Biochemical responses induced by SiO2-ZnO nanoparticles in Zea mays plants under water deficit conditions

Nanotechnology (NT) holds promise as a tool to improve crop yields and address current and future limitations in agricultural production by enhancing plant tolerance to abiotic stresses, such as droughts. Silicon nanoparticles (NPSi) are beneficial in mitigating biotic and abiotic stresses. However, the impact of the combined synthesis of NPSi with metals (SiZnONP) under drought stress conditions is poorly understood. An experiment was conducted to investigate the effect of Si NPs on the growth of maize (Zea mays) under water deficit conditions in a greenhouse. Four levels of SiNP and SiZnONP (0, 50, 100, and 200 mg/L) were applied weekly as a foliar spray after maize sowing. Two water levels (100% and 35% of soil water-holding capacity) were introduced 50 days after sowing for the remaining growth period. The lowest biomass, stem diameter, leave number, and height were observed in the plants under drought stress (control). The SiNP treatments improved plant growth indicators and photosynthesis, especially in drought stress grains. The improvement in maize growth was consistent across different levels of Si NPs, with the highest effect seen with NPsSi-ZnO at 50 mg/L (81.05±1.2 cm). In plants treated with SiZnONPs, the levels of proline, peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) [771. 97 μg/mg, 4.48 ± 0.2 UI/mg; 19.28 ±0.11 UI/mg, and 0.27 ± 0.06 UI/mg] were higher compared to plants under drought stress conditions [650 ± 31.44 μg/mg, 2.93 ± 0.61 UI/mg; 14.58 ±021 UI/mg, and 0.17 ± 0.03 UI/mg]. However, the levels of H₂O₂ showed an opposite trend. The application of SiNPs notably enhanced the histological features of roots under drought conditions.