The effect of high partial pressures of oxygen on photosynthesis in Chlorella—I. : The effect on end products of photosynthesis

Abstract

During periods of photosynthesis in 14CO 2 of up to 70 min at concentrations of carbon dioxide up to 4 per cent, the major end products were sucrose and a polyglucan. At the lower concentrations of carbon dioxide the addition of isonicotinyl hydrazide (INH) stimulated the production of glycollate and glycine but did not affect the total fixation. Raising the partial pressure of oxygen or the addition of iodoacetamide increased the production of glycollate but decreased the total fixation. At higher concentrations of carbon dioxide both the inhibition of photosynthesis by oxygen and the stimulation in production of glycollate were decreased; whereas the inhibition of photosynthesis by iodoacetamide increased. Carbon-14 was incorporated into the sugar phosphates of the photosynthetic cycle during short term photosynthesis and the further metabolism of this carbon studied during photosynthesis in 12CO 2. The main radioactive products were sucrose and polyglucan. At low concentrations of carbon dioxide, raising the partial pressure of oxygen or the addition of INH led to an accumulation of glycollate. Similar effects of high partial pressure of oxygen and addition of INH were found on the products of photometabolism of exogenous [U- 14C]glucose in carbon dioxide free conditions.