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

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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.