Hui Wu, Yajuan Zhou, Benlin Shi
Waterlogging stress adversely affects the growth and physiological performance of Capsicum annuum by limiting root-zone oxygen availability and inducing oxidative stress. This study investigated the potential of foliar-applied functionalized zinc oxide nanoparticles (ZnO-NPs) to mitigate waterlogging-induced stress under controlled conditions. Functionalized ZnO-NPs were applied at concentrations of 100–300 mg/L during vegetative and pre-flowering stages. Compared with untreated waterlogged plants, ZnO-NP-treated plants exhibited improved germination performance, relative water content, chlorophyll retention, and antioxidant enzyme activities. The activities of Superoxide Dismutase (SOD), Catalase (CAT), and Peroxidase (POD) increased, while Hydrogen Peroxide (H 2 O 2 ) and Superoxide Radical (O 2 ˙ - ) accumulation decreased under nanoparticle treatments. Structural and physicochemical characterization using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR) confirmed ZnO nanoparticle crystallinity and suggested interactions between the functionalized nanoparticles and leaf tissues. Statistical analysis indicated significant treatment effects on measured stress-response parameters. Among the tested treatments, 300 mg/L ZnO-NPs (T5) produced the highest relative water content (86.7%) and antioxidant enzyme activities (SOD: 48, CAT: 42, POD: 40 U mg -1 ). These findings suggest that foliar application of functionalized ZnO-NPs may enhance the physiological and antioxidant responses of Capsicum annuum under waterlogging stress. However, further studies are required to evaluate the underlying mechanisms, long-term performance, and biosafety aspects of nanoparticle application.