Which of the following statements is incorrect ?

To determine which statement is incorrect, let us analyze the process of photophosphorylation in photosynthesis step-by-step:

1. Non-Cyclic Photophosphorylation:
This process occurs in the grana lamellae, which contain both Photosystem I (PS I) and Photosystem II (PS II). During this non-cyclic electron flow, electrons released from PS II do not return to the starting reaction center but are instead used to reduce NADP⁺ to NADPH + H⁺. Concurrently, a proton gradient is established across the thylakoid membrane, driving the synthesis of ATP. Thus, the statement "Both ATP and NADPH+H⁺ are synthesized during non-cyclic photophosphorylation" is correct.
Similarly, the statement "Grana lamellae have both PS I and PS II" is also correct.

2. Stroma Lamellae Structure:
The stroma lamellae (membranes connecting the grana) lack Photosystem II (PS II) and the enzyme NADP reductase. They only contain Photosystem I (PS I). Therefore, the statement "Stroma lamellae have PS I only and lack NADP reductase" is correct.

3. Cyclic Photophosphorylation:
Because the stroma lamellae lack PS II and NADP reductase, electrons in these membranes undergo cyclic flow. Light-excited electrons from the reaction center of PS I (P700) are passed through an electron transport chain and eventually cycled back to the same reaction center (PS I). This cyclic movement drives the synthesis of ATP only, and does not produce NADPH + H⁺. Crucially, cyclic photophosphorylation involves only Photosystem I (PS I). It does not involve Photosystem II (PS II).
Therefore, the statement "Cyclic photophosphorylation involves both PS I and PS II" is incorrect.

Conclusion:
The incorrect statement is: "Cyclic photophosphorylation involves both PS I and PS II."