Dual Enhancement of Maize Drought Resistance by Molybdenum Nanodots: Driving Leaf Metabolism and Shaping the Phyllosphere Microenvironment

Agricultural productivity is compromised by drought events. We investigate how small-sized molybdenum nanodots (MNDs) can increase maize ( Zea mays L.) seedling shoot fresh and dry weights under drought stress. Because the oxygen vacancies endow MNDs with excellent reactive oxygen species (ROS) scavenging ability, MNDs protect photosynthesis via scavenging efficacies against superoxide anions (O 2 •– ) by 23.6% and hydrogen peroxide (H 2 O 2 ) by 22.8%, improving the net photosynthetic rate (Pn, +53.9%) and maximum photosynthetic efficiency (+13.1%). This drives the carbon–nitrogen metabolic network and secondary metabolism in leaves and increases levels of proline (+36.2%) and malic acid (+50.0%) to maintain osmotic and redox homeostasis. MNDs also affect the phyllosphere, fostering conditions that favor drought tolerance (e.g., increased dissolved organic carbon leads to greater dominance of Bacteroidota and Proteobacteria, and restoration of nutrient cycles through enhanced nitrogen fixation, cellulose degradation, and phosphate solubilization). MNDs improve maize seedling survival through dual-directional empowerment under drought stress. This reveals the potential of nanomaterial-mediated resilience to address climate change and food shortage.