Photoinhibition of photosynthesis without net loss of photosystem II components in Populus deltoides.

ABSTRACT

The photoinhibition of photosynthesis was investigated on intact attached leaves and isolated thylakoid membranes of Populus deltoides. Our studies demonstrate that in intact leaves photoinhibition takes place under high irradiance which is more pronounced at higher temperatures. No net loss of Dl and other proteins associated with photosystem II (PSII) were observed even after 64 % photoinhibition suggesting that the degradation of polypeptides associated with PSII is not the only key step responsible for photoinhibition as observed by other workers. Electron transport studies in isolated thylakoid membranes suggested water oxidation complex as one of the damaged site during high light exposure. The possible mechanisms of photoinhibition without net loss of D1 protein are discussed.