# Lead Tolerance and Enrichment Characteristics of Three Hydroponically Grown Ormamental Plants
## 3 Results and Discussion
### Effects of Pb Stress on the Root Architecture of Ornamental Plants  
Lead stress also had a significant effect on the change in root architecture of ornamental plants (_p_ < 0.05). As the Pb concentration increased, the root length, root surface area, root volume, and root average diameter of the tested ornamental plants also exhibited different degrees of change (Figure 3). Compared with the CK, the root length of _T. patula_, _S. nigrum_, and _M. jalapa_ decreased by 6.0% to 52.3% (62.49 to 544.55 cm), 4.7% to 66.1% (12.81 to 182.22 cm), and 31.7% to 70.3% (48.64 to 107.66 cm) (with the exception of _T. patula_, which increased by 8.3% under the 100 mg/L treatment) with mean values of 30.9%, 35.5%, and 52.1%, respectively. The root surface area decreased by 35.9% to 55.8% (48.51 to 75.43 cm\({}^{2}\)), 17.8% to 76.4% (10.32 to 44.39 cm\({}^{2}\)), and 20.7% to 84.2% (10.40 to 42.27 cm\({}^{2}\)) (with the exception of _T. patula_, which increased by 13.5% and 0.7% under the 100 mg/L treatments, respectively) with mean values of 45.8%, 42.8%, and 53.7%, respectively. The root volume decreased by 7.9% to 59.4% (0.17 to 1.25 cm\({}^{3}\)), 9.9% to 73.3% (0.15 to 1.13 cm\({}^{3}\)), and 34.9% to 70.6% (0.93 to 1.88 cm\({}^{3}\)) (with the exception of _T. patula_, which increased by 29.7% under the 100 mg/L treatment) with mean values of 31.7%, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Oranamental** & & & **Pb Content (mg/kg)** & & **Enrichment Coefficient** & **Translocation** \\ \cline{3-6}
**Variety** & **Treatments** & & **Shoot** & **Shoot** & **Root** & **Factor** \\ \hline _T. patula_ & CK & 43.2 \(\pm\) 6.91 e & 55.1 \(\pm\) 6.99 e & - & - & - \\  & T1 & 359.4 \(\pm\) 28.1 d & 2432.2 \(\pm\) 178.8 d & 3.59 & 24.3 & 0.15 \\  & T2 & 574.1 \(\pm\) 47.2 c & 5284.3 \(\pm\) 517.7 c & 2.87 & 26.4 & 0.11 \\  & T3 & 862.1 \(\pm\) 47.8 b & 8370.7 \(\pm\) 466.5 b & 1.72 & 16.7 & 0.10 \\  & T4 & 1074.1 \(\pm\) 111.8 a & 11,698.4 \(\pm\) 672.6 a & 1.07 & 11.7 & 0.09 \\ \hline _S. nigrum_ & CK & 32.1 \(\pm\) 3.40 e & 54.5 \(\pm\) 7.29 e & - & - & - \\  & T1 & 503.8 \(\pm\) 34.0 d & 2197.6 \(\pm\) 213.8 d & 5.04 & 22.0 & 0.23 \\  & T2 & 656.7 \(\pm\) 41.2 c & 4073.0 \(\pm\) 205.7 c & 3.28 & 20.4 & 0.16 \\  & T3 & 838.6 \(\pm\) 42.9 b & 6671.4 \(\pm\) 244.3 b & 1.68 & 13.3 & 0.13 \\  & T4 & 958.7 \(\pm\) 40.7 a & 9835.4 \(\pm\) 180.7 a & 0.96 & 9.84 & 0.10 \\ \hline _M. jalapa_ & CK & 38.5 \(\pm\) 4.58 e & 47.1 \(\pm\) 5.72 e & - & - & - \\  & T1 & 150.8 \(\pm\) 14.2 d & 1472.4 \(\pm\) 29.2 d & 1.51 & 14.7 & 0.10 \\  & T2 & 339.4 \(\pm\) 25.5 c & 2603.9 \(\pm\) 19.9 c & 1.70 & 13.0 & 0.13 \\  & T3 & 642.3 \(\pm\) 41.8 b & 4900.2 \(\pm\) 93.4 b & 1.28 & 9.80 & 0.13 \\  & T4 & 975.3 \(\pm\) 26.0 a & 8139.0 \(\pm\) 207.2 a & 0.98 & 8.14 & 0.12 \\ \hline \hline \end{tabular} _T. patula_, _Tegetes perula_. _S. nigrum_, _S. nigrum_ and _M. jalapa_, _M. jalapa_. CK, the Pb concentration in hydroponic solutions was set to 0 mg/L. Tl, the Pb concentration in hydroponic solutions was set to 100 mg/L. Tl, the Pb concentration in hydroponic solutions was set to 100 mg/L. Tl, the Pb concentration in hydroponic solutions was set to 500 mg/L, and T4, the Pb concentration in hydroponic solutions was set to 1000 mg/L. The different lowercase letters in the same column indicate significant differences (_p_ < 0.05).  
\end{table} 
Table 1: Pb content, enrichment coefficients, and translocation factors of tested ornamentals under Pb stress. 36.0%, and 50.4%, respectively. The root average diameter decreased by 30.5% to 75.9% (0.002 to 0.04 mm), 25.3% to 78.9% (0.09 to 0.41 mm), and 5.1% to 28.5% (0.02 to 0.13 mm), with mean values of 5.1%, 44.0%, and 16.8%, respectively. However, the root average diameter of _M. jalapa_ increased by 13.9% and 42.6% under the 100 mg/L and 200 mg/L treatments, respectively. The results show that the roots of the tested ornamental plants were poisoned by the heavy metal Pb to different degrees, inhibiting the growth of the root system.