Melatonin and hydrogen sulfide crosstalk enhances maize seed germination under salt stress through antioxidant system

Melatonin (MT) and hydrogen sulfide (H 2 S) act as signaling molecules that improve plant tolerance to abiotic stresses, especially salt stress. Maize ( Zea mays L.) is an important industrial crop, and salt stress causes oxidative damage in maize, which inhibits seed germination. However, how MT and H 2 S regulate maize germination under salt stress remains unclear. In this study, maize seeds were primed with MT, NaHS (an H 2 S donor), their combinations, or the corresponding inhibitors, and then germinated under 150 mM NaCl. Data are presented as mean ± SE from at least three independent biological replicates. The results showed that priming with MT and NaHS, alone or combined, significantly increased the germination percentage of maize seeds under salt stress. Moreover, H 2 S significantly increased SNAT activity and endogenous MT levels under salt stress, while MT biosynthesis inhibitors weakened these effects, suggesting crosstalk between MT and H 2 S during maize seed germination. Additionally, compared with MT and H 2 S individual priming, combined priming with MT and H 2 S significantly upregulated the expression of ZmSOD and increased the activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase (APX). Moreover, MT and H 2 S increased the content of flavonoid (FLA) and carotenoids (CAR), while reducing H 2 O 2 content, relative electrical conductivity (REC), and malondialdehyde (MDA) content. They also increased tissue vitality and soluble protein (SP) content. These findings suggest that MT–H 2 S crosstalk is associated with priming-enhanced maize seed germination under salt stress, accompanied by activating antioxidant system vitality and reducing reactive oxygen species (ROS) accumulation, offering a potential strategy for improving seed vigor in saline-alkaline agriculture.