Light-induced decrease in the PS II activity of spinach thylakoids and PS II membranes monitored by chlorophyll fluorescence Fv/Fm.

<p>(<b>A</b>) The thylakoids. (<b>B</b>) The PSII membranes. The samples were incubated in solution B and kept in the dark or illuminated with white light with given light intensities (100–1,000 µmol photons m⁻² s⁻¹) at either 20°C (brown bars) or 30°C (green bars) for 10 min. Dark control kept at 4°C is also shown (blue bars). After incubation in the dark for 30 min on ice, chlorophyll fluorescence was measured with a Mini-PAM at 25°C. The data are the means of three measurements±S.D.