Impact of Abiotic Stresses on Plant Uptake and Accumulation of Cerium Oxide Nanoparticles.

Dietary consumption of plants exposed to cerium oxide nanoparticles (CeO₂NPs) has been recognized as one of the most important pathways for human exposure to this emerging material. Consequently, numerous studies have been performed to investigate the extent of plant uptake and accumulation of CeO₂NPs and the underlying mechanisms. Almost all previous studies were conducted in well controlled environments, with often optimal growth conditions for plants. However, evidences have emerged that plant uptake and accumulation of CeO₂NPs in environmentally stressed conditions differ from those grown in well controlled conditions. Therefore, there is an imperative need to understand the plant uptake of CeO₂NPs at environmentally relevant conditions to realistically evaluate the risks of dietary consumption of CeO₂NPs affected plants. As a response, we examined the uptake and accumulation of CeO₂NPs by different plant species in the presence of various environmental stresses and our results indeed indicate that abiotic stresses play significant roles in the interactions of plants and CeO₂NPs. For example, after irrigation with 100 mM NaCl for forty days, Brassica in CeO₂NPs-laden soil accumulated significantly higher Ce in both root and leaf tissues than plants irrigated with tap water. Similarly, Brassica accumulated substantially higher Ce in both root and leaf tissues when 1.0 mg/kg of cadmium was co-present in the soil. Clearly, plants display a significantly different capacity to accumulate Ce in their tissues in environmentally relevant conditions than in controlled environments. Caution, therefore, must be exercised to extrapolate results obtained in a greenhouse to the natural environment. Detailed results regarding the role of abiotic stresses on plant uptake and accumulation of CeO₂NPs will be presented and mechanistic insights discussed.