Integrated physiological, transcriptomic, and metabolomic analyses elucidate the mechanism of salt tolerance in Reaumuria soongorica mediated by exogenous H₂S

Exogenous substances intervention constitutes a pivotal strategy for plant breeding and improvement, and is crucial for the remediation of saline-alkaline soils and the development of high-quality halophytic germplasm resources. Hydrogen sulfide (H₂S) is a novel gaseous signaling molecule that plays an important role in response to abiotic stress. For this purpose, this study integrates physiological and molecular biological research methods, focused on the cultivation of Reaumuria soongorica seedlings as the main research content, with R. soongorica roots as its main research object. This study aims to explore the regulatory effects of exogenous H₂S on R. soongorica at the seedling stage under salt stress and assess its potential to improve salt tolerance after seedling establishment. Under salt stress, the activities of antioxidant enzymes in R. soongorica root increased, but high salt stress led to membrane lipid peroxidation and ion imbalance. Exogenous NaHS enhanced salt tolerance by enhancing antioxidant capacity, optimising osmolytes adjustment and maintaining ion homeostasis. This effect is particularly pronounced under 200 mM NaCl stress. Meanwhile, exogenous H₂S optimised carbon allocation toward root morphogenesis through the regulation of key carbon metabolism genes. It suppressed the energy-intensive proline OAT synthesis pathway while activating the “ALDH7A1–ADC” synergistic axis, thereby reducing energy expenditure while maintaining osmolyte balance. Concurrently, H₂S fine-tuned starch degradation and trehalose metabolism, thereby coordinating energy supply with osmolyte regulation. Collectively, these mechanisms improved growth and salt tolerance in R. soongorica root. Salt stress inhibited the root growth of R. soongorica. NaHS pretreatment enhanced antioxidant defense, regulated osmolytes balance, maintained ion homeostasis, and optimised energy allocation through a tripartite regulation mechanism involving proline-soluble sugars-starch. This effectively improved the salt tolerance of R. soongorica in the early growth stage. Therefore, it is crucial to develop preparations primarily composed of NaHS as a donor for seed pretreatment or seedling-stage application. Moreover, integrating H₂S treatment with existing agronomic practices such as slightly saline irrigation and soil conditioner application can form a low-cost, high-efficiency crop improvement technology for saline-alkali land is of great significance.