Effect of Cerium Oxide Nanoparticles on Rice: A Study Involving the Antioxidant Defense System and In Vivo Fluorescence Imaging

Abstract

Previous studies have reported the uptake of cerium oxide nanoparticles (<i>n</i>CeO₂) by plants, but their physiological impacts are not yet well understood. This research was aimed to study the impact of <i>n</i>CeO₂ on the oxidative stress and antioxidant defense system in germinating rice seeds. The seeds were germinated for 10 days in <i>n</i>CeO₂ suspension at 62.5, 125, 250, and 500 mg L^–1 concentrations. The Ce uptake, growth performance, stress levels, membrane damage, and antioxidant responses in seedlings were analyzed. Ce in tissues increased with increased <i>n</i>CeO₂ concentrations, but the seedlings showed no visible signs of toxicity. Biochemical assays and in vivo imaging of H₂O₂ revealed that, relative to the control, the 62.5 and 125 mg <i>n</i>CeO₂ L^–1 treatments significantly reduced the H₂O₂ generation in both shoots and roots. Enhanced electrolyte leakage and lipid peroxidation were found in the shoots of seedlings grown at 500 mg <i>n</i>CeO₂ L^–1. Altered enzyme activities and levels of ascorbate and free thiols resulting in enhanced membrane damage and photosynthetic stress in the shoots were observed at 500 mg <i>n</i>CeO₂ L^–1. These findings demonstrate a <i>n</i>CeO₂ concentration-dependent modification of oxidative stress and antioxidant defense system in rice seedlings