Photoinhibition of Reaction Centers of Photosystems I and II in Intact Bryopsis Chloroplasts under Anaerobic Conditions.

Illumination of intact Bryopsis corticulans chloroplasts under anaerobic conditions induced a decline of chlorophyll fluorescence and photoinhibition of Photosystems I and II. The time course of the light-induced decline of chlorophyll fluorescence and the decreases of activities of reactions sensitized by Photosystems I and II were compared. Photosystem I activity decreased in parallel with the disappearance of active P700. The time course of the destruction of the reaction center of Photosystem II was similar to that of photoinhibition of 2,6-dichlorophenolindophenol-Hill reaction.It appears that the initial events in photoinhibition are the destruction of the reaction centers of Photosystems I and II and that the reaction centers that are inhibited become quenchers of chlorophyll fluorescence.Effects of inhibitors of electron transfer and of an electron donor to Photosystem I showed that photoinhibition was related to Photosystem I activity.