Mitigating cypermethrin stress in Amaranthus hybridus L.: Efficacy of foliar-applied salicylic acid on growth, enzyme activity, and metabolite profiles

The study aimed to evaluate the role of foliar-applied salicylic acid (SA) (5-50 µM) in mitigating the effects of cypermethrin (CYP) stress on Amaranthus hybridus L., at its recommended (100 PPM) and double dose (200 PPM). CYP application at recommended dose proliferated the growth of the crop, while the double dose affected negatively. SA boosted the performance of the CYP-treated plants by reducing oxidative radical formation via increasing the activity of catalase, superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione s-transferase, dehydroascorbate reductase, ascorbate, and proline. SA increased photosynthetic activity by increasing the leaf area, chlorophyll content and regulating the level of intracellular CO₂, stomatal conductance, and transpiration in the CYP-treated plants. The fresh weight of the crop showed maximal increase with 10 µM SA (57 %) at recommended dose and with 20 µM SA (36.8 %) at double dose of CYP. Additionally, CYP residues showed maximum decline with 10 µM and 20 µM SA application in 100P and 200P plants, respectively. UHPLC-MS analysis showed increased levels of crucial secondary metabolites such as antheraxanthin, violaxanthin, kaempferol, rutin, cinnamic acid, ferulic acid, trigonelline, coumarin, scoparone, esculin, caryophyllene oxide, jasmonal with SA supplementation at 10 µM with 100P and at 20 µM with 200P treatments. The observed changes in enzyme activities, physiology and metabolite profiles underscore the potential of SA in mitigating pesticide-induced stress and enhancing plant growth and health. This study could further be explored in future by combining SA with other phytohormones and applying omics approaches could enhance crop resilience across diverse environments.