Leaf sodium homeostasis controlled by salt gland is associated with salt tolerance in mangrove plant Avicennia marina.

This article investigates the salinity tolerance mechanisms of Avicennia marina, a mangrove species with salt-secreting glands, by examining seedling growth, photosynthesis, ion content, ultrastructure, ion fluxes, and gene expression under varying NaCl concentrations (0–600 mM). Results show that low salinity (200 mM NaCl) enhances biomass and photosynthetic activity, while salinity above 400 mM inhibits growth and damages chloroplast ultrastructure. Salt glands in the leaf adaxial epidermis actively secrete excess sodium and chloride, maintaining leaf Na+ homeostasis despite increasing root Na+ levels, with maximal Na+ efflux and upregulation of Na+/H+ antiporters (SOS1, NHX1), H+-ATPases (AHA1, VHA-c1), and K+ channels (AKT1, HAK5, GORK) at 400 mM NaCl. The study highlights the coordinated physiological and molecular responses in salt glands that enable A. marina to regulate ion balance and tolerate saline intertidal environments.