*2.6. Statistical Procedures*

All data were subjected to Shapiro–Wilk and Levene's test, in order to check for normal distribution and homoscedasticity, respectively, then to a 'As concentration × rootstock' analysis of variance (ANOVA), according to the split-plot experimental layout adopted in the greenhouse. Percentage data were Bliss' transformed before the ANOVA (untransformed data are reported and discussed), while multiple means comparison was performed through Fisher's protected least significant difference (LSD) test (*p* = 0.05). The As concentrations in root, shoot, and pulp were subjected at principal component analysis (PCA) to verify the interaction between the different factors able to synthetize the considered variables. All calculations were performed using the Excel (Microsoft Corporation, Redmond, WA, USA) and JMP 11.0 statistical software package (SAS Institute, Cary, NC, USA).

#### *2.7. Microclimate Conditions Inside the Greenhouse*

During the experiment, the average mean temperature progressively increased from 18.6 to 26.4 ◦C (on day 12 and 36 after transplanting, respectively), while relative humidity showed an opposite trend, as it passed from 63.7% to 40.5% (on day 11 and 33 after transplanting, respectively). Solar radiation amply paralleled the trend of mean temperature, as it progressively increased passing from 10.45 to 15.02 MJ m−<sup>2</sup> (on day 11 and 36 after transplanting, respectively). As regards the spatial variability among main plots, the differences in terms of mean temperature, relative humidity, and solar radiation never exceeded 0.2 ◦C, 2.1%, and 0.8 MJ m<sup>−</sup>2, respectively.

### **3. Results**
