Ameliorating heavy metal-induced oxidative stress in valerian: The role of melatonin Scientific paper

Abstract

Heavy metals ubiquitously found in soil and water, represent a serious environmental problem that disrupts plant mineral nutrition homeostasis, osmo­tic balance and metabolism. The application of some biostimulants can alleviate these disruptions. Melatonin as a signal molecule, and antioxidant plays an imp­ort­ant role in plant growth and stress tolerance due to its ability to directly neut­ralize reactive oxygen and nitrogen species. The reduction or mitigation of heavy metals adverse effects in valerian plants grown in open field conditions using melatonin was investigated in this study. High-pressure liquid chromatography coupled with a fluorescence detector was used to identify and quantify melatonin concentration in valerian root extracts. Also, the physiological and biochemical status of plants under abiotic stress was examined, especially in 100 µM mela­tonin pre-treated plants. Higher concentrations of endogenous melatonin were measured in roots of Cd and Zn treated plants. Melatonin application alleviated the negative effect of Cd, particularly evident in Cd-melatonin treatment which restored or enhanced bioactive compound levels. Melatonin effectively mitigates Cd and Zn-induced stress in valerian by enhancing both non-enzymatic and enz­ym­atic antioxidant systems and promoting the synthesis of protective com­pounds. These findings highlight melatonin’s potential as a sustainable biostim­ul­ant to support plant resilience and productivity in heavy metal-stressed envi­ron­ments.