Abscisic Acid-Loaded ZnO Nanoparticles as Drought Tolerance Inducers in Zea mays L. with Physiological and Biochemical Attributes

This research aimed toward bioengineering of Zinc oxide nanoparticles (ZnO NPs) using Rosa canina L. aqueous extract followed by conjugation with Abscisic acid (ABA) for inducing drought-tolerant properties in Zea mays L under water stress. The impact of six different treatments using seed imbibition (SI) and foliar spray (FS) methods upon physio-morphological and biochemical properties of Z. mays L. was studied. These included ABA-SI, ABA-FS, ABA-ZnO-SI, ABA-ZnO-FS, ZnO-SI, and ZnO-FS, drought control (DC), and untreated healthy control (HC). Both ZnO and ABA-ZnO NPs showed distinct UV–Visible peaks at 438 nm and 339 nm with mean sizes of 20.17 nm and 14.05 nm, respectively. Scanning Electron Microscopy coupled with Energy-Dispersive X-ray identified 60.14% Zn in ZnO NPs with irregular surface topology and 56.72% Zn in ABA-ZnO NPs with semi-cylindrical morphology. Among treated maize plants, ABA-ZnO-SI displayed prominent results with increased root length (32.89 ± 1.25 cm), relative water content (20.4 ± 2.9%), total chlorophyll content [10.73 ± 0.18 mgg −1 Fresh weight (FW)], carotenoid content (190.4 ± 0.56 mg g −1 FW), cob length (27.94 ± 1.32 cm), cob weight (25.64 ± 0.42 g), and short anthesis-silking interval (3 days). Stomatal opening (0.95 ± 0.24%) and leaf damage index (29.86 ± 0.19%) were reduced in ABA-ZnO-SI treatment compared to DC. A significant amount of proline (4.40 ± 0.01 µmoles g −1 FW) with reduced lipid peroxidation (0.24 ± 0.02-mM malondialdehyde) and highest antioxidant activities (IC50: 332.8 ± 0.46 µg/ml) with maximum levels of catalase (2.87 ± 0.05 Uml −1 ), ascorbate peroxidase (3.41 ± 0.02 Uml −1 ), and guaiacol peroxidase (3.10 ± 0.06 Uml −1 ) were observed in ABA-ZnO-SI-treated plants. Given the promising outcomes, current research work has brought forward a potential drought tolerance treatment for Z. mays L. which might serve as productive agricultural progress in upcoming years.