Figure 2.

Effect of shifting light/dark-entrained cultures to a new light condition on the cell cycle phase patterns of Prochlorococcus marinus PCC9511. A, distribution of cells in G₁ (blue), S (red) and G₂ (green) phases for small volume batch cultures of PCC9511 acclimated under LL and shifted to HL conditions. B, HL acclimated cultures were followed during one L/D cycle then shifted to HL+UV conditions. The experiment was done in duplicates shown by filled and empty symbols. Note that only the UV radiation curve is shown in graph B since the visible light curve is the same as in graph A. Black arrows indicate the time point of the shift. White and black bars indicate light and dark periods. The dashed line indicates the growth irradiance curve (right axis). Abbreviations as in Fig. 1.