Vegetative morphology- A general account of phyllotaxy and Modification of Leaves.pdf

The phyllotaxy of leaves is an important aspect of plant morphology and leaf modification is an interesting episode for all plant science students. This presentation offers a bird's eye view of phyllotaxy along with the modification of leaves with its relevance in plant taxonomy.

1. MORPHOLOGY OF
LEAVES
Presented by:
Dr. N. Sannigrahi,
Associate Professor,
Department of Botany,
Nistarini College,
Purulia,
D.B. Road, Purulia
(W.B)
723101, INDIA

2. PHYLLOTAXY
Thearrangementofleavesonthestemorbranchesistheimportant
issueinthevegetativemorphologyofleaves,
Ithasanuniqueimportantinplanttaxonomy,
Whentheleavesdevelopasaclusterorinarosettefromtheveryshort
stem,theyarecalledradicalleaves(Leavesdonotdevelopfromroot
generally),
Theleavesdeveloponthestemwithshortorlongbranchesbetween
themarecalledcaulineleaves,
Thenumberofleavesonnodesmaybeoneormoreandtheyarrange
inadefinitesequence.
Theleafarrangementonthestemorphyllotaxyandvariationsinsize
andshapearedoubtlessinpartcorrelatedwiththeexposureofthe
photosyntheticsurfacetolight”(EamsandMacDaniels,1947),
Themodeofthearrangementofleavesonthestemorbranchesis
calledphyllotaxy.

3. TYPES OF PHYLLOTAXY
Phyllotaxyofthreetypes-
i.Alternate,
ii.Opposite,
iii.Whorled.
ALTERNATE
Oneleafdevelopsfromeachnode,
Theleavesarearrangedinspiralmannerallroundthestem,
Maybeoffivetypes-
Distichous(1/2Phyllotaxy)e.g.membersofPoaceae,Orchidaceae,
Tristichous(1/3phyllotaxy)e.g.membersofCyperaceae,
Pentastichous(2/5phyllotaxy)e.g.Malvaceae,Moraceae,
Octastichous(1/6phyllotaxy)e.g.Apocynaceae,Cariacaceae,
Parastichous(5/3,8/21phyllotaxy)e.g.PhoenixspofArecaceae

4. TYPES OF PHYLLOTAXY

5. FIBONACCI SERIES
Thefundamentaltypeofleafarrangementmaybeexpressedas
fractionlike½,1/3,2/5,3/8,5/13.8/21andsoon.
Hereeachsucceedingfractionisthesumoftwopreviousnumerator
anddenominator,
Thenumeratoristhenumberofturnsorspiralsaroundthestembefore
oneleafisdirectlyabovetoanother.
Thedenominatoristhenumberofleavesintheturnsorspiral.
Thesequencehasbeenobtainedlike½+1/3=2/5,1/3+2/5=3/8andso
on.
Thespiralarrangementofleavescanbeinterpretedintermsof
divergenceusingmathematicalcalculation.,
ThisisknownasFibonacciseriesandthemeanofangleofdivergence
ofsuccessiveleavesarecalledFibonacciangle.Thisseriesisalso
calledSchimes-BrownSeries.
Indistichous(1/2)phyllotaxy,thereonetwistandtwoleavesbefore
oneleafisdirectlyaboveoneanother.Thustheanglewouldbe180º
(360/2)andsoon.

6. TYPES OF PHYLLOTAXY

7. TYPES OF PHYLLOTAXY
OPPOSITEPHYLLOTAXY
Whentwoleavesareattachedateachnodeoppositetoeachotheri.e.
makesanangulardistanceof180,itiscalledoppositetype.
Itistwotypes-DecussateandSuperposed.
DECUSSATE
Whenconsecutivepairofoppositeleavesarearrangedatrightangleto
eachother,itiscalledoppositedecussatetypelikeOcimumsanctum,
Calotropisproceraetc.
SUPERPOSED
Whentheconsecutivepairofoppositeleavesarearrangedinone
planei.e.onesetofleavesabovetheother,itiscalledsuperposedasin
QuisqualisspofCombretaceae,HiptagemadablotaofMalpighiaceae,
PsidiumguajavaofMyrtaceaeetc.
WHORLED whenmorethantwoleavesdevelopfromeachnode
formingawhorlcalledwhorledphyllotaxyasinNeriumindicumof
Apocynaceae,AlstoniascholarisofApocynaceae.

8. MODIFICATIONS OF LEAF
Asapartofsecondaryfunctionslikestorageoffood,toadapt
adversity,andotherissues,laminaorleafbladesundergone
modificationsasfollows:
LEAFTENDRILS:Laminabecomesmodifiedeitherpartiallyor
whollyintotendriltoclimbupbythefollowingmethods.
A.entireleafinwildpea,PisumsativumofFabaceae,
TerminalleafletsinPisumsativum,
PetioleinClematisgourianaofRananculaceae,
Leafapexinglorylily,GloriosasuperbaofLiliaceae,
StipulesinSmilaxmacrophyllaofLiliaceae.
LEAFSPINES
Eitherwholeorpartoflaminaperformasdefensiveorganfor
protectionortoreducetherateoftranspirationasfollows’
StipulesmodifiedintospinesofZizyphusmauritianaofRhamnaceae,
AcaciaarabicaofFabaceae.
ApexoflaminaintospinesasPhoenixsylvestrisofArecaceae.

9. MODIFICATIONS OF LEAF

10. MODIFICATIONS OF LEAF
MarginoflaminabecomesspinyinMexicanpoppy,Argemonemexicana
ofPapaveraceae.
ApexandmarginbothmodifiedintospinesinAloeperfoliataofLiliaceae,
Leafofaxillarybudbecomesmodifiedintospinesinpricklypear,
OpuntiadilleniiofCactaceae,
Leavesaremodifiedintospinesinbarberry,Berberisvulgarisof
Berberidaceae,
LeavesaremodifiedintospinesasthickthornsinUlexspofFabaceae.
FLESHYLEAVES
Forstorageofwater,mucilageandfoodmaterialsasstoragetissue.
Leavesbecomemodifiedincommonxerophytesandalsoinhalophytes
likeBasellarubraofBasellaceae,SalsolakaliofChenopodiaceae,Aloesp
ofAgavaceaeetc.
LEAFHOOKS
Threeterminalleafletsofcompoundleavesbecomemodifiedintosharp,
curvedandpointedhooksforclimbinginBignoniaanguiscatiof
Bignoniaceae.

11. Bignonia sp.

12. MODIFICATIONS OF LEAF
PHYLLODE-Petiolebecomesfattenedinaverticalplaneandtakes
uptheappearanceofleafbladearecalledphyllode.Here,laminadoes
notdevelopatallorfallsoffatanearlystageofdevelopmentin
AcaciaauriculiformisinFabaceae.
ROOT-LIKESTRUCTURE;Inaquaticplants,submergedleaves
aremodifiedintoslenderrootlikestructurewhichhelpinabsorption
ofwaterbutmistakenasrootbecauseoftheabsenceofrootsinwater
milfoil,MyriophyllumindicumofHaloragidaceae.
PITCHERSHAPEDLEAVES
Theleafismodifiedintopitcherwithaliddevelopsfromtheapex;
theanteriorpartscoilsliketendrilandhelppitchertoremainerect
whiletheposteriorpartbecomesflattenedlikealeaf.Thepitcher
containswateranddigestivejuiceandcatchestheinsettocollect
nitrogenfromtheirbodyasfoundinPitcherplant,Nepenthes
khasianaofNepenthaceae.Althoughdebateisthereoverthe
morphologyofthepitcherplants.

13. Myriophyllumsp. Of Haloragidaceae

14. MODIFICATIONS OF LEAF
Anotherkindofnon-insectivorousinnaturemainlystoreswaterfor
thefutureuseslikeDischidiarafflesianaofAsclepiadaceae.Being
epiphyticinnature,itbearsanapicalopeningwithoutanylidand
becomesfilledwithwaterduringrain.Fromthestalkofthepitcher,
rootletsdevelopandtherootletsenterintothecavityofthepitcher
andabsorbwaterandhumus.
BLADDER
Thebladderwort,UtriculariastelarisofLentibulariaceae,arootless
herb,iscommonlyfoundinponds.Thesubmergedleavesaremuch
segmented.Someofthesegmentsbecomemodifiedintobladder-like
structure.Theycantrapinsectstonourishtheirrequirednitrogen
uptake.
So,thesearethedifferenttypeofmodificationsoflaminaandthese
areundergonemodificationsforthesakeoftheirimportantbiological
resourcesalongwithaddressthestressderivedfromtheenvironment
inthelongjourneyoftheirlifeprocesses.

15. BLADDERWORT, Urticulariavulgaris.

16. HETEROPHYLLY
Anumberoffoliageleaveshavedifferentforms.Thesedifferent
formsofleavesofthesameplantarecalledheterophylly.
Itmaybeaquaticandlandplants.
Aquaticplantsaretwokinds-submergedandfloating.
Thesubmergedleavesarenarrowandfinelydissectedwhilethe
floatingleavesarelargerinsizeandlobed.
Itisfoundinchestnut,TrapabispinosaofOnagraceae,watercrew
root,RanunculusaquatilisofRananculaceae,Limnophylla
heterophyllaetc.
Inlandplants,ArtocarpuschaplasaandFucusheterophyllusof
Moraceae,CoriandrumsativumofApiaceae,Goldfussiaglomerataof
Acanthaceaeetc.
MarshyplacesalsonourishestheseheterophyllylikeGardenia
difformisofAcanthaceae,Inpteridophytes,Dymoglossum
piloselloidesandPterisludensofPolypodiaceaeareexamplesofthis
behavior.

17. Trapa bispinosa

18. ANISOPHYLLY
Theplantshavingoppositeleavesareunequalinsizeisknownas
anisophylly.ItisfoundinPelloniadaveananaofUrticaceae,
GoldfussiaglomerataofAcanthaceaeetc.
TAXONOMY ANDPHYLLOTAXY
SAMconsistsagroupofpluripotentcellsfromleaves,stemsand
flowersareoriginated.ManyfamilieslikeMoraceae,Brassicaceae,
Asteraceae,Myrtaceaeetcareidentifiedwiththehelpofphyllotaxy.
Inadditiontothat,thereareothergroupsofplantswhereanisophylly
andheterophyllyarethekeyfeaturesusedinplanttaxonomy.
Themodificationofleafingeneralandthepetioleandlamina
modificationsalsoofferedaseriesoffeaturesusednotablyinplant
taxonomy.
Phyllotaxyisakeyfeaturesusedinthepreparationofkeysinthe
identificationofplantsamongtheheterogeneouselements.

19. LET A HUNDRED FLOWERS BLOOM”

20. THANKS FOR YOUR VISIT
REFERENCES:
1.DifferentWebPagesforstudymaterialsandcontent,
2.Googleforimagesforbetterillustrations,
3.ATextbookofBotany,Vol.II-Bhattacharya,Hait,Ghosh
Disclaimer:
Thispresentationhasbeendevelopedtoenrichtheonlinefreestudy
materialsforacademicfraternitywithoutanyfinancialinterests.
Thepresenteralwaystakesthepleasureandhappinesstoreachthe
unreached.