## 3 Results
### The Accumulation and Translocation of Pb, Zn, Cd, and Cu in M. cordata
Moreover, we found that the colored complexes from Pb and Cu treatments occurred in the mature areas of the root tips, and the Cu treatment induced lateral root formation in advance (Figure 4a). Overall, the effect of leaf staining was not obvious, except that the leaf veins in the leaves of the _M. cordata_ exposed to Cd and Zn were stained deeper than others (Figure 5a), which was consistent with the total metal content in the stems, not in the leaves (Figure 5b,c). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Treatment** & **Metal Detected** & \
\begin{tabular}{c} **Metal Content in Roots** \\ **(ug-Piant-1)** \\ \end{tabular} &
\begin{tabular}{c} **Metal Content in Stons** \\ **Shoots (ug-Piant-1)** \\ \end{tabular} & **TF** \\ \hline CK & & ND 1 & ND & ND \\ Pb100 & Pb & 738.4 \(\pm\) 33.3 & 55.9 \(\pm\) 2.8 & 0.08 b \\ Pb500 & Pb & 585.2 b \(\pm\) 25.7 & 62.7 \(\pm\) 7.0 & 0.11 b \\ Pb1000 & & 205.6 c \(\pm\) 11.8 & 64.0 \(\pm\) 4.2 & 0.31 a \\ \hline CK & & 200.4 b \(\pm\) 12.2 & 162.6 \(\pm\) 4.6 & 0.82 c \\ Zn100 & Zn & 508.0 a \(\pm\) 39.0 & 1402.2 \(\pm\) 39.0 & 2.84 b \\ Zn500 & Zn100 & 223.6 b \(\pm\) 17.4 & 920.1 b \(\pm\) 28.7 & 4.16 a \\ Zn1000 & & 139.0 c \(\pm\) 11.1 & 607.6 \(\pm\) 54.8 & 4.44 a \\ \hline CK & & ND & ND & ND \\ Cd100 & Cd & 123.6 c \(\pm\) 7.7 & 235.6 b \(\pm\) 8.3 & 1.92 a \\ Cd500 & & 401.0 b \(\pm\) 30.2 & 382.1 a \(\pm\) 18.7 & 0.96 b \\ Cd1000 & & 356.5 a \(\pm\) 23.0 & 266.8 b \(\pm\) 10.3 & 0.50 b \\ \hline CK & & 130.0 c \(\pm\) 11.1 & 16.0 d \(\pm\) 0.8 & 1.25 a \\ Cu100 & Cu & 374.2 b \(\pm\) 15.9 & 44.2 c \(\pm\) 0.6 & 0.12 c \\ Cu500 & Cu & 489.4 a \(\pm\) 18.3 & 97.7 b \(\pm\) 5.9 & 0.20 c \\ Cu1000 & & 415.4 b \(\pm\) 15.9 & 192.7 a \(\pm\) 14.1 & 0.46 b \\ \hline \hline \end{tabular} \({}^{1}\) ND, not detected. Values are means \(\pm\) SEs (\(n=3\)) of three different experiments. Means denoted by different letters refer to the significant differences (\(p<0.05\), Duncan’s test).  
\end{table} 
Table 2: Metal content and translocation factor (TF) per plant of _M. cordata_ under control (CK) and different concentrations of Cd, Pb, Cu, and Zn after 20 days of exposure. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Treatment** & **Metal Detected** & \
\begin{tabular}{c} **Metal Content in Roots** \\ **(ug-Piant-1)** \\ \end{tabular} &
\begin{tabular}{c} **Metal Content in Stons** \\ **Shoots (ug-Piant-1)** \\ \end{tabular} & **TF** \\ \hline CK & & ND 1 & ND \\ Pb100 & Pb & 738.4 \(\pm\) 33.3 & 55.9 \(\pm\) 2.8 & 0.08 b \\ Pb500 & Pb & 585.2 b \(\pm\) 25.7 & 62.7 a \(\pm\) 7.0 & 0.11 b \\ Pb1000 & & 205.6 c \(\pm\) 11.8 & 64.0 a \(\pm\) 4.2 & 0.31 a \\ \hline CK & & 200.4 b \(\pm\) 12.2 & 162.6 d \(\pm\) 4.6 & 0.82 c \\ Zn100 & Zn & 508.0 a \(\pm\) 39.0 & 1402.0 a \(\pm\) 39.0 & 2.84 b \\ Zn500 & Zn & 223.6 b \(\pm\) 17.4 & 920.1 b \(\pm\) 28.7 & 4.16 a \\ Zn1000 & & 139.0 c \(\pm\) 11.1 & 607.6 c \(\pm\) 54.8 & 4.44 a \\ \hline CK & & ND & ND \\ Cd100 & Cd & 123.6 c \(\pm\) 7.7 & 235.6 b \(\pm\) 8.3 & 1.92 a \\ Cd500 & & 401.0 b \(\pm\) 30.2 & 382.1 a \(\pm\) 18.7 & 0.96 b \\ Cd1000 & & 536.5 a \(\pm\) 23.0 & 266.8 b \(\pm\) 10.3 & 0.50 b \\ \hline CK & & 130.0 c \(\pm\) 11.1 & 16.0 d \(\pm\) 0.8 & 1.25 a \\ Cu1000 & Cu & 374.2 b \(\pm\) 15.9 & 44.2 c \(\pm\) 0.6 & 0.12 c \\ Cu500 & Cu & 489.4 a \(\pm\) 18.3 & 97.7 b \(\pm\) 5.9 & 0.20 c \\ Cu1000 & & 415.4 b \(\pm\) 15.9 & 192.7 a \(\pm\) 14.1 & 0.46 b \\ \hline \hline \end{tabular} \({}^{1}\) ND, not detected. Values are means \(\pm\) SEs (\(n=3\)) of three different experiments. Means denoted by different letters refer to the significant differences (\(p<0.05\), Duncan’s test).  
\end{table} 
Table 1: Contents of Pb, Zn, Cd, and Cu in roots, stems, and leaves of _M. cordata_ under control (CK) and different concentrations of Cd, Pb, Cu, and Zn after 20 days of exposure. Figure 4: Dithizone staining in root tips (**a**) and metal content in roots (**b**) of _M. cordata_ under control (CK) and 100 umol\(\cdot\)L\({}^{-1}\) Cd, Pb, Cu, and Zn after 20 days of exposure.