Melatonin induced reversibility of vanadium toxicity in muskmelon by regulating antioxidant defense and glyoxalase systems

Agricultural lands with vanadium (V), pose a significant and widespread threat to crop production worldwide. The study was designed to explore the melatonin (ME) treatment in reducing the V-induced phytotoxicity in muskmelon. The muskmelon seedlings were grown hydroponically and subjected to V (40mgL−1) stress and exogenously treated with ME (100 μmol L−1) to mitigate the V-induced toxicity. The results showed that V toxicity displayed a remarkably adverse effect on seedling growth and biomass, primarily by impeding root development, the photosynthesis system and the activities of antioxidants. Contrarily, the application of ME mitigated the V-induced growth damage and significantly improved root attributes, photosynthetic efficiency, leaf gas exchange parameters and mineral homeostasis by reducing V accumulation in leaves and roots. Additionally, a significant reduction in the accumulation of reactive oxygen species (ROS), malondialdehyde (MDA) along with a decrease in electrolyte leakage was observed in muskmelon seedlings treated with ME under V-stress. This reduction was attributed to the enhancement in the activities of antioxidants in leaves/roots such as ascorbate (AsA), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione peroxidase (GPX), glutathione S-transferase (GST) as compared to the V stressed plants. Moreover, ME also upregulated the chlorophyll biosynthesis and antioxidants genes expression in muskmelon. Given these findings, ME treatment exhibited a significant improvement in growth attributes, photosynthesis efficiency and the activities of antioxidants (enzymatic and non-enzymatic) by regulating their expression of genes against V-stress with considerable reduction in oxidative damage. Environmental Implication Vanadium (V) contamination is a significant hazard to ecosystem sustainability, agricultural production, and human health due to unregulated anthropogenic activity worldwide. Although melatonin (ME) has the potential to increase the tolerance of plants to vanadium stress, the mechanism by which it mitigates the phytotoxicity of vanadium in muskmelon has yet to be investigated. We revealed how melatonin influences V stress tolerance in muskmelon plants. Our findings show that the activities of the glyoxalase and antioxidants system regulated by melatonin mitigate V phytotoxicity and lower V concentration in the leaves and roots of muskmelon. As a result, the results may prove beneficial in the design of environmentally sustainable approaches to phytoremediation and the mitigation of V residues in crops with regard to environmental and food safety.