Green synthesized zinc oxide nanoparticles enhance maize tolerance against drought stress by improving plant water balance, antioxidant defense, and osmotic adjustment

Abiotic stress has a significant influence on plant growth and development, with drought being a particularly damaging ecological condition that inhibits maize growth and production. Nanotechnology provides a novel technique for increasing agricultural yield under challenging conditions. A pot experiment was performed to investigate the mediatory effect of green-synthesized zinc oxide nanoparticles (ZnO-NPs) from moringa leaf extract in improving maize tolerance to drought. The experiment contained two factors: a) stress, including control-no stress (100% field capacity) and drought stress (50% field capacity), and b) foliar application, including control-no spray, water spray, and ZnO-NPs foliar application (50, 100, and 150 ppm). Results revealed that drought stress decreased the morphological attributes such as SFW by 28% and LAI by 26%, and photosynthetic pigments such as total chlorophyll contents by 20% and carotenoids by 24%, while the foliar application of ZnO-NPs (100 ppm) among the other treatments significantly increased these morphological attributes by 44% and 34% respectively, and photosynthetic pigments by 38% and by 44% respectively under drought stress conditions. The drought stress caused an increase in the MDA by 22% and H 2 O 2 by 50% as compared to control conditions. In contrast, the foliar-applied ZnO-NPs (100 ppm) lowered the production of ROS by 42% and by 43%, by improving the enzymatic antioxidant activity like SOD by 37% and POD by 28% under drought stress. Remarkable increases in the osmoprotactants accumulation, such as proline by 36% and TSS by 29%, were observed by the foliar-applied ZnO-NPs (100 ppm) to overcome the adverse effects under drought stress. The study found that green-synthesized ZnO-NPs improve maize tolerance to drought by enhancing water status, antioxidant efficiency, and osmotic adjustment, suggesting that nanoparticle-mediated stress alleviation is a viable agricultural technique. Future study needs to focus on cellular, molecular pathways and field confirmation of long-term environmental effects. Moreover, all the foliar-applied treatments performed better as observed NP100> NP150> NP50> WS> control. • Drought stress adversely affects the growth of maize plants. • The use of green synthesized ZnO-NPs is a sustainable approach to mitigate drought stress. • ZnO-NPs show remarkable improvement in growth, plant water status, antioxidant defense system, and osmolyte accumulation in maize plants. • Reduce the overproduction of ROS in drought-exposed plants to enhance tolerance against drought stress.