Effects of water stress on glycolate metabolism in the leaves of rice seedlings (Oryza sativa)

To investigate the effects of water stress on glycolate metabolism, seedlings of a drought-tolerant cultivar (N-22) and a susceptible cultivar (Jaya) of Oryza sativa L. were subjected to water stress for 5, 8 or 10 days. Increasing the duration of water-deficit-stress produced a proportional decrease in relative water content and leaf water potential, reduced glycolate content and catalase (EC 1.11.1.6) activity, but increased glycolate oxidase (EC 1.1.3.1) activity, hydrogen peroxide and glyoxylate contents in the leaves of both cultivars. In a radiotracer experiment, with increasing duration of water stress, the proportion of label increased in 3-phosphoglycerate, glycolate, glycine and serine. The drought-tolerant cultivar (N-22) was affected less than the susceptible cultivar (Jaya). The glycolate pathway metabolism is discussed in relation to photorespiration and the effects of water stress.