Melatonin priming enhances the seed germination and seedling performance of Salvia miltiorrhiza under salt stress

Salt stress imposes a remarkable effect on how plants grow and their productivity levels. Although melatonin is well-known for its capacity to improve seed germination and promote plant growth when plants are exposed to stressful environments, its role in seed priming remains underexplored. This study elucidated how melatonin priming influenced the traditional Chinese medicinal herb Salvia miltiorrhiza 's seed germination and seedling growth in the presence of salt stress. The results revealed that 20 μM melatonin priming enhanced germination energy, germination percentage, and plant biomass; increased root antioxidant enzyme activity; elevated K + and GA 3 levels; and improved the K + /Na + ratio. Moreover, it upregulated the expression of key genes related to GA biosynthesis ( SmKO and SmKAO1 ) while reducing the levels of MDA, H 2 O 2 , ABA, and Na + , as well as the ABA/GA 3 ratio, and downregulated the expression of ABA, H 2 O 2 , and tanshinone biosynthesis genes ( SmNCED3 , SmNCED5 , SmRbohD , SmRbohF , SmCYP76AH1 , and SmKSL1 ). Moreover, exogenous ABA increased the levels of both tanshinone and H 2 O 2 in the presence of salt stress, while H 2 O 2 in turn facilitated the accumulation of tanshinone. Overall, melatonin priming effectively enhances seed germination in the context of salt stress and promotes seedling performance by stimulating GA production, inhibiting ABA, and regulating tanshinone accumulation in response to H₂O₂ levels. These results demonstrate how melatonin may contribute to promoting plant growth in salt stressed environments, which is essential for strategies focused on the sustainable use of saline alkali land. Seed priming with 20 μM melatonin enhanced the germination energy and germination percentage of S. miltiorrhiza seeds under salt stress, promoting seedling performance by stimulating GA, inhibiting ABA, and decreasing H 2 O 2 levels in response to salt stress. • 20 µM melatonin priming enhanced S. miltiorrhiza seed germination under salt stress. • Melatonin priming stimulated GA and inhibited ABA in roots under salt stress. • Melatonin priming decreased root tanshinone by reducing H 2 O 2 under salt stress.