Stoichiometry and Homeostasis of Sodium and Potassium Underpins Growth Adaptation of Suaeda salsa in the Yellow River Delta Wetland

ABSTRACT Sodium (Na) and potassium (K), along with their physiological trade‐offs, play essential roles in maintaining osmotic pressure and ion homeostasis of halophytes inhabiting salt‐alkali wetlands. However, the existence of robust Na‐K homeostasis and the mechanistic linkage of its stoichiometry to plant growth under saline conditions remains poorly understood. Here, we investigated the costal wetlands dominated by halophyte ( Suaeda salsa ) in the Yellow River Delta of China, employing 33 sampling sites to analyze Na‐K stoichiometry and homeostasis across soil and plant tissues, and to assess their effects on plant growth. Results revealed significant differences in Na‐K stoichiometry across soil and plant tissues of S. salsa . Leaf Na content and Na:K ratio were 3.08–6.04 times and 2.76–9.37 times higher, respectively, than those in soil and other two tissues, whereas K content of plant tissues was only 49.08%–61.34% of those in soil. Robust and positive homeostasis of Na, K, Na:K ratio, and Na‐K relationships within plant tissues of S. salsa . By contrast, soil‐ S. salsa interfaces exhibited very few significant relationships for Na, K, Na:K ratio, Na‐K, with K and Na‐K relationships being more robust than the corresponding relationship drawing in Na and Na:K ratio. Notably, while soil Na‐K stoichiometry showed limited correlations with plant density and biomass, tissue Na‐K stoichiometry, particularly in stem Na content and Na:K ratio, was strongly associated with plant height, highlighting their central role in mediating the growth responses of S. salsa . These results suggest that S. salsa maintains stringent internal Na‐K homeostasis independent of soil variability, with tissue Na‐K stoichiometry serving as a better predictor of plant performance than soil ionicity. The internal Na‐K coordination underpins the ecological adaptation of S. salsa in the costal wetlands of the Yellow River Delta.