Cadmium tolerance and accumulation of Althaea rosea Cav. and its potential as a hyperaccumulator under chemical enhancement.

The role of ornamental plants has drawn much attention as the urban pollution levels exacerbate. Althaea rosea Cav. had showed its strong tolerance and accumulation ability of Cd in our previous work, thus, the effects of ethylenediamine triacetic acid (EDTA), ethylenegluatarotriacetic acid (EGTA) and sodium dodecyl sulfate (SDS) on its Cd phytoremediation capacity were further investigated in this work. It reconfirmed that the species had strong tolerance and accumulation ability of Cd. Particularly, the species can be regarded as a potential Cd-hyperaccumulator through applying chemical agents. However, different chelators and surfactants had great differences in affecting hyperaccumulating characteristics of the species. EGTA and SDS could not only increase the dry biomass of the plants, but also promote Cd accumulation in shoots and roots. On the contrary, EDTA was toxic to the species by restraining the growth of plants, although it could promote Cd accumulation in shoots and roots of the plants to a certain extent. Thus, EGTA and SDS were effective in enhancing phytoremediation with Althaea rosea Cav. for Cd contaminated soils, while EDTA is ineffective in this regard.

Identification and chemical enhancement of two ornamental plants for phytoremediation.

With an increase in the contamination of urban areas, more and more attention has been paid to the role of ornamental plants in remedying contaminated soils. Thus, cadmium (Cd) tolerance and accumulation characteristics of Calendula officinalis and Althaea rosea as ornamental plants under the concentration gradient experiment with single Cd, as well as the effect of ethylenegluatarotriacetic acid (EGTA) and sodium dodecyl sulfate (SDS) on their Cd phytoremediation capacity under the chemically enhanced experiment was further investigated. It was showed that they had strong tolerance and accumulation capacity of Cd under single Cd treatments, thus they had great potential to be used for Cd contaminated soil remediation. Furthermore, under chemically enhanced treatments, the great efficiency was found through applying EGTA and SDS, they could not only increase the dry biomass of the plants, but also promote the Cd accumulation in shoots and roots. Particularly, Althaea rosea can be regarded as a potential Cd-hyperaccumulator through applying chemical agents. In conclusion, the two ornamental plants are promising to be used for phytoremediation.

Growth responses of three ornamental plants to Cd and Cd-Pb stress and their metal accumulation characteristics.

Up to now, there was no document on ornamental plants that had been applied to phytoremediation, which can remedy contaminated environment and beautify it at the same time. Thus, the growth responses and possible phytoremediation ability of three ornamental plants selected from the previous preliminary experiments were further examined under single Cd or combined Cd-Pb stress. The results showed that these tested plants had higher tolerance to Cd and Pb contamination and could effectively accumulate the metals, especially for Calendula officinalis and Althaea rosea. For C. officinalis, it grew normally in soils containing 100 mg kg(-1) Cd without suffering phytotoxicity, and the Cd concentration in the roots was up to 1084 mg kg(-1) while the Cd concentration in the shoots was 284 mg kg(-1). For A. rosea, the Cd accumulation in the shoots was higher than that in the roots when the Cd concentration in soils was <100 mg kg(-1), and reached 100 mg kg(-1) as the criteria of a Cd hyperaccumulator when the Cd concentration in soils was 100 mg kg(-1). Their accumulation and tolerance to Cd and Pb were further demonstrated through the hydroponic-culture method. And A. rosea had a great potential as a possible Cd hyperaccumulator under favorable or induced conditions. Furthermore, the interactive effects of Cd and Pb in the three ornamentals were complicated, not only additive, antagonistic or synergistic, but also related to many factors including concentration combinations of heavy metals, plant species and various parts of plants. Thus, it can be forecasted that this work will provide a new way for phytoremediation of contaminated soils.