Effects of temperature and CO2 concentration on photosynthetic CO2 fixation by Chlorella

The rates of photosynthetic CO2 fixation by Chlorella vulgaris llh, grown under high CO2, were determined between 4 to 37°C with air containing from 300 to 13,000 ppm COa. When the CO2 level was increased, both the rate of photosynthesis and the optimum temperature for maximum photosynthesis increased. The maximum photosynthetic rate was reached at 12°C with 300 ppm CO2. Among the photosynthetic products fromed at 300 ppm CC>2, glycolate decreased greatly when the temperature was raised from 20 to 30°C. At 3,000 ppm CC>2 an insignificant amount of glycolate was formed at all temperatures, whereas C-incorporation into the insoluble fraction, sucrose, and the lipid fraction was significantly higher than at 300 ppm CG"2. The G in sucrose was greatly increased and the radioactivity in the insoluble fraction decreased when the temperature was raised from 28 to 36°C.