Features of salt glands and identification of DEGs in S. alterniflora under salt stress. A Coastal salt marsh environment with S. alterniflora. Scale bar = 0.5 cm. B, C Representative images of leaf (B) and stem (C) of S. alterniflora in coastal salt marshes. Scale bars in B and C are 0.5 cm and 100 mm, respectively. D Leaf surface exudate composition from plants grown in a coastal salt marsh. E–G Root and shoot Na⁺ (E) and K⁺ (F) contents and Na⁺/K⁺ ratios (G) in S. alterniflora seedlings (n = 5). Values are mean ± standard deviation. Different letters indicate significant differences at P < 0.05 (Duncan’s multiple range test). H–J Unique and overlapping (H) DEGs, (I) upregulated DEGs, and (J) downregulated DEGs among three NaCl treatments compared with the 0 mM NaCl control. (J) Summary of up- and downregulated DEGs after treatment with each salt concentration.