## 3 Results
### Relationship between HMs Contents in Soil and in Plants  
The analysis of the HM content in hemp plants revealed different behaviours depending on the metal analysed or the plant fraction observed. To understand the distribution of the HMs in the different parts of hemp plants, Table 2 shows the metal concentrations observed, for each cultivated variety, in the two experimental sites. In Table 2, as expected, differences in HM concentrations were significant between Site 3 (polluted site) and Site 5 (unpolluted site) for all metals considered. The hemp variety Uso 31 seems to be that which tends to accumulate the highest concentrations of Cd and Zn. The concentrations of metals in the different cultivars varied in the two sites considered and this behaviour is highlighted by the significant site \(\times\) variety interaction. Once again, the trend of the contents of Zn and Cd were similar. The highest concentrations of HMs were observed in the variety Uso 31 followed by Felina 32, both in Site 3 (polluted), while the other highest value was found in Futura 75 of Site 5 (unpolluted). These different ranks determine the significant interaction observed. Basically, no significant variety \(\times\) parts and site \(\times\) variety \(\times\) parts interactions were observed but Site \(\times\) parts of plants interaction were significant (Table 2). The Pb value in leaves was 8.77 mg kg\({}^{-1}\) in Site 3, and 9.33 mg kg\({}^{-1}\) in Site 5, whereas Pb in seeds was significantly higher and almost double in Site 5 (2.80 mg kg\({}^{-1}\)) that in Site 3 (1.54 mg kg\({}^{-1}\)), that was classified as polluted. Comparable values in leaves and seeds between sites 3 and 5 were observed. The biplot where scores and loadings obtained by the PCA were represented together were reported in Figure 2. The biplot graphically represents the main correlation existing between concentrations of HMs in part of the plants and the corresponding HMs contents in the soil where plants were cultivated. The first two principal components account for 90.2% of the total variance and, hence, provide a good representation of the relations among the variables. The disposition and the magnitude of the blue vectors obtained by the PCA provide qualitative information on the correlation between the variables. In Figure 2 the vectors, which represented available and total HMs content in the soil, are disposed essentially in the same direction of the scores representing the polluted site (Site 3). This arrangement indicates a greater presence of HMs in soil, both total and available concentrations, at Site 3. The vectors of HMs in soil are arranged in the same direction as the vectors that represent the concentrations of the metals (Zn, Cd and Pb) contained in the different parts of the plant. This indicates essentially a greater presence of HMs in the different parts of the plants at Site 3. Unlike other metals, different directions are observed for Pb content in seeds and leaves. The total Pb observed in soil in Site 5 (not polluted) was significantly lower than in Site 3 as already statistically observed (Table 1) and is contrary to what was observed for metals concentrations in parts of plants. Indeed, the observed Pb was statistically equal (leaves) if not higher (seeds) in plants of Site 5 compared with those of Site 3 (polluted also for Pb). As shown in Figure 2, the same directions of metal in plants and in soils do not seem to distinguish between available and total metal contents in soils.