Zinc-Based Nano-Priming Enhances Physiological and Functional Responses of Maize Seedlings

The physiological and functional responses of maize seedlings imbibed with zinc sulfate, commercial zinc oxide nanoparticles, and nanoparticles synthesized with Moringa oleífera, at 0, 5, 10, 15, 20, and 25 ppm, were evaluated. Vigor percentage, germination, abnormal seedlings, ungerminated seeds, plumule length and radicle length, dry plumule weight, and dry radicle weight were determined. In addition, phenolic concentration, antioxidant activity, and enzymatic activity were determined. ZnO NPs showed the highest %V and %G values (68.23% and 77.34%). ZnSO4 limited plumule (19.30%) and radicle (23.95%) development as concentrations increased. The highest dry weight of plumule was obtained using ZnO M-NPs (42.99 mg), ZnSO4 (48.92 mg), and ZnO NPs (51.89 mg) at 5 ppm, compared to the control (38.43 mg). ZnO M-NPs increased the content of free phenolics (9.26%) in the plumule, and ZnO NPs induced the highest accumulation of phenolics in the radicle (17.77%). Both NPs showed higher antioxidant capacity by the FRAP and ABTS methods in relation to control. ZnO M-NPs showed lower CAT activity in the plumule and radicle (1.06 and 1.39 U/g of FW at 5 and 25 ppm, respectively). ZnO NPs showed higher CAT activity in the plumule (3.85 U/g of FW at 5 ppm) and higher Apx activity in the radicle (6.15 U/g of FW at 20 ppm). The physiological and functional responses of maize seedlings depended on both the Zn source and concentration.