Effects of glyphosate on the biosynthetic pathways in leaf disks of pea plants.

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Using submerged leaf disks prepared from pea plants, the effects of glyphosate on the biosynthetic pathway of pigments, shikimic acid pathway, glycolysis and TCA cycle were surveyed.Incorporation of 14C-glucose into each fraction of chlorophylls, carotenes and xanthophylls was inhibited by the glyphosate treatment (Table 1).Incorporation of 14C-glucose into aromatic amino acids was inhibited by the glyphosate treatment. In the treatment with a glyphosate concentration lower than 1mM, a higher radio-activity of shikimic acid was observed and glyphosate seemed to inhibit 5-enolpyruvylshikimate-3-phosphate synthase (EPSP synthase). When the concentration of glyphosate was higher than 10mM, the incorporation of 14C-glucose into shikimic acid was very low, presumably due to the herbicide-inhibition effect of 3-deoxy-D-arabinoheptulosonate-7-phosphate synthase (DAHP synthase) on the production of shikimic acid (Table 2).Incorporation of 14C-glucose into the metabolites in the glycolysis and TCA cycle was not inhibited by the glyphosate treatment (Table 3).It was assumed that glyphosate mainly inhibited EPSP synthase and partially DAHP synthase and the pathways from acetyl CoA to carotenoids and also from TCA cycle to δ-aminolevulinic acid, respectively, and that these inhibitions acted synergically with the herbicidal action persisting for a relatively long period of time after the application.
日本雑草学会の論文