.FILMFORMINGTYPE:
Thistypeformsathinfilmcoatingonthesurfaceofleafandinhibits
thelossofwatervapourfromtheleaf.Aformingfilmpermeableto
CO2andO2butnottowater.
Mostlyreducescuticulartranspiration.
E.g.Colourlessplastics,Siliconeoils,lowviscosityWaxes,Hexa-
decanol,Ethylalcoholetc.
3.REFLECTIVETYPE:
Thistypeofchemicalsincreasesthelightreflectionbytheleaves,
thusdecreasingtheleaftemperature.
ThewaterlossisreducedwithoutaffectingtheCO
2assimilation.
E.g.Kaolinite(Kaolin),Limewater(Limewash)

759. (I)WEATHER FACTOR
1.Light:
Lightispresentthenonlystomatawillbeopenedbutindarktheydonot.
2.Temperature:
Ifthetemperatureismore,therewillbemoreratesoftranspirationandviceversa.
Ahightemperatureopensstomataevenindarkness.
Besidesincreaseintemperature,itlowerstherelativehumidityoftheairandincreasesvapour
pressureinsidetranspiringorgan.
For10°Criseinatmospherictemperature,vapourpressureinsideleavesdoubleswhilerelative
humiditydecreasesby50%,Consequently,rateoftranspirationincreases.
3.Humidity:
Ifthehumidityismoretherewillbealessrateoftranspirationandvice-versa,becauseinhumid
conditiontheabsorptionrateisless.
4.Wind:
Windwhileblowingthroughplantremoveswatervaporfromthevicinityofplantandultimatelyit
increasestherateoftranspirationduetodrycondition.
DPDofatmosphericairishigheratlowrelativehumidity,moreofwatervapourswilldiffuseout
oftheleafinteriorascomparedtohighRHwhenDPDislower.
Transpirationislowerinthestillairbecausewatervapoursaccumulatearoundthetranspiring
organsandreducetheDPDoftheair.
Windvelocityupto20-30km/hrtherateoftranspirationisnormal,at40-50km/hrincreases
transpirationbyopening.
EXTERNAL FACTORS: Environmental Factors

760. 5.Atmosphericpressure:
Loweratmosphericpressureathigheraltitudetherateoftranspiration
increasebuttheincreaseisoffset(balanced)bytheprevailinglow
temperatureattheseheights.
Lowatmosphericpressureenhancesevaporation,producesaircurrentsand
increasestherateoftranspiration.
1.AvailableSoilwater:
Ifthewaterissufficientinthesoilthereisproperabsorptionofwaterby
plantandultimatelyitincreasestherateoftranspirationandvice-versa.
Adecreaseinwateruptakebytherootcausespartialdehydrationoftheleaf
cellsresultinginclosureofstomataandwilting.
(II) Soil Factors

761. A.PlantFactors B. Environmental Factors
Stomatafrequency:
Nos.ofstomata,Sizeofstomata,Positionofstomata,Shrunkenstomata
I)WeatherFactorsII)Soil
Factors
StructuralpeculariesofLeaf:
Simple leaf, Compound leaf, Palmatelycompound leaf, Pinnately
compound leaf, Thickness of Cuticle
1.Light 1.Available
soil water
LeafArea
LAI:Alargeleafareawillshowmoretranspirationthanplantwithless
leafarea.Therateoftranspirationdecreasesinacanopyduetodensity
offoliage,shadingeffectanddecreaseofairmovementinsidethe
canopy.
Stationarylayerofair(boundarylayer):Thethickerthestationarylayer,
theloweristherateoftranspiration.
TypeofMesophyll:CompactMesophylllayer(havingmoreofpalisade
tissueandfewerintercellularspaces)reducestranspirationthanloose
mesophyll.
2(A).Temp.
2(B). Vital
activities:
Theyproduced
heat from
energy by
respirationthat
increase
transpiration.
Root-shootratio:
Alowroot/shootratioincreasestherateoftranspirationwhileahigh
ratiodecreasestherateoftranspiration.
3.Atmospheric
Humidity.
Leaforientation
Uprightleafposition
Straightleafposition
4.Wind
Watercontentoftheleaves:
Watercontentismoreintheleaves,increasestherateoftranspiration.
5.Atmospheric
Pressure
MucilageandSolutes:
Theydecreasetherateoftranspirationbyholdingwatertenaciously.
Spray&dusts
Fungalinfection:Increasestherateoftranspirationduetodestructionoftheleaf
cuticle,lossofmorewater.(PeainfectedbyPeronosporaviciae).
INTERNAL FACTORS : FACTORS AFFECTING TRANSPIRATION

762. GUTTATION

763. Strawberryleaf

764. Equisetum spp.
Prayer plant –Marantaarundinacea

765. NO. STOMATA NO. GUTTATION BY HYDATHODES
1Theyarefoundinepidermisofleaves,stemsand
fruits.
1Theyarefoundonthetipsandmarginsof
youngleavesattheirveinendings.
2Itistheopeningpresentforlossofwaterin
thegaseousform.
2Itistheopeningpresentforlossofwaterinthe
liquidform.
3Theyaresurroundedbypairsofchlorophyllous
guardcells.
3Theyaresurroundedbyaringofcuticularised
achlorophyllouscells.
4 Thestomataleadstoacavityintotheinteriorofthe
epidermiscalledastherespiratorychamberor
substomatalchamber.
4 Thehydathodeisfollowedbya
largeintercellularspaceorairchamber.The
looselyarrangedcellsbeneaththeairchamber
attheendofthexylemelementareknown
asepithem.
5 Thestomataaresurroundedbysubsidiary
epidermalcells.
5 Subsidiarycellsareabsent.
6 Thestomatahavenoconnectionwithmainends. 6 Theyaresituatedontheveinends.
7 Theiropeningandclosingisregulatedbyguard
cells.
7Theyarealwaysopennotregulatedbyguard
cells.
8Usuallythestomataremainopenduringtheday
timeandclosedduringthenighttime
8 Thehydathoderemainsopenduringthedayas
wellasthenighttime.
9 Theyareconcernedwiththeprocessof‘transpi-
ration’.
9 Theyareconcernedwiththeprocessof
‘guttation’.
10Stomataltranspirationiscontrolledbytheopening
andclosingofthestomata.
10Guttationtakesplaceduetotherootpressure.
11Theguardcellssurroundingthestomatacontain
chloroplasts.
11Thecellssurroundingthehydathodesdonot
containchloroplasts.
DIFFERENCE BETWEEN STOMATA AND HYDATHODES

766. END

767. TRANSPIRATION IN RELATION TO PRODUCTIVITY:
Theimportanceofwateruseefficiency(WUE)ininfluencinggrain
yieldunderwaterlimitedconditionscanbeexplainedbythefollowing
modelgivebyPassioura.
GrainYield=TxTExHI
Where,
•T=Totaltranspirationbythecropcanopy
•TE=TranspirationEfficiencyorWUE
•HI=HarvestIndex(EconomicFractionofDrymatter)
Thisrelationshipprovidesananalyticaltooltoselectthegenotypewith
highlevelsofTandTE.

768. SIGNIFICANCE / IMPORTANCE OF TRANSPIRATION:
Transpiration is advantageous because…
It creates suction force and help in the ascent of sap.
It helps in the absorption of water and minerals by roots.
It helps in evaporating excess amount of water from moist soil.
It plays a role in translocation of food from one part of the plant to the
other.
It brings opening and closure of stomata which indirectly influences
the gaseous exchange for the processes of photosynthesis and
respiration.
It helps in dissipating the excess energy absorbed from the sun,
which will otherwise raise the leaf temperature.
It maintains suitable temperature of leaves by imparting a cooling
effect.

769. •AIM:-
Todeterminethestomatalfrequencyandstomatalindex
ofsomeplants.
•PRINCIPLE:-
Thenumberofstomataperunitareaoftheleafis
describedasStomatalfrequency.
StomatalIndex(SI):
Itisdefinedasthepercentofstomataascomparedto
alltheepidermalcells(includingthecellscontaining
stomata)inaunitareaofleaf.
I=S×100
T
Where,I=StomatalIndex,S=Numberofstomataper
unitarea,T=Totalnumberofepidermalcellsperunitarea
(Nos.ofepidermalcells+Nos.ofStomatalcells)

770. •EXPERIMENTNO.1:-
Todeterminethephenomenon oftranspirationthrough
stomata.
MATERIALS:
Apottedhealthyplant,abelljarwhichcancoverthepotted
plant,arubbersheetoroilcloth,aglasssheetandgreaseare
requiredfortheexperiment.
PROCEDURE:
Thepotisproperlycoveredeitherwithrubbersheetoroilcloth
leavingouttheaerialpartsoftheplant.Thisisdonetoprevent
directevaporationofwaterfromsoilsurfaceandfromthesurface
ofpot.Thispotiskeptonglassplateandcoveredairtightbythe
belljarwithgreaseonitsrim.Observationsaremadeafter
sometime.
CONCLUSION:
Thewaterdropsappearontheinnerwallofthebelljarwhich
comefromtheonlyplantbyphenomenonoftranspiration.

774. Floweringisanimportantphaseoflifecyclebecausethetransitionfromvegetative
growthtoreproductivephaseinvolvesseveralchangesinthephysiologyofplant.
Floweringisadecisive(determining)stage.Itrequiredefiniteperiodofvegetative
growth.Theperiodmayvaryfromplanttoplant.E.g.Fruitingtreerequiresseveralyearstoflower
whileanannualherbflowersinafewmonthsonly.
Physiologicalmechanismresponsibleforfloweringhasbeenfoundtocontrolledby
(i)Periodicityoflight(photoperiodism)and
(ii)Temperature(vernalisation)
Thetroleoflighthasbeenstudiedinphotosynthesis,growthanddevelopmentwheretheintensity
andqualityoflightplayanimportantrole.Thephenomenonofphotoperiodismwasfirstobserved
anddiscoveredbyGarnerandAllard(1920)thatthemutantvarietyoftobacco(Nicotiana
tabacum)MarylandMammothflowerswhentherelativelengthofthedaywasshorterthanthe
lengthofthedarkperiod,ledtothediscoveryphotoperiodism.
Thusthephenomenoninwhichtheinfluenceofdaylengthonplantsisstudiediscalled
photoperiodism.
Itmayalsodefinedastherelativelengthrelativelengthofthedayandnight.
Onthebasisoflengthofphotoperiodrequirements,theyhaveclassifiedplantsinto:
(i)Shortdayplants
(ii)Longdayplants
(iii)Day-neutralplants
PP. No. 485

775. “Theresponseofplantstotherelativelength
oflightanddarkperiodandorderofsequenceof
lightanddarktoinduceflowering”.
Eachandeveryplantspeciesrequireadefinite
numberofcycleofdarkandlightperiodforflower
induction.
PP. No. 485

776. (1920)
GARNER ALLARD
Discovered the phenomenon of photoperiodism and coined
the term PHOTOPERIODISM
PP. No. 485

777. 1.Shortdayplants(SDP):
Forfloweringofshortdayplantsthedaylengthmustnotexceeda
certaincriticalvalue,thedaylengthrequiredislessthenacertaincritical
length..Suchplantsrequirethedaylengthlessthanthecriticalday
lengthforflowerinductioniscalledshortdayplants.
“Aparticularperiodofdaylightgiventoplantfor
drastic/extreme/profuseincreaseinfloweringisknownascriticaldaylength”.
Thecriticaldaylengthisvariesfromspeciestospecies.
Theseplantsrequirearelativelyshortdaylightperiod(usually8-10
hours)andacontinuousdarkperiodofabout14-16hoursforsubsequent
flowering.TheseplantsarealsoknownasShortdayplantsorLong-night
plants.
PP. No. 485

778. THREE CATEGORIES
OF PLANTS
Theseplantsarenotcapableoffloweringifshortdarkandshortlightareprovided
alternately.
Hilman(1959)showedthatshort-dayplantsarecapableoffloweringevenifkept
continuousindarkbutprovidedwithsucrose.
Thisshowsthattheshort-dayplantsrequirelightperiodonlyforthecarryingon
photosynthesis.
Inshort–dayplantsfloweringcanbeinducedevenduringlongdaysbyincreasingthe
darkperiodbyputtingtheminthedarkforsometimebeforesunsetoraftersunrise.
Intheseplants,cuttingshortofthelightperiodupto2hoursorlessinducesflowering
inthem.
PP. No. 486

779. Coffee
Corn
Datura
Karnchoe
Hemp
Potato
Onion
Rice
Sesame
Soybean
Straw berry
Sugarcane
Sunnhemp
Tobacco
General plants:
Aster
Begonia
Chrysanthemum
Cocklebur
Cosmos
Dahlia
Duckweed
Pharbitisnil
Poinsettia
Tuberose
Examples of short day plants:
Ornamental plants:
PP. No. 486

780. Kalanchoetomentosa
Coffeaarabica
CrotolariaJuncea
Asters
PP. No. 486

781. Begoniasemperflorens
Cocklebur plants(Xanthium strumarium)
Cosmosbipinnatus Duckweedfloweringaquatic plants
PP. No. 486

782. Pharbitisnil
Poinsettia
Tuberose
PP. No. 486

783. Dahlia
PP. No. 486

784. Dark
Critical Day
Length
---Dotted line
A B C D E F
Light
Case
Phenomenon occur in
SHORT DAY PLANTS:
PP. No. 486

785. Plants are placed in
Control conditions

786. Example of Long day plants:
Alfalfa
Barley
Chicory
Dill seed
Mustard
Oat
Opium
Rye
Sugar beet
Wheat
Blue grass
Henbane
Petunia
Sweet clover grass
General plants:
Ornamental plants:Vege. Salad plants:
Beet
Cabbage
Lettuce
Peppermint
Radish
Spinach
Turnip
2.Longdayplants(LDP):
PP. No. 487

787. 2.Longdayplants(LDP):
Longdayplantsrequirephoto/lightperiodofmorethancriticallengthwhich
mayvaryfrom14-16hours.
Thebestfloweringlongdayplantsusuallyoccursincontinuouslight.
Forfloweringtheyrequiredeithernodarkperiodoraveryshortdarkperiod.
Aflash/briefexposureofwhite/redlightinthedarkperiodorthe
prolongationoflightperiodstimulatesfloweringinlongdayplantsevenduring
shortdayperiod.Here,darknesshasaninhibitoryeffectonflowering.
Longdayplantsrequire16hourslightperiodin24hourscanmadetroflower
ifitisprovidedwithacycleof8hroflightperiodand4hrofdarkperiod.
Inlongdayplants,thedarknesshasaninhibitoryeffectonflowering.
TheseplantsarealsocalledasLongdayplantsorshortnightplants.
Inlongdayplants,lightperiodiscritical.

788. 321321

789. No. Event SD PlantsLD Plants
A9hrlight+15hrdark Flower Vegetative
B9hrlight+Whitelight(Artificial)+15hr
dark
? ?
C9hrlight+Redlight(600-700nm)+15hr
dark
? ?
D9hrlight+FarRedlight(700-760nm)+15
hrdark
? ?
E9hrlight+Redlight+FarRedlight+15hr
dark
? ?
F9hrlight+FarRedlight+Redlight+15hr
dark
? ?

790. No. Event SD PlantsLD Plants
A9hrlight+15hrdark Flower Vegetative
B9hrlight+Whitelight(Artificial)+15hr
dark
VegetativeFlower
C9hrlight+Redlight(600-700nm)+15hr
dark
VegetativeFlower
D9hrlight+FarRedlight(700-760nm)+15
hrdark
Flower Vegetative
E9hrlight+Redlight+FarRedlight+15hr
dark
FlowerVegetative
F9hrlight+FarRedlight+Redlight+15hr
dark
Vegetative Flower

791. Chicory
Dill seed
Sugar beet
Henbane
PP. No. 487

792. Blue grass Petunia
Opium Sweet clover grass
PP. No. 487

793. DNplantsinwhichfloweringoccursirrespectiveofthedaylength
ortheygivetheleastresponsetochangeindaylengthOrlightisnotmore
affectonflowering.Theseplantscanflowerevenifthelightperiodis
providedfromfewhourstocontinuousillumination.
Theseplantsflowerinallphotoperiodrangingfrom5hoursto24
hourscontinuousexposure.
3.Dayneutralplants(DNPs):
Brinjal
Peas
Carrot
Chilli
Cucumber
Onion
Tomato
Kidney bean
Lima bean
Indian bean
Balsum
Jerusalamartichoke
•Thesiteofperceptionofphotoperiodicstimulusis
perceivedbyleavesorinPharbitisnilbythefully
expandedcotyledons.
Cotton
Sunflower
Ornamental plants:Oil seed plants:Vegetable plants:
PP. No. 487

794. Balsam
Jerusalamartichoke
PP. No. 487

796. Differences between short day and long day plants
No. Short day plant No. Long day plant
1Plants flowered when
photoperiodislessthanthe
criticaldaylength.
1Plants flower when
photoperiodismorethanthe
criticaldaylength.
2Interruptionduringlight
periodwithdarknessinhibit
flowering.
2Interruptionduringlight
periodwithdarknessdoes
notinhibitflowering.
3Long, continuous and
uninterrupteddarkperiodis
criticalforflowering.
3Darkperiodisnotcriticalfor
flowering.
4Floweringdoesnotoccur
underalternatingcyclesof
shortdayandshortdark
period.
4Floweringoccurs under
alternatingcyclesofshort
dayfollowedbyshorterdark
period.
5Give Examples Give Examples

797. Basedonexperientialfindingsithasbeenobservedthatacontinuedfavourablephotoperiods
tillblossomingisnotessentialbutshortandappropriatephotoperiodsisrequiredfor
productionofflowers.
“Floweringwillalsooccurifaplantreceivesinductivecyclesafterintervalsofunfavourable
photoperiods(i.e.,discontinuousinductivecycles.)Plantsmayrequireoneormoreinductive
cyclesforflowering.
Definition:
Photoperiodicinduction:
Thisphenomenon/persistenceofproducingphotoperiodiceffect/influenceiscalled
photoperiodicinduction.”
‘ANAPPROPRIATEPHOTOPERIODIN24HOURSCYCLECONSTITUTESONEINDUCTIVECYCLE.
Forinstance,Xanthium,Pharbitisnil,Loliumetc.,(ashortdayplant)requiresonlyone(1)day
inductivecycleandnormallyflowersafterabout64-days.Itcanbemadetoflowerevenafter
13daysifithasreceived4-8inductivecycles.
2daysinsoybean(SDP),3daysinhenbaneor15-20daysinbeetorevenmore.
Thedarkinterruptionofthedayhadlittleornoeffect,butnightinterruptionbylight
inhibitedfloweringinshortdayplantsandpromotedfloweringinlongdayplants.
Ifaplantwhichhasreceivedsufficientinductivecyclesissubsequentlyplacedunder
unfavourablephotoperiods,itwillstillflower.
Continuousinductivecyclespromoteearlyfloweringthandiscontinuousinductivecycles.
PP. No. 487

798. Thesekindofobservationsonphoto-inductiveperceptionwasmadeby
Knott(1934)andconfirmedbyChailakhyan(1936)thatphoto-inductionisperceivedby
leaves.
Chailakhyanhadmadefirstexperimentforphoto-inductiveperceptionon
Xanthiumpennysylvanicum(Cocklebur).Heisolatedleavesandasingleleafinthe
plantcapableofreceivingphoto-inductiveinfluencehavebeenobserved.
Thesensitivityofperceivingphoto-inductionisincreasewithgrowthoffully
expandedleafanddecreasesintheolderleaves.Thus,itdependsontheageofplant.
Cockleburplantwillflowerifithaspreviouslybeenkeptundershort-day
conditions.Iftheplantisdefoliatedandthenkeptundershortdaycondition,itwillnot
flower.
Xanthium pennysylvanicum(Cocklebur)
PP. No. 488

799. Acarefulobservationrevealsthefactthatthroughphotoperiod
influenceisinduceinleavesandflowerareformedelsewhereinthespecialized
region(translocatedtotheapicaltip,subsequentlycausingtheinitiationoffloral
primordial)ofplant.Meansstimulusmusttravelfromleavestoflowerforming
regionthroughphloem.
Wardlaw(1966),hisexperimentalfindingstatedthatstimulustravels
inphloem(independenttothetransportofphotosynthate)attherateof10-24
mm/hrwhileassimilate(photosynthate)at1000mm/hr.Duringthefurther
observationitwasdeterminedthatstimulusmovesattherateof
Shortdayplant:2.4cm/hr
Longdayplant:30cm/hr
However,thedegreeofstimulusmobilityvariesfromplanttoplant.
PP. No. 488

800. Thetransmissionofstimulusindicatethatitistheformofsomechemical.
Chailakhyan(1937)namedthisflowerinducingchemical“FLORIGEN”(InLatinflorameansflower
andgenonmeanstoproduce.
Leafdetectthephotoperiodbutbudbecomestheflower(stimulusflorigentransmitfromleafto
bud).
Chailakhyanhadmadegraftingexperimentforknowingthechemicalnatureofstimulus
(florigen)onMarylandmammothvarietyoftobaccoforflowerinduction.
Inthisexperimentabranchorleafofplantwhichreceivedtheproperphotoperiodicinduction
couldinducedfloweringinaplantexposedtounfavorablephotoperiods.
Bysuchexperimentslongdayplantscouldbemadetoflowerundershortdaythrough
grafting.
GraftingexperimentofMarylandmammothvarietyoftobacco(SDP)withHyoscyamusniger
(LDP).
Theproductionofflorigenisdependoncriticallengthofthedayornight
Itissurprisingthathormones,ionslikecalciumandironcanalsoinducedplantstoflower.
Severalplantssuchasbulbs,winterwheatwouldnotfloweruntiltheyexperienceacold
environment.
Wellenseik(1973)observedthatLunaria(abiennialplant)wouldnotflowerunlessitis
subjectedtocoldtreatment.Thiseffectcannotbereplacedbyphotoperiodictreatment,but
itsannualvarietycanflowerwhensubjectedtolongdays.
Italsobringonemorefactthatthereisgeneticphotoperiodicandvernalisationrelationship
responsibleforflowering.
PP. No. 488

801. PP. No. 489

802. Scion:
SDPs (Tuberose)
grafted to LDPs
Root Stock:
LDPs (Petunia)
SD condition
induced LDPs to flower
SDPs(Tuberose)whengraftedtoLDPs(Petunia)inSDconditioninduced
LDPstoflower(seeinnextslide).
Florigenisproducedinresponsetodifferentenvironmentalconditions.
PP. No. 489

803. Graftingexperimentsincockleburplantshaveevenprovedthatthefloralhormone
canbetranslocatedfromoneplanttoanother.
Forexample,ifonebranchedcockleburplant(Fig.18.4A)whichhasbeenexposedto
shortdayconditionsisgraftedtoanothercockleburplantkeptunderlongdayconditions,
floweringoccursonboththeplants(Fig.18.4B).
Obviously,thefloralhormonehasbeentransmittedtothereceptorplantthrough
graftunion.Butifacockleburplantisgraftedtoanothersimilarplantbothofwhichhavebeen
keptunderlongdayconditions,floweringwillnotoccuroneitherofthetwoplants(Fig.18.4C).
PP. No. 489

804. Accordingtothistheory,photoperiodsaffectthedailyendogenousrhythms
(everydayinternalactivities)whichconsistoftwophases:
(a)Photophilousphase:
Itoccursinlightandischaracterizebyintensivephotosynthesisandweak
respiration.Inthisphase,syntheticprocess(anabolicactivities)aredominant.
(a)Skotophilousphase:
Itoccursindarkandischaracterizebyintensiverespiration.Inthisphase,
hydrolyticactivitiesareincreasedanddecompositionofstarchintosugartake
place(catabolicactivities).
Severaltheorieshavebeenproposedbyscientiststoexplainphysiologyofflowering
andconceptsofphotoperiodism.Theimportanttheoriesareasfollowing:
1.Theoryofendogenousrhythms
2.Phytochrometheory
3.Theoryonrelationoflightanddarkreaction
PP. No. 489

805. Similarly,Bunning(1958)assumesthepresenceofendogenousrhythmsconsistof
twohalfcycles.
Thefirsthalfcycleoccursindayfor12hrs.andiscalledphotophilousphase.During
this,anabolicprocesspredominatesincludingfloweringinplants.
Theothersecondhalfcycleisdarkfor12hrs,itissensitiveanddecomposition
activitiesareactivatediscalledskotophilousphase.Inthis,catabolicprocess
(dehydrationofstarch)predominates.
InL.D.plantsoscillatorisclose/neartophotophilousphase.TheL.D.plantshavea
criticaldaylengthof15hoursandsomelightremaininphotophlilus(12hrs.)and
restofotherperiod(3hrs.)isfallsintheskotophilousphase.Underthese
conditionsinL.D.plantswillflower.
InS.D.plantsoscillatorispresentclose/neartoskotophilousphase,SDplantshave
acriticaldaylengthof9hours.Thisperiodisremained/fallwithinthephotophilous
phase(aspercalculationof12hrslight&12hrsdarkinnight).Lightduring
scotophilphase(3hrs.)willinhibitphotoprocesswhichisinitiatedduring
photophase.
AccordingtoviewofscientistBunning,inthismethodsomekindoftimeregulating
mechanismispresentinthecelliscalled“oscillator.”
Oscillatoristhoughttobeautomaticactingwithauto-fluctuativeprocesses.
PP. No. 489

806. PhytochromeTheorybelievesthatthePerceptionoflightinphotoperiodismtake
placethroughphotoreceptorchromo-protein(Chromo=Color)pigmentcalledas
“phytochrome”.Ithastwointer-convertibleforms.
Phytocromeispresentintheplasmamembraneofcellsandithastwocomponents,
chromophoreandprotein.Phytochromeispresentinroots,coleoptiles,stems,hypocotyls,
cotyledons,petioles,leafblades,vegetativebuds,flowertissues,seedsanddevelopingfruitsof
higherplants.
Thepigment,phytochromeexistsintwodifferentformsi.e.,redlightabsorbingform
whichisdesignatedasPrandfarredlightabsorbingformwhichisdesignatedasPfr.
Active
form
Inactive
form
P
660 P
730
PP. No. 490

807. PP. No. 490

808. Undershortdayphotoperiods,P660whichabsorbedlightat660nmandthisformis
retainedforlongerperiod,whichstimulatesfloweringofshort-dayplantsand
suppressesfloweringoflongdayplants.
On Oppositely,
Underlong-dayphotoperiods,P730whichabsorbedlightat730nmandthisformis
retainedforlongerperiod,whichstimulatesfloweringoflong-dayplantsand
suppressesfloweringofshortayplants.
PP. No. 490

809. PP. No. 490

810. DifferencesbetweenPrandPfrformsofphytochrome
No. Pr form No. Pfrform
1Itisbluegreenincolour. 1Itislightgreenincolour.
2Itisaninactiveformof
phytochromeanditdoesnot
showphytochromeresponses.
2Itisanactiveformof
phytochromeandhenceshows
phytochromeresponses.
3Ithasmaximumabsorptionin
redregion(about670nm).
3Ithasmaximumabsorptionin
far-redregion(about730nm).
4PrformisconvertedintoPfr
formindaytimeinredregion
(660-670nm).
4PfrformconvertedintoPrform
duringnighttimeinfarred
region(730-735nm).
5Itisdiffusedthroughoutthe
Cytosol.
5Itisfoundindiscreteareasof
cytosol.
6ThePrformcontainsmany
doublebondsinpyrrolerings.
6ThePfrformhelpsin
rearrangeddoublebondsinall
pyrrolerings.
PP. No. 490

811. LobimenkaandScheglova(1938)proposethishypothesisandaccordingto
thistheory,floweringisdependsonphysiologicalprocess(photosynthesis
&Respiration)duringtheperiodoflightanddarkreactions.
Theyobservedtheratioofenergyinbetweenphotosynthesis&Respiration
isalmostequalinlongdayandlowerinshortdayplants,meanslight
reactionisfullydecomposedthephotosyntheticproductsinSDPsbutpartly
(less)inLDPs,whichisreverseindarkreaction.
Thishypothesis,furthersupportedbystudiesoninhibitors(cynide,sodium
azideanddinitrophenol)suppressedoxidativeprocessesinLDPsmeansit
inhibitthefloweringinLDPsandpromotethefloweringinSDPs.But
oxidativeprocessesinSDPsmeansitinhibitthefloweringinSDPsand
promotethefloweringinLDPs.
However,theeffectsofinhibitorsarenotfullyconvincingindarknessunder
longdaycondition,hencethistheoryisnotwidelyaccepted.
PP. No. 490

812. Chailakhyan(1968)proposedthishypothesisbynamed“Conceptoftwophase
flowering”inwhichhepresumedthatfloweringplantpassestwophasesoflife.
1.Flowerstemformationphase:Thisphaserequiresmetabolicchangesasobserved
underLDspeciesflowerunderLDcondition:
Thedaylengthaffectsaplantmetabolismbyincreasingcarbohydratecontents
andmetalcontainingoxidasesinleaves,auxinsinstemapicesandgibberellinsin
leaves,butdecreaseincontentofNitrogenouscompounds.
2.Flowerformationphase:Thisphaserequiresmetabolicchangesasobservedunder
SDspeciesflowerunderSDcondition:
TheprocessisfollowedbyincreasingNitrogenouscompoundsreduce
respiration,oxidasesinleaves,metabolitesofnucleicacid,metabolisminstem
apicesandanthesininleaves.
Chailakhyanassumedthattworeversekindofmetabolisminvolvedin
floweringisanadaptationoccurredduringthecourseofevolutioninSDPs&LDPs.
Butthistheoryhastwodifficultiesthat...
(i)Theinfluenceofdaylengthissimilaronthecontentsofnutrientsandhormonal
substancesinbothlongday&shortdayplants,isnotbelievable.
(ii)Existenceofanthesininleavesisnotproved.
PP. No. 491

813. (1) PHOTOPERIODISM IN RICE:
Kar&Adhikari(1945):Wintervarietiesofrice,flowerearlierundershortdays(SD).
SircarandGhose(1947):Summervarietiesofrice,delayinfloweringundershortdays(SD)duetohigh
temperaturetreatment.
Misra,1954:Reportedwhileworkingon4longdaysvarietiesofrice,givendifferentresponseundershort
photoperiodandconcludedthatresponseofshortphotoperiodvariedfromvarietytovariety.
GhoseandShastry(1954):workedon50varietiesofriceandsucceededinproducingsynchronisefloweringfor
hybridizationprogrammebygivingan8-hoursto30daysphotoperiod.Oldseedlingrequired30days
treatmentofphotoperiod.
(2) PHOTOPERIODISM IN WHEAT:
Kar(1940),Pal&Murty(1951)andMisra(1958):Revealedthatlongphotoperiodincreasedfloweringin
Indianwheatsfornormalgrowth,andyieldbutitrequirelowtemperatureatearlystagesandhigh
temperatureatearformation.Longphotoperiodhastenearingbutreducesizeofearsandsuppresstillering.
ChinoyandNanda(1951&1957):SummerTheystatedthatthevariesNP16,NNP52,andPBC591treated
withlongphotoperiodsduringgerminationshowedshortingofvegetativegrowth.Shortdaysphotoperiod
reducedstemelongation,decreaseweightofplantandlesstilleringduetoreductioninthedurationof
photosynthesis.Theexperimentalfiningsrevealedthattheabsorptionofnutrientsisdeterminedmoreorless
bypatternofgrowthimposedbyphotoperiod.
Nanda,ChinoyandSirohi(1958to1961):Theyhavedonemanyexperimentsonwheatandconfirmedthat
shortdayandlongdaytreatmentsreducethegrainstrawratio.Inshortday,duetoreductioninNAR(Net
assimilationrateandinlongdayduetointerferencewithsynthesisofregulatorysubstances(planthormones
(auxins,cytokinins,gibberellins,abscisicacidandethylenearegrowthregulatorysubstances).The
photoperiodictreatmentaffectsonnos.offertilepollengrains,weightofearandnos.ofgrains/ear.

814. (3) PHOTOPERIODISM IN SUGARCANE:
VijayasardhyandNarsimhan(1953):
Theyobservedthatanyvariationindaylengthsuppressthefloweringinsugarcaneby
alterationinvegetativephasebeforetheformationoffloralprimordial,delayflowering.If
photoperiodischangedafterflowering,thereisnomarkedeffectonplant.
However,darkperiodisprolongedof4hrsafternormalnightproduced
simultaneous(atexactlythesametime)floweringinbothearlyandlatevarietiesofsugarcane
whichisadvantageousforbreeders,acrossingbetweenthemispossible.Theeffectof,darkperiod
wasincreasewiththeageoftheplant.
(4) PHOTOPERIODISM IN JUTE:
Kundu,Basak&sarkar(1959):
Theyobservedthatphotoperiodof10-12hrsisinducedfloweringininboth
thespeciesofjutei.e.CorchorurusolitoriusandC.Capsularis(shortdaysPlants)in30
days.Butthecriticalperiodis12½hrsbeyondwhichfloweringisretarded.

815. 1.HasteningofEarheadproduction:
DuringlonglightexposurePhotoperiodismisanexamplefor
physiologicalpreconditioning.Thestimulusisgivenatonetime
andtheresponseisobservedaftermonths.Exposuretolonger
photoperiodshastensflowering.
Example,wheatislonglightexposure,Prformisconvertedinto
Pfrformandfloweringisinitiated.Theadvantageisthatcropcan
harvestearlier.Ifdarkperiodisgreater,PfrisconvertedintoPr
formthatinhibitsflowering.
2.Thephytochromemediatedphotoresponsesinplants:
Itisusefulinphotoperiodism,seedgermination,sexexpression,
buddormancy,rhizomeformation,leafabscission,epinasty,flower
induction,proteinsynthesis,pigmentsynthesis,auxincatabolism,
respirationandstomataldifferentiation.

816. 3.Annualplantsfloweredtwiceinyear:
Thevegetativegrowth,timeoffloweringandfruitingindifferent
speciescanbecontrolledartificiallybygivingvaryinglengthof
day,henceinannualplantsp.,floweringmaycometwiceinyear
therebyfarmersgetbenefittwocropsanddoublingtheiryield.
4.Synchronousfloweringforbreedingpurpose:
Normally,crossingisnotpossiblewhenthereisaearly(f)andlate
variety(m)orvice-versa.Butbycontrollinglengthofaday
artificiallythathelpsinbroughtflowersatasametime
(synchronousflowering)invarietiestherebycrossingispossible
otherwiseitisnotfeasibleinnature.Hence,breedingpointof
view,itisveryimportantaspect.
5.SeasonalProductionApproachinPolyhouse:
Commercialproductionofflowerscanbeincreasedevenunder
differentseasonsundercontrolledcondition(Polyhouse).

818. Klippartin1857,whileworkingwithtwovarietiesofwheatthewinterandspringwheat,
noticedthelowtemperaturerequirementforflowering.
T.D.Lysenkoin1920sThetermvernalizationwascoinedbyhimandtheoriginalRussian
wordis“Jarovizacija”–Atruemeaningofitis“transformationofwinterformstospring”.
Lysenko(1929-30)observedthat,ifseedsofwinterwheataregerminatedinaniceboxand
subjectedtosuitablelight,moisture,thesecanbeshowninspringseasonandwillflowerwith
springvarietiesofwheat.
Chourad(1960)hasdefinedvernalizationasthe“Acquisitionoftheabilitytoflowerbya
chillingtreatment.
F.G.GregoryandO.N.Purvis(1961)havealsocontributedtothestudyonvernalization.
Purvisstatedthatseedmustcontainatleast90%wateroftheirabsolutedryweightfor
adequatevernalization.
Thistypeofagriculturalpracticesresultsinshorteningoftheintervalbetweensowingand
flowering.
VernalizationmethodcanbesuccessfullyappliedinfamiliesGraminae(oat,Wheat),
leguminaceae(Pea,Clover),Cruciferae(Cabbage)etc.
Inmanyplantsthefloweringisinfluencednotonlybythecorrectphotoperiodbutalsoby
thetemperature.

819. Definition:
“AcquisitionorAccelerationoftheabilityofplantsto
flowerearlierduetothestimulationofflorigenhormone
bycoldtreatment(s)iscalled“Vernalization”.

820. Hyoscyamusniger(henbane),hastwotypesofplantsoneisannualandotheris
biennial.Bothofthemarelongdayplantsandwhenexposedtoshortdaywillgrow
vegetatively.Eventhebiennialtypecanbemadetoflowerifitstendaysoldseedling
aresubjectedtocoldtreatment(vernalised).
PRACTICAL UTILITY OF VERNALIZATION: EXPLOITED BY RUSSIAN SCIENTIST LYSENKO
Cropcanbeproducedearlierbecauseofvernalizationshortensthevegetative
periodofplants&induceflowering.
Cropcanbegrownintheregionswheretheydonotnaturallyreproduced;
PlantBreedingworkcanbeaccelerated.
IncoldercountrieslikeRussia,whereinthewintersaresevere,vernalizationhas
beenofgreatimportanceinagriculture.Bythisprocesscertaincropplantscould
bemadetoescapetheharmfuleffectsofseverewinters,thusimprovingthecrop
production.
InwarmercountrieslikeIndiavernalizationpracticehasnotbeeninusemainly
becauseit’sacostlyprocessandwintersarecomparativelynotveryservewinter
astoharmthecropplantslikeinRussia.

821. Thetermed“Vernalization”wasgivenby
Lysenko(1928).
Scientist Lysenko

822. SiteofVernalization:
Apicalmeristem,Embryo,Youngleaves(Cabbage)
ThestemapexmainlyperceivetheeffectofVernalizationbut
Wellensick(1961-62)hassucceededinvernalizingleavesandroots
ofLunariabiennis.
TransmissionofVernalizationEffect:
Throughcelldivisionfromaparentcelltodaughtercellbutnot
throughagraftunionasincaseofphotoperiodism.Insomeplants
vernalizationcanbeaffectedonlyaftersomevegetativegrowth.
Devernalization:
Itistheprocessbywhichthevernalizedseedscanbedevernalized
byreverseeffecti.e.seededareagaintreatedwithhigher
temperature(25-40°C).Devernalizationcanbeaffectedbyexposure
ofvernalizedplantstohightemperature,highnitrogenous
atmosphereandHighCO2inatmosphere(20%).

823. Intheprocessofvernalization,thecompletionofonestageisabsolutelynecessaryfor
thecommencementofnextone.Eachofthesestagesrequired–suitabledoseoftemperature,
humidity,light,aerationetc.Inlackofanyone,furtherprocessischecked.
(A)Thermostage:
FirststageisquitenecessaryalsoreferredasvernalizationstageorLysenkostage.
Conditionsrequiredforsuccessfulpassageare
(i)Temperature:Lowtemperaturerangingfrom0ºCto20ºC,accordingtospecies.
(ii)Moisture:Moistureisequalimportantforneatcompletionofstage.
(iii)Aeration:Properaerationisrequiredotherwisemaybecomeacriticalfactor.
(iv)Time:Timeorperiodforcompletionofthermostageisnotmaintained,theresponseof
vernalizationisdecreased.
(B)Photostage:
Whenthermostageiscomplete,plantpassthroughanotherstagecalledphotostageThereis
pronoucedeffectofrelatvelengthofday&nightonflowerproduction.Thisphenomenonis
morecorrectlycalledphotoperiodism.
(C)Gametogenesisstage:
Whileitispoorlyknown,itisaquitenecessaryforseedformationinconnectionwiththe
formationofsexualelements[(malegamete-microspores)+(femalegamete-megaspores)].
Thephotoperiodrequirementforthisstageislittleshorterthanphotostageingeneral.

824. Forvernalization,theseedsareallowedtogerminateforsometime.
Givencoldtreatmentsbykeepingthemat0-5ºC.
After,coldtreatmentseedlingareallowedtodryforsometimeandthen
sown.Theyshouldnotbesownimmediatelyafterthecoldtreatment.The
dryingperiodshouldnotbelongotherwiseresponseofvernalization
decreases.
Theresponseofvernalizationdecreasesiftheperiodofvernalizationis
interruptedbyperiodsofheattreatment.
Notonlyseedsbutisolatedembryoscanbevernalized.

826. GregoryandPulvisperformedaseriesofexperiments&concludedthatleaf
numbersaredecidingfactorinvernalizationforflowering.
PohlandCholodny(1935)statedthatsomesubstancesofhormonalnaturefoundin
leavesandareresponsibleforvernalization.Theyfurtherobservedthattheitself
embryodevoidofhormonesforgrowth,itmustreceivedfromendosperm.
Maxmovaperformedanexperimentinwhichendospermsofspringandwinter
varietiesofcerealsweresuccessfullyinterchanged.
GregoryandPulvis(1936)observedthatexcisedembryoseparatedcompletekly
fromendospermandgrownonagarmediumcontaining2%glucoseandmineral
nutrientscanbevernalizedinthesamewayasseeds.Bythisexperimentitcanbe
concludedthatembryoisaloneabletosynthesishormonesandnotreceived
hormonesfromendosperm.
Butintheabsenceofsugarsupplytheexcisedembryofailstoshow
vernalizationresponse.
Lysenko(1934)proposedthePhasicdevelopmenttheoryinwhichgrowthand
developmentofanannualseedplantconsistsofseriesofphaseswhichmust
occurinsomepredeterminedsequence.Commencement willtakeplaceonlywhen
precedingphaseisover.Thephasesrequiredifferentexternalconditionsfor
completionlikelightandtemperature.Vernalizationacceleratesthethermophase.

828. Melchers(1936)statedthereisexistsahormonewhichisresponsibleforflowering.In
someplantsgibberellinssprayonshootsunvernalizedplantcaninduceflowering.The
hormonehasbeennamed“vernalin”byMelchers(1939).
LangandMelcher(1966)postulatedthathormonecalledvernalinisproducedonthe
meristematicshootapexoftheembryoduetovernalizationtreatmentwhichis
responsibleforflowering.
Langstatedthatthereisadirectconnectionbetweenvernalinandflorigen.He
proposedthefollowingscheme:
Hormonal Theory of G Melchers:
Hesuggestedthatlowtemperatureinducestheformationofvernalin.It
initiatesthesynthesisoftheflowerstimulus.Thevernalinhasnotyetbeenisolated.
Butsomeindirectevidencesupportstheexistenceofvernalin.Heperformedtwo
experiments:
(a)Hegraftedaplantpart,stem,ofavernalizedhenbane(Hyoscyamus)toa–non-
vernalizedhenbaneplant.Hefoundthatthenon-vernalisedhenbaneflowered.
(b)Florigenalsopassesthroughgraftunion.Somephysiologistssuggestthatflorigen
maybevernalizationstimulus.
TheexperimentsofMelchersandLangproveditwrong.Theygraftednon-
vemalizedhenbane(Hyoscyainusniger)planttovernalizedMarylandMammoth
tobaccoplant.Thehenbaneplantflowered.Thestimulustransmittedfromtobacco
planttothehenbanemaybethroughphotoinductivecycleornon-inductive.
Low temp.
Thermo-induced
condition Vernalin Florigen Floweing

829. HORMONAL THEORIES :
FirstHormonalPathwaywasproposedbyLangandMelchers(1947)isschematically
shownbelow.
D
Highertemp.
Cold Normaltemperature
A B C Flowering
Precursor Thermo-labile
Accordingtothescheme,precursorAisconvertedintoathermo-labile
compoundBduringcoldtreatment.Undernormalconditions,BchangesintoCwhich
ultimatelycausesflowering.ButathighertemperatureBisconvertedintoDand
floweringdoesnottakeplace(devernalization).
Chailakhyan(1968)
Herefuted(disproved)theLang’sexperimentbecauseunderlongdayconditions
vernalinsturnintogibberellins.Vernalinhormoneisprecursorofgibberellin.Vernalinis
doubtfulhormone.
HironoandRedei(1966)
Hesuggestedgibberelins,uridylicacidandpyrimidinebasescanreplaced
vernalization.

830. VERNALIZATION OF DIFFERENT
CROPS IN INDIA:
1.Rice
2.Wheat
3.Barley
4.Pea
5.Arhar
6.Gram
7.Mustard
8.Linseed
9.Sugarcane
10.Jute
Cereals
Pulses
Oilseeds
Others

831. Indiabeinganon-industrialcountry,itswealthliesinagriculture.Butto
theill-luckofIndianpeasants,uncertaintiesofweatherconditionsoffergreat
hindrancesinmaintainingagoodcrop.Indianclimatedoesnotallowcropsto
standforalongperiodoftimeinanormalstate.
Duringtheperiodofdevelopment,cropsareusuallydamagedbyfrost,
hightemperature,excessiverainfallandfloods.InIndia,peas(Pisumsativum)
andarhars(Cajanuscajan)cropsaredamagedeveryyearbyfrost.
Similarly,certainstrainsofwheatatmilkstageofmaturationsadoften
damagedbyhightemperatureandsummercropslikemelonsandwatermelons
fallaneasyvictimtotheearlysettinginofrains.
Undersuchcircumstancesutilizingvernalizationifthecropcouldbe
harvestedwithinabriefspanduringwhichnoadverseconditionsmaysetin,the
conditionofIndianpeasantrycanbeactuallybettered.Vernalizationmayresolve
thisproblems.
ThesekindsoftemptationsandconsiderationsinvitedIndianscientists.
likeotherEuropeancountries,India,too,becameluredbythepracticalutilityof
vernalization.
Variousattemptsweremadetovernalizeplants.Scientificlaboratories
wereopenedandbothagriculturistsandscientistsworkedregularlyoncrop
plantslikewheat,barley,sugarcaneandpeas.Butthatwasahardtimeto
achieveanygoalandsoonenthusiasmevaporatedbecausetheexperiments
performedcouldnotyieldanypositiveresult.
VERNALIZATION IN INDIA:

832. Atthesametime,againstfailurefromdifferentplacesVivekanand
Laboratories,Almora,offeredpromisingresultsonvernalizationofanumberofcrop
plantslikemustard(Brassicajuncea),pea,wheatandlinseed(Linumusitatissimum).
SenandChakravartyvernalisedB.junceaT-27attwodifferentstages,(i)
soonaftersprouting,seedswithupslitseedcoatsoakedinwaterfor24hours.The
resultshoweddefinitiveearlinessofabout23daysintheflowering.
RICE:
KarandAdhikary(1945)andSircar(1948)reportedthatlowtemperature
vernalisationinducedsomelatenessinfloweringricecrops.Thechiefobjectiveofrice
vernalisationwastofindpossibilitiessavingthecropfromfloodanddrought.
ParijaandPillay(1944)observedthatpre-sowinglowtemperatureandanaerobiosis
inducedfloodresistanceincertainvarietiesofricecrops.
HidayatullaandSen(1941)andKarandAdhikary(1945)reportedthatpre-sowing
hightemperatureappearedtoinduceearlyfloweringinanumberofvarieties.
WHEAT:
Kar(1940,1943),PalandMurty(1941)andSenandChakravartv(1945)foundthat
wheat,ingeneral,didnotrespondtovernalization.
Itmaybeduetotheirshortlifecycle.
Chinoy(1963)reportedthatvernalizedseedsofNP165underlong-day,treatment
scoredincreasedauxincontent.

833. JUTE:
Kar(1943)studiedtheeffectofvernalisationonjute(Corchoruscapsularis)and
foundthatpresowingcoldtreatmentofseedsledtodelayedgermination,increased
productionofgreenpigmentsinleavesandmorevigorousgrowthinearlystate,but
nosignificanteffectcouldbeobservedinthedateofflowering.
SenGuptaandSen(1943-44)reportedsimilarresults,i.e.,noeffectofcold
treatmentasfloweringtimeoronvegetativegrowth.
SenGupta(1953)observedthatcoldtreatmentswithlongerperiodsledtosome
earliness(upto40days)ofloweringandfruiting.Thesefindingswerelater
confirmedbyKundu,BasakandSarcar(1959).
PULSES:
PalandMurty(1941)andPillay(1944)foundthatGram(Cicersp.)respondedto
vernalisationwhichcouldflowerundernaturaldaysinsummer.

834. World’s Biggest Seed with Embryonic Root
or Radicle
•TheRoyalBotanicGardeninEdinburgh
germinatedthisbowlingball-likecoco
demer(Lodiceamaldivica)palm.
•Theseedweighs35lb(16kg)andcan
produceatreethatwillliveupto300
years.
•Scottishbotanistsputinadarkcase,
andnowaroothasdeveloped.Itwill
produceoneleafayearforthenextfew
years.Thetreewillbegintoflowerin
20-30yearsandproduceitsownseeds
afteranotherfivetosevenyears(Seed
formationDt.10-09-2003).
•Source:http://www.crocus.co.uk/whatsgoingon/regionalscotland/
Radical

836. Chilakhyan’shypothesis: This hypothesis
assumes that flowering hormone –florigen is a
complex of two types of substances –
gibberellinand anthesins. Gibberellinis
essential for growth of the plant stems and
anthesinsare required for flower formation.
According to him, flowering in all annual seed
plants requires two phases: (i) Floral stem
formation phase (ii) Flower formation phase.
First phase involves increased carbohydrate
metabolism and respiration with increased
content of GA in leaves. Second phase requires
intensive nitrogen metabolism, higher content
of anthesinsin leaves and nucleic acid
metabolites in stem buds. Long day conditions
favour the first phase while short day
conditions favour second phase. In long day
plants gibberellins are critical, while anthesins
are critical in short day plants. However,
anthesin is hypothetical; it has not been
isolated as yet.

837. PHOTOPERIODISM IN SUGARCANE:
J.Midmore(1956)studiedtheEffectsofphotoperiodonfloweringand
fertilityofsugarcane(Saccharumspp.)andrevealedthatthenightlightbreakregime
(NLB)iseffectivetreatmenttodelayfloweringwheninterruptedthenatural
inductivedaylengths.
Clonesrespondedtoa10mindifferencebetweeninductivedaylengths.
WhentheNLBwasfollowedbynaturaldays(shorterthannormalforinductionof
flower)allstagesofdevelopmentwerehastenedandalsoproducedmalesterile
plant.
(i)WhenPeriodsofNLBafterfloralinitiationingeneraldelayeddevelopment.
(ii)Whenappliedatthespikeletinitiationstage,floweringofcloneswasdelayedby
1–2weeksandpollenfertilitywasreduced.
(iii)Whenappliedattheearlierstageofbranchinitiation,floweringofsomeclones
wasdelayedfloweringandothersweredidnotemerge.
(iv)WhenappliedatFlagleavesinflorescenceemergebutflowerslongerthanthose
ofcontrolplants.

838. Arabidopsisthalianaasa
modelsystem:
Infloweringplants,the
transitionfromvegetative
growthtofloweringis
controlled by both
developmental and
environmentalsignals.
Epigenetics-flowerthatcomesfromcold;AmodelfortheactionofthePolycomb
groupproteinVRN2invernalization,basedontheresultsofGendallet
al.vrn2mutantsshowanincreasedDNAsesensitivityofFLCaftervernalization
suggestingthatVRN2changesthestructureattheFLClocusbyrecruitingaprotein
complexwithchromatinremodelingactivity.Thiscouldestablishormaintainthe
epigeneticmark,whichenablestheplanttorememberperiodsofcoldtemperature
forseveralweeks.
FLOWERING LOCUS C (FLC) blocks
flowering prior to vernalization
After vernalization
Protein
recruiting a protein
complex with chromatin

839. TheGA-deficientna-1mutant,
elongatesdramaticallywhengraftedto
aNAstockwithmatureleavesofpea
plant.
Thena-1plantontheleftwas
ungrafted,andremainedshort.
Ungrafted
GA-deficient
short plant
Arabidopsis;Winterannualrequirescold
treatmentforfloweringbutRapidrecycler
doesnotrequirevernalization
Gibberellinsareknowntoovercomebothcoldtreatmentand
photoperiodictreatmentinlongdayplants,butithasnoeffectonshortday
plants.Synthesisofsomeunknownsubstancecalled‘Vernalin’duringtheperiod
vernalizationhasbeenclearlydemonstratedbygraftingexperiments.

840. →If,winter(Oct.-Nov.)varietiesofwheat:SonalikaandRye:PusaRabi,plantedinspringseason
(Feb.)onlyvegetativegrowthisoccur,supposeifitflowered,it1.delayflowering,2.delayseed
setting3.poorseeddevelopmentinsummerand4.givelowyield.
ThewinterryecalledSecalecerealeorPetkusryeisabinnialplantwhichrequirescold
treatmentforsuccessfulcultivationasoneseasoncrop.Thegrainsoftheseplantsareknownfor
theirhardinessandqualityforthepurposeofmillingandbaking.
Procedure:Imbibed/soakedseeds(inwater)aretreatedwithchillingtemperaturei.e.2-
5°Cfor5-6weeks(1.5monthbeforeFeb,i.e.15
th
Dec.)itproducesnormalfloweringinspring
season,goodseeddevelopmentandharvesthighyield.
→Byshorteningthevegetativeperiodofcerealsbychillingtreatmentprovidestheescaping
mechanismagainstdroughtcondition(May-June)thatsetthetimeofripeningperiodofcrop.
→Flowerscanbeproduceinoutofseason.
→Cropyieldcanbeincreasedthroughvernalizationtreatment.
→Infact,farmersusedtocultivatethisvarietyaftersubjectingthewaterimbibedgrainstocold
treatmentandgrowingtheminthespringandharvestinginthesameinsummer.Amongmany
plants,Petkusrye(shortdayplants)wasthefirsttobeusedforexperimentation.
TheotherexamplesareHyoscyamusniger(longdayplant)Triticumaestivatum(CV
winterwheat),Lunariabienensis,Arabidopsisthalliana,Loliumperennial,BetaVulgaris,Brassica
oleracea,andothers.

841. •Cropscanbeproducedearlierandcropscanbegrownintheregion
wheretheydonotgrownaturally.
•Plantbreedingcanbeacceleratedbytheapplicationofvernalization
technique.
•Itincreasethecoldanddroughtresistancepoweroftheplant.
•Helpstoreduceincidenceofdiseasesinseveralplants.
•Enhancetheyieldofcrops.
•Vernalizationisrequiredtobreakdormancyandinducegrowth.
•Offseasonvegetablesandcropsandflowerscanbeproducedby
vernalization.
•Mayhelptoresolvetheadverseconditionduringtheperiodof
developmentofcrops.
•Devernalizationhelpsinthecontroloffloweringofonion,garlic,potato,
andotherno.ofplants.
•Itshortensthevegetativeperiodandhastenfloweringperiodwhichwill
makeabenefittothefarmer.
IMPORTANCE OF VERNALIZATION:

842. CONDITIONS NECESSARY FOR VERNALIZATION:
1.Ageoftheplant:
Itdeterminestheresponsivenessoftheplanttocoldstimulusanditdiffersin
differentspecies.Incaseofbiennialvarietyofhenbane(Hyoscyamusniger),the
plantswillrespondonlywhentheyareinrosettestageandhavecompletedatleast
10daysofgrowth.
2.Appropriatelowtemperatureanddurationoftheexposure:
Mostsuitabletemperatureis1-6°C.Theeffectivenessdecreasesfrom0to-4°Cand
Temp.above7°C--14°Carealmostineffectiveinvernalizingtheplants.
3.Oxygen:
Oxygenrequirementlowbutabsolute.Vernalizingisanaerobicprocessand
requiresrespiratoryenergy.Initsabsence,coldtreatmentbecomescompletely
ineffective.IfrespiratoryinhibitorsareusedVernalizationdecreases.
4.Water:
Sufficientamountofwaterisalsoessential.Vernalizationindryseedsisnot
possible.

843. Lecture-28

846. DEFINITION:
Translocationoforganicsolutes:Themovementoforganicfood
materialsorthesolutesinsolublefromoneplacetoanotherin
higherplantsiscalledastranslocationoforganicsolutes.
WhyTranslocationoforganicsolutesisessentialinhigherplants?
because:
(i)Inhigherplants,onlythegreenpartscanmanufacturefoodand
itmustbesuppliedtoothernon-greenpartsforconsumptionand
alsoforstorage.
(ii)Duringthegerminationoftheseeds,theinsolublereservefood
materialoftheseedisconvertedintosolubleformandis
suppliedtothegrowingregionsofyoungseedlingtillithas
developeditsownphotosyntheticsystemi.e.,leaves.
Translocationoforganicsolutesalwaystakesplacefromthe
regionofhigherconcentrationofsolubleformi.e.,thesupply
end(source)totheregionoflowerconcentrationofitssoluble
formi.e.,theconsumptionend(sink).
PP. No. 361

847. DIRECTIONS OF TRANSLOCATION:
Translocation of organic solutes may take place in the following
directions:
1. Downward Translocation:
Mostly, the organic food material is manufactured by leaves and is
trans located downward to stem and the roots for consumption and
storage.
2. Upward Translocation:
It takes place mainly during the germination of seeds, tubers etc.
when stored food after being converted into soluble form is
supplied to the upper growing parts of the young seeding till it has
developed green leaves.
Upward translocation of solutes also takes place through stem:
(i) To buds which resume growth in the spring
(ii) To developing leaves situated closer to its apex
(iii) To opening flowers and developing fruits which are situated
near the ends of the branches.
3. Radial Translocation:
Radial(horizontal)translocationoforganicsolutesalsotakesplace
inplantsparticularlyinstemfromthecentralcellsofthepithto
cortexcells.
PP. No. 361

848. 1.PATHOFDOWNWARD TRANSLOCATION :
Downwardtranslocationoftheorganicsolutestakesplacethroughphloem.
ThisviewissupportedbythefollowingFIVEEvidences:
(i)Tissuesotherthanphloemcannotaccountfordownwardtranslocation:
Ascentofsaptakesplacethroughxylem,sonaturallyorganicsolutes
arenottranslocatedthroughit.Thecellsofthegroundtissuearestructurally
neithersuitablefortranslocationnortheycontainsolubleorganicsolutes
whichcouldbetranslocated.
Thesexylemcellsusuallyhaveorganicsolutesininsolubleform.Thus,
onlyphloemisleftwhichcanaccountfortranslocationoftheorganicsolutesin
solubleform.Theendtoendarrangementofthesievetubesinphloemwhose
crosswalls(sieveplates)areperforatedbysieveporesformcontinuous
channelsandisbestsuitedforit(Fig.15.1).
Further,inCucurbitswheretheleavesareusuallylarger,thestem
containsbicollateralvascularbundlestocopewiththerapidtranslocationof
foodmaterialsthroughit.
(ii) Blocking of phloem:
Translocation of food materials stops when sieve pores are plugged
due to the deposition of a chemical compound, the callose.
PP. No. 362

849. CollateralVascularBundles-
1.Thistypeofvascularbundleisfoundin
bothdicotandmonocotstems.
2.Itisconjointandmaybeopenorclosed
typedependingonthepresenceand
absenceoffascicularcambium.
3.Presenceofonepatchofphloem
towardsoutersideandonepatchofxylem
towardsinnerside.Astripofcambiummay
ormaynotbepresentbetweenphloem
andxylempatches.
Example:Tridax,Zea.
BicollateralVascularBundle:
1.Itisconfinedtocertaindicotstemonly.
2.Itisalsoconjointbutalwaysopentype
duetopresenceoffascicularcambium.
3.Itconsistsoftwopatchesofphloem
(outerandinner),twostripsofcambium
(outerandinner)onepatchofxylematthe
center.
Example:Cucurbia.

850. PP. No. 362

851. (iii) Chemical analysis of phloem sap:
Cellsofphloemcontainlargequantitiesoforganicsolutes
mainlysugarssuchassucroseinsolubleform.
(iv)Isotopicstudies:
Ithasbeenobservedthatifaleafoftheplantisallowed
tophotosynthesizeinpresenceoflabelled
13
CO
2
thetranslocationof
carbohydrateslabelledwith
13
Cisotopetakesplacethroughthe
stem.But,ifsomesegmentsofthestemincludingphloem,no
movementofcarbohydratescouldbedetectedupward.
PP. No. 362

852. (v)Ringingexperiment:
Ifaringofbarkincluding
phloemisremovedfromthestemof
aplant,thedownwardtranslocation
offoodmaterialstopsandfood
materialaccumulatesjustabovethe
ring.
Asaresultaftersometime,
thetissueabovetheringswellsand
mayevendevelopadv.roots(Fig.
15.2)whilethelowerpartsofthe
plantbelowtheringedportion
graduallydryup.
PP. No. 362

854. 2. Path of Upward Translocation:
Translocation of organic solutes takes place through phloem, but
under certain conditions it may take place through xylem.
3.Path of Radial Translocation:
Radial translocation of organic solutes also takes place in
plants from the cells of the pith to cortex via medullary rays.
PP. No. 363

855. medullaryrays

856. PP. No. 363

857. Varioustheorieshavebeenputforwardtoexplain
themechanismofphloemconductionbuttheyarenotfully
satisfactory.AmongthemMunch’s(1930)hypothesisis
mostconvincing.
MUNCH’S MASS FLOW OR PRESSURE FLOW HYPOTHESIS:
ThishypothesisputforwardbyMunch(1930)and
elaboratedbyCraft(1938)andothers.
Translocationoforganicsolutestakesplaceinmass
throughphloemalongagradientofturgorpressurefrom
theregionofhigherconc.ofsolublesolutesi.e.,supplyend
totheregionoflowerconc.i.e.,consumptionend.
Theprincipleinvolvedinthishypothesiscanbe
explainedbyasimplephysicalsystemasshowninFig.
PP. No. 363

858. Diagram illustrate the principle
of Munch mass for hypothesis
Two membranes Xand Y
permeableonlytowateranddippinginwater
areconnectedbyatubeTtoformaclosed
system.Membrane Xcontainsmore
concentrated sugarsolutionthanin
membraneY.
Duetohigherosmoticpressureof
theconcentrated sugar solutionin
membrane X,waterentersintoitsothatits
turgorpressureisincreased.Theincreasein
theturgorpressureresultsinmassflowof
sugarsolutiontomembrane Ythroughthe
tubeTtilltheconcentrationofsugarsolution
inboththemembranesisequal.
Asaresultofphotosynthesis,
mesophyllcellsintheleavescontainhigher
concentrationoforganicfoodmaterialin
theminsolubleformandcorrespondto
membraneXorsupplyend.Thecellsofstem
androotswherethefoodmaterialisutilized
orconvertedintoinsolubleformcorrespond
tomembrane Yorconsumptionend.While
thesievetubesinphloemwhichareplaced
endtoendcorrespondtothetubeT.
PP. No. 363

859. Mesophyllcellsdraw/absorbedwaterfromthexylemoftheleafduetohigherosmotic
pressureandsuctionpressureoftheirsapsothattheirturgorpressureisincreased.
Theturgorpressureinthecellsofstemandtherootsiscomparativelylowandhence,the
solubleorganicsolutesbegintoflowenmassfrommesophyllthroughphloemdowntothecells
ofstemandtherootsunderthegradientofturgorpressure.
Inthecellsofstemandtherootstheorganicsolutesareeitherconsumedorconvertedinto
insolubleformandtheexcesswaterisreleasedintoxylemthroughcambium(BelowFig.).
PP. No. 364
Fig.15.4
The diagram showing
mechanismof solute
translocationaccordingtoa
theMunch’shypothesis

860. DEMERITS OF MUNCH’S HYPOTHESIS :
(1)Thishypothesisaccountsforthetranslocationinonly
onedirectionatatime,althoughtheremaybe
simultaneousupwardanddownward translocationof
solutes.
(2)Thereisconsiderabledoubtregardingthemagnitudeof
theturgorpressureatthesupplyendwhichmaynotbe
sufficientenoughtoovercometheresistanceofferedby
thesieveplatesinthetranslocationofsolutesthrough
sievetubes.
(3)Turgorpressuremaynotalwaysbehigheratthesupply
end.
(4)Thishypothesisisbasedonpurelyphysicalassumptions
anddoesnottakeintoaccountthefactthatwholeofthe
translocationprocessismaydependentupontheplant’s
metabolismandthemetabolicenergy.
PP. No. 364

861. (1)PROTOPLASMIC STREAMING THEORY:
AccordingtothishypothesisfirstproposedbyDeVries(1885)
andlatersupportedbyCurtis(1935)protoplasmicstreamingoccurs
insievetubeelementsofphloemandthesolutemoleculescaughtupin
thecirculatingcytoplasmarecarriedfromoneendtotheother
endofsievetubefromwheretheydiffusetothenextsievetubeelements
throughthecytoplasmicstrandsinthesieveplates.
Thistheorywassupportedbecause:
(i)Itaccountedforsimultaneousmovementofsolutesinbothupwardanddownwarddirections
inthesamesievetubeand
(ii)Thatthefactorslikelowtemperatureandoxygendeficiencywhichretardprotoplasmic
streamingalsocheckedthetranslocationofsolutes.
But,thestrongestobjectionagainstthistheoryisthattheprotoplasmicstreaminghas
notbeenobservedinmaturesievetubeelements.
Protoplasmictheoryhasrecentlybeenre-emphasizedbyCany(1952)andThaine(1962,64)who
observedthe‘transcellularstrands’(cytoplasmicstrands)traversingthesievetubeelementsin
petiolartissue.
Theyalsoobserved:
(i)Themovementofsoluteparticlesfromonesievetubeelementtoanother
(ii)Particlesmovinginoppositedirectionsinadjacenttranscellularstrandsinthesamesieve
tubeelement.
PP. No. 364-365

862. (2)INTERFACIAL FLOWHYPOTHESIS :
AccordingtothishypothesisproposedbyVandenHonert(1932)thesolute
particlescouldmovealongtheinterfacessuchasbetweenthevacuoleandthe
protoplast.Butthistheorydidnotfindsupport,themainobjectionagainstthistheory
being
(i)thelackofevidencesinsupportofsuchamechanisminplantsand
(ii)thattheplantmembranesarenotstaticbutconstantlychanging.
(3)ACTIVATED DIFFUSIONHYPOTHESIS :
AccordingtothishypothesisputforwardbyMasonandPhillis(1936)the
protoplasmofsievetubeelementsinsomewayhastensthediffusionofthesolutes
probably
(i)byactivatingthediffusingmoleculesor
(ii)bydecreasingtheresistanceoftheprotoplasmtotheirdiffusion.Althoughthey
couldthinkoftheparticipationoftherespiratoryenergyduringthisprocessbut
wereunabletogivedetailsofsuchamechanism,andhence,thistheoryalsohasnot
beenaccepted.
(4)ELECTRO-OSMOTICTHEORY:
AccordingtothistheoryputforwardbyFensom(1957)andSpanner(1958)
thetranslocationofsolutesthroughsievetubestakesplaceprobablyduetoanelectric
potentialacrossthesieveplates.Theelectric-potentialcouldbemaintainedbythe
circulationofK
+
atthesieveplates.Butduetolackofevidencesthistheorycouldnotbe
elaboratedfurther.
PP. No. 365

863. PP. No. 365

864. Translocation:
Itistheprocessbywhichmovementof
carbohydrates/sugarthroughvascularsystem
(Phloem)fromoneparttotheotherpartsofthe
plantiscalledtranslocation.
Plasmodesmeta
PP. No. 365
Phloem consists of several types of
cells:
sievetubecells,companion
cells,and thevascular
parenchymacells.
Sievecellsaretubularcellswith
endwallsknownassieveplates.
Sievecellslosttheirnucleibut
remainalive,asemptycell.
Parenchyma cell

865. Source
Sink
PP. No. 365

866. •Source is the location where food is produced
(photosynthesizing leaves or storage tissue).
•Sink is the location where all plant parts are
meet their own nutritional needs (roots and
stems).
First Paragraph Information :
PP. No. 365

867. No. Source: No. Sink:
1.Itistheregionsofphoto-assimilates
production
1.Regions of photo-assimilates
consumption
2.Exportphoto-assimilates 2.Importphoto-assimilates
3.Sourceisoccurinchlorophylloustissues3.Sourceisoccuringrowingregions–
Stem&Root
4.Highsugarconcentrationat“source”
(sugarloadedsite)
4.Sugarunloadedat“sink”whereitis
metabolizedorconvertedtostarch
5.ATP:energyisrequiredwhensugar
movesfromasourcetoasinkby
osmoticpressure.
5.ATP:energyisrequiredwhensugaris
convertedintostarchasastorageor
metabolizedforvariousfunctions.
6.e.g.Leaves,stipules,fruitwall,young
stem,pedicel,awns,peduncle,calyx,
bractetc.
6.e.g.Storageorgans–FruitandSeed
7.Sourceislimitedinthesuchcropslike
wheat,rice,pulsesandoilseeds
7.Sinkislimitedinthesuchcropslike
sorghum,maize,bajraandragi.
8.Auxinpromotessourceuptake 8.Cytokininincreasesphoto-assimilates
importinsink.
Additional Information:
PP. No. 365

868. Last paragraph of PP. No. 365:

869. PP. No. 365

870. (1.)ApoplasticMovement/Pathway:
Transportofassimilates/Photosynthates/foodmaterialsfromonecell
toanothercellthroughcellwallisknownasApoplasticPathway.
(2)SymplasticMovement/Pathway:
Transportofassimilates/Photosynthates/foodmaterialsfromonecell
toanothercellthroughplasmodesmataincytoplasmisknownas
symplasticPathway.
Transport of food materials from root to xylem
PP. No. 365

871. FoodmovesthroughthephloembyaPressure-FlowMechanismORMassFlowMechanism.
Sugarmoves(byanenergy-requiringATP)fromasource(usuallyleaves)toasink(usually
rootsorfruit)byosmoticpressure.Translocationofsugarintoasieveelementincrease
osmoticpotentialthatcauseswatertoenterinsievecell.Now,sugar+watermixture
(phloemsap)increasingthepressure,hencesaptoflowtowardanareaoflowerpressure,
thesinkthroughcompanioncells.Inthesink,thesugaristransferredfromthephloemto
sink(fruit)byfurtherATPisrequiringandstarchisusedinforvariousmetabolicfunctions.
Excesswateragainre-backintoxylem.
Phloem loading for Sugar
Translocation:
Themesophyllcells(symplast)of
leafsynthesissugarthatmoveinto
companioncellsandfinallytransferinto
phloemsievetubescellsthrough
plasmodesmata iscalled“phloem
loading”.
Phloemunloading:
Thesugar(photosynthates)are
transferfromphloemsievetubeelements
tothecellsofasinkiscalled“phloem
unloading”.
Sourcesareplaceswheresugars
arebeingproduced.
Sinksareplaceswheresugaris
beingconsumedorstored.Ifitisunableto
utilize,itinhibitorreducephotosynthesis.
ATP
Require
ATP
Require
Water
Re-back
into Xylem
PP. No. 365

872. Inlatercase,thesugarsareactively
loadedfromapoplasttosievetubesby
anenergydriventransportlocatedin
thePlasmaMembraneofthesecells.
Themechanismofphloemloadingin
suchcaseiscalledSucrose-H+
symportorcotransportmechanism.
Accordingtothismechanismprotons
(H+)arepumpedoutthroughthe
plasmamembraneusingtheenergy
fromATPandATPasecarrierenzyme,
sothatconcentrationofH+becomes
outside(intheapoplast)thaninside
thecell.
Spontaneoustendencytowardsthe
equilibriumcausesprotonstodiffuse
backintothecytoplasmthrough
plasmamembrane coupledwith
transportofsucrosefromapoplastto
cytoplasmthroughSucrose-H+
symporterlocatedplasmamembrane.
Cell wall
Apoplast
Cytoplasm
Symplast
Plasma
Membrane
PP. No. 366
Fig. 15.5 Sucrose -H+ Symportor Co-transport Mechanism
Phloemloadingisspecificandselectivefortransportsugars&differedinvariousspp..

873. Details Apoplasticloading /
Movement / Pathway
Symplasticloading /
Movement / Pathway
Types of sugar transportSucrose Sucrose + other oligo-
sachharides
Types of companion cells in
small veins
Ordinary ortransfer cellsIntermediary cells
No. of plasmodesmata
connecting sieve tubes
(including companion cells)
Fewer Abundant
Table 15. 1 patterns in apoplasticand syplasticphloem loading
PP. No. 366
Experimentalfindingsrevealedthatthepatternsinapoplasticandsyplasticphloem
loadingisrelateswithtypeofsugar,typeofcompanioncells9ordinary,transferor
intermediatery)andnos.ofplasmodesmata.
Tosomeextent,phloemloadingisalsorelateswiththefamilyofplant,itshabit
(shrubs,vinesandherbs)anddifferentclimates(temperate,tropicalorarid).

874. ASSIMILATES PARTITIONING
Theproductsofcarbonassimilationorphotosynthesissuchashexoses;sucrose,
starchetc(i.e..fixedcarbon)arecalledasphotosynthatesorphoto-assimilatcsor
simplyasassimilates.
Theseassimilatesareproducedingreenleavesofhigherplantswhichconstitute
thesources.Withinvariouscompartmentsofphotosynthesizingcells(sources),these
assimilatesare
(i)Metabolicallyutilized,
(ii)Storedor
(iii)Convertedintotransportsugarsmainlysucroseforexporttovarioussinks
(throughphloem)suchasyoungleaves,roots,tubers,stems,fruitsandseeds.
Atthesinks,assimilatesaremetabolicallyutilizedand/orstoredinreceivercells
ofsinks.Dependinguponthenatureandspecificrequirementofthesinks,the
photo-assimilatcsaredifferentiallydistributedindifferentsinks.Thisdifferential
distributionofphoto-assirnitatesindifferentsinksofplantiscalledasassimilates
partitioning.
PP. No. 367

875. Usually,theamountofassimilatestransportedtotheharvestorganismuchmorein
comparisontootherorgansoftheplant.
Therefore,transportofassimilatesandtheirpartitioningareofgreatresearchinterest
inagriculturalplantphysiologybecauseoftheirrolesincropproductivity.
Althoughattemptstoincreasephotosyntheticactivitiesoftheleaveshavemetwithonly
verylittlesuccess,buttheharvestindex(j.e.,theratiooftheharvestyieldsuchgrainsto
thetotalshootyield)oryieldsofmanycropplantssuchasoats,barley,wheat,cotton,
soybean,peanutsetc.,hasconsiderablybeenincreasedduringrecentyearsbysustained
plantbreedingeffortsinselectinganddevelopingvarietieswithimprovedtransportof
assimilatestoedibleoreconomicallyimportantportionsoftheplant.
PP. No. 367

877. FACTORS AFFECTING TRANSLOCATION AND
ASSIMILATES PARTITIONING IN HIGHER PLANTS
1.Competitionamongsinktissueforavailabletranslocatedassimilates:
Competitionamongvarioussinktissuesororganssuchasyoungleaves,
stems,rootsfruitsandseedsfortransportsugarsisanimportantfactorindetermining
translocationpat.terninwholeplant.
Experimentshaveshownthatifasinkisremovedfromaplant,thereis
increasedtranslocationofassimilatestoothercompetingsinks.
Reproductivetissuessuchasfruitsandseedsforinstance,cancompetewith
growingvegetativetissuessuchasyoungleavesandroots.Ontheotherhand,sudden
anddrasticcurtailingofsources(suchasbyshadingalltheleavesexceptone)and
keepingthesinksintactinsugarbeetandbeanplants,resultedinincreasedsupplyof
assimilatestoyoungleavesthanlorootsindicatingtherebythatyoungleavesare
strongersinksthanrootsintheseplants.
Thesinkstrengthi.e.,theabilityofthesinktomobilizephotosynthatesor
assimilatestowarditdependsonsinksizeandsinkactivity:
Sink strength = Sink size X Sink activity
Sinksizeisthetotalweightofthesinktissuewhilesinkactivityisdefinedas
therateofuptakeofassimilatesperunitweightofthesink.Sinkactivityisinturn
governedbyvariousenzymesthatareinvolvedinmetabolicutilizationandstorageof
assimiltes.
PP. No. 368

878. 2.Photosynthesisandsinkdemand:
Rateofphotosynthesis(i.e..thenetamountofcarbonfixedperunitareaof
lealperunittime)isstronglyinfluencedbysinkdemands.
Asubstantialincreaseinsink/sourceratioresultsinincreasedrateof
photosynthesisinthesourceleaves.
Rateofphotosynthesisdeclineswhensinkdemanddecreasesorinother
wordssink/sourceratioisdecreased.
Undersuchcondition,rateofphotosynthesisismarkedlyinhibitedespecially
inthoseplantswhichusuallystorestarchinsteadofsucroseduringtheday.
Itisbelievedthatunderreducedsinkdemandinplant,assimilatespileupin
theleaves(sources)whichcauseproductinhibitionofphotosynthetic
reactions.
PP. No. 368

879. 3.LongDistanceSignalsBetweenSourcesandSinks:
Thesignalsbetweensourcesandsinksmaybephysicalsuchasturgorpressureorchemicalsuchas
phytohormones(plantgrowthregulators).
(i)TurgorPressure:
Rapidphloemunloadingresultsindecreaseofturgorpressureinsieveelementsofphloeminsink
tissueswhichistransmittedtothesourcesviainterconnectingsystemofsieveelements.Consequently,
rapidphloemloadingoccursinsieveelementsofphloematthesourceswhichincreasestheirturgorand
thetranslocationofassimilatesfromsourcestosinksisincreased.
Rateoftranslocationofassimilatesororganicsoluteswouldbedecreasedifphloemunloadingatthe
sinksisslow.
Itisbelievedthatturgoraffectstransportofassimilatesacrosstheplasmamembranesbymodifying
theactivitiesofprotonpumpingATPaselocatedinthemembranes.
(ii)PhytohormonesorPlantGrowthRegulators:
Phytohormonessuchasauxin,gibberellins,cytokininsandABAaretransportedthroughoutthe
plantinvascularsystemandevidencesarenowaccumulatingthatthesegrowthregulatorsmightregulate
source-Sinkrelationshipsatleastpartiallyandaffectassimilatespartitioningbycontrollinggrowthof
sinks,senescenceofleavesandotherdevelopmentalprocesses.
Thebeststudiedcasesinvolveremobilizationofstoredreservesinstoragetissuessuchastaproots
orsugarcanestemparenchyma,fromwheretheyaredirectedtonewtypicallyreproductivesinks.
Formationofthesenewreproductivesinksisitselfoftenunderthecontrolofgrowthregulators.These
newsinktissuesmayinturnalsosynthesizeandreleasegrowthregulatorswhichactasstrongmobilizing
agents.
AccordingtoGiffordandEvans(1981),combinationsofplantgrowthregulatorsmayhave
additive,synergisticorinhibitoryeffectsonassimilatespartitioning.
PP. No. 368-369

880. 4.Plasmodesmata:
Itplayimportantroleinphloemloadingandunloading-large
pressuredifferencesbetweentheclosedcells.Closingof
plasmodesmataandsieveporesareoperatesbydepositionofcallose
whichregulatedbycytoplasmiccalciumlevel,markedlyinhibits
translocation.
PP. No. 369

882. •How does plants transport water & carbohydrates or minerals?
–Mass-flowor pressure-
flowhypothesis:

883. X-Source sink Relationship / interaction:
1. Source sink equilibrium
2. Small surplus source for stress
3. High source size during sink differentiation
4. Improve strength by activity
5. Synchrony of sink -organ development
6. Increased HI is reached –increase DMA
7. Reduce photorespiration in C3 plants
Additional Information:

884. X Limitations:
Source: wheat, rice, pulses, oilseeds
Sink: bajra, ragi
Transport:sorghum,maize(greenleafatharvest;senescenceofphloemParenchyma)
Sink limitation:
Late anthesis(Long Vegetative phase)
Indeterminate (Vegetative & Reproductive growth)
Vegetative growth at Reproductive phase
Less sink number and size
Hormonal imbalance
Any Stress
Multi-sink demand (nodules supply 25 –75 % of N demand)
Source limitation:
Low canopy photosynthesis
Low optimum LAI
Slow peak LAI (lag vegetative growth)
Low LAD at filling
Early leaf senescence
Stress –nutrients, water
Additional Information:

885. ABA inhibit sucrose uptake in source (Loading)
Auxinpromotes source uptake
Starch accumulation in chloroplast inhibit photosynthesis
ABA in leaves causes closer of stomata (Inhibit CO2 fixation)
Cytokinindelays senescence of source and sink
Cytokininin sink increases photo-assimilates import
Ethylene induces senescence process.
Additional Information:

886. Radialtransportofboronusesseveralplasmamembrane–localized
transporters:theBORexportersandtheNIPinfluxcarriers.
BOR1localizestotheendodermisandpericycleandgetentryinxylemvessel.
BOR4typeboronissecretingfromtherootwhichisdetoxifiedbyepidermal
cellsanddisposed/eliminatedfromthecellimmedietly.
BNIP5localizestotheepidermal,corticalandendodermalcells,
BNIP6islocalizedbetweenthexylemandthephloemflowsandthen
transportedintoPhloem,butnotinxylem.
IntheapoplasticdistributionofboronislimitedbytheCasparianring(barrier)
inendodermis.OutoftwoBoronmolecules,onlyoneisenterinpericycle.
Boron transport as an example that combines different transport mechanisms

887. Duringthefirstvisiblesignsoftuberization,a
transitionoccurredfromapoplasticphloemunloadingto
symplastictransport.Afterthatswitchonsymplasticsucrose
unloadingbysucrosemetabolism(severalgenesare
responsible).
Theactivityofinvertaseenzymeinnontuberizingand
tuberizingstolonsrevealedamarkeddeclineinthesub-
apicalregionofswellingstolonsindicatingswitchfrom
apoplastictosymplasticunloading.
However,cellwall–boundinvertaseactivityremained
highintheapical1to2mmoftuberizingstolons.Theapical
andlateraltuberbudsfunctiontosucroseunloadingand
metabolism.
Phloem unloading in potato plants in early
stages of tuberization:

888. Symplastictransport(left)
usesplasmodesmatathat
interconnect the
cytoplasmsofneighboring
cells. A modified
endoplasmicreticulum
(ER)formspartofthe
plasmodesmatastructure.
Apoplastic transport
(right)involvespassive
diffusionofmoleculesin
theextracellularspace,the
cellwall.Transcellular
transport (center)
combines apoplastic
transportwithasecretion-
andendocytosis-basedor
channel-andcarrier-based
transportpathwaytocross
plasmamembranes.

889. Translocation of Assimilates by Phloem
loading & Unloading ORSource –Sink Concept
•Pressureflowduetotranslocationor
movementoffoodfrom“source”to
“sink(s)”.
1Highsugarconcentrationat
“source”(sugarloadedsite)
2Sugardilutedwithwaterfrom
xylemcreatingpressureforflow
3Sugarunloadedat“sink”whereit
ismetabolizedorconvertedto
starch
4Excesswaterflowstoxylemback
to“source”
5Watergoesupwardinxylemvessel
throughtranspirationstream.
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