Toxicity of copper oxide nanoparticles on Spirodela polyrrhiza: assessing physiological parameters

Abstract: The surface characteristics of nanoparticles cause their influx into the environment and lead to their interaction with fungi, algae, and plants. In the present study, the toxic effects of copper oxide nanoparticles were studied on the higher aquatic plant Spirodela polyrrhiza. Copper oxide nanoparticles were synthesized using green sonochemistry and their surface specifications were determined using XRD and SEM. The entrance and uptake of CuO nanoparticles in the roots of S. polyrrhiza was confirmed using fluorescence microscopy. The toxicity of CuO nanoparticles on S. polyrrhiza was investigated by measuring the growth rate (relative frond number), enzymatic activities (peroxidase, superoxide dismutase, and catalase) and content of photosynthetic pigments. In all experiments, the negative effects of CuO nanoparticles on the growth of S. polyrrhiza were confirmed by means of growth and enzymatic and pigment assays. Accordingly, significant changes in antioxidant enzyme activity were achieved. Catalase, peroxidase, and superoxide dismutase activity were increased due to the plant's defence system for scavenging the reactive oxygen species. In addition, relative frond number and chlorophyll content were reduced owing to possible phytotoxicity generated by CuO nanoparticles. Graphical Abstract: [Figure not available: see fulltext.]