The Role of Glycolic Acid Metabolism in Opening of Leaf Stomata

Abstract

Inhibitors of the oxidation of glycolic acid, a-hydroxysulfonates, inhibited stomatal opening in the light in tobacco leaf disks at concentrations similar to those which cause glycolic acid to accumulate in the same tissue. Stomatal closing by [alpha]-hydroxysulfonates was reversed in a competitive manner by glycolic acid supplied to the leaf disks, as had previously been shown to occur with the isolated glycolate oxidase. O2 in the atmosphere surrounding the tissue was essential for rapid rates of stomatal opening in the light and also for the synthesis of glycolic acid. At greater than normal concentration of CO2 in air, stomata closed in the light and glycolic acid synthesis was also inhibited. The CO2-induced closing of stomata was reversed by providing glycolic acid to the leaf disks. It was concluded that the results are consistent with a requirement for the synthesis and oxldative metabolism of glycolic acid in the process of stomatal opening in the light.