Photoreduction of NADP⁺ in photosystem II

Aim of this minireview is to integrate possible evidences concerning NADP+ reduction in photosystem II (PS II). Investigations of this photoreaction show that under conditions when the first quinone acceptor, QA, is in its reduced state (QA-), electrons are transferred from reduced pheophytin (Pheo-) to NADP⁺, indicating that PS II can reduce NADP⁺ without the participation of PS I. On the basis of own experimental material and data, an alternate pathway for electron transfer in PS II reaction centres of higher plants is suggested. Some problems concerning Z-scheme are discussed.