Enhancing rice salt Tolerance: Mechanisms of compound functional liquid in alleviating salt stress during the seedling stage.

Rice (Oryza sativa) is one of the most important staple crops worldwide; however, salt stress significantly limits its growth and productivity. This study systematically investigates the growth-protective mechanisms of Compound Functional Liquid (CFL) in alleviating salt stress during the seedling stage of rice. The results indicate that under salt stress, CFL significantly improved the rehydration survival rate of rice, promoted its growth and development, and enhanced its osmotic regulation capacity. Additionally, CFL significantly reduced MDA levels, upregulated the expression of genes such as OsAPX, OsP5CS3, and OsDREB, and increased the activity of antioxidant enzymes. To explore the molecular mechanisms, 128 DEGs exhibiting continuous changes across various stress periods were identified through transcriptome sequencing. KEGG analysis demonstrated significant enrichment in pathways related to plant hormone signal transduction and peroxisome function. Metabolomic analysis revealed 1227 DAMs, which were primarily enriched in glutathione metabolism, ABC transporters, and the TCA cycle. Integrated analysis indicated that during the S1 period, pathways associated with carbon metabolism and ABC transporters were enriched, while in S2, amino acid metabolism and plant hormone signaling were predominant. In S3, glutathione metabolism and antioxidant pathways showed the highest enrichment. WGCNA identified key modules (yellow-green, cyan, green, and red) associated with salt stress, and GO analysis indicated involvement in fatty acid metabolism, carbon metabolism, plant hormone signaling, and photosynthesis. RLK and MYB transcription factors were identified for each stage. This study elucidates how CFL enhances rice salt tolerance through multi-layered and multi-pathway mechanisms under salt stress.