Unlocking the role of melatonin to alleviate nickel phytotoxicity in sunflower (Helianthus annuus L.)

Nickel contamination in agriculture soils severely restricts sunflower growth and disrupts important physiological and biochemical process, making it necessary to identify effective approaches for improving plant tolerance.In this study, two sunflower cultivars, FH-701 (V1) and FH-741 (V2), were exposed to different nickel concentrations (0, 40, and 80 mg kg ⁻¹ ) and treated with varying levels of exogenous melatonin (0, 25 and 50 µM) to evaluate its protective effects against nickel induced stress.The results showed that 50 µM melatonin application enhanced plant growth, increased chlorophyll content, improved antioxidant defense (SOD, POD, CAT), maintained better ion balance and reduced oxidative markers (MDA, H2O2) caused by nickel toxicity.According to this study, sunflower cultivar FH-741 had better growth as compared to FH-701.The results of present findings indicate that MEL is a plant growth regulator that has lessen Ni-induced oxidative damage in sunflower plants by altering secondary metabolites and antioxidant defense while maintaining ion homeostasis.