## 3 Results and Discussion
### Chlorophyll and Carotenoids  
Plants showed good health conditions during the entire experimental period, as no visual stress symptoms such as chlorosis or leaf necrosis were observed, unlike the symptoms reported by [31] in plants exposed to high Cu concentrations. The contents of chlorophyll a (Chla), chlorophyll b (Chlb), and total chlorophylls (Chla+b), as reported in Table 5, showed significant differences among the treatments. The highest pigment concentrations were observed in plants grown on the unamended contaminated substrate (CP). In contrast, plants grown on CP + CI exhibited the lowest Chla and Chla+b values, suggesting that amendments may have influenced pigment production. Carotenoid contents (Cx+c) followed a similar trend to Chlb, with higher values in CP compared to the other treatments. Carotenoids, including ca \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Substrates** & **Ca** & **Cb** & **Cx+c** & **Ca+Cb** & **Ca/Cb** & **(Cx+c)/(Ca+b)** \\  & **(mg g\({}^{-1}\))** & **(mg g\({}^{-1}\))** & **(mg g\({}^{-1}\))** & **(mg g\({}^{-1}\))** & \\ \hline B & 1.11 \(\pm\) 0.03 b & 0.4 \(\pm\) 0.02 b & 0.37 \(\pm\) 0.01 b & 1.52 \(\pm\) 0.05 b & 2.81 \(\pm\) 0.1 a & 0.24 \(\pm\) 0.01 c \\ CP & 1.46 \(\pm\) 0.05 a & 0.52 \(\pm\) 0.02 a & 0.5 \(\pm\) 0.02 a & 1.99 \(\pm\) 0.07 a & 2.81 \(\pm\) 2 a & 0.25 \(\pm\) 0 c \\ CP + CI & 0.87 \(\pm\) 0.04 c & 0.32 \(\pm\) 0.02 b & 0.38 \(\pm\) 0.01 b & 1.19 \(\pm\) 0.06 c & 2.75 \(\pm\) 0.04 a & 0.32 \(\pm\) 0.01 a \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Plant chlorophyll and carotenoid content and plant chlorophyll and carotenoid relationships in the tested substrates. (Means \(\pm\) SE, \(n\) = 3). Different letters indicate significant differences among substrates at \(p\leq\) 0.05.  
are known to contribute to the protection of photosynthetic structures under conditions of oxidative stress [57]. Under environmental stress, chlorophyll content often decreases, while carotenoid content tends to increase [58]. An increase in the Cx+c/Chla+b ratio is typically associated with stress responses [59]. However, in our study, this ratio was significantly lower in CP, suggesting no evident oxidative stress, despite the high metal concentrations. The Chla/Chlb ratio remained similar across all treatments, indicating no major alteration in pigment composition, in agreement with [39]. This suggests that the photosynthetic apparatus was not negatively affected by metal contamination. Metal stress typically leads to chlorophyll degradation and photosynthesis inhibition. For example, Ref. [60] described the substitution of Mg\({}^{2+}\) in chlorophyll molecules by toxic metals such as Cd, Pb, or Zn, which can damage the photosynthetic system. However, responses vary across species. Some halophytes, such as _Tamariz gallica_ exposed to As and NaCl [61], showed no significant changes in chlorophyll and carotenoid content, similar to what was observed in this study. Ref. [62] reported no Cd-induced reduction in chlorophyll in _Atriplex nummuralia_, while [10] found that Pb reduced chlorophyll in _Atriplex halimus_, but Zn had no effect. Similarly, Ref. [63] observed a reduction in chlorophyll with increasing Cd concentrations, and [64] reported chlorophyll degradation under Cu stress. In contrast, Ref. [31] observed no significant changes in photosynthetic pigments in _Atriplex halimus_ grown in Cu-polluted substrate. This variability suggests that chlorophyll content alone may not be a reliable stress indicator in this species, particularly during early growth stages. In our study, the high chlorophyll content observed in CP plants aligns with the results of [16], who reported increased chlorophyll levels in _Atriplex halimus_ grown in As-contaminated substrates. Additionally, Ref. [10] suggested that Pb may have a stimulatory effect on chlorophyll synthesis, consistent with the higher pigment concentrations observed in CP in this experiment.