*2.5. Data Analysis*

Statistical analysis was carried out with three-, two- and one-way analysis of variance (ANOVA). When necessary, data were subjected to logarithmic transformation prior to analysis, which effectively homogenized the variances and produced approximately normal distributions. A posteriori comparison of individual means was performed using Tukey's test (*p* < 0.05). Differences between treatments for the different measured variables were tested using one-way ANOVA. Data are expressed as mean ± standard deviation (SD). Sp–ICP–MS data on nanoceria size distribution were processed by means of Syngistix Nano Application Module software (PerkinElmer Waltham, MA, USA) and interpolated with polynomial curves.

The *n*CeO2 concentration range (0–2000 mg <sup>L</sup>−1) was chosen considering that the large body of literature studies reporting the effects of *n*CeO2 on plant physiology used Ce concentrations in the range 1–1000 mg L−<sup>1</sup> [4,37], while the phytotoxicity test, as recommended by the USEPA approach, used the 2000 mg L−<sup>1</sup> level [38].
