Figure 4.

Effects of light and the removal of NaCl on the recovery of PSII and PSI activities in wild-type and desA⁺ cells after NaCl-induced inactivation. Wild-type and desA⁺ cells were incubated for 7 and 16 h, respectively, in darkness in the presence of 0.5 m NaCl. Then cells were further incubated in light at 70 μE m⁻² s⁻¹ in the presence of lincomycin at 200 μg mL⁻¹ or in its absence. After incubation for 30 h in light, the cells were collected by centrifugation, resuspended in fresh BG-11 medium with no added NaCl, and incubated in light for a further 10 h. At designated times, a portion of the cell suspension was withdrawn. A, The oxygen-evolving activity of PS II was measured after addition of 1.0 mm BQ to the suspension. The oxygen-evolving activities of wild-type and desA⁺ cells that corresponded to 100% were 527 ± 36 and 543 ± 33 μmol O₂ mg⁻¹ Chl h⁻¹, respectively. B, PSI activity was measured by monitoring the uptake of oxygen after the addition of 15 μm DCMU, 0.1 mm DCIP, 5 mm sodium ascorbate, and 0.1 mm MV to the suspension. The oxygen-uptake activities of wild-type and desA⁺ cells that corresponded to 100% were 315 ± 26 and 309 ± 21 μmol O₂ mg⁻¹ Chl h⁻¹, respectively. ▪ and □, Wild-type cells; ● and ○, desA⁺ cells in the absence of lincomycin. Wild-type (▿) and desA⁺ (▵) cells in the presence of lincomycin. Each point and bar represent the average ± se of results from four independent experiments.