Differential physiological and biochemical impacts of nano vs micron Cu at two phenological growth stages in bell pepper (Capsicum annuum) plant

The aim of this study was to determine the physiological and biochemical impacts of copper nanoparticles and bulk particles (nCu and bCu) at the vegetative stage (VS) and reproductive stage (RS), in bell pepper (Capsicum annuum) plants. Thirty-day-old seedlings were transplanted to soil amended with 0 (control), 62.5, 125, or 500 mg Cu/kg and evaluated at half life cycle (45 days post transplantation, VS) and full life cycle (90 days post transplantation, RS). At VS, 500 mg nCu/kg treatment significantly increased root length (58.46%) and root dry weight (187.18%), compared with control (p <= 0.1). Additionally, at VS, all plant tissues accumulated significantly higher amounts of Cu from bCu treatments, compared with the corresponding nCu treatments as well as compared with control (p <= 0.05). Contrarily, at RS, Cu in leaves of plants exposed to 500 mg nCu/kg was higher by 1510%, compared to plants exposed to the same concentration of bCu (p <= 0.05). Furthermore, for the RS at 500 mg/kg, nCu increased photosynthesis (42%) and stomatal conductance (51%), while at 62.5 mg/kg, increased transpiration (31%), compared to its bulk counterpart (p <= 0.05). None of the copper treatments affected total sugar, carotenoid, chlorophyll, and vitamin C contents in the fruit, and the root and leaf enzyme activity for the RS study. Overall, the 500 mg nCu/kg treatment had a fertilizing effect and resulted in higher Cu bioaccumulation in the root and leaf tissue over long term exposure.