Chapter-5-Photosynthesis stages and growth

it tells the process of photosynthesis

1. PHYSIOLOGICAL PROCESSES AFFECTING CROP PRODUCTION

2. Growth and development of crops result from the interaction of various physiological proces s es , namel y : Photosynthesis Respiration Transpiration Translocation These proc e sse s for m th e basi s fo r cr o p yield.

3. PHOTOSYNTHESIS- a chemical reaction Autotrophic Process: Plants and plant-like organisms, algae, make their energy (glucose) from sunlight. Stored as carbohydrate in their bodies.

4. PHOTOSYNTHESIS is considered as the most important biological process. Why? Makes organic molecules (glucose) out of inorganic materials (carbon dioxide and water). It begins all food chains/webs. Thus all life is supported by this process. It also makes oxygen gas!!

5. Photosynthesis -starts to ecological food webs!

6. What do plants need for photosynthesis? Water Carbon dioxide Light chlorophyll

7. Pho t o- syn t h e sis means "putting together with light." Plants use sunlight to turn water and carbon dioxide into glucose. Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. Autotrophs make glucose and heterotrophs are consumers of it.

8. TWO TYPES OF PHOTOSYNTHESIS ANOXYGENIC PHOTOSYNTHESIS is the phototrophic process of obigate anaerobes, where light energy is captured and converted to ATP, without the production of oxygen. Water is therefore not used as an electron donor . O X Y G ENIC PHO T O S YNTHESIS i s th e mos t common and is seen in plants, algae and cyanobacteria. It is a non-cyclic photosynthetic electron chain where water i s th e initia l el e c t ron do n o r an d , a s a consequ e nce, molecula r oxyge n i s free d a s a bypro d uct.

9. Photosynthesis Carbon dioxide + water glucose + o x y g e n sun l i g ht absorbed by chlorophyll 6 CO 2 + 6 H 2 O + energy  C 6 H 12 O 6 + 6 O 2

10. SIGNIFICANCE OF PHO T OSYNT H ESIS Green plants possess the green pigment, chlorophyll whi c h ca n capture , transform , translo c at e an d store energy which is readily available for all forms of life on th i s planet. Photosynthesis is a process in which light energy is con v erte d in t o c hem i ca l energ y . E x c ep t gree n p l ants , n o othe r orga n is m ca n dire c t l y u t iliz e sola r energ y t o s ynthesiz e f ood ; hence t he y are dependent on green plants for their survival.

11. SIGNIFICANCE OF PHO T OSYNT H ESIS During photosynthesis, oxygen liberated into the atmosphere makes the environment livable for all aero b i c orga n isms. Plants an d plan t produ c t s ar e t h e ma j o r f oo d s ourc es o f almos t al l orga n ism s o n th e ea r th. Fossil fuels like coal, gas, and oil represent the pho t os y n t he t i c produ c t s o f t h e plant s be l ongin g t o ea r ly geologica l period s .

12. Plant leaves have many types of cells!

13. THE PHOTOSYNTHETIC ORGAN LEA F - chie f si t e o f p h otosynthesis. STR U C T U R A L P A R TS upper and lower epidermis - stomates mesop h yl l cell s - chlor o p h yll vas c ul a r bu n dl e s - t ransport The Mesop h yll o upper side: - palisade parenchyma - regular shaped pa l isad e cells o lowe r side : - spo n g y p a re n chy m a - irr e g u lar shaped

14. S T OMA TA This opening how plants exchange gases! Check it! Can you name the two important gases that go in and out of the leaves? Why are the stomata located on the underside of leaves?

15. Plant Cells

16. The photograph below is an elodea leaf (magnification X 400). Individual cells are clearly visible. The tiny green structures within the cells are chloroplasts this is where ph o tosynthes i s happens.

17. Chloroplasts make the sugars! "Thanks for the Glucose!"

18. Ch l orop l asts make the oxygen too!

19. Photosynthesis Glucose provides the energy and carbon needed to make other plant materials like wax and proteins.

20. Leaves are green because they contain the pigment: CHLOROPHYLL Leaves have a large surface area to absorb as much light as possible

21. PHOTOSYNTHETIC PIGMENTS The p h o t os y n t h e t i c p i g m e n t s o f h i g h e r p l a n t s ar e d i v i d e d i n to tw o c l a ss es: CAROTENOIDS (carotene and xanthophyll) absorb light in the regions of the spectrum not absorbed by the chlorophylls and transfer that energy to chlorophyll to b e use d i n photosy n thesis. CHLOROPHYLL- the principal pigment involved in photosynthesis. It is a large molecule and absorbs light maximally in the violet blue and in the red region of the visible spectrum and reflects green light and thus leave s appea r gree n i n colo r . ( R OYG B I V)

22. Visible light is only a small part of the electromagnetic spectrum (all forms of light).

23. Chlorophyll… Locatio n a t th e p artitio n betwee n t w o adja c ent thylakoids. Its basic unit is a porphyrin ring system, a structure composed of four pyrrole nuclei joined b y carbo n linkages. The cente r o f porphyri n i s oc cupie d b y a s ing l e magnesiu m atom.

24. PHOTOSYNTHETIC PIGMENTS 2 KIN D S O F C HLORO P H Y LL chlorophyll a (bluish green)- can be found in all autotrophic organisms except photosynthetic bacteria. chlorophyll b (yellowish green) R A T I O : 3a:1 b • OTH E R P IG M E NT S : ca r otene , x anthop h y ll LIGH T ABS OR P T I ON : mo s t in t en s e i n r e d an d blu e and lowe s t i n g r e en

25. A bso r bin g Ligh t E nerg y t o mak e chemica l energ y : GLUCOSE! Pigmen t s : Ab s or b di f f eren t c olor s o f white ligh t ( R OY G B IV) Ma i n pigmen t : Chloroph y l l a - R E ACTION CENTERS! A c c es s or y pigmen t s : Chlo r oph y l l b , x anthophyll, ca r o t enoid s - HA R V E STING C E NTER These pig m en t s , t ha t i s t h e r eactio n cente r an d the harvesting center are packed into functional clusters calle d ph o tosyste m s

26. About 250-400 Chl-a molecules constitute a single pho t os y ste m . T wo di f f eren t photosy s t em s have different forms of chlorophyll a in their reaction centres. I n photosy s te m I ( P S I) , chlo r oph y l l – a with maximum absorption at 700 nm (P700) and in photosy s te m I I ( P S I I), chlo r oph y l l – a wi t h peak absorption at 680 nm (P680), act as reaction centres . (P stand s f o r pigmen t ). The primar y f unctio n o f th e t wo pho t os y ste m s, whi c h in t era c t with ea c h othe r i s t o tra p th e solar energy and convert it into the chemical energy also calle d as s imi l a t ory power ( A TP an d N A D P H2 ) . 

27. PHOTOSYSTEM I PHOTOSYSTEM II Maximum Light Absorption 700 nm wavelength (P700) 680 nm wavelength (P680) Primary Electron A cce p t or iron protein (Fe-S- protein) PHEOPHYTIN -is a modified chlorophyll-a molecule with 2 hydrogen atoms in place of magnesium ion. Electron Carriers plastocyanin, ferredoxin and cytochromes. heophytin, plastoquinone, and cytochromes.

28. LI G HT A B SOR P TI O N In general, leaves absorb about 83% of light, while reflecting 12% and transmitting 5% Of the 83% absorbed, only 4% is actually used by the plants during photosynthesis, the remainder is dissipated as heat

29. PHOTOCHEMICAL and BIOSYNTHETIC PHASE The entir e p r oce s s o f pho t os y n t hesi s t ake s plac e inside the chloroplast. Photosynthesis involves two successive steps --- light reactions and dark reactions. LI G HT RE A CTION S - tak e plac e i n th e gran a o f the chloropla s t s where chlorophy l l c a n b e foun d lo c a t e d on th e membranes D A RK R E A CTION S - tak e plac e a t th e strom a o f the chloroplasts where it is absent from chlorophyll.

30. LIGHT REACTION… The light reaction of light dependent reaction occurs in the chloroplast of the mesophyll cells of th e l eave s . The mai n purpos e o f th e ligh t reaction i s to generat e organi c mole c ule s suc h a s A TP and NA D PH w hi c h ar e neede d fo r th e sub s equent dar k re a ct i ons.

31. LIGHT REACTION… STEPS! Ch l orophyl l absorb s th e red an d blu e segment of the white light and photosynthesis occurs most e f fi c ien t l y a t the s e w ave l ength s . When th e ligh t fall s o n th e plant , th e chlorophyll pigment absorbs this light and electron in it gets excited. This process occurs as a photosystem. Re m embe r photos y stem s ? ? The P S I an d P S II.

32. LIGHT REACTION… STEPS! The chloroph y l l pigmen t s which ar e ex c i t e d giv e up the i r electron s an d t o c ompensate fo r th e los s of electrons , water i s spli t t o release f ou r hydroge n ions an d fou r electron s an d oxy g en. The electrons finally reach the reaction center where they combine with NADP+ and reduce it to NADPH. NADP+ - Nicotinamide adenine dinucleotide phosphate. NADPH - Dihydronicotinamide adenine dinucleotide phosphate.

33. LIGHT REACTION… STEPS! While th e electron s ar e t ake n car e o f , t h e buil t u p of hyd r oge n ion s insid e th e thylakoi d lume n i s o f equal importance. The hyd r oge n ion s buildi n g u p in s id e th e lumen creates a positive gradient and in the presence of the enzyme ATP synthetase, these hydrogen ions combine with A DP i n th e nearb y region t o for m A T P . The oxygen that is a waste product is released by the plan t in t o th e atm o sphe r e an d som e o f i t i s use d in photorespi r at i o n i f th e plan t s need s to.

34. Sun Chlorophyll passes energy down through the electron transport chain. to AD P bonds P forming ATP oxygen r ele a s e d s p li ts H 2 O H + NADP + NADPH for the use in light-independent reactions Light energy transfers to chlorophyll. Energized electrons provide energy that At each step along the transport chain, the electrons lose energy.

35. In plants and simple animals, waste products are removed by diffusion . Plants, for example, excrete O 2 , a product of photosynthesis.

36. LIGHT REACTION… The en d p r oduc t o f ligh t rea c t ion , A TP an d N A D P H ar e use d t o f i x CO2. The s ynthesi s o f A TP b y t h e ligh t - induced ph o sph o ry l atio n (addit i o n o f a pho s pha t e g r ou p t o a molecule ) o f A DP i s kno w n a s photophospho r ylation T wo t ype s o f pho t ophospho r ylatio n ar e non - cyclic ph o tophosp h ory l atio n an d th e Cycl i c phtophosphorylation.

37. NON-CYCLIC PHTOPHOSPHORYLATION. CYCLIC PHTOPHOSPHORYLATION. Both PSI and PSII are functional. Only PSI is functional. Water is the primary source of the electrons molecule and returns to the same and H+. It gets photolysed through the process called Photolysis; NADP is the final acceptor of the electrons and H+ ions. Electron comes from the chlorophyll P700 molecule and returns to the same chlorophyll P700 Oxygen is evolved as a bye product. Oxygen is not evolved because there is no photolysis of water. This mainly takes place in all green plants and cyanobacteria except photosynthetic eubacteria. This process is found mainly in photosynthetic eubacteria e.g. purple sulphur bacteria.

38. DARK REACTION… Oc c ur s i n th e stroma Primary process by which inorganic carbon is con v erte d t o carbon. CO2 is reduced by the reducing power generated in t h e firs t ste p an d carboh y drate s ar e produ c ed Carbon fixation reactions produce sugar in the leaves o f th e plan t fro m whe r e i t i s expo r te d t o othe r t i s s ue s of the plant as source of both organic molecule and energ y f o r gro w t h an d me t abolism.

39. DARK REACTION… The end product of light reaction, ATP and NADPH ar e use d t o f i x CO2. Oc c u r bo t h i n th e p r esen c e o r absenc e o f ligh t . The end product of light reaction, ATP and NADPH ar e use d t o f i x CO2. The ca r bo n dio x id e fixa t ion / redu c t io n into ca r boh y drate s ca n oc c u r vi a thre e pathway s :

40. DARK REACTION… 3 Pathways 1. C A L V I N B E N S O N C Y CL E / R E D U CTIVE PE N T OSE PATHWAY F i xatio n an d red u ctio n of o ne m o l ecu l e of CO2 requires three molecules of ATP and 2 NADPH. Occu r s i n t he mesophy l l ce l l ch l or o p l ast CO2 accepto r i s R UBP R U BP car b oxy l as e enzy m e i s needed The f i r s t stabl e prod u c t i s 3 - P GA

41. DARK REACTION… 3 Pathways 2 . C 4 O R H A TCH S LA C K P A TH W A Y - First product is 4- C oxaloacetic acid. STEPS are ca r box y la t io n o f P E P t o OA A , P E P ca r box y las e is en z ym e involved redu c t i o n o f O A A t o mala t e o r asp a rta t e decarboxylation of malate in the bundle sheath cells t o for m py r uvi c acid transfe r o f py r uvi c aci d t o th e mesop h yl l cell f ixatio n o f ca r bo n dio x id e t o f or m 3 - PGA P re s en c e o f K R A NZ A N A T OM Y .

42. DARK REACTION… 3 Pathways 3 . C A M O R CR A SS ULA C E AN A C I D M E T A B OL I S M P A TH W A Y – operate s i n o r chid s , pineapple , o t her succulent plants wherein stomates are closed during the da y an d op e n du r in g th e night.

43. F A CT OR S AFF E CTING PHO T OS Y NTHE S IS Factors a f fectin g p h otosynth e si s ca n be d i vi d e d i n t o t wo gen e ral categ o ries, Internal External (envi r onmen t al ) fac t ors.

44. INTER N AL F A C T O R S CHLOROPHYLL The amount of chlorophyll present has a direct relationship with the rate of photosynthesis because this pigment is directly involved in trapping light energy re s pon s ibl e fo r t h e ligh t reac t i on s .

45. INTER N AL F A C T O R S LE A F AGE A N D A N A T OMY Newly expanding leaves show gradual increase in rate of photosynthesis and the maximum is reached when the leaves achieve full size. Chloroplast functions decline as the leaves age. Rate of photosynthesis is influenced by va r ia t io n in number, structure and distribution of stomata, si z e an d distributio n o f in t e r c e llula r s p a c es relat i v e propo r t io n o f palisad e an d s pong y t is s ue s and ( iv ) t hic k ne s s o f cu t icle.

46. INTER N AL F A C T O R S D E MAN D F O R PHO T OS Y NTH A TE : Rapidly growing plants show increased rate of photosynthesis in compariso n t o ma t ur e plan t s.

47. E X TERN A L F A C T O R S R e m e m b er … C O NC E PT O F LI M ITI N G FACTORS! W h a t ar e th e ex t er n a l fa c tor s ? ? ? The m a jo r ex t er n a l fa c tor s w h ic h a f fe c t th e rate o f p h ot o sy n th e si s are temperature, light, carbon dioxide, w a te r , an d mi n er a l el e m e nt s .

48. E X TERN A L F A C T O R S LIGHT: The rate of photosynthesis increases with increase of intensity of light within physiological limits or rate of photosynthesis is directly proportional to light intensity.

49. E X TERN A L F A C T O R S TEMPERATURE: Very high and very low temperature affect the rate of pho t os y n t hesi s adve r sel y . Rate of photosynthesis will rise with temperature from 5°-37°C beyond which there is a rapid fall, as t h e en z yme s involve d i n th e p r oce s s o f t h e da r k reac t i o n ar e denature d a t hig h te m perature. Between 5°-35°C, with every 10°C rise in t empera t ur e rate o f photosynthesi s double s .

50. E X TERN A L F A C T O R S

51. E X TERN A L F A C T O R S CA R BON D I OXID E : Since carbon dioxide being one of the raw materials for photosynthesis, its concentration affects the rate o f pho t os y n t hesi s markedl y . B eca u s e o f i t s ve r y lo w con c entra t io n (0.03 % ) i n the atmosphere, it acts as limiting factor in natural photosynthesis.

52. E X TERN A L F A C T O R S WATER Water has an indirect effect on the rate of photosynthesis. Loss of water in the soil is immediately felt by the leave s , whi c h ge t wilted an d the i r stoma t a clo s e down thus hampering the absorption of CO2 from the atmosphere. This cau s e s declin e i n p h otosynthesi s .

53. E X TERN A L F A C T O R S WATER Water has an indirect effect on the rate of photosynthesis. Loss of water in the soil is immediately felt by the leave s , whi c h ge t wilted an d the i r stoma t a clo s e down thus hampering the absorption of CO2 from the atmosphere. This cau s e s declin e i n p h otosynthesi s .

54. E X TERN A L F A C T O R S M I N E RAL EL E MENTS S om e minera l elemen t s lik e magnesium , cop p er , manganese and chloride ions, which are components o f pho t os y n t he t i c enz y mes , an d magnesiu m a s a component of chlorophylls are important. T hei r de f icienc y would a f f ec t th e r a t e of photosy n thesi s indire c t l y b y a f fec t in g th e s y nthesi s of photosynthetic enzymes and chlorophyll.

55. END OF PRESENTATION!....