Exogenous H2S Enhances Salt Tolerance in Sorghum Seedlings by Stimulating the AsA-GSH Cycle in Chloroplasts to Improve Photosynthesis

Chang Liu^1*Sitong Liu¹Xin Hu¹Xiaolong Shi¹Chunjuan Liu¹Lu Sun^2*Yufei Zhou^1*

• ¹Shenyang Agricultural University, Shenyang, China
• ²Shenyang Institute of Technology, Fushun, China

Soil salinization endangers global food security by harming crop yields, particularly in areas where sorghum is predominantly cultivated. This study delved into the potential of exogenous hydrogen sulfide (H2S) to improve the salt resistance of sorghum seedlings by influencing the ascorbate-glutathione (AsA-GSH) cycle in chloroplasts, ultimately improving photosynthetic efficiency under saline conditions. The findings indicatedWe found that under salt stress, sorghum seedlings showed stunted growth, increased reactive oxygen species (ROS), and weakened antioxidants, causing oxidative damage. Exogenous H2S effectively mitigated these adverse effects through the activation of the AsA-GSH cycle in chloroplasts. This activation resulted in the maintenance of reduced AsA and GSH pools, while increasing their oxidized forms, DHA and GSSG, respectively. As a result, the activities of several critical enzymes within the AsA-GSH cycle, including ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR), were significantly enhanced, suggesting a vital role for H2S in preserving cellular redox homeostasis and counteracting oxidative stress. Additionally, application of H2S bolstered the photosynthetic capacity of sorghum seedlings under salt stress by maintaining chlorophyll levels and chloroplast integrity, and by modulating chlorophyll fluorescence parameters, which protected photosystem II from damage. The study also observed that H2S facilitated electron transfer from the PSII reaction center to plastoquinone, suggesting a role in managing excess energy under stress. This research suggests that exogenous H2S application can mitigate the negative impacts of salt stress on sorghum seedlings through activation of the AsA-GSH cycle and enhancement of photosynthetic performance, thus providing a strategy to improve crop resilience against soil salinization and support agricultural sustainability.