Keywords: Arsenic, Heavy metal, Mung bean, Oxidative stress, Salicylic acid
Arsenic (As) is a widespread toxic heavy metal which lowers plant growth and development. Salicylic acid (SA) is a prominent signaling molecule in plants and is involved in response to environmental stresses. In this study, the possible role of SA in alleviating As toxicity was investigated on mung bean. Seeds after treatment with SA (0, 0.25, 0.5 and 1 mM) were sown in pots and were exposed to As stress (0 or 50 mg kg− 1 soil). It was found that As toxicity markedly lowered chlorophyll value, relative water content (RWC), shoot length, shoot and root biomass, leaf area and seed yield, whereas it enhanced As accumulation in roots, shoots and seeds, malondialdehyde (MDA) and proline contents and also activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR). Nonetheless, pre-sowing of seeds in SA (especially 1 mM) significantly reduced As contents in roots, shoots, and seeds, but further increased proline content and antioxidant enzyme activities, led to decreased MDA content. In SA-treated plants, also chlorophyll value, RWC, shoot length, shoot and root biomass, leaf area and seed yield were enhanced under As toxicity conditions. These results suggest that exogenous application of SA could improve As toxicity tolerance in mung bean plants through reducing As uptake and accumulation in different plant parts, enhancing activities of antioxidant enzymes and proline content, a decline of lipid peroxidation, improving chlorophyll value and plant water status.
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