Reduction kinetics of the photo-oxidized chlorophyll a+II in the nanosecond range : Measurements of the absorption changes at 688 nm under repetitive flash excitation

Abstract

The 688 nm absorption changes (Δ A 688), indicating the photochemical turnover of chlorophyll a II (Chl a II) have been investigated under repetitive laser flash excitation conditions in spinach chlorplasts. It was found that under steady state conditions about 50–60% of the photo-oxidized primary donor of Photosystem II (PS II), Chl a + II, becomes re-reduced with a biphasic kinetics in the nanosecond time scale with half-life times of about 50 ns and 400 ns. The remaining Chl a + II becomes re-reduced in the microsecond range.