Synergistic application of melatonin and silicon alleviates chromium stress in Brassica napus through regulation of antioxidative defense system and ethylene metabolism

Abstract

Melatonin (MT) reacts with oxygenated compounds to form 2-hydroxymelatonin (2-HMT). The potential role of 2-HMT and silicon (Si) in moderation of chromium (Cr) stress in Brassica napus was evaluated in this study. B. napus seedlings have reduced growth and phytochemical attributes when grown in Cr-contaminated pots. Application of 2-HMT and Si, alone or as combined treatment, minimized Cr-stress in B. napus seedlings. Supplementation of 2-HMT and Si improved stomatal conductance (Gs), transpiration rate (Tr) and intercellular CO2 concentration (Ci) in B. napus seedlings subjected in Cr-toxic soil. Combined application of 2-HMT and Si prominently enhanced antioxidantive enzymes activity i.e., SOD (superoxide-dismutase), APX (ascorbate-peroxidase) and CAT (catalase) enzyme in B. napus seedlings, compared to seedlings treated with MT-only. Moreover, 2-HMT and Si also reduced MDA (malondialdehyde) content, H2O2 (hydrogen peroxide) content and EL (electrolyte leakage) in B. napus seedlings of Cr-amended soil. Co-supplementation of 2-HMT and Si significantly enhanced ethylene level in B. napus seedlings grown in Cr-contaminated soil, as compared to rest of treated seedlings. Increased ethylene level activates antioxidantive defence system. Therefore, it is suggested that combined treatment of 2-HMT and Si can be useful to eliminate abiotic stresses in other crops.