[Effect of membrane-active compounds on the energized state when pea chloroplast photosystem I and photosystem II are operating separately]

Effects of membrane-active compounds on photo-induced atebrin fluorescence quenching were studied on a pea chloroplast suspension. An observation of atebrin fluorescence separately with PSI and PSII revealed that the quenching was faster in preparations where PSI only was operable. The dark recovery of fluorescence occurred at the same rate in both photosystems. In the presence of low concentrations of methylamine or NH4Cl there was an acceleration of the fluorescence dark recovery, with PSII it occurred to be a greater extent. In the presence of valinomycin the acceleration was faster with PSI. Measurements of the rates of dark relaxation of electrochromic absorbance changes (with the maximum at 520 nm) induced by a single laser pulse also demonstrated the difference between the two photosystems.