**4.4 The impact of different concentrations of some heavy metals on some growth indicators of** *Lantana camera* **under** *in vitro* **culture conditions**

### *4.4.1 Cadmium (Cd)*

The data in **Table 7** indicate that there is no significant effect of the heavy metal cadmium concentrations in plantlet height, compared with the control treatment. It is also noted from the same table that there is no significant effect in each of the characteristics of the leaf numbers and the shoot dry weights among all treatments. While the addition of the cadmium heavy metal to the MS medium had a significant effect, as the plantlets treated with a concentration of 0.8 mg L−1 were significantly superior in the total shoot fresh weights, reaching 0.461 g, compared with the other treatments [27].

The data of the phytoremediation in **Table 7** for the *Lantana camera* plant show that there is no significant effect of different cadmium concentrations among all treatments in each of the shoot numbers plantlet−1, leaf area (cm2 ), and total chlorophyll content of the leaves (mg.100 g−1 fresh weight) (**Figure 3**).

The reason may be attributed to the use of plants to absorb these heavy metals from the culture media and translocate them to the vegetative organs or convert them into volatile compounds using the phytovolatilization technique. This technique exploits the ability of some plants to convert some heavy elements into volatile compounds for disposal [38].

The reason for this may be because the plant is a natural phytoremediator, as it can accumulate the contaminant, break it down, or assemble it in its biomass, and it is characterized by being a fast-growing plant and having a large biomass and having a widespread root system [39].

The data in **Table 8** show the effect of cadmium on the root growth indicators of the *L. camara* plantlets. It is noted that there are no significant differences in the number of main roots per plantlet in all treatments. It is also observed from the same table that there were no significant differences among all cadmium treatments in each of the root length and dry weight characteristics, while the data are shown in the same table



*The Efficiency of Phytoremediation of the Big-Sage Plant in Accumulating Some Heavy Metals… DOI: http://dx.doi.org/10.5772/intechopen.109640*

### **Figure 3.**

*Effect of different concentration of cadmium on plantlet growth of* Lantana camara *shrub [37].*


### **Table 8.**

*Effect of different concentrations of cadmium on some root growth of* Lantana camara *shrub [37].*

that there was a significant effect in the fresh weight of the roots in the MS medium to which the cadmium heavy metal was added. The MS medium supplemented with 0.8 mg L−1 cadmium was significantly superior in the root fresh weight, reaching 0.114 g. This is explained as the ideal concentration of *L. camara*. Despite the toxicity of the lead element, the big-sage shrub showed a phytoremediator for this heavy metal.

This can be explained by our findings is the ability of the big-sage plant to accumulate and be tolerant to cadmium heavy metal. Al-Wahaibi [40] indicated the characteristics of the accumulating plants when they absorb heavy elements, they stimulate the form of chelating compounds that surround the atoms of the contaminating elements and keep them within the vacuoles found in the cells of plant tissues.

### *4.4.2 Cobalt (Co)*

**Table 9** shows the effect of different concentrations of the heavy element cobalt on the vegetative growth indicators (**Figure 4**). The data showed that there was no significant effect on the characteristics of each of the plant's height (cm), leaf numbers, and the fresh and dry weights of the shoots (g) among all treatments [27].


**Table 9.** *Effect of different concentrations of cobalt on some vegetative growth of* Lantana camara *shrub [37].* *The Efficiency of Phytoremediation of the Big-Sage Plant in Accumulating Some Heavy Metals… DOI: http://dx.doi.org/10.5772/intechopen.109640*

**Figure 4.** *Effect of different concentration of cobalt on plantlet growth of* Lantana camara *shrub [37].*

**Table 9** includes the effect of different cobalt heavy metal concentrations on the shoot numbers per plantlet. There was no significant effect of the element cobalt in this characteristic among all treatments. The addition of cobalt to the MS medium had no significant effect on the total chlorophyll content of leaves in all treatments.

The different concentrations of the heavy element cobalt had a significant effect on the leaf area. The treatment with 0.8 mg L−1 cobalt showed a significant effect on the leaf area, reaching 3.00 cm2 compared with other treatments, except for the treatment with 0.6 mg L−1 cobalt, which did not differ significantly from it, reaching 2.70 cm2 .

The reason for this is that the heavy metal ions that enter the cell are associated with the chelators and companions. These chelating compounds remove the toxicity of metals by transporting minerals to the cytosol, while the companion transfer minerals to the organelles to reach the proteins that require metal. There are many chelating metal compounds and well-known chelators in plants, including phytochelatins, metallothioneins, organic acids, and amino acids [41].

The data of **Table 10** showed the effect of adding different cobalt concentrations of the MS medium on root growth indicators of *L. camara*. It was observed that there


### **Table 10.**

*Effect of different concentrations of cobalt on some root growth of* Lantana camara *shrub [37].*



*The Efficiency of Phytoremediation of the Big-Sage Plant in Accumulating Some Heavy Metals… DOI: http://dx.doi.org/10.5772/intechopen.109640*

was no significant effect on some root growth characteristics, including the main root numbers per the plantlet, root length, and root dry weights.

The contamination of the MS medium with cobalt had a significant effect on the total root fresh weights. The treatment at 0.8 mg L−1 cobalt was significantly superior in this characteristic, reaching 0.055 g compared with the treatments at 0.6 mg L−1 cobalt and the control, which reached 0.026 g.

The reason for this may be that plants exposed to high levels of cobalt, more than the permissible levels of heavy metals, show symptoms of toxicity due to excessive treatment of cobalt, which is more than what most species need. Moreover, cobalt toxicity rarely occurs when plants are exposed to low levels [42]. Therefore, the *L. camara* shrub showed tolerance for this heavy metal.

*4.4.3 Lead (Pb)*

The data in **Table 11** show that there are no significant differences in the characteristics of vegetative organs, plantlet height (cm), leaf numbers, and fresh and dry weights of the shoot (g) of *L. camara* shrub grown in MS media that supplemented with different concentrations of lead heavy metal (**Figure 5**) [27].

The data in **Table 11** show that there were no significant differences when the MS medium was contaminated with lead after 1 month of the experiment in each of the characteristics of the number of leaves per shoot, leaf area (cm2 ), and total chlorophyll content of leaves (mg 100 g−1 fresh weight).

The data of **Table 12** indicate that there are no significant differences when adding lead at the different concentrations in the MS medium in each of the characteristics of the main root numbers per the plantlet, root length (cm), and the fresh and dry weights of the root parts (g).

This can be explained by the limited transport of lead through the root, as a result of the precluding caused by the Casparian strip in the root endodermis, which prevents the translocation of lead through the endodermis to the central vascular cylinder tissues.


### **Table 12.**

*Effect of different concentrations of lead on some root growth of* Lantana camara *shrub [37].*

Whereas the accumulation of lead depends on the species, variety, and plant organ, and then increases in the accumulation within the root organs compared with the vegetative organs, and then a decrease occurs in some characteristics of the vegetative organs such as total fresh weight of the shoots when the concentration of lead is increased, which causes a difference in the characteristics of the roots at the expense of the characteristics of the vegetative parts [43].
