Delayed fluorescence emitted from light harvesting complex II and photosystem II of higher plants in the 100 ns–5 μs time domain

AbstractThis study presents the first report on delayed fluorescence (DF) emitted from spinach thylakoids, D1/D2/Cytb-559 preparations and solubilized light harvesting complex II (LHCII) in the ns time domain after excitation with saturating laser flashes. The use of a new commercially available multichannel plate with rapid gating permitted a sufficient suppression of detector distortions due to the strong prompt fluorescence. The following results were obtained: (a) in dark-adapted thylakoids, the DF amplitudes at 100 ns and 5 μs after each flash of a train of saturating actinic pulses exhibit characteristic period four oscillations of opposite sign: the DF amplitudes at 100 ns oscillate in the same manner as the quantum yield of prompt fluorescence, whereas those at 5 μs resemble the oscillation of the μs kinetics of P680+ reduction in samples with an intact water oxidizing complex, (b) the quantum yield of total DF emission in the range up to a few μs is estimated to be