Size-distributions of antenna and acceptor-pool of Photosystem II

A study is described of the heterogeneous kinetics of Photosystem II (PSII) electron transport in osmotically swollen spinach chloroplasts ('blebs') on illumination by a series of laser flashes. The existence of a broad distribution of the number of plastoquinone molecules rapidly accessible for reduction by PSII is confirmed by chlorophyll fluorescence yield and electroluminescence measurements as a function of the number of preilluminating flashes. The oscillation of electroluminescence with flash number as a function of flash energy was used to calculate the best-fitting antenna-size distribution of the oxygen evolving PSII. The results suggest that, in blebs at least, electrogenic charge separation leading to electron transport from water to the plastoquinone pool is carried out by PSII beta as well as PSII alpha.