Strigolactone and Hydrogen Sulfide Regulate Carbohydrate Metabolism and Ion Homeostasis Through H ⁺ ‐ <scp>ATPase</scp> Activity and K ⁺ Retention Under Salt Stress

This study investigates the roles of strigolactones (SL) and endogenous hydrogen sulfide (H₂S) in regulating physiological processes in tomato seedlings under NaCl-induced stress. Exposure of the seedlings to 100 mM NaCl stress reduced K⁺ content by 21% while increasing Na⁺ accumulation by 69%, disrupting the K⁺/Na⁺ ratio and impairing H⁺-ATPase activity. However, the application of SL improved H⁺-ATPase activity and K⁺ uptake and reduced Na⁺ accumulation. However, the application of 1 μM dl-propargylglycine (PAG; an H₂S biosynthesis inhibitor) negated these positive effects of SL, suggesting that H₂S plays a crucial role in SL-mediated ion homeostasis. NaCl stress also elevated the levels of reactive oxygen species, which were significantly reduced upon SL treatment. On the other hand, the application of PAG reversed these effects, confirming the involvement of H₂S in mitigating oxidative stress. Moreover, SL modulated carbohydrate metabolism by promoting starch accumulation and enhancing the activity of key enzymes such as sucrose synthase and soluble acid invertase. This process helps maintain osmoprotection and energy balance under stress conditions. However, these effects were abolished by H₂S biosynthesis inhibitor PAG, indicating its critical role in SL-mediated sugar metabolism. Overall, the results indicate that SL mitigates NaCl-induced stress by regulating H⁺-ATPase activity, maintaining ion homeostasis, reducing oxidative damage, and regulating carbohydrate metabolism via H₂S-dependent mechanisms. These findings highlight the potential of SL and H₂S to improve plant tolerance to NaCl stress.