Hydrogen-rich water alleviates drought stress in tomato: Insights from physiological, molecular, and ionic perspectives

Highlight s • Hydrogen-rich water can enhance the antioxidant capacity of tomatoes, reduce damage, and help maintain water balance. • Hydrogen-rich water strengthens tomatoes' drought resistance by regulating gene expression and stomata. • Hydrogen-rich water can stabilize ions in tomato roots and enhance the transmission of stress signals. • Hydrogen-rich water can improve the nutrition of tomato fruits, and optimize carbon allocation and protein status. Drought stress limits tomato yield and quality, challenging sustainable agriculture. Hydrogen (H₂), emerging as a versatile gas signaling molecule, has shown promising potential in enhancing plant stress tolerance. In this study, we investigated hydrogen-rich water (HRW) effects on drought resistance and fruit quality in two tomato cultivars ( AC, microTom ). HRW elevated antioxidant enzyme activities, reduced malondialdehyde, promoted proline accumulation, thereby maintaining osmotic balance. It up-regulated SlNCED5 and abscisic acid (ABA) biosynthesis genes, activating ABA signaling to reduce stomatal aperture and water loss. In this study, we used Non-invasive Micro-test (NMT) to analyze the ion flow under drought stress, and established the direct correlation between the ion dynamics and stress signal transduction at the cellular level. HRW increased soluble sugar, sucrose, and starch contents in microTom fruits, optimizing carbon allocation and improving the tertiary structure of fruit protein. Collectively, these findings indicate that HRW enhances tomato drought resistance through a synergistic multi-pathway regulatory network involving "antioxidation–stomatal regulation–gene expression–ion dynamics". This study lays a theoretical foundation for the targeted application of H 2 -based technologies in water-saving tomato cultivation.