Temperature‐Induced Synchrony and Biochemical Responses of Astasia longa Grown on Ethanol

SYNOPSIS. Optimal growth of the colorless flagellate, Astasia longa, in terms of generation time occurred at 25–30 C. Above and below this interval, generation time increased. In contrast, length of the lag phase was constant over a wide temperature range, 18–32 C. At 13 C dry weight of Astasia was 15% greater than at 28.5. Alcohol‐ether soluble material accounted for 72% of the dry weight increase at 13, while RNA and protein contents of the cells were the same at both temperatures. Rates of synthesis of dry weight, RNA, protein and lipid per μl oxygen consumed were all reduced at 13 C; however, lipid synthesis was the least affected. Cell division in Astasia was synchronized repetitively by cold (13–15 C) and warm (28.5 C) temperature cycles. Under best conditions, cell division began immediately at the onset of the warm period. Cellular preparations for cytokinesis apparently were at least partially completed in the cold, and raising the temperature released a block to cell division.