Mitigating stress and boosting metabolites through the impact of ZnO nanoparticles on Stevia rebaudiana and Ocimum basilicum

Plant growth is usually compromised by abiotic and biotic stressors that decrease germination, yield, and synthesis of useful metabolites. Zinc oxide nanoparticles (ZnO-NPs) have exhibited potential in increasing plant tolerance and metabolic yield. This research assesses the impact of ZnO-NPs on Stevia rebaudiana and Ocimum basilicum in a randomized pot experiment with seed priming at concentrations of 0–250 mg L−1. The nanoparticles were identified through UV-vis spectroscopy (maximum absorption at 380 nm), FTIR, and XRD, proving their crystalline hexagonal wurtzite nature and functional groups (C = O, C-O, O-H). Germination in O. basilicum was highest at 50 mg L−1, with maximum shoot and root growth at 100 mg L−1, whereas Stevia showed a positive response only at 50 mg L−1. GC-MS analysis revealed remarkable enhancement of fatty acids, phenols, and terpenes in ZnO-NP treatment. These observations imply ZnO-NPs have the potential to promote plant growth and secondary metabolite production, yet species- and dose-dependent effects need to be considered with care.