Salt stress reduces rice yield by altering leaf membrane lipid metabolism and physiological traits (in salt-tolerant genotype)

While salinity stress represents a dominant abiotic limitation to global rice productivity, systematic elucidation of the interconnected dynamics between physiological traits and membrane lipid remodeling under differential salt regimes is critically deficient. To bridge this mechanistic knowledge gap, four controlled pot-based trials were implemented using the commercially deployed salt-tolerant cultivar 'Xindao 22' (Oryza sativa L.), with systematic exposure to defined NaCl concentration gradients spanning 0-51.3 mM. Our aim was to map the relationships among grain yield, leaf physiological responses, and lipid-metabolic adjustments under progressively severe salt stress. Results demonstrated that rice yield and its component traits declined in a concentration-dependent manner, with the most pronounced reduction (60.6 %) occurring at 51.3 mM NaCl. Under 17.1 and 34.2 mM salinity conditions, rice plants exhibited enhanced antioxidant enzyme activities, accumulated twenty-three unique metabolites, and enriched three key pathways, with phosphatidylethanolamine (PE) emerging as the predominant lipid metabolite. Under high-salinity conditions, osmolyte levels increased markedly accompanied by the emergence of seventy-four distinctive metabolites and seven enriched pathways, with PE, phosphatidylcholine (PC), and lysophosphatidylcholine (LPC) identified as major contributors to membrane remodeling. This study reveals the divergent physiological and lipid metabolic responses of rice under varying salt concentrations, deepens our understanding of the molecular mechanisms underlying salt tolerance, and provides theoretical support for salt-tolerant breeding programs. Future research could explore the response differences among diverse salt-tolerant rice genotypes and the metabolic regulatory mechanisms under the interaction of multiple abiotic stresses.