Acceleration of the Decay of Membrane Potential after Energization of Chloroplasts in Intact Zea mays Leaves

The relationship between dissipation of the flash-induced membranepotential across the thylakoid membrane and the high energystate was studied in Zea mays leaves. The dark decay of theflash-induced 515-nm absorbance change was accelerated by shortpreillumination of the leaf. No acceleration of the decay bypreillumination was observed when leaves were incubated in argonor CO² gas or treated with DCMU. These effects of preilluminationand incubation were reversible. The delayed fluorescence from chlorophyll a was reversibly decreasedby incubating leaves in argon or CO² gas, though the modes ofdepression were somewhat different from each other. In leavesincubated in argon or CO² gas, the phase of slow decrease ofthe intensity of prompt fluorescence during illumination reversiblydisappeared. The results suggested that the dissipation of membrane potentialgenerated by a flash was accelerated after the energizationof chloroplasts in leaves, probably by increased H^– permeabilityof the thylakoid membrane. O2 was important in maintaining (indarkness) and forming (under illumination) the high energy statein chloroplasts in intact leaves. (Received October 1, 1980; Accepted December 15, 1980)