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Processes affected by CO 2 1) Pathways that consume CO 2 2) pathways that release CO 2

Processes affected by CO 2 1) Pathways that consume CO 2 2) pathways that release CO 2 3) transpiration & stomatal number. C4 and CAM photosynthesis Adaptations that reduce PR & water loss Both fix CO 2 with a different enzyme. C4 and CAM photosynthesis

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Processes affected by CO 2 1) Pathways that consume CO 2 2) pathways that release CO 2

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  1. Processes affected by CO2 • 1) Pathways that consume CO2 • 2) pathways that release CO2 • 3) transpiration & stomatal number

  2. C4 and CAM photosynthesis Adaptations that reduce PR & water loss Both fix CO2 with a different enzyme

  3. C4 and CAM photosynthesis Adaptations that reduce PR & water loss Both fix CO2 with a different enzyme later release CO2 to be fixed by rubisco use energy to increase [CO2] at rubisco

  4. C4 and CAM photosynthesis • Adaptations that reduce PR & water loss • Both fix CO2 with a different enzyme • later release CO2 to be fixed by rubisco • use energy to increase [CO2] at rubisco • C4 isolates rubisco spatially (e.g. corn)

  5. C4 and CAM photosynthesis Adaptations that reduce PR & water loss Both fix CO2 with a different enzyme later release CO2 to be fixed by rubisco use energy to increase [CO2] at rubisco C4 isolates rubisco spatially (e.g. corn) CAM isolates rubisco temporally (e.g. cacti)

  6. C4 and CAM photosynthesis C4 isolates rubisco spatially (e.g. corn) CAM isolates rubisco temporally(e.g. cacti) Advantages: 1) increases [CO2] at rubisco

  7. C4 and CAM photosynthesis • Advantages: 1) increases [CO2] at rubisco • reduces PR • prevents CO2 from escaping

  8. C4 and CAM photosynthesis • Advantages: 1) increases [CO2] at rubisco • reduces PR • CO2 compensation point where CO2 uptake by PS = CO2 loss by “dark” respiration is 20-100 ppm in C3

  9. C4 and CAM photosynthesis CO2 compensation point where CO2 uptake by PS = CO2 loss by “dark” respiration is 20-100 ppm in C3 0-5 ppm in C4 & CAM

  10. C4 and CAM photosynthesis CO2 compensation point where CO2 uptake by PS = CO2 loss by “dark” respiration is 20-100 ppm in C3 0-5 ppm in C4 & CAM C4 and CAM also get saturated at lower pCO2

  11. C4 and CAM photosynthesis • Advantages: 1) increases [CO2] at rubisco • 2) reduces water loss

  12. C4 and CAM photosynthesis • reduces water loss: don't need to open stomata as wide • C3 plants lose 500 -1000 H2O/CO2 fixed • C4 plants lose 200 - 350 • CAM plants lose 50 - 100

  13. C4 photosynthesis = spatial isolation C4 plants have Kranz anatomy Mesophyll cells fix CO2 with PEP carboxylase Bundle sheath cells make CH20 by Calvin cycle

  14. C4 photosynthesis = spatial isolation C4 plants have Krantz anatomy Mesophyll fix CO2 with PEP carboxylase Send 4C product to B-S cell

  15. C4 photosynthesis = spatial isolation B-S cells convert 4C to pyruvate releasing CO2 Calvin cycle fixes it Change pyruvate to PEP in mesophyll

  16. C4 photosynthesis = spatial isolation B-S cells convert 4C to pyruvate releasing CO2 Calvin cycle fixes it Change pyruvate to PEP in mesophyll Has evolved independently >50 times!

  17. C4 photosynthesis = spatial isolation Has evolved independently >50 times! Found in 18 families: both monocots & dicots Some have C3 and C4 spp!

  18. C4 photosynthesis = spatial isolation Has evolved independently >50 times! Found in 18 families: both monocots & dicots Some have C3 and C4 spp! 3 ways to shuttle C!

  19. C4 photosynthesis = spatial isolation 3 ways to shuttle C! All generate C4 acid in Mesophyll & release CO2 in BS, but details vary

  20. C4 photosynthesis = spatial isolation Has evolved independently >50 times! 3 ways to shuttle C! Can occur w/in same cell! 3 diff spp do it 3 diff ways!

  21. C4 photosynthesis = spatial isolation • Benefits over C3 • 1) no PR • 2) less water loss

  22. C4 photosynthesis = spatial isolation • Benefits over C3 • 1) no PR • 2) less water loss • Disadvantage • C4 use 30 ATP/ glucose; C3 use 18 ATP

  23. C4 photosynthesis = spatial isolation • Benefits over C3 • 1) no PR • 2) less water loss • Disadvantage • C4 use 30 ATP/ glucose • C3 use 18 ATP • Lower Quantum • efficiency

  24. C4 photosynthesis = spatial isolation • C4 use 30 ATP/ glucose; C3 use 18 ATP • At high T C4 grow better • At high CO2 C3 grow better • Both T and CO2 are going up! • Hard to predict which • will do better!

  25. Crassulacean acid metabolism (CAM) Also uses C3 & C4 pathways Uses C4 pathway at night: open stomata, let CO2 in Close stomata & use C3 pathway during day

  26. Crassulacean acid metabolism (CAM) At night open stomata, let CO2 in Fix with PEP carboxylase build up C4 acids all night stored in vacuole

  27. Crassulacean acid metabolism (CAM) • During day • close stomata • decarboxylate stored C4 acids • fix CO2 using Calvin cycle

  28. Crassulacean acid metabolism (CAM) • advantages • 1) no PR • 2) minimal water loss • 3) photosynthesize when have lots of energy

  29. Crassulacean acid metabolism (CAM) • advantages • 1) no PR • 2) minimal water loss • 3) photosynthesize when have lots of energy • disadvantages • 1) can’t store much C4 acid • 2) uses lots of energy

  30. Crassulacean acid metabolism (CAM) CAM is mainly used in dry environments Some aquatic plants do CAM

  31. Crassulacean acid metabolism (CAM) Some aquatic plants do CAM Take up CO2 at night when concentration is higher: can be very low during the day! also some in tropical rainforests! >20,000 CAM spp!

  32. Crassulacean acid metabolism (CAM) CAM is mainly used in dry environments Facultative CAM induce CAM during drought, do C3 when humid

  33. Crassulacean acid metabolism (CAM) CAM is mainly used in dry environments Facultative CAM induce CAM during drought, do C3 when humid Inactivate PEPC & open stomata normally

  34. Crassulacean acid metabolism (CAM) CAM is mainly used in dry environments Facultative CAM induce CAM during drought, do C3 when humid Inactivate PEPC & open stomata normally Can tell by d13C

  35. Crassulacean acid metabolism (CAM) • Can tell by 13C • rubisco discriminates against 13C, so C3 plants have 13C of -280/00 if it can choose • CAM & C4 have 13C of -140/00 because 13C diffuses more slowly

  36. Crassulacean acid metabolism (CAM) • Can tell byd13C • rubisco discriminates against 13C, so C3 plants haved13C of -280/00 if it can choose • CAM & C4 haved13C of -140/00 because 13C diffuses more slowly • Can tell if sugar came from C3 or C4/CAM byd13C

  37. Crassulacean acid metabolism (CAM) • Can tell byd13C • rubisco discriminates against 13C, so C3 plants haved13C of -280/00 if it can choose • CAM & C4 haved13C of -140/00 because although use up most CO2 in leaf 13C diffuses more slowly • Can tell if sugar came from C3 or C4/CAM byd13C • Also tells about stomatal • opening &water use efficiency

  38. Processes affected by [Sugar] Photosynthesis Sugars Energy Biosynthesis Storage Structure Osmotic regulation Signaling molecules

  39. Processes affected by [Sugar]

  40. Processes affected by [Sugar] • 1) Flowering: adding sucrose promotes early flowering

  41. Processes affected by [Sugar] • Flowering: adding sucrose promotes early flowering • [Sucrose] @ • apex in induction

  42. Processes affected by [Sugar] • Flowering: adding sucrose promotes early flowering • [Sucrose] @ • apex in induction • affects FT & • LFY expression, • also mir399

  43. Processes affected by [Sugar] • Flowering • Photosynthesis

  44. Processes affected by [Sugar] • Photosynthesis • Sugar turns down • light & dark rxns

  45. Processes affected by [Sugar] • Photosynthesis • Sugar turns down • light & dark rxns • Represses rbcS & • CAB genes

  46. Processes affected by [Sugar] • Photosynthesis • Sugar turns down light & dark rxns • Sensed by hexokinase: acts as both an enzyme and a sensor • Catalytically-inactive mutants still sense glucose! • Form complex in nucleus with subunits of the proteasome and of the vacuolar H+ pump!

  47. AtHXK1-DependentGene Expression WT vs. gin2 Sucrose metabolism Starch biosynthesis Respiration Photosynthesis Photorespiration Fatty acid synthesis & mobilization HXK1/GIN2 Flavonoid synthesis Cell wall synthesis Nitrogen metabolism Defense ROS scavenging / DetoxificationAntioxidant protection Cytokinin signalingAuxin signaling Light signalingCa2+ signaling Upregulated in gin2 Downregulated in gin2

  48. Processes affected by [Sugar] • Photosynthesis • Sugar turns down light & dark rxns • Affects partitioning inside cells • 1 in 6 G3P becomes (CH2O)n • either becomes starch in • cp (to store in cell)

  49. Processes affected by [Sugar] • Photosynthesis • Sugar turns down light & dark rxns • Affects partitioning inside cells • 1 in 6 G3P becomes (CH2O)n • either becomes starch in • cp (to store in cell) • or is converted to • DHAP & exported • to cytoplasm to • make sucrose

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