Decreased Glutathione Levels Enhance the Susceptibility of Maize Seedlings to Metolachlor

The effect of decreased glutathione levels on the action of the herbicide metolachlor was studied in shoots of maize seedlings. Metolachlor inhibited growth by impairing the length, the dry weight, and the fresh weight of maize shoots. Conversely, buthionine-S,R-sulfoximine (BSO), an inhibitor of γ-glutamylcysteine synthetase (EC 6.3.2.2.), when applied in concentrations of up to 2 mM had no effect on shoot growth, but it decreased the glutathione content up to 22-fold compared to untreated plants. When 100 μM metolachlor and various BSO levels were applied together, the growth of the shoots was inhibited with increasing concentrations of BSO. This growth inhibition significantly correlated with the decreased glutathione content. As BSO increased the metolachlordependent activity of glutathione transferase, our results suggest that decreased intracellular glutathione levels obtained with BSO are one of the limiting factors for the tolerance of maize plants to metolachlor.