Erratum

Glycolate synthesis was inhibited 40–50% in illuminated tobacco leaf disks, which have rapid rates of photorespiration, when floated on 20 mm potassium glycidate (2,3-epoxypropionate), an epoxide similar in structure to glycolate. The inhibitor also decreased the release of photorespiratory CO₂ about 40%, and the specificity of glycidate was demonstrated by the 40–50% increase in rate of photosynthetic CO₂ uptake observed in its presence. The importance of glycolate synthesis and metabolism in the production of photorespiratory CO₂ and the role of glycolate in diminishing net photosynthesis in species with rapid rates of photorespiration was thus further confirmed. L-(or 2S)-Glycidate was slightly more active than DL-glycidate, but glycidate was more effective as a specific inhibitor in leaf tissue than several other epoxide analogs of glycolate examined. The products of photosynthetic ¹⁴O₂ fixation after 3 or 4 min of uptake were proportionately altered in the presence of glycidate, and the specific radioactivity of the ¹⁴C]glycolate produced was closer to that of the ¹⁴CO₂ supplied. Glycidate inhibited glycolate synthesis in tobacco leaf disks irreversibly, since the degree of inhibition was the same for at least 2 hr after the inhibitor solution was removed. Glycidate also blocked glycolate synthesis in maize leaf disks, tissue with low rates of photorespiration, but large increases in net photosynthesis were not observed in maize with glycidate, because glycolate synthesis is normally only about 10% as rapid in maize as in tobacco. The demonstration of increases in net photosynthesis of 40–50% when glycolate synthesis (and photorespiration) is blocked with glycidate indicates in an independent manner that the biochemical or genetic control of photorespiration should permit large increases in plant productivity in plant species possessing rapid rates of photorespiration.