Ascorbic Acid and Vanillic Acid Application Alleviate the Lead Toxicity in Lycopersicon esculentum by Modulating Key Biochemical Attributes and Antioxidant Defense Systems

Lead (Pb) toxicity suppresses plant growth and productivity and poses human health concerns. While Ascorbic acid (AsA) and vanillic acid (VA) are reported to impart multiple benefits to plants exposed to abiotic stresses. In this study, the influence of WS, AsA (0, and 1.5 mM) and VA (0, and 0.5 mM) application was evaluated to improve the performance of tomato cultivars i.e., Nagina and Roma, under Pb stress (1280 & mu;M). Our results showed an apparent decline in growth, biomass, photosynthetic pigments, relative water content (RWC), total soluble proteins, total free amino acid (TFAA), anthocyanin contents, and nutrient acquisition (Ca, Mg, Zn and Fe) and enhanced levels of ROS and MDA production under Pb stress. Further, reduced glutathione (GSH) levels diminished with a simultaneous rise in oxidized glutathione levels (GSSG). Plants subjected to Pb stress remarkably increased the Pb accumulation in roots, shoots, and leaves maximally in Roma than in Nagina. However, exogenous AsA and VA effectively mitigated the metal phytotoxic effects by strengthening the activities of antioxidant enzymes and level of antioxidants. Ascorbic acid and VA remarkably increased the cytosolutes accumulation, including anthocyanin, endogenous AsA, soluble sugars, proline, free amino acids, and total soluble proteins under Pb stress. Ascorbic acid and VA-mediated drop in oxidative stress diminished membrane damage and improved nutrient acquisition under Pb stress. In conclusion, AsA and VA applications improved the Pb tolerance in tomato plants by modulating plant growth, decreasing Pb buildup, and activating the antioxidant defense system. Both AsA and VA markedly regulated the uptake and distribution of Pb in tomato plants, abridging the degree of metal phytotoxic effect.