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ERIE Research Projects

Phytoremediation using macroalgal species, Chara australis

Participants:

ERIE Fellows: Bernadette Clabeaux, Biology
Faculty: Mary A. Bisson, Biology

Key terms:

Phytoremediation, Cadmium, Chara australis

Summary:

Bernadette Clabeaux is investigating the utilization of plants and vegetation for ecosystem restoration purposes. Her research involves employing the macroalgal species, Chara australis, as a model plant for the remediation of soils contaminated with cadmium (Cd). The remediation process, termed phytoremediation, involves the accumulation of Cd from the soil by Chara rhizoids, which are root-like structures, and subsequent translocation of the contaminant to aboveground shoot tissues. In practice, once Cd is localized to aboveground shoot tissues, the plant tissues can be harvested, incinerated and disposed of properly, reducing the levels of contaminants in soils.

Clabeaux's preliminary results show that Chara is capable of accumulating Cd within its rhizoids, and translocating it to shoot tissues. As Cd concentration in the soil increases from 0 to 20 ppm Cd, the amount of Cd taken up by Chara rhizoids and shoots also increases to levels above that present in the soil (Figure 1).Cd uptake by Chara Shoots and Rhizoids

 

Figure 1: Cadmium accumulation by Chara australis shoots and rhizoids as a function of soil Cd concentration.

 

 

 

To visualize Cd localization, staining of live Chara shoots and rhizoids with Dithizone reagent was performed. Cd was shown to be localized within the cytoplasm of shoots and rhizoids, along the cell wall of shoots and rhizoids, and within the apoplast of the nodal complex (Figure 2).

Cd in Chara shoot Figure 2: Localization of Cd in Chara shoot exposed to 20 ppm Cd for 90 days.  Staining was performed in live Chara cells with dithizone reagent, which forms a rust-colored precipitate when bound to cadmium (solid arrow). Cytoplasmic “tails” (dashed arrow) indicate Cd localization within the cytoplasm. Control shoot cells stained with dithizone show no precipitate formation.

 

Preliminary evidence suggests that the mechanism of Cd uptake in Chara may be via zinc (Zn)transporters, since the inhibition of Chara growth by Cd was alleviated by the addition of low levels of Zn, and vice versa. The effect of Zn on Cd uptake in Chara will be investigated in the near future. In addition, tolerance mechanisms of Chara will be studied by measuring the levels of glutathione and phytochelatins (both indicators of heavy metal stress) produced by the plant in response to Cd exposure.

Clabeaux's current results indicate that Chara spp. are  potential candidates for the remediation of soils in contaminated aquatic environments.

 

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