Question:

Which of the following is incorrect about the light reactions of photosynthesis?

Light energy provides energy for the photolysis of water through excitation of the reaction centre of PS-II

P680 and P700 are the reaction centres of PS-I and PS-II respectively

Reactions of the two photosystems are needed for the reduction of NADP

NADPH is not produced in cyclic electrons transport in light reactions

Solution:

Photosystem II has an absorption peak of approximately 680 nanometers, and the reaction center pigment is called P680, while that of PSI has an absorption peak of approximately 700 nanometers and is called P700. Sunlight provides energy for the splitting of water during the light reaction. The Z scheme of the light reaction is a non-cyclic flow of electrons and involves both PS I and PS II to produce NADPH, while cyclic photophosphorylation does not pass electrons to NADP, and NADPH is not produced. So, the correct option is B.