Figure 11.

PSII maximum photochemical yield (F_V/F_M) correlates with content of functional PSII determined from oxygen evolution. T. pseudonana cultures were grown at 18°C under 30, 90, 180, or 270 μmol photons m⁻² s⁻¹ for many generations. We used a modulated fluorometer to measure F_V/F_M and an oxygen flash yield protocol to determine their content of active PSII. We then shifted the cultures to 90, 180, 270, 450, 1,000, 1,400, 1,800, or 2,200 μmol photons m⁻² s⁻¹ for 30 to 90 min, with or without lincomycin, and then remeasured F_V/F_M and active PSII content. open circles: cultures measured with active PSII repair; closed circles: cultures measured in the presence of the chloroplast translation inhibitor lincomycin to block PSII repair. Line shows the linear regression for the pooled data since an F test found no significant difference between the slopes for the data with or without lincomycin. R² = 0.89, dotted lines show 95% confidence interval for linear regression line. y intercept for pooled data = 33.6% ± 2.3%. Diatom PSII photoinactivation, repair, and protection.