Figure 5.

Effect of H₂O₂ on the balance between PSII damage and repair. To estimate the initial PSII repair capacity of Synechococcus sp. WH7803, cells acclimated to LL (A) and HL (B) were maintained under their initial growth irradiance (triangles and squares for LL and HL cells, respectively) or shifted to dark (upside down triangles and diamonds, respectively) in the presence (black symbols) or absence (white symbols) of lincomycin (Lin). F_v/F_m was then followed for 2 h. The effect of H₂O₂ on PSII damage and repair in LL (C) and HL (D) cells was estimated on cells maintained under their initial growth irradiance or shifted in the dark, by measuring the F_v/F_m 2 h after the addition of lincomycin (dashed bars) or water (open bars) and of 0 μm (white bars), 25 μm (light gray bars), or 750 μm (dark gray bars) H₂O₂. These data are based on three independent experiments and are expressed as means ± sd.