## 3 Results and Discussion
### Biomass Growth  
_Atriplex halimus_ plant cuttings were evaluated for root and sprout quality and for biomass growth at the end of the experiment (week 8). The rooting and sprouting quality scores are reported in Table 4, where the best scores were observed in plants grown in the control soil (B) and in the polluted substrate amended (CP + CI), highlighting that amendments improve rooting and sprouting performance. However, sprout scores in both contaminated substrates remained lower than those in the control, indicating that shoot development was overall more affected by substrate conditions. Figure 1: Plant survival in the tested substrates at week 5 (mid-term) and week 8 (end). Dry biomass measurements further clarified the observed differences in sprout and root performance. As shown in Figure 2A, sprout dry weight was significantly higher in the control substrate (B) compared to both CP and CP + CI, confirming the trend already observed in the sprouting quality scores (Table 4). In contrast, root biomass was higher in CP and CP + CI (49.3 mg and 64.9 mg, respectively), while the control (B) recorded the lowest value (13.7 mg). This result diverges from previous findings [23,31], where root biomass was typically reduced in contaminated soils. In our study, root development seemed to be enhanced in polluted substrates, possibly reflecting a plastic response to environmental stress [47,48], whereby the plant allocates more biomass to root systems to improve resource acquisition under suboptimal conditions. Importantly, despite its lower biomass, the control substrate showed the highest root quality score (Table 4), indicating the formation of healthy and branched roots. As per the evaluation criteria (Table 1), such scores reflect morphological features (number, length, health, branching) rather than mass. This supports the idea that root quality and biomass may reflect distinct aspects of plant adaptation, with _A. halimus_ developing structurally functional roots in optimal conditions (B) and more massive root systems in stressed environments (CP, CP + CI). In contrast, sprout biomass was significantly higher in the control substrate (B) (367 mg dry weight) compared to 147 mg in CP + CI and 139 mg in CP. These results suggest that metal contamination may have hindered aerial growth, while root development was not equally affected. Similar effects were reported in previous studies with _Atriplex halimus_[16,31,49] and _Halimione portulacoides_[23]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Roots**} & \multicolumn{3}{c}{**Sprouts**} \\  & **B** & **CP** & **CP + CI** & **B** & **CP** & **CP + CI** \\ \hline \multirow{2}{*}{Score} & 2.8 \(\pm\) 0.2 & 1.6 \(\pm\) 0.2 & 2.8 \(\pm\) 0.2 & 4.0 \(\pm\) 0 & 1.8 \(\pm\) 0.4 & 2.4 \(\pm\) 0.2 \\  & (a) & (b) & (a) & (a) & (b) & (b) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Evaluation of stage and quality of rooting and sprouting (Means \(\pm\) SE, \(n\) = 5). Different letters indicate significant differences among substrates at \(p\leq\) 0.05. Figure 2: Dry weight (**A**) and water content of roots and sprouts (**B**) in the tested substrates. Bars indicate SE (5 replicates). Different letters indicate, separately for roots and sprouts, significant differences among substrates at \(p\leq\) 0.05. No statistically significant correlations were detected between stem biomass and either sprout or root biomass (assuming Spearman coefficient of 0.4 and 0.01, respectively), confirming that the original stem did not influence the production of new biomass/tissues, as already reported by [50] for willow and poplar, and by [51] for willow. This suggests that cutting performance was mainly determined by the interaction with the substrate. Amendments improved root growth, especially in CP + CI, but did not significantly enhance sprout biomass within the 8-week experimental period. It is conceivable that a longer experimental duration may be required to observe the positive effects of compost on shoot development.