Green synthesis of copper oxide nanoparticles for seed priming applications

Abstract Copper oxide nanoparticles were synthesised using a solar-assisted method using temple waste flower extract as a natural reducing and stabilising agent. This process promotes waste reuse and supports sustainable nanomaterial production. X-ray diffraction confirmed pure CuO NPs after heating at 400 °C. Energy-dispersive x-ray spectroscopy showed a Cu–O composition, with some trace elements from the extract. Fourier-transform infrared spectra displayed specific Cu–O peaks along with functional groups. The synthesis method uses renewable solar energy, eliminating the need for mechanical stirring and lowering the carbon footprint. This approach fits with the sustainable development goals. CuO NPs were tested as nano-seed priming agents for Aahan F1 tomato seeds, using concentrations ranging from 5 to 100 mg l −1 . The germination percentage showed a concentration-dependent trend, peaking at 94% for 50 mg l −1 ( p < 0.0001). Moderate doses of 25–35 mg l −1 resulted in about 79% germination. However, both lower 5–15 mg l −1 and higher 70–100 mg l −1 concentrations reduced germination to 73% or less. The best performance at 50 mg l −1 may be to lower oxidative stress markers, better nutrient uptake, balanced auxin–gibberellin activity and noticeable increases in shoot and root length as well as biomass. In contrast, the highest concentration of 100 mg l −1 led to oxidative damage, loss of chlorophyll, lower water content, and stunted growth. The traits of the NPs, such as size and surface charge, affected how they were absorbed, moved around, and regulated hormones, impacting plant responses.