Figure 2.

Model of melatonin action under acidity and/or alkalinity stress. Melatonin triggers the accumulation of auxin, polyamines, and nitric oxide. Furthermore, managing ion homeostasis by decreasing Na+ content and increasing K⁺ content. Melatonin reduced oxidative stress by triggering the antioxidant machinery and decreasing chlorophyll degradation. Exogenous melatonin induces NO generation, which subsequently upregulates the expression level of defense genes.