The Effect of Glyoxylate on Photosynthesis and Photorespiration by Isolated Soybean Mesophyll Cells

Abstract

Incubating isolated soybean leaf mesophyll cells with glyoxylate increased the rates of CO(2) fixation by as much as 150%. In order to cause this stimulation, the glyoxylate must be presented to the cells before the NaHCO(3). Significant stimulation was observed 15 seconds after beginning the glyoxylate treatment. The glyoxylate-dependent stimulation was increased by high O(2) concentrations and decreased by high CO(2) concentrations. Glyoxylate treatment resulted in a 71% inhibition in the rate of CO(2) incorporation into glycolate and glycine. Glyoxylate may be stimulating net photosynthesis solely by decreasing photorespiration or it may be increasing the amount of CO(2) fixed by both decreasing photorespiration and increasing gross photosynthesis. Ribulose bisphosphate carboxylase, when preactivated and assayed in situ, was unaffected by the glyoxylate treatment.