Mechanistic insights into the role of nano-fertilizers in enhancing maize drought resilience via antioxidant and physiological pathways

Drought stress poses a critical threat to global maize (Zea mays L.) production, impairing physiological and biochemical functions and significantly reducing crop yield. This study evaluated the potential of foliar-applied nano-fertilizers - zinc (Zn), iron (Fe), and silica (Si) nanoparticles - in mitigating drought-induced damage in maize across two consecutive growing seasons (2023-2024). A factorial experiment was conducted under controlled greenhouse conditions with 12 treatment combinations comprising three drought levels (non-drought, moderate, severe) and four nano-fertilizer regimes (control, Zn, Fe, Si). Comprehensive physiological and biochemical parameters were measured, including photosynthetic pigments, antioxidant enzyme activities, oxidative stress markers, proline, protein content, and gas exchange traits (photosynthesis and transpiration rates). Results showed that drought stress significantly reduced chlorophyll and carotenoid content, impaired photosynthesis, and elevated oxidative damage. However, nano-fertilizer treatments - particularly nano-Fe and nano-Zn - enhanced chlorophyll retention, increased antioxidant enzyme activities and seed yield, and lowered malondialdehyde (MDA), electrolyte leakage (EL), and hydrogen peroxide (H2O2) accumulation. Nano-Si notably improved transpiration and proline accumulation, aiding osmotic adjustment. Among treatments, moderate drought combined with nano-Fe (MDNFe) and Zn (MDNZn) consistently outperformed controls, demonstrating improved pigment stability, enzymatic protection, and physiological performance. Correlation analysis revealed strong positive associations between chlorophyll content and photosynthetic traits (r > 0.98), and between antioxidant activity and stress mitigation indicators. This study provides mechanistic insights into the nano-enabled resilience of maize under drought stress and highlights the synergistic role of micronutrient nanoparticles in enhancing plant antioxidant and osmoprotective responses. The findings advocate for the integration of nano-Zn, nano-Fe, and nano-Si into sustainable drought management practices to promote climate-resilient maize cultivation.