Effects of the Size and Shape of PHMB-Stabilized CuO Nanoparticles on Morphometric and Biochemical Parameters of Spring Wheat (Triticum aestivum L.) Seedlings

Due to the increasing use of nanomaterials in agriculture, the effects of copper(II) oxide nanoparticles (CuO NPs) on plants are of considerable interest. This study analyzes the effect of CuO NPs synthesized by chemical precipitation and electrical explosion of a wire, as well as a commercial CuO NP sample, all stabilized with the antimicrobial polymer polyhexamethylene biguanide hydrochloride (PHMB), on spring wheat (Triticum aestivum L.) seedlings. X-ray diffraction analysis and scanning electron microscopy have revealed significant differences among the samples in phase purity, particle size, and morphology (rod-shaped, spherical, and flake-like particles). Rod-shaped nanoparticles from the commercial sample exhibited the highest colloidal stability in aqueous dispersions. Bioassays have shown that all CuO NP dispersions enhanced seed germination and biomass accumulation, particularly in roots, while seedling length was reduced. The strongest stimulatory effect, including increased chlorophyll content and catalase activity, has been recorded for the commercial CuO NP sample at a concentration of 100 mg/kg. Copper accumulated predominantly in the above-ground parts of the plants. Overall, the results indicate that nanostructured CuO–PHMB complexes may represent an effective approach for improving the growth of spring wheat. However, long-term studies are needed to assess their ecological safety.