On the formation of glycolate in photosynthesizing Chlorella using a new gas-liquid chromatography method.

Suspensions of Chlorella vulgaris were allowed to photosynthesise with two concentrations of (14)CO2 (101 and 543 ppm) in 80% oxygen, and the incorporation of (14)C into glycolate and 3-phosphoglyceric acid (3-PGA) was followed. The relative specific activity (RSA) of the glycolate formed at both CO2 concentrations decreased initially and then increased slowly. The RSA of glycolate was much lower when the suspension photosynthesised in 101 ppm (14)CO2 compared to 543 ppm. The RSA of 3-PGA was nearly always lower than that of glycolate and the results suggest that refixed dark respiratory CO2 or respiratory 3-PGA, or both, substantially contribute to the total 3-PGA in the algae. It is concluded that glycolate is formed from recent photosynthate as well as from storage material, but the relative contribution of these substrates depends on the conditions under which the algae are grown, as well as those obtaining at the time of glycolate excretion.