Figure 1.

Effect of the interval between flash excitations and presence of oxygen on the loss of PSII activity and degradation of the D1 protein. Spinach thylakoids were exposed for 4 h to 360 laser flashes at 40-s dark intervals under aerobic (FL) or anaerobic (FL + N₂) conditions or to 4 h of continuous low light (LL, 20 μmol m⁻²·s⁻¹). Alternatively, a total of 360 flashes were given at 100-ms intervals followed by 4 h of further incubation in the dark (FF). PSII activity was measured by TL (A and B, dotted column) and DCIP reduction (B, horizontal line column). D1 protein content was determined by Western blot analysis (B, vertical line column).