C4 physiology

Question 1

ACi curve C4 has

Answer 1

higher PS
higher Vcmax - rate of PS
lower compensation point

than C3

Question 2

C4 at low light

Answer 2

even at low light has a higher compensation point than C3
steep increase of PS with small increase in light

light limiting prortion is steeper in C4 plants

Question 3

under some condition c3>c4

Answer 3

• additional ATP req for fixing C - increase photon requirements
• at low temps quantum yield c3>c4
  BUT - at high temps quantum yield C3

Question 4

do C4 planst conduct any photorespiration?

Answer 4

• enzymes for PCO cycles present
• some O2 inhibition of ps
• leakage of CO2 decreases quantum yield

Question 5

quantum yield in C4 (11% leakage) > quantum yield C3

give numbers

Answer 5

c4 11% = 0.063 mol co2 mol-1 photon

c3 = 0.054 mol co2 mol-1 photon

Question 6

NUE of C4 plants.

T does what

Answer 6

increase in T decresae in rubisco as % leaf protein

opposite of C3

Question 7

NUE significantly higher in `C4 despite increased investment in PEPC

Answer 7

• saved N can be used for investment in roots esp in nutrient poor soils

Question 8

WHat enzyme might limit C4 plants further south

Answer 8

low temperature tolerance in PPDK
PPDK the rate limiting step for regeneration of PEP.
a miscanthus species increase abundances of PPDK in response to low temperatures
-> engineer this