Zinc alleviates cadmium induced heavy metal stress by stimulating antioxidative defense in soybean [Glycine max (L.) Merr.] crop

Abstract

The interaction between cadmium- a toxic metal and zinc- an essential micronutrient was investigated in influencing the activity of various antioxidant enzymes and related metabolites in soybean [Glycine max (L.) Merr.]. Higher levels of cadmium (Cd) stimulate the activity of potential enzymes like ascorbate peroxidase (APX), superoxide dismutase (SOD) accompanied by the buildup of non-enzymatic metabolites, hydrogen peroxide (H2O2), malondialdehyde (MDA) and proline due to rise in oxidative stress of plants. Also, the reduced activity of catalase (CAT), glutathione reductase (GR) and ascorbic acid (AsA) content was based upon Cd treatment levels. Application of zinc (Zn) combination enhances the activity of enzymes like APX, GR, CAT and SOD in Cd treatments, also confirmed with the depleted levels of H2O2. Zn alone treatment had no significant effect on the activity of such enzymes indicating the toxicity owing to Cd treatments only. The accumulation behavior of other non-enzymatic metabolites like MDA, proline and ascorbic acid also get reversed with metal combination treatment. Moreover, the efficacy of Zn was more when applied in higher concentrations with low Cd. Thus, Zn plays a key role in plants to counter heavy metal stress by elevating antioxidative defense with higher activity of enzymes and reduced levels of non-enzymatic metabolites, and efficacy of Zn in combination is dose dependent.