Photosynthetic Apparatus Formation during the Cell Cycle of Chlorella

Synchronous cell division in cultures of Chlorella vulgaris Beijerinck was induced by intermittent illumination: 9 hours light, 6 hours darkness. The rate of photosynthetic O₂ evolution per cell increases 4-fold in a one-step manner at the beginning of the light period, to the same extent as the increase in cell number. Over the division cycle, the following accumulation times during the light period were found: chlorophyll a, between 2 and 8 hours, chlorophyll b, between 5 and 8 hours, reaction centers of photosystems I and II, between 2 and 6 hours; and cytochrome f, between 2.5 and 5 hours. Cytochrome f accumulation is closely followed by an increase in amplitude of the rapid phase in light-induced absorption increase at 520 nanometers and in intensity of the delayed light emission. Enhancement of the delayed fluorescence yield per flash under continuous illumination (caused by the establishment of the pH difference across the thylakoid membrane) is maximal by the first hour of the light period.