Phytotoxicity of Y2O3 nanoparticles and Y3+ ions on rice seedlings under hydroponic culture

Due to the characteristics of both rare earth elements (REEs) and nanoparticles (NPs), Y2O3 NPs have been widely used in the fields of medicine, military industry, and agriculture, especially in the areas of electricity, light, magnetism, and catalysis. Given this widespread use, it is inevitable that Y2O3 NPs and soluble Y3+ will enter bodies of water through the processes involved in their preparation, application, and disposal. We sought to investigate the toxicities of Y2O3 NPs and Y3+ ions on rice seedlings (Oryza sativa L.), as well as the uptake and distribution of Y2O3 NPs under hydroponic conditions. Our results indicated that Y2O3 NPs and released Y3+ had no significant effect on the germination rate of rice. However, high concentrations of Y2O3 NPs (50 and 100 mg/L) delayed seed germination. As for rice root elongation, low concentrations (1, 5, and 10 mg/L) of Y2O3 NPs had a positive effect. Notably, when Y2O3 NPs concentration reached 20 mg/L and higher, root elongation was significantly inhibited. According to the physiological and biochemical characteristics of rice seedlings under Y stress, Y2O3 NPs ranging from 20 to 100 mg/L significantly reduced chlorophyll contents and root activity. Using ICP-MS and TEM analyses, Y2O3 NPs and Y3+ were shown to be mainly absorbed and accumulated in the roots. With Y2O3 NPs exposure, the Y transport coefficient from the roots to the shoots of rice was 1.94–7.55%. Comparatively, Y3+ ions had an insignificant effect on plant growth, with the phytotoxicity of Y being mainly produced by Y2O3 NPs.