Mechanisms of exogenous quercetin in enhancing soybean salt tolerance through regulating ion homeostasis, phytohormone signaling, and flavonoid metabolism

Increasing soil salinization poses a severe threat to global agricultural production. Quercetin, a natural compound known to effectively alleviate abiotic stress, has an unclear molecular regulatory mechanism in enhancing soybean salt tolerance. To investigate its mechanism of action, this study established control (CK), quercetin treatment (Q), salt stress (S), and quercetin plus salt stress (QS) groups. By integrating physiological indices with transcriptomic and metabolomic analyses, we systematically elucidated the molecular mechanisms by which exogenous quercetin enhances salt tolerance in soybeans. The results demonstrated that quercetin treatment not only significantly improved root growth and ionic homeostasis (increased K+/Na+ ratio) under salt stress but also enhanced energy supply by reinforcing sucrose metabolism and the TCA cycle. Furthermore, it coordinately regulated key genes in the ABA and JA signaling pathways to bolster stress responses, while simultaneously promoting proline accumulation and reprogramming the flavonoid metabolic pathway. Thereby, a multifaceted regulatory network for salt tolerance was constructed. This study provides new insights into the role of quercetin in plant stress resistance and offers a theoretical basis for crop breeding for improved stress tolerance.