Glycolate and Glycine Production in Chlamydomonas segnis Adapting to Low and High Carbon Dioxide Tensions

Abstract

Rates of 14 C-incorporation into total ethanol water-soluble compounds, including glycolate and glycine, by Chlamydomonas segnis adapting to either air or 5% C 2 were compared during photosynthesis at a suboptimal concentration of inorganic carbon. In zoospores adapting to air, 14 C-incorporation into C 3 and C 4 compounds was enhanced without reduction in the apparent rate of glycolate and glycine synthesis. In zoospores adapting to 5% CO 2 , 14 C-incorporation into C 3 compounds was decreased without increase in the apparent rate of glycolate and glycine synthesis. These observations are inconsistent with the proposal that the function of a CO 2 -concentrating mechanism, inducrd during zoospore adaptation to air, is to suppress glycolate produetion by the oxygenase reaction of ribulose 1,5-bisphosphate carboxylase-oxygenase. They also indicate that a decline in the efficiPncy of this meehanism during zoospore adaptation to 5% CO 2 would not stimulate this reaction.