Lithium (Li) pollution in agricultural soils poses a significant environmental hazard, impairing crop growth by inducing oxidative stress and disrupting nutrient homeostasis. Not only does Li⁺ compete with K⁺ for uptake, but Li-induced reactive oxygen species (ROS) accumulation may potentially trigger massive K + loss via ROS-sensitive K + -efflux channels, leading to major disruption in the cell’s metabolic activity and programmed cell death. Melatonin (Mel) has emerged as a potential mitigator of abiotic stresses, but its role in regulating ROS levels and K⁺ transport under Li toxicity remains unexplored. Here, we employed an integrated approach, combining non-invasive microelectrode ion flux estimation, confocal imaging, and qPCR analysis, to demonstrate that Mel alleviates Li-induced K⁺ loss in wheat via several concurrent mechanisms: (i) suppressing NADPH oxidase ( RBOH )-derived ROS production while enhancing antioxidant activities; (2) modulating Ca²⁺ signalling by regulating Ca²⁺-ATPases ( ACA / CAX ) and CBL / CIPK ; (3) downregulating the K⁺-efflux channel GORK and upregulating influx transporters ( HAK5 , AKT1 ) to restore K⁺ retention; and (4) regulating plasma membrane H⁺-ATPase activity. Our results show that Mel simultaneously regulates ROS and K⁺ homeostasis to confer Li tolerance, providing critical insights for sustainable phytoremediation and safe crop production in Li-affected soils. • Lithium is an emerging contaminant that poses a serious threat to agriculture • Li-induced ROS accumulation and triggered K + -efflux • Melatonin suppressed RBOH -derived ROS accumulation and enhanced antioxidants under Li stress • Melatonin restores K + homeostasis by regulating plasma membrane H⁺-ATPase activity and Ca 2+ signalling
Khan et al. (Sun,) studied this question.