Comparative effects of copper nanoparticles and copper oxide nanoparticles on physiological characteristics and mineral element accumulation in Brassica chinensis L

In this study, the short-term toxicity of Cu NPs, CuO NPs, and CuSO4 on bok choy (Brassica chinensis L.) under hydroponic conditions was evaluated using indicators such as biomass, net photosynthesis rate, root morphology, enzyme activity, and Cu accumulation and subcellular distribution. Results showed that CuO NPs exposure notably increased the biomass, root length, and root tip number by 22.0%, 22.7%, and 82.9%, respectively, whereas Cu NPs and CuSO4 significantly reduced root biomass, net photosynthetic rate (PN), and root length by 31.2% and 44.2%, 24.5% and 32.2%, and 43.4% and 40.6%, respectively. In addition, Cu NPs, CuO NPs and CuSO4 exposure increased the distribution of Cu in soluble component and cell wall. Moreover, short-term exposure to different Cu forms significantly affected mineral element accumulation in bok choy. For instance, Cu NPs exposure reduced the concentrations of Mg, Ca and Mn in edible part by 21.7%, 16.1% and 23.2%, respectively. CuSO4 exposure reduced the concentrations of Mg and Ca in edible part by 12.3% and 50.1%, respectively. CuO NPs caused a significant increase of 30.4% for Ca concentration in root, 34.5% and 34.5% for K and Mn concentration in edible part. Over all, CuO NPs exposure was beneficial for plant growth. These findings help understand the phytotoxic effect of different Cu forms on bok choy, and CuO NPs has the potential to be applied to improve nutrition and prompt growth in edible plants.