Deciphering the role of zinc oxide nanoparticles on physiochemical attributes of Zea mays exposed to saline conditions through modulation in antioxidant enzyme defensive system

Abstract: Use of zinc oxide nanoparticles (ZnO--NPs) has the potential to increase the plant growth and development in agricultural sectors. Mode of application of NPs to plants is also of considerable importance. In present study, zinc oxide nanoparticles were prepared by using black seed extract and zinc salt. Characterized zinc oxide nanoparticles were then used to treat Zea mays L. in two types of treatments namely nano-priming and foliar nano-spray of zinc oxide nanoparticles. For each treatment a range of concentration was used i.e., 100, 200, 400, and 1000 mg/L. Experiment was conducted in randomized complete block design. Hydropriming was used as a control. Whereas foliar spray was given after 30, 45, and 60 days of sowing. Plants were harvested after 90 days and various growth, physiological, biochemical, yield and stress parameters were studied. Results showed that monodispersed nanoparticles of average size of 45.56 nm were synthesized. Priming with ZnO--NPs showed better results as compared to foliar spray of ZnO--NPs. Highest germination (100%), Leaf length (350 cm), plant height (65 cm), and no. of leaves (10 leaves per plant) were recorded for corn plants with seed priming treatment of 200 mg/L of ZnO--NPs. These values were significantly higher than comparative positive control treatment values (salt-treated plants) as well. Whereas biochemical analysis also supported the results of growth parameters i.e., ZnO--NPs treated plants (200-1000 mg/L) showed higher values of sugar (0.6 mg), chlorophyll (1800 mg) and carotenoid content (400 mg). Protein and proline content was higher for zinc salt-treated (positive control) plants. Photosynthetic rate, CO2 sub-stomatal conductance, stomatal conductance and rate of transpiration was also higher for ZnO--NPs treated plants particularly in nano-primed plants. Whereas study of yield attributes showed highest cob length (14 cm), cob weight (80 g), cobs per plant (4) in ZnO--NPs treated plants that was significantly higher than the both controls. Stress studies of plant samples showed that peroxidase activity was highest in plants treated with 1000 mg/L zinc salt-treated salts, both in case of priming and foliar spray. Whereas catalase activity was found highest in ZnO--NPs (200 mg/L) foliar spray treated plants. Zinc content analysis of plant sample showed significantly higher amount of zinc in ZnO--NPs treated corn plants. It is concluded from present study that ZnO--NPs in priming treatment significantly enhanced the growth and yield attributes of corn plants through the balance of biochemical and stress indicators. Priming and foliar spray of ZnO--NPs also fortified the crop with enhanced zinc content. Future study with combination of both priming and foliar spray may be further optimized. & COPY; 2023 SAAB. Published by Elsevier B.V. All rights reserved