Studies on the vegetative life cycle ofChlamydomonas reinhardiDangeard in synchronous culture I. Some characteristics of the cell cycle

摘要

Cells ofChlamydomonas reinhardiDangeard were grown synchronously under a 12 hr light-12 hr dark regime. Time courses of nuclear division, chloroplast division,“apparent cytokinesis”and zoospore liberation were followed during the vegetative cell cycle in the synchronous culture. Liberation of zoospores occurred at about 23–24 hr after the beginning of the light period at 25°C. Four zoospores were produced per mother cell under the conditions used. At lower temperatures, the process of zoospore liberation as well as length of the cell cycle was markedly prolonged, but the number of zoospores produced per mother cell was approximately the same. At different light intensities, lengths of the cell cycle were virtually the same, while the number of zoospores liberated was larger at higher rather than at lower light intensities.During the dark period, nuclear division, chloroplast division and apparent cytokinesis took place, in diis order, and proceeded less synchronously than did the process of zoospore liberation. When the 12 hr dark period was replaced with a 12 hr light period during one cycle, the time of initiation as well as the duration of zoospore liberation was litde affected in most cases, whereas nuclear division, chloroplast division and apparent cytokinesis were considerably accelerated by extended illumination. When algal cells which had been exposed to light for 24 hr were further incubated in the light, zoospore liberation started much earlier and proceeded far less synchronously, compared with that under 12 hr light-12 hr dark alter