Effect of cerium oxide nanoparticles on rice: a study involving the antioxidant defense system and in vivo fluorescence imaging.

Previous studies have reported the uptake of cerium oxide nanoparticles (nCeO2) by plants, but their physiological impacts are not yet well understood. This research was aimed to study the impact of nCeO2 on the oxidative stress and antioxidant defense system in germinating rice seeds. The seeds were germinated for 10 days in nCeO2 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 nCeO2 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 nCeO2 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 nCeO2 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 nCeO2 L(-1). These findings demonstrate a nCeO2 concentration-dependent modification of oxidative stress and antioxidant defense system in rice seedlings.