The production of glycollate during photosynthesis in Chlorella

Abstract

Blackman (1905) deduced from his study of the effect of external factors on the rate of photosynthesis that photosynthesis must include both photochemical and thermochemical processes. Later it appeared probable that the fixation of carbon dioxide was a thermochemical process driven in the direction of the formation of reduced carbon compounds by reaction with some product of the photochemical process. Work with radioactive carbon isotopes has confirmed this viewpoint. Calvin and his colleagues (Bassham & Calvin 1957) utilized the radioactive isotope of carbon, carbon-14. In the first type of experiment the percentage radioactivity in any one compound as a fraction of the total activity fixed was measured. By extrapolation it was possible to estimate which compound would have 100% of the radioactivity immediately after the addition of tracer and was therefore the first intermediate formed. It was found to be phosphoglyceric acid (PGA). From the shape of the time course of the percentage activity for individual compounds it was possible