Question

2. Under what circumstances might it be useful for a plant to use the cyclic pathway?

Answer 1

Cyclic path way or cyclic photophosphorylation occurs in plants when the available wvelength of light is more than 680 nm. In which case only photosystem ! can occur. Also in stroma lamella , cyclic photophosphorylation only occurs. Even when there is more accumulation of NADPH than it is consumed, cyclic photophosphorylation occurs.

During cyclic phosphorylation, electrons emitted by PS1 come back to PS1 again after passing through the ETC, no NADPH formed. This cyclic path way produces only ATP and does not produce NADPH. It is important for the plant to under go cyclic path way because photosynthesis needs more ATP than NADPH. For every C fixed in photosynthesis, 3 ATP and 2 NADPH molecules are needed.