Abstract
The present study investigates the role of exogenous glutathione (GSH) in conferring high temperature stress (HT, 42°C) tolerance in mung bean (Vigna radiata L. cv. Binamoog-1) seedlings by modulating the antioxidant defense and methylglyoxal (MG) detoxification systems. Six-day-old seedlings were exposed to HT stress with or without exogenous GSH (0.5mM for 24h as pretreatment) for 24 and 48h. Heat stress at any duration significantly increased lipid peroxidation (MDA), H2O2, MG, and Proline (Pro) content, generation rate of O2− and lipoxygenase (LOX) activity; decreased leaf chlorophyll (chl) and leaf relative water content (RWC), and the level of ascorbate (AsA); increased endogenous GSH and GSSG (glutathione disulfide); decreased the GSH/GSSG ratio. For both treatment durations, activities of ascorbate peroxidase (APX), glutathione reductase (GR), glutathione-S-transferase (GST) increased; the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione peroxidase (GPX), catalase (CAT) and glyoxalase I (Gly I) decreased; the activity of glyoxalase II (Gly II) increased at 48h. Mung bean seedlings pretreated with exogenous GSH under HT improved chl and leaf RWC; increased APX (only after 24h), MDHAR, DHAR, GR, GPX, GST (increased only after 24h), CAT, Gly I and Gly II activities; improved endogenous GSH content and the GSH/GSSG ratio; lowered GSSG content. Glutathione supplementation with drought stress significantly decreased MDA, H2O2 and MG content, O2− generation rate and LOX activity. Pretreatment with GSH resulted in better physiological performance, improved antioxidant and glyoxalase systems, and reduced MG and oxidative stress under 24h of HT stress, compared with that of 48h. The results suggest that exogenous GSH enhances mung bean seedling tolerance of short-term HT stress by modulating the antioxidant and glyoxalase systems and by improving physiological adaptation.
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