The induction curve of delayed luminescence emitted from 0.5 to 2.5 ms after excitation of dark-adapted intact chloroplasts of the green alga,Bryopsis maxima, showed three transient peaks, L1, L2and L3(in order of appearance), at about 0.1, 1 and 5 s after theonset of intermittent illumination. Intact chloroplasts were needed for L2to appear, whereas L1and L3were present in hypotonically treated chloroplasts.L1and L2are related to the electric field generated across the thylakoid membranesbecause the two peaks parallelled the appearance of the first and second peaks of electrochromic absorption changes at 560 nm and they were totally abolished by valinomycin and CCCP. A smaller contribution to the L1and L2of the proton activity gradient across the membranes, or of pH changes inside or outside the membranes, was suggested by the partial suppression of the transient by NH4CI.L3is related to the proton gradient or pH changes because the transient was inhibited by NH4CI and CCCP but enhanced byN,N′-dicyclohexylcarbodiimide. In the presenceof valinomycin, which somewhat lowered the peak height of L3, the kinetics of delayed luminescence parallelled that of fluorescence. Electrogenic reactions which occur sequentially during the dark to light transition of the photosynthetic machinery in intact chloroplasts is discussed in connection with transient changes in delayed luminescenc
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