C3, C4, and CAM plants all have the same goal, to make carbohydrates. What happens to the triose-phosphates made in the Calvin cycle? 1. Used to synthesize starch for storage in chloroplast. 2. Exported from chloroplast for sucrose synthesis in the cytosol. How is starch vs. sucrose synthesis regulated? Why is it regulated?
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C3, C4, and CAM plants all have the same goal, to make carbohydrates. What happens to the triose-phosphates made in the Calvin cycle? 1.Used to synthesize.
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C3, C4, and CAM plants all have the same goal,
to make carbohydrates.
What happens to the triose-phosphates made in the Calvin cycle?
1. Used to synthesize starch for storage in chloroplast.
2. Exported from chloroplast for sucrose synthesis in the cytosol.
How is starch vs. sucrose synthesis regulated?
Why is it regulated?
Triose phosphates produced in the Calvin cycle can be used for starch or sucrose synthesis.
Triose-P
Starch
Sucrose
Calvincycle
cytosol
chloroplast
Fig. 8.15Starch is synthesized in the chloroplast.
Fig. 8.14
When [Pi] is high, triose-P is exportedin exchange for Pi & used to synthesizesucrose.
If [Pi] is low, thentriose-P is retainedin chloroplast andused to synthesizestarch.
Starch vs. sucrose synthesis is regulated by level of cytosolic Pi as it affects triose-P export from chloroplast.
= (Radiation emitted + Conduction/Convection loss + Evaporation)
Leaf temperature and photosynthesis
Which is C3 and C4?
C4
C3
Why does the quantum yield of C3 plants decrease with increasing temperature? Why is the quantum yield of C4plants insensitive to temperature?
Fig 9.23
Photosynthetic responses to CO2 History of atmospheric CO2
Fig. 9.16
Current trend of rising CO2
The Mauna LoaCO2 record
Fig. 9.16
Photosynthetic response to CO2 of C3 & C4 plants
Photosynthetic response to temperature
Fig. 9.22CO2-temperatureinteraction in a C3plant.
Why does the temp.for maximum phot.increase at elevatedCO2?
2. Second approachHenry’s Law: concentration of a gas dissolved in water is proportional to the gas partial pressure (or [gas] at same total pressure) above the water.
Changing the gas partial pressure produces a proportional change in dissolved concentration.
ExamplesIf dissolved concentration is 11.68µM at 345ppm CO2, then the dissolved concentration is 2 x 11.68 if gas concentration is 2 X 345ppm.
At 250ppm CO2, dissolved CO2 is 11.68 x 250/345 = 8.46 µM.