Glycolic Acid Labeling During Photosynthesis with 14CO2 and Tritiated Water

Abstract
Chlorella pyrenoidosa were allowed to photosynthesize for short periods of time in the presence of C14O2 and TO. Analysis of tritium and C14 labeling of photosynthetic inter-mediate compounds showed that the T C14 ratio of glycolic acid was comparable to that of intermediate compounds of the photosynthetic C reduction cycle when photosynthesis was performed in nearly 100% oxygen and only slightly higher under steady-state conditions. It is concluded that formation of labeled glycolic acid as a consequence of its proposed hydrogen transport role in photosynthesis is quantitatively of limited importance compared to the net synthesis of glycolic acid from CO2.