Seed Nanopriming\nwith Green-Synthesized Cu-Based Nanoparticles\nfor Maize Plants with Improved Tolerance to Hydric Stress

Nanopriming with green-synthesized nanoparticles (NPs)\nhas the\npotential to optimize crop performance under different conditions.\nThis work investigated the implications of nanopriming of maize seeds\nwith green-synthesized Cu-based NPs (ascorbic acid/starch, ACu, and\ngreen tea extract, GTCu) on the nutritional and morphophysiological\ntraits of maize plants. Seeds Zea mays cv. Balu 787 were treated with different concentrations (14.5, 29,\n58, and 116 mg Cu L<sup>–1</sup>) of both NPs, compared to\nhydropriming (CONT) and unprimed seeds (TEST). In a laboratory, seeds\nwere germinated under different water conditions, while the long-term\neffects of seed nanopriming were evaluated in a greenhouse experiment\nwith plants under different water conditions. The ionomic profile\nand morphophysiological traits of the plants were evaluated. In germination\nwith water, both NPs increased the seedling Cu content by 37%, while\nin germination with PEG-6000, ACu and GTCu increased germination by\n53 and 131%, respectively, compared with TEST and CONT. Without water\nrestriction, hydropriming and ACu provided higher concentrations of\nmany elements in seedling tissues. Under water deficit, only ACu stood\nout compared to the other treatments. GTCu promoted nutritional imbalance\nin both germination conditions. Although both NPs improved the water\nuse efficiency of plants, ACu stood out for providing a better root/shoot\nratio, helping the plants to be more tolerant to water deficit. GTCu\nprovided greater shoot growth combined with lesser induction of root\ngrowth, leading to higher susceptibility to water deficit. In both\nexperimental conditions, the dose of 58 mg Cu L<sup>–1</sup> was highlighted, due to the induction of the greatest effects on\nseedling/plant development. The results suggest differences in the\nadsorption/absorption of NPs, with ACu triggering more positive effects\non maize plants than GTCu. Overall, this study highlights the potential\ncontribution of green nanotechnology in inducing plant growth and\ntolerance to abiotic stress by seed nanopriming.