Titanium dioxide nanoparticles and hydrogen sulphide synergize to alleviate salinity stress in tomato seedlings

• NaCl stress significantly reduce the growth and development of tomato seedlings • NaCl heightened ROS accumulation and thus severely damage the essential metabolic system of tomato seedlings • TiO 2 NPs protects tomato seedlings against NaCl caused stress through synergistic interaction withH 2 S • TiO 2 NPs and H 2 S reduced the over production of ROS, and enhanced antioxidants and sucrose metabolic processes Salinity stress significantly constrains agricultural output by interfering with essential physiological and biochemical mechanisms disrupting photosynthesis, nutrient assimilation, and redox homeostasis. Here, we show that titanium dioxide nanoparticles (TiO₂-NPs) synergize with endogenous hydrogen sulphide (H₂S) signaling to enhance salinity tolerance in tomato ( Lycopersicum esculantum L.) seedlings. Under NaCl stress, TiO₂-NPs attenuated oxidative damage by reducing reactive oxygen species (ROS) accumulation and lipid peroxidationby upregulating both enzymatic (SOD, CAT, APX, POD, GR, MDHAR, DHAR) and non-enzymatic (ascorbate, glutathione) antioxidant defences, sustaining the AsA-GSH cycle and improving photosynthetic attributes. Inhibition of H₂S biosynthesis by DL-propargylglycine (PAG) stifled these protective effects, whereas supplementation with sodium hydrosulphide (NaHS) partially restored them, confirming the central role of H₂S in TiO₂-NPs-mediated tolerance. TiO₂–H₂S co-treatment improved uptake of Mg, Ca, Zn, and Fe and maintained nitric oxide balance under salt stress. The interaction between nanoparticles and gasotransmitters enhances redox regulation, photosynthetic efficiency, and nutrient assimilation, thereby contributing to increased salt tolerance. These findings provide mechanistic details and a practical framework for using nano-based, signaling-guided strategies in managing salinity stress in crops. This study suggests that combining nanotechnology with gasotransmitter signaling could offer effective, sustainable ways to boost crop tolerance to salinity stress.