Physiological and biochemical changes in sorghum under combined heavy metal stress: An adaptive defence against oxidative stress

Abstract In this study, the combined effects of five different heavy metals (HMs) (As, Ni, Cd, Pb and Cu) on sorghum (Sorghum bicolor (L.) Moench) seedlings were assessed with morpho-physiological and biochemical variations. Overall, the growth, total biomass and chlorophyll and relative water contents in the leaves of the plants were decreased whereas electrolyte leakage was found to be increased in the higher concentrations (up to 500 μM) of HMs. The upraised level of compatible soluble solutes such as proline, malondialdehyde (MDA), glutathione (GSH), soluble proteins and higher accumulation of H2O2 were witnessed in HMs stressed plants. The HMs treated and control plants were examined for the level of anti-oxidative defense systems such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR). There was substantial collinearity between HMs concentrations and its physiological, biochemical and the antioxidant enzyme activities which can be used as biomarkers to observe HMs polluted sorghum plants. This study clearly deciphered the adaptive defense mechanisms of sorghum towards combined HMs induced toxicity.