Spinach disks were illuminated at varying intensities, in either high or low CO2 buffer.
At very high light intensities the curves plateau. The plateau in the LOW-CO2 curve is best explained by:
- Acheck_circle
CO2 has become a limiting factor; more light cannot speed the Calvin cycle
- B
Water becomes the limiting factor at low CO2
- C
Oxygen has reached toxic levels for the leaf
- D
Chlorophyll is denatured by intense light
Explanation
At saturating light, the Calvin cycle can't keep pace if CO2 is scarce. The plateau height reflects whichever Calvin-cycle reactant is limiting.