Characteristics of cadmium uptake in two contrasting ecotypes of the hyperaccumulator Thlaspi caerulescens

Abstract

Uptake of Cd and Zn by intact seedlings of two contrasting ecotypes of the hyperaccumulator Thlaspi caerulescens was characterized using radioactive tracers. Uptake of Cd and Zn at 2 degrees C was assumed to represent mainly apoplastic binding in the roots, whereas the difference in uptake between 22 degrees C and 2 degrees C represented metabolically dependent influx. There was no significant difference between the two ecotypes in the apoplastic binding of Cd or Zn. Metabolically dependent uptake of Cd was 4.5-fold higher in the high Cd-accumulating ecotype, Ganges, than in the low Cd-accumulating ecotype, Prayon. By contrast, there was only a 1.5-fold difference in the Zn uptake between the two ecotypes. For the Ganges ecotype, Cd uptake could be described by Michaelis-Menten kinetics with a V(max) of 143 nmol g(-1) root FW h(-1) and a K(m) of 0.45 microM. Uptake of Cd by the Ganges ecotype was not inhibited by La, Zn, Cu, Co, Mn, Ni or Fe(II), and neither by increasing the Ca concentration. By contrast, addition of La, Zn or Mn, or increasing the Ca concentration in the uptake solution decreased Cd uptake by Prayon. Uptake of Ca was larger in Prayon than in Ganges. The results suggest that Cd uptake by the low Cd-accumulating ecotype (Prayon) may be mediated partly via Ca channels or transporters for Zn and Mn. By contrast, there may exist a highly selective Cd transport system in the root cell membranes of the high Cd-accumulating ecotype (Ganges) of T. caerulescens.

Effect of Mineral-Based Amendments on Rice (Oryza sativa L.) Growth and Cadmium Content in Plant and Polluted Soil

“…The three amendments were within the permissible reference standards for agricultural use (GB4284-1984), indicating that they could be used in practice. Previous studies have shown that the application of alkaline substances containing Ca, Mg, and Si significantly reduced the availability of Cd in paddy soil and its uptake by rice through change in soil pH (Welch and Norvell, 1999;Zhao, Hamon et al, 2002). This is also shown by the present study with increasing amounts of amendments, especially with bone char, followed by sepiolite.…”

Phytoremediation Potential of Aquatic Macrophyte, Azolla

“…During metal interaction in Cd/Zn hyperaccumulator Arabidopsis halleri, a decrease in the uptake of Cd was observed by roots with the increase in Zn concentrations. This clearly demonstrates that Cd influx is largely due to Zn transporters that have a strong preference for Zn over Cd (Zhao et al 2002). Similarly, the preference of Zn over Ni by some Zn-/Ni-hyperaccumulators supplied with the same concentrations of heavy metals, also strongly suggests that a Zn transporter system might be involved in Ni entry into the roots of Thlaspi caerulescens (Assuncao et al 2008).…”

Accumulation of Pb, Cu, and Zn in native plants growing on contaminated sites and their potential accumulation capacity in Heqing, Yunnan

“…Translocation factors higher than 1 indicated a very efficient ability to transport metal from roots to shoots, most likely due to efficient metal transport systems (Zhao et al, 2002). The translocation factors for Pb ranged from 0.02 to 0.93, with the highest value in the sample of A. lactiflora and the lowest for S. china.…”