Nanoparticle-Based Elicitation Strategy Using ZnO Enhances Bioactive Compound Accumulation in Adventitious Root Cultures of Talinum paniculatum (Jacq.) Gaertn

Abstract

Nanoparticle elicitation has attracted attention as an approach to enhance secondary metabolite production in plant in vitro cultures. This study investigated the effects of zinc oxide nanoparticles (ZnO-NPs) on biomass growth, secondary metabolite accumulation, oxidative stress, and antioxidant defense responses in adventitious root cultures of Talinum paniculatum. Four-week-old adventitious roots were treated with ZnO-NPs at concentrations of 0, 50, 100, and 150 mg L⁻¹ for two weeks. Biomass parameters, saponin and stigmasterol contents, DPPH radical scavenging activity, oxidative stress markers, and antioxidant enzyme activities were analyzed. ZnO-NP treatments significantly reduced fresh and dry biomass compared with the control, indicating growth inhibition under nanoparticle exposure. Conversely, ZnO-NPs enhanced the accumulation of saponin and stigmasterol, with the highest levels generally observed at 100 mg L⁻¹. Antioxidant capacity increased significantly in ZnO-NP–treated roots, accompanied by elevated malondialdehyde and hydrogen peroxide contents. Activities of superoxide dismutase, catalase, and ascorbate peroxidase were significantly enhanced, suggesting activation of antioxidant defense mechanisms. These results indicate that ZnO-NPs act as effective abiotic elicitors in T. paniculatum adventitious root cultures by inducing controlled oxidative signaling that promotes secondary metabolite biosynthesis despite reduced biomass accumulation.