Postillumination respiration of maize in relation to oxygen concentration and glycolic Acid metabolism.
Prior illumination in CO(2)-free air enhances a respiration from maize (Zea mays L.) leaves different in onset and duration from the postillumination burst of photorespiration. The course of respiration after brief illumination of attached leaves was measured as CO(2) efflux in darkness into CO(2)-free atmospheres with four O(2) concentrations. The peak of CO(2) efflux following illumination was suppressed by 2.23% O(2), was completely eliminated by 0.04% O(2), and was not stimulated by 40% O(2) compared with air. Compared with air, steady dark respiration was suppressed by 0.04% O(2) but was not affected by 2.23% nor 40% O(2). Excision and subsequent uptake of distilled water through the vascular system nearly eliminated the enhanced respiration.Several metabolites fed to excised leaves through the vascular system during illumination doubled or tripled the respiration of maize in darkness. The sensitivity to 2.23% O(2) of the respiration of glycolic acid in the dark imitated the sensitivity to O(2) of attached leaves.The respiration of glycolic acid was inhibited by alpha-hydroxy-2-pyridinemethanesulfonate.While attached leaves and leaves fed glycolic acid both released little CO(2) into CO(2)-free air in bright light, declining illuminance caused a larger and prompter CO(2) efflux from leaves fed glycolic acid than from attached leaves. Leaves fed glycolic acid plus 3-(p-chlorophenyl)-1, 1-dimethyl urea released more CO(2) into CO(2)-free air in bright light than did controls fed glycolic acid.
Heichel
G H
GH
Department of Ecology and Climatology, The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06504.