Impacts of copper oxide nanoparticles on bell pepper (Capsicum annum L.) plants: a full life cycle study

Abstract

Several studies have explored the effects of copper nanoparticles (NPs) on different edible plants. However, no studies on bell pepper (Capsicum annum L.) plants have been reported. In this study, plants were grown for a full life-cycle assessment (90 days of exposure) in natural soil amended with nano CuO (nCuO), bulk CuO (bCuO), and ionic copper (CuCl₂) at 0, 125, 250, and 500 mg kg⁻¹. Based on our experimental findings, none of the treatments significantly affected stem elongation, plant dry biomass, foliar area, leaf chlorophyll content, and fruit productivity of bell pepper. However, ionic copper significantly decreased the gas exchange parameters, evapotranspiration, stomatal conductance, and photosynthesis by an average of 41%, 59%, and 38%, respectively, compared to the other treatments at select concentrations (p ≤ 0.05). The ICP-OES data showed that, except for bCuO at 500 mg kg⁻¹, at 250 mg kg⁻¹ and above, the three compounds significantly increased root Cu (196%, 184%, and 184%) with respect to the control. Only at 500 mg kg⁻¹, ionic Cu gave significantly higher root Cu compared to the other Cu treatments. Additionally, at 125 mg kg⁻¹, leaf P was 41% lower for nCuO, compared to the bCuO treatment. At 500 mg kg⁻¹, nCuO reduced Zn by 55% in leaves and 47% in fruits, compared to the control (p ≤ 0.05); however, it is premature to assert that the reduction in fruit Zn compromises the nutritional quality of bell pepper. Overall, this investigation showed that, at the concentrations tested, nCuO presented low toxicity to bell pepper, with rare differences between nano and bulk treatment responses.