Shifts in N and δ15N in wheat and barley exposed to cerium oxide nanoparticles


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, and 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 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.

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Environmental engineered nanomaterial, Isotope, Nitrogen, Synchrotron micro-XRF

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