From Abiotic Stress to Emerging Environmental Pollutants: Expanding Roles of Melatonin and NO in Plant Defense.

In the current era of industrial expansion, the environmental landscape is characterized by an evolving spectrum of contaminants, exposing plants to new types of stress. Plants are forced to employ defensive strategies to survive these conditions. Melatonin (MT) is an amine signaling molecule involved in plant defense processes. Its protective properties in response to various environmental stressors have recently been intensively studied. Melatonin-mediated growth and defense responses result from a multifaceted signaling architecture that involves a wide range of molecules. Among them, nitric oxide (NO) is a key contributor. This review synthesizes existing knowledge of the MT contributions in mitigating well-established abiotic stresses, particularly in connection with NO signaling, and explores the potential to apply these findings to emerging environmental pollutants, such as microplastics, nanoparticles, and surfactants.