Dose-Dependent Effects of Copper Oxide Nanoparticles on Biomass, Secondary Metabolite Production, and Physiological Stress in Talinum paniculatum Adventitious Root Cultures

Abstract

Copper oxide nanoparticles (CuO-NPs) are increasingly explored as effective abiotic elicitors capable of modulating plant metabolism through redox-related mechanisms. This study evaluated the concentration-dependent effects of CuO-NPs on biomass production, secondary metabolite accumulation, oxidative stress responses, antioxidant capacity, and antioxidant enzyme activities in adventitious root cultures of Talinum paniculatum. Adventitious roots were treated with CuO-NPs at concentrations of 0, 50, 100, and 150 mg L⁻¹ for two weeks under in vitro conditions. Biomass production was determined using fresh and dry weight measurements, whereas saponin and stigmasterol contents were analyzed by high-performance liquid chromatography. Physiological stress indicators were assessed through malondialdehyde and hydrogen peroxide levels, antioxidant capacity using DPPH radical scavenging activity, and enzymatic antioxidant responses through superoxide dismutase, catalase, and ascorbate peroxidase activities. Moderate CuO-NPs concentrations (50–100 mg L⁻¹) significantly enhanced secondary metabolite accumulation and antioxidant responses, accompanied by moderate elevations in physiological stress indicators. Conversely, exposure to 150 mg L⁻¹ CuO-NPs negatively affected biomass accumulation and antioxidant responses, suggesting metabolic suppression under excessive oxidative conditions. These results demonstrate that CuO-NPs function as effective elicitors at appropriate concentrations for improving secondary metabolite production in T. paniculatum adventitious root cultures.