Botany - Photosynthesis in Higher Plants Question with Solution | TestHub

Cyclic photophosphorylation also occurs when only light of wavelengths beyond $680 \mathrm{nm}$ are available for excitation. When only PS I is functional, the electron is circulated within the photosystem I, and the phosphorylation occur due to the cyclic flow of electrons. A possible location where this could be happening is in the stroma lamellae. While the membrane or lamellae of the grana have both PS I and PS II the stroma lamellae membranes lack PS II as well as NADP reductase enzyme. The excited electron does not pass on to NADP$+$ but is cycled back to the PS I complex through the electron transport chain. The cyclic flow, hence, results only in the synthesis of ATP, but not of $\mathrm{NADPH}+\mathrm{H}+.$