Effects of temperature on glycolate metabolism in Chlorella

The effect of temperature on the products of photosynthetic carbon metabolism was studied in Chlorella vulgaris 11h cells which had been grown with air enriched with 2-3% CO2. During the test period, 300 ppm of (14)CO2 was used. On raising the temperature from 20 to 36°C during photosynthetic (14)CO2 fixation, (14)CO2-incorporation into glycolate immediately stopped whereas that into sucrose was greatly enhanced. When the temperature was lowered from 36 to 20°C, (14)C-glycolate formation was greatly enhanced, but sucrose formation slowed. No significant change in the rate of total (14)CO2 fixation was induced by either temperature change. At 20°C the radioactivity incorporated into glycolate was about 20% of the total (14)C fixed, but it decreased to less than 2% at 32°C. When α-hydroxy-2-pyridinemethane-sulfonate was added, the percent incorporation of (14)C into glycolate was enhanced to 30% at 20°C as well as at 32°C. The increase in (14)C-incorporation into glycolate was accompanied by a decrease in sucrose and glucose-polymer, although the total (14)CO2 fixation was not significantly affected by this inhibitor; most of the labelled glycolate appeared in the algal medium.