Figure 3.

Photomicrographs of cells in synchronized cultures of Chlamydomonas reinhardtii grown in incident light 500 μmol m⁻² s⁻¹ at 30 °C (A–C) or 39 °C (D–H). The cultivation temperature and the cell age in hours are indicated in the pictures. The control cells, grown at 30 °C, divided at 18 h and thereafter entered a new cell cycle sequence similar to the one depicted in panels A–C. In contrast, the cells grown at 39 °C did not divide even after prolonged cultivation. They attained a maximum size after about 29 h of growth and started to lose chlorophyll (F). After 33 h, the majority of the cells lost chlorophyll and accumulated enormous amounts of starch in the form of grains (G), which can be visualized by staining with Lugol solution (H). Cultures at both 30 and 39 °C started from the same initial culture, so the cells depicted in panel A for 30 °C reflect also the cells present at 0 h at 39 °C. Bar = 10 µm.