Exploring the mechanisms by which sodium promotes growth of euhalophytes under potassium deficiency: A case study of Suaeda salsa

Suaeda salsa L . is a leaf succulent euhalophyte. Its leaves are rich in secondary metabolites, such as polyphenols and flavonoids, which enhance its salt tolerance and have industrial value in pharmaceuticals, antioxidants, and food additives . Its growth is promoted under moderate salinity conditions . However, the mechanisms by which euhalophytes maintain a balance between growth and salt stress tolerance have not been elucidated, especially under K + deficiency. Here, we used multi-omics and physiology analyses to investigate the role of Na⁺ in the growth and metabolic processes of S. salsa . Exogenous NaCl application significantly enhanced the photosynthetic efficiency of S. sals a under K⁺ deficiency, including the net photosynthetic rate, PSII photochemistry (Fv/Fm), photochemical quenching (qP), non-photochemical quenching (NPQ), and the activities of enzymes such as ferredoxin-NADP + reductase (FNR) and Rubisco. Meanwhile, transcriptomic analysis revealed that NaCl treatment upregulated genes related to photosynthetic subunits, light-harvesting complexes (LHCs), and key Calvin cycle enzymes, including phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and Rubisco. These findings provide strong molecular evidence for the observed recovery of photosynthetic efficiency in NaCl-treated S. salsa under K⁺ deficiency. Furthermore, the relative contents of flavonoids and isoflavonoids, including isorhamnetin, isolupalbigenin, osajin, corylin, and wedelolactone, as well as unsaturated fatty acids (9-Hexadecenoic acid), were significantly upregulated treating with NaCl and KCl. These results suggest that S. salsa can utilize Na⁺ to enhance photosynthesis under high salinity and low K⁺ conditions, thereby enabling it to balance salt tolerance and growth. Our findings elucidate the key mechanisms underlying the critical role of Na + in the physiological and metabolic processes of halophytes, providing a theoretical basis for the development of saline agriculture. • Na + prompted the growth of S. salsa by enhancing photosynthetic capacity • Na + upregulates genes for photosynthesis of S. salsa under low K + condition • Na + enhanced the secondary metabolism of S . salsa .