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Adaptations to Photosynthesis

Adaptations to Photosynthesis. Where do plants get the water they need to perform photosynthesis?. Root cells absorb water, which is transported to the leaves via the xylem. Where do plants get the CO 2 they need to perform photosynthesis?. The atmosphere!.

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Adaptations to Photosynthesis

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  1. Adaptations to Photosynthesis

  2. Where do plants get the water they need to perform photosynthesis? Root cells absorb water, which is transported to the leaves via the xylem

  3. Where do plants get the CO2 they need to perform photosynthesis? The atmosphere!

  4. How does CO2 get from the atmosphere into plants? Through stomata (that also allow for transpiration)

  5. When the weather is hot and dry, guard cells ↓ the size of the stomata to try and save water. • As a result, [CO2] in leaves ↓ • [O2] (formed in light reactions) ↑

  6. Why is this a problem? Because O2 and CO2 compete for Rubisco’s active site.

  7. Rubisco catalyzes 2 Rxn’s • The addition of CO2 to RuBP (carboxylationrxn in the Calvin Cycle) • The addition of O2 to RuBP (oxidation rxn)

  8. Photorespiration • Occurs when oxygen binds to rubisco • Results in oxidation of RuBP • Forms glycolate, which releases CO2

  9. Photorespiration • Occurs most often on hot, dry, bright days Why is this a problem? • ↓ production of CHO (because it removes PGA from Calvin Cycle)

  10. Photorespiration 2 Ways to  Photorespiration • C4 Photosynthesis • Crassulacean Acid Metabolism (CAM) Both use the Calvin cycle, but concentrate CO2 where rubisco is found (thus lowering photorespiration)

  11. C4 Plants How? • Do C4 photosynthesis Sugar Cane Corn

  12. C4 Leaf Anatomy Pg 169

  13. C4 Leaf Anatomy 2 Types of Photosynthetic Cells • Bundle-sheath cells • Mesophyll cells Pg 169

  14. Pg 169

  15. C4 Photosynthesis • CO2 attaches to PEP • Forms oxaloacetate (OAA) (a 4C compound)

  16. C4 Photosynthesis • OAA is converted to malate and transported into bundle-sheath cells

  17. C4 Photosynthesis • CO2 is removed from malate • Pyruvate is formed and diffuses back into mesophyll where it is converted into PEP

  18. C4 Photosynthesis • Bundle-sheath cells are impermeable to CO2 –so it is concentrated where the Calvin Cycle takes place • Photorespiration is minimized and sugar production is maximized

  19. CAM Plants • Water-storing plants • include cacti, pineapple and other succulent plants.

  20. CAM Plants • Follow an identical biochemical pathway to C4 plants – but the reactions take place in the SAME cell – at different times of day

  21. CAM Plants Dark – open stomata • CO2 is fixed and produces malate • Stored in vacuole until daytime

  22. CAM Plants Daylight – closed stomata • Light reactions produce ATP and NADPH for Calvin cycle, malate exits vacuole and is decarboxylated • CO2 is fixed by rubisco and enters Calvin Cycle

  23. C4 vs CAM • C4 vs CAM - both minimize PHOTORESPIRATION:C4-happens in different compartments of leafCAM- happens in same compartment but different time of day

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