Uptake and utilization of alanine-1-14C by freshwater algae.

Experiments were conducted x^ith Chlorella pyrenoidosa, Cosmarium formosulum, and Gloeocapsa sp. to determine their relative heterotrophic capacity at various conditions. Cultures were incubated in nutrient media with 0.5 uc DL-alanine-l-^C added at various temperature (10C, 20C, 30C) and illumination (0 ft-c, 2137 ft-c, 8547 ft-c) conditions. A temperature increase resulted in an increase in alanine uptake in Ck pyrenoidosa and C. formosulum. Uptake decreased in Gloeocapsa at 20C but increased at 30C. High light intensity and darkness stimulated uptake in C. pyrenoidosa and C. formosulum and uptake was minimal at 2137 ft-c. Uptake occurred at all illumination conditions with Gloeocapsa, but was maximum at 2137 ft-c. Alanine was incorporated into cytoplasmic protein in C. pyrenoidosa and C.. formosulum but a significant amount was incorporated into protein in Gloeocapsa only at 2137 ft-c. These species were concluded to be facultative heterotrophs.