Effects of water stress on the Mossbauer spectrum of Fe2+/Fe3+ components in cucumber PSII particles

There were four doublets in the Mossbauer spectrum of cucumber ( Cucumis sativus L.) photosystem II (PS II) particles. According to the value of isomer shift and quadrupole splitting, they represented oxidized cytochrome b559 (Cyt-b559), reduced Cyt-b559, Fe3+-quinone (Q) complex, and Fe2+-Q complex respectively. After water-stress, the electron transport rate between Q(A) (primary quinone electron acceptor of PS II)/Q(B)(secondary quinone electron acceptor of PS II) was affected and the absorption doublets of Fe2+ disappeared, suggesting that the reduced Cyt-b559 and Fe2+-Q complex had been oxidized. The results indicated that water-stress had changed the redox status of iron in the iron-quinone complex. Iron took part in electron transport through the change from a state of reduction to oxidation.