Effect of CuO Nanoparticles from Yerba Mate on Germination and Initial Growth of Lettuce and Tomato Seeds

Green nanotechnology is recognized as a sustainable and environmentally friendly approach for the synthesis of metal nanoparticles (NPs). In this study, yerba mate (Ilex paraguariensis) extract was used as a natural reducing and stabilizing agent for the synthesis of copper oxide nanoparticles (CuO NPs), offering an alternative to conventionally used chemical reagents. The synthesis of the NPs was optimized by analyzing the effects of reaction temperature and the amount of metal precursor used. The results showed that higher temperatures favored the conversion yield, with a maximum of 26.75% at 80 °C. The CuO nanoparticles exhibited crystallite sizes of 22.9 nm, a hydrodynamic diameter of 63.41 nm, and a composition of 34.42% oxygen and 65.59% copper. CuO NPs exhibited beneficial effects on Lactuca sativa and Solanum lycopersicum seeds, enhancing germination and promoting seedling growth from the early stages. At 25 mg/L, 30–50% of tomato seeds germinated by the second day, while 80% of lettuce seeds germinated during the first day, both of which were higher than the control. Additionally, treated seedlings displayed higher dry biomass, a sign of higher metabolic activity. The results show that CuO nanoparticles synthesized through an ecological approach increased the vigor of lettuce and tomato seeds, encouraging future fieldwork in the area. This strategy opens new possibilities for improving plant development while minimizing environmental impacts, integrating nanotechnology with sustainable agricultural practices.