Which of the following statements is incorrect?

In the light‑dependent reactions of photosynthesis, two distinct pathways generate chemical energy: non‑cyclic (linear) photophosphorylation and cyclic photophosphorylation.

Non‑cyclic photophosphorylation uses both Photosystem II (PS II) and Photosystem I (PS I). Water is split at PS II, releasing O₂, electrons travel through the plastoquinone pool, cytochrome b₆f complex, and plastocyanin to PS I, and finally reduce NADP⁺ to NADPH while also producing ATP via the proton gradient.

Cyclic photophosphorylation, however, is a pathway that **only** involves PS I. The excited electrons from PS I are transferred to ferredoxin, then to the cytochrome b₆f complex and back to the plastoquinone pool, completing a circuit that pumps protons into the thylakoid lumen. This proton motive force drives ATP synthesis, but no NADPH is formed because the electrons never reach NADP⁺.

Therefore, the statement “Cyclic photophosphorylation involves both PS I and PS II” is incorrect—it should state that cyclic photophosphorylation **uses only PS I** and does not involve PS II.