MITIGATING CADMIUM-INDUCED TOXICITY IN TURNIP (BRASSICA RAPA) THROUGH EXOGENOUS APPLICATION OF VANILLIC ACID

Abstract

Cadmium (Cd) contamination in agricultural soils poses a severe threat to crop productivity and food safety, particularly in root vegetables like turnip (Brassica rapa), where it induces morphological stunting, biomass reduction, photosynthetic impairment through chlorophyll degradation, oxidative stress via reactive oxygen species (ROS) overproduction, lipid peroxidation (elevated MDA), and methylglyoxal (MG) accumulation leading to cytotoxicity. This toxicity disrupts nutrient homeostasis, water relations, and enzyme activities while overwhelming endogenous antioxidant and glyoxalase defense systems. Exogenous application of vanillic acid (VA), a phenolic compound derived from the phenylpropanoid pathway, emerges as an effective phytoprotectant strategy. VA pretreatment (typically 2–4 mM) mitigates Cd-induced damage by restoring growth parameters and biomass, preserving chlorophyll content and photosynthetic efficiency, improving stomatal conductance and leaf turgidity, and reducing physiological drought symptoms. Biochemically, VA upregulates key antioxidant enzymes (SOD, CAT, POD, APX) and the ascorbate-glutathione (AsA-GSH) cycle, lowers H₂O₂ and MDA levels, enhances glyoxalase I and II activities for efficient MG detoxification, and promotes accumulation of osmoprotectants like proline. Furthermore, VA strengthens metal sequestration by boosting phytochelatin synthesis and vacuolar compartmentalization, modulates heavy metal transporter genes (e.g., ZIP, NRAMP, HMA families), and integrates with hormone signaling (ABA, SA, NO) and secondary metabolism for cell wall reinforcement. Comparative analyses highlight VA’s advantages over other agents like biochar, selenium, or citric acid due to its dual role in internal tolerance and minimal environmental footprint. These mechanisms collectively enhance Cd tolerance, support safer food production, and improve phytoremediation potential in Brassica rapa. Future directions include nano-formulations for targeted delivery, genetic engineering of the VA biosynthetic pathway, and exploration of rhizosphere microbiota synergies. Overall, exogenous vanillic acid offers a sustainable, eco-friendly approach to counteract cadmium toxicity, ensuring agricultural resilience and food security in contaminated regions