C3 and c4 plants ,characteristic ,cycles and significance

Detail on C3 and C4 plants

1. C3 and c4 plants ,their characteristics and Cycles

2. photosynthesis The process by which plant convert light energy into chemical energy

3. Types of photosynthetic There are three main types of photosynthesis C3 PHOYOSYNTHESIS C4 PHOTOSYNTHESIS CAM PHOYOSYNTHESIS

4. C3 plants C3 plants are those plant which fix and reduce inorganic carbon compound using only C3 pathway in photosynthesis Most of the plant are C3 Usually on dicot Examples Wheat Barley Rye Tobacco Soya bean trees Shrubs

5. Characteristic of C3 plants Distribution : C3 plants make 85% of the plant kingdom Photosynthesis: C3 photosynthesis take place in them CO2 fixation: Carbon dioxide fixation take place only through C3 cycle Leaves: In their leaves large air spaces bordered by loosely arranged mesophyll cells ,mesophyll cell but not bundle sheath cells contain chloroplast Stomata : Stomata open at day time and close at night Environmental Adaptation: They are mostly present in temperate environment

6. Leave structure

7. C3 cycle or photosynthesis This is called C3 cycle because the first product of photosynthesis is 3-carbon compound It is a multistep process in which the CO 2 is fixed into stable organic product It occurs virtually in all leaf of mesophyll cells I is also known as Calvin cycle

8. Steps of c3 cycle There are three main steps in c3 cycle Carbon fixation Reduction Regeneration of co2 accecptor RuBP

9. 1. Carcondioxide fixation In carbon fixation, three molecules of CO 2 from the atmosphere combines with a five-carbon acceptor molecule called ribulose-1,5-bisphosphate ( RuBP ).  The resulting six-carbon compound is then split into two molecules of the three-carbon compound, 3-phosphoglyceric acid (3-PGA). This reaction is catalyzed by the enzyme RuBP carboxylase/ oxygenase , also known as RuBisCO . Due to the key role it plays in photosynthesis, RuBisCo is probably the most abundant enzyme on Earth.

10. 2. Reduction Each molecule of PGA receive additional phosphate from ATP of light reaction forming 1,3biphosphoglycertae,then this reduce to glyceraldehydes 3 phosphate by receiving pair of electron donated by NADPH of light reaction This is same 3-C sugar that is formed during Glycolysis by splitting of glucose In this way fixed carbon is reduce to energy rich G3P by using energy from ATP and NADPH of light reaction and store in it G3P is not glucose it is carbohydrate form directly from Calvin cycle and then use to make glucose ,starch etc 3 molecule of co2 combine with 3 molecule of RuBP form six molecule of G3P ,but only one molecule leave the cycle and use in making glucose Remaining 5 molecule of RuBP recycle to regenerate 3 molecule of five carbon compound RuBP

11. Regeneration Through series pf complex reaction the carbon skeleton of 5 molecule of three carbon G3P are rearranged in 3 molecule of five cabon RuP Each RuP is posphorylated to ribulose biphosphate ,with which cycle has started

12. C3 pathway

13. Significance of c3 cycle It is main biochemical pathway during the dark reaction of photosynthesis It result in the synthesis of carbohydrate from CO 2 assililmilation It store ATP energy formed during light reaction in carbohydrate molecule as food energy Hydrocarbon skeleton of G3P can use to form Fatty acid and glycerol to make plant oil Amino acids ,starch and cellulose

14. C4 plants C4 plants are those that use c4 pathway for photosynthesis Usually they are monocots They are only found in angiosperms Examples : Grasses Shorgum Millets Maiz Sugercan

15. Characteristics of C4 plants Distribution : They contribute 3% of kingdom plantae Photosynthesis : C4 photosynthesis take place in them CO 2 fixation: Carbon dioxide fixation take place through C3 pathway in bundle sheath cells and through C4 pathway in mesophyll cell Leaves : Their leaves are thin , closer arrangement of vascular bundle Smaller air spaces then C3 plant , veins surrounded by thick walled BSC and further by mesophyll cells Mesophyll and BSC contain chloroplast but BSC have much larger

16. Stomata : Open during day close at night Environmental Adaptation: Tropical or semi-tropical areas Areas of high light intensity areas of high temperature , drought conditions

17. C4 LEAVE ,Krantz anatomy

18. C4 cycle It is alternate path of c3 cycle to fix CO 2 In this cycle first stable compound is 4-carbon compound is known as oxaloacetate .hence it is called C4 cycle This pathway is also known as Hatch and Slack pathway as they work out the pathway in 1966 This pathway is commonly seen in grasses ,sugar can ,maize and sorghum

19. C4 cycle involve two carboxylation reaction one in chloroplast of mesophyll cells and other in chloroplast of bundle sheath cells There are two steps in C4 cycle Reaction occurring in mesophlyy cells Formation of oxaloacetate Formation of malic acid and aspertic acid Reaction occuring in bundle sheath cells Formation of pyruvic acid Formation of phosphoenol pyruvic acid

20. Reaction in mesophyll cells Formation of oxaloacetate : The primary acceptor of co2 in this cycle is 3csrbon compound—phosphoenol pyruvic acid The PEP combine with co2 and form 4-carbon acid oxaloacetic acid in the presence of PEP Carboxylases. The enzyme remain present in large amount in mesophyll cells.

21. Formation of malic acid and aspartic : Oxaloacetic acid is quite unstable and is converted either into malic acid or aspartic acid. The oxaloacetic acid is reduced to malic acid by using light-generated NADPH +. This reaction is catalyzed by enzyme malic dehydrogenase . The oxaloacetic acid can also be converted into aspartic acid in presence of enzymes aspartic transminase. The C4 acids i.e. malic acid and aspartic acid are then transported to the chloroplasts of the bundle sheath .

22. Reaction occurring in bundle sheath cell chloroplast: Formation of pyruvic acid- In bundle sheath chloroplast, the malic acid undergoes oxidative decarboxylation to yield pyruvic acid and CO2 in presence of malic enzymes. The CO2 and NADPH + Produced by oxidative decarboxylation of malic enter into Calvin cycle. The CO 2 combines with ribulose diphosphates ( RuDP ) to yield 2 molecules of phosphoglyceric acid (PGA) CO2 + RuDP 2moles of PGA

23. Formation of phosphoenol pyruvate : The pyruvic acid produce by oxidative decarboxylatioon is transported back to the mesophyll cells where it is phosphorylated to phosphoenol pyruvate with the help of pyruvate diakinase This enzyme is also used in break down of ATP in light reaction

24. C4 pathway

25. Significance of C4 cycle C4 cycle increase the photosynthetic yield two to three times more then C3 plants C4 plant perform high rate of photosynthesis even when stomata are nearly closed C4 cycle increase the adaptability of C4 plant to high temperature and light intensities They can grow very well in saline soil because of C4 organic acid

26. difference C3 plants C4 Plants In c3 plants photosynthesis occur in mesophyll In C4 plant photosynthesis occur in both mesophyll cells and bundle sheath cell In this carbon dioxide accecptor is RuBisco In this carbon dioxide acceptor is PEP carboxylase Krantz anatomy of leaf is absent Krantz anatomy of leaf is present The first stable compound is 3 –c 3 phospho Glyceric acid First stable compound is 4-c oxaloacetate Optimum temperature is 20 - 25  Optimum temperature is 35-40 