Mechanistic Response of Salicylic Acid Against Cypermethrin Induced Stress in Radish: an Insight of Physiological, Biochemical and Metabolic Changes

Pesticides are widely used to enhance crop productivity; however, excessive application can lead to residue accumulation in edible plant parts and adversely affect growth and physiology. This study evaluated the protective role of salicylic acid (SA) in radish (Raphanus sativus) exposed to cypermethrin (CYP). The plants were foliarly pretreated with SA (100–800 µM) and subsequently exposed to CYP at recommended (150 ppm) and double (300 ppm) doses. CYP, especially at the higher dose, markedly impaired physiological and biochemical traits. SA pretreatment, particularly at 200 µM, mitigated oxidative stress by reducing H₂O₂, SOR, and TBARS accumulation while enhancing antioxidant activities. Improvements in chlorophyll content, stomatal traits, and photosynthetic performance were also observed. Moreover, 200 µM SA increased root fresh biomass by 41.1% and 44.4% under recommended and double CYP doses, respectively, and reduced CYP residues in roots by 36–39%, while promoting formation of less toxic metabolites, 3-phenoxybenzoic acid (3-PBA) and 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (DCCA). Metabolomic analysis revealed that SA enhanced defense-related compounds, including phenylpropanoids, oxylipins, sphingolipids, and glutathione. Under high stress, SA pretreatment triggered an emergency metabolic response to generate energy and redox power for defense, whereas under lower stress, it promoted a balanced priming state, strengthening signaling and secondary metabolism. These results demonstrate that SA can serve as a phytohormone-based strategy to mitigate pesticide toxicity, improve stress tolerance, and enhance crop quality under intensive cultivation.