Optimizing SiO₂ Nanoparticle Structures to Enhance Drought Resistance in Tomato (Solanum lycopersicum L.): Insights into Nanoparticle Dissolution and Plant Stress Response

Drought stress significantly limits crop productivity and poses a critical threat to global food security. Silica nanoparticles (SiO₂NPs) have shown a potential to mitigate drought stress, but the role of the nanostructure on overall efficacy remains unclear. This study evaluated solid (SSiO₂NPs), porous (PSiO₂NPs), and hollow (HSiO₂NPs) SiO₂NPs for their effects on drought-stressed tomatoes (Solanum lycopersicum L.). Silicic acid release rates followed the order: HSiO₂NPs > PSiO₂NPs > SSiO₂NPs > Bulk-SiO₂. Compared to untreated controls, foliar application of PSiO₂NPs and HSiO₂NPs under drought stress significantly improved shoot Si concentrations and plants’ dry weight. These treatments also enhanced antioxidant enzyme activities (catalase, peroxidase, and superoxide dismutase) and phytohormone-targeted metabolome levels (jasmonic acid, salicylic acid, and auxin), contributing to greater drought tolerance. Conversely, SSiO₂NPs, silicic acid, and Bulk-SiO₂ had minimal impact on plant dry weight or physiological responses. These results highlight the importance of nanoparticles architecture in alleviating drought stress and promoting sustainable agriculture.