Influence of Magnesium Deficiency on Induction of Activity of Antioxidative Enzymes and Increased Tolerance to Active Oxygen-Generating Herbicides in Cucumber and Kidney Bean Plants

摘要

The influence of a deficient (7μM) or sufficient (1000μM) supply of Biagnesium (Mg~(2+)) on the content of Mg~(2+), chlorophyll and protein, and the activity of guperoxide dismutase (SOD), ascorbate per-oxidase (AP) and glutathione reductase (GR) were studied in cucumber (Cucumis sativus L.) and kidney bean (Phaseolus vul-garis L.) plants over an 11-day period. Tolerance of kidney bean to paraquat and oxy-fluorfen dependent injury were also determined with intact primary leaves. Mg~(2+) content inthe primary leaves of cucumber and kidney bean plants grown in nutrient solution with sufficient Mg~(2+) supply was increased, while that in the leaves of plants grown with insufficient Mg~(2+) was very low. Mg~(2+) deficiency caused more severe chlorosis and protein reduction in cucumber than in kidney bean. The activities of AP, GR and SOD of Mg~(2+)-deficient cucumber leaves were greatly enhanced compared to those of Mg~(2+)-suffi-cient leaves. In Mg~(2+)-deficient kidney bean leaves, AP and SOD activities were enhanced, but GR activity was decreased. The results suggested that Mg~(2+) deficiency enhances the antioxidative enzymes in plants. Foliar application of paraquat and oxyfluorfen, active oxygen-generating herbicides, to kidney bean plants caused herbicidal damage. However, the chlorosis and water loss of kidney bean by the herbicides were much lower in Mg~(2+)-deficient leaves than in Mg~(2+)-sufficient ones. The data demonstrated that Mg~(2+)-deficient kidney bean plants became highly tolerant to paraquat and oxyfluorfen injury.