Lecture # 7 Photosynthesis and the environment and synthesis

Question 1

Net photosynthesis of C3 in high light

Answer 1

An = net photosynthetic (assimilation) rate (umol’s m s)
VCO2 = PCR, carboxylic rate of RUBISCO = gross photosynthesis
VO2 = PCO, oxygenation rate of RUBISCO (photorespiration) every 2 PCO cycles release 1 CO2 fixed by PCR
R= respiration rate (I.e leaf mitochondria, or roots etc)

Ex: An = Vco2 - 0.5 Vo2 - R
24 = 30 - 0.5 *10 -1
30 = typical gross photysynthetic rate
10 = PCR 3: PCO 1

Question 2

PAR / Light

Answer 2

An = V CO2 - 0.5Vo2 - R
Intensity
- Saturation point
Point of diminishing returns
- Compensation point
In low light, respiration may exceed photosynthesis
- Photoinhibition
* In very high light damage may occur

Question 3

CO2 An = VCO2 - 0.5VoO2 - R

Answer 3

-Saturation
-low (CO2)
-Compensation point
- CO2 fertilization

Question 4

Temperature responses of net photosynthesis

Answer 4

At a certain temperature points like canopy temperature Crop CO2 up take is greater, C3 cycle. However, as temperature gets greater photorespiration is greater than the C3 cycle.

Question 5

Post-fixation feedback

Answer 5

Prevent of phloem transport
No Pi in cytoskeleton
No TP export from chloroplast
Inc. starch synthesis
-…no ATP formation
- no RuBP regeneration
Low photosynthesis

Other notes:
PPP (C-compound synthesis ) comes from Trisphosphate
Glu 1 phosphate is then oxidized and loses Pi and converted into Starch = storage
(This happens inside the chloroplast stroma and cell cytosol)