In vivo phytotoxic effect of yttrium-oxide nanoparticles on the growth, uptake and translocation of tomato seedlings (Lycopersicon esculentum).

The potential toxicity and ecological risks of rare-earth nanoparticles in the environment have become a concern due to their widespread application and inevitable releases. The integration of hydroponics experiments, partial least squares structural equation modeling (PLS-SEM), and Transmission Electron Microscopy (TEM) were utilized to investigate the physiological toxicity, uptake and translocation of yttrium oxide nanoparticles (Y ₂ O ₃ NPs) under different hydroponic treatments (1, 5, 10, 20, 50 and 100 mg·L ^-1 of Y ₂ O ₃ NPs, 19.2 mg·L ^-1 Y(NO ₃ ) ₃ and control) in tomato (Lycopersicon esculentum) seedlings. The results indicated that Y ₂ O ₃ NPs had a phytotoxic effect on tomato seedlings' germination, morphology, physiology, and oxidative stress. The Y ₂ O ₃ NPs and soluble Y ^III reduced the root elongation, bud elongation, root activity, chlorophyll, soluble protein content and superoxide dismutase and accelerated the proline and malondialdehyde in the plant with increasing concentrations. The phytotoxic effects of Y ₂ O ₃ NPs on tomato seedlings had a higher phytotoxic effect than soluble Y ^III under the all treatments. The inhibition rates of different levels of Y ₂ O ₃ NPs in shoot and root biomass ranged from 0.2% to 6.3% and 1.0-11.3%, respectively. The bioaccumulation and translocation factors were less than 1, which suggested that Y ₂ O ₃ NPs significantly suppressed shoot and root biomass of tomato seedlings and easily bioaccumulated in the root. The observations were consistent with the process of concentration-dependent uptake and translocation factor and confirmed by TEM. Y ₂ O ₃ NPs penetrate the epidermis, enter the cell wall, and exist in the intercellular space and cytoplasm of mesophyll cells of tomato seedlings by endocytic pathway. Moreover, PLS-SEM revealed that the concentration of NPs significantly negatively affects the morphology and physiology, leading to the change in biomass of plants. This study demonstrated the possible pathway of Y ₂ O ₃ NPs in uptake, phytotoxicity and translocation of Y ₂ O ₃ NPs in tomato seedlings.
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