Identifying the Phytotoxicity of Biosynthesized Metal Oxide Nanoparticles and Their Impact on Antioxidative Enzymatic Activity in Maize Under Drought Stress

Maize (<i>Zea mays</i> L.), an important crop used for animal feed and human consumption, is currently threatened by water shortage. Recently, the usage of nanomaterials has attracted worldwide attention due to their applications in various fields. This research aimed to evaluate the comparative efficacy of different metal oxide nanoparticles for mitigating drought stress in maize. Iron oxide, manganese oxide, and copper nanoparticles were biosynthesized from the leaf extract of <i>Conocarpus erectus</i> L. and characterized via UV-Vis, XRD, FTIR, and SEM. The synthesized nanomaterials were initially optimized at different concentrations (0, 25, 50, 75, and 100 ppm). The optimized doses of each nanoparticle were then applied to maize plants under different drought stress levels (50% FC, 75% FC, and 100% FC). Compared to the control, the application of nanomaterials significantly improved the growth parameters of the maize by 30% at 50% FC, 27% at 75% FC, and 26% at 100% FC. The chlorophyll content also improved significantly at different levels of drought stress by 35%, 32%, and 29% as compared to the control, respectively. The antioxidants (CAT, POD, SOD, and APX) also improved significantly at different levels of drought by 37%, 34%, and 31%, as compared to control, respectively. Moreover, the use of nanoparticles resulted in a significant decrease in cellular oxidative stress (MDA, H₂O₂) parameters by 23% at 50%FC, 26% at 75% FC, and 27% at 100% FC. Biosynthesized FeO NPs, MnO NPs, and Cu NPs have demonstrated significant potential in mitigating drought stress in maize, suggesting a promising approach to enhance crop performance under water-limited conditions. Further research is recommended to explore the long-term impacts and practical applications of these findings in sustainable agriculture.