*Article* **Single and Repeated Applications of Cerium Oxide Nanoparticles Differently Affect the Growth and Biomass Accumulation of** *Silene flos-cuculi* **L. (***Caryophyllaceae***)**

**Daniel Lizzi 1,2, Alessandro Mattiello 1, Barbara Piani 1, Emanuele Gava 3, Guido Fellet <sup>1</sup> and Luca Marchiol 1,\***


**Abstract:** Cerium oxide nanoparticles (*n*CeO2) have a wide variety of applications in industry. Models demonstrated that *n*CeO2 can reach environmental compartments. Studies regarding the relationships between plants and *n*CeO2 considered only crop species, whereas a relevant knowledge gap exists regarding wild plant species. Specimens of *Silene flos-cuculi* (*Caryophyllaceae*) were grown in greenhouse conditions in a substrate amended with a single dose (D1) and two and three doses (D2 and D3) of 20 mg kg−<sup>1</sup> and 200 mg kg−<sup>1</sup> *n*CeO2 suspensions, respectively. sp-ICP-MS and ICP-MS data demonstrated that *n*CeO2 was taken up by plant roots and translocated towards aerial plant fractions. Biometric variables showed that plants responded negatively to the treatments with a shortage in biomass of roots and stems. Although not at relevant concentrations, Ce was accumulated mainly in roots and plant leaves.

**Keywords:** cerium oxide nanoparticles; terrestrial ecosystem; wild plant species; plant growth
