The effects of cerium oxide nanoparticles (CeO2-NPs) on 15N/14N ratio (δ15N) in wheat and barley were investigated. Seedlings were exposed to 0 and 500 mg CeO2-NPs/L (Ce-0 and Ce-500, respectively) in hydroponic suspension supplied with NH4NO3, NH4 +, or NO3 -. N uptake and δ15N discrimination (i.e. differences in δ15N of plant and δ15N of N source) were measured. Results showed that N content and 15N abundance decreased in wheat but increased in barley. Ce-500 only induced whole-plant δ15N discrimination (-1.48‰, P ≤ 0.10) with a simultaneous decrease (P ≤ 0.05) in whole-plant δ15N (-3.24‰) compared to Ce-0 (-2.74‰) in wheat in NH4 +. Ce-500 decreased (P ≤ 0.01) root δ15N of wheat in NH4NO3 and NH4 + (3.23 and -2.25‰, respectively) compared to Ce-0 (4.96 and -1.27‰, respectively), but increased (P ≤ 0.05) root δ15N of wheat in NO3 - (3.27‰) compared to Ce-0 (2.60‰). Synchrotron micro-XRF revealed the presence of CeO2-NPs in shoots of wheat and barley regardless of N source. Although the longer-term consequences of CeO2-NP exposure on N uptake and metabolism are unknown, the results clearly show the potential for ENMs to interfere with plant metabolism of critical plant nutrients such as N even when toxicity is not observed.

中文翻译：

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暴露于氧化铈纳米粒子的小麦和大麦中 N 和 δ15N 的变化

研究了氧化铈纳米粒子 (CeO2-NPs) 对小麦和大麦中 15N/14N 比值 (δ15N) 的影响。将幼苗暴露于含有 NH4NO3、NH4 + 或 NO3 - 的水培悬浮液中的 0 和 500 mg CeO2-NPs/L（分别为 Ce-0 和 Ce-500）。测量氮吸收和δ15N辨别（即植物的δ15N和氮源的δ15N的差异）。结果表明，小麦的氮含量和 15N 丰度下降，而大麦的氮含量和 15N 丰度则增加。与小麦中的 Ce-0 (-2.74‰) 相比，Ce-500 仅诱导全株 δ15N 歧视 (-1.48‰，P ≤ 0.10)，同时全株 δ15N (-3.24‰) 降低 (P ≤ 0.05)在NH4+中。与Ce-0（分别为4.96和-1.27‰）相比，Ce-500在NH4NO3和NH4+中降低（P≤0.01）小麦根部δ15N（分别为3.23和-2.25‰），但增加（P≤0.05）根部δ15N小麦中 NO3 中的 δ15N - (3.27‰) 与 Ce-0 (2.60‰) 相比。同步加速器微型 XRF 揭示了无论氮源如何，小麦和大麦的芽中都存在 CeO2-NP。尽管 CeO2-NP 暴露对氮吸收和代谢的长期影响尚不清楚，但结果清楚地表明，即使没有观察到毒性，ENM 也有可能干扰植物关键营养物质（例如氮）的代谢。