Research PaperEffect of biologically synthesized copper oxide nanoparticles on metabolism and antioxidant activity to the crop plants Solanum lycopersicum and Brassica oleracea var. botrytis

- Copper oxide nanoparticles (CuO NPs) were rapidly synthesized at room temperature by flower extract of Morus alba.
- The FTIR spectra indicate that flower extract mediated CuO NPs sample is rich in secondary metabolites which might be responsible for the reduction of Cu ions into Cu NPs.
- The seedlings of Brassica oleracea ver. botrytis and Solanum lycopersicum were exposed to different concentrations of CuO NPs in the sand medium.
- NPs are more actively accumulated by tomato plants than cauliflower possibly due to the difference in root morphology.
- In stress condition the accumulation of superoxides appeared to be traced in vascular tissue while H2O2 accumulation was found in the mesophyll tissue.

Study on the ecological effect of metal oxide nanomaterials (NMs) has quickly amplified over the precedent years because it is assumed that these NMs will sooner or later be released into the environment. The present study deals with biologically oriented process for the green synthesis of copper oxide nanoparticles (CuO NPs) by using Morus alba leaf extract as reducing agent. Powder X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis revealed the monoclinic phase and 20-40 nm size respectively. The presence of reducing and capping agents revealed by Fourier transform infrared (FTIR) spectroscopy. The seedlings of Brassica oleracea var. botrytis and Solanum lycopersicum were exposed to 10, 50, 100, and 500 mg L−1 concentrations of CuO NPs in the sand medium. Bioaccumulation of Cu was also investigated by atomic absorption spectroscopy (AAS). Plant exposure to 100 and 500 mg L−1 of CuO NPs has resulted in significant reduction of total chlorophyll and sugar content in the two test plants while 10 mg L−1 of NPs slightly increased the pigment and sugar content in tomato plants only. Augmentation of lipid peroxidation, electrolyte leakage, and antioxidant enzyme activity was observed in a dose dependent manner upon plants exposure to CuO NPs. Deposition of lignin in roots of both plants treated with the highest concentration of CuO NPs was observed. Histochemical analysis of leaves of treated plant with nitroblue tetrazolium and 3′3′ diaminobenzidine showed a concentration dependent increase in superoxide and hydrogen peroxide formation in leaves. The green synthesis of CuO NPs was carried out by using Morus alba leaf extract. Accumulation of NPs more actively by tomato plants as compared to cauliflower was possibly due to the difference in root morphology. The histochemical visualization highlights the spatial organization of oxidant biochemistry occurring in response to metal stress.