Cd Accumulation in Hyperaccumulators 21 Rhizosphere Mobilization and Root Uptake

There are three mechanisms by which hyperaccumulator plants most likely obtain Cd from the soil: (1) rhizospheric and microbial mobilization of Cd; (2) active foraging for Cd, by means of enhanced root growth and root branching in regions of Cd enrichment; and (3) effective transporters facilitating Cd uptake from soil to roots in hyperaccumulating plants (Whiting et al. 2000).

Table 1 Cd hyperaccumulators discovered worldwide

Family

Species

Shoot Cd concentration

(mgkg-1,DW)

Growth condition

Hyperaccumulation of other metals

Locality discovered

References

Asteraceae

Bidens pilosa L.

303(leaf)

100 mg kg-1 Cd in soil

-

China

Sun et al. (2009)

Corydalis

102

0.5 mg L"1 Cd in

-

Thailand

Tanhan et al. (2007)

pterygopetala

solution

P i cris divari cata

246 (mean)

Pb/Zn mine

Zn

China

Tang et al. (2009a)

Athyriaceae

Athyrium yokoscense

164.8 (leaf)

mineralized soil

Pb

Japan

Nishizono et al. (1987) and Kamachi et al. (2005)

Brassicaceae

Ara bis gemmifera

1,810

Cd-polluted sites

Zn

Takenaka(2003)

Arabis panicidata

457 (mean)

Pb/Zn mine

Zn/Pb

China

Tang et al. (2009b)

Arabidopsis

281

metallophyte

Zn

France

Dahmani-Muller

halleri

grassland

et al. (2000)

Biscutella

198 (leaf)

4 mg L"1 Cd in

Pb

Poland

Pielichowska and

laevigata

solution

Wierzbicka (2004) and Wenzel and Jockwer (1999)

Rorippa globosa

104.5

25 mg kg"1 Cd in soil

China

Wei and Zhou (2006)

Thlaspi

14,000

500 |iM Cd in solution

Zn/Ni

France

Lombi et al. (2000)

caerulescens

Cd^+ 100 mg kg"1 Zn in soil

France

Lombi et al. (2000)

164

Field survey

-

UK

Baker et al. (1994)

Thlaspi

830

Zn/Ni

Austria

Lombi et al. (2000)

goesingense

Family

Species

Shoot Cd concentration

Growth condition

Hyperaccumulation Locality of other metals discovered

References

Thlaspi praecox

Caprifoliaceae

Chenopodiaceae Crassulaceae

Iridaceae

Poaceae

Rosaceae

Solanaceae Violaceae

Thlaspi rotundifolium Lonicera japonica 403

Beta vulgaris Sedum alfredii

Iris iactea

Echinochloa polystachya Potentilla griffithii Solanum nigrum Viola baoshanensis

5,960 (maximum) 108

233(leaf)

1,670

500 mg kg

Cd"+ 100 mg kg"1 Zn in soil Pb mine Zn/Pb

Mineralized soil Pb

50 mg L"1 Cd in solution 100 mg kg-1 Cd in soil 200 |iM Cd in solution Zn

80 mg L"1 Cd in solution 100 mg L_1 Cd in solution

20 mg L_1 Cd in Zn solution 100 mg kg-1 Cd in soil Pb/Zn mine -

Slovenia Vogel-Mikus et al.

Austria Wenzel and Jockwer

China Yang et al. (2002,

2004)

Mexico Solis-Dominguez et al. (2007) China Hu et al. (2009) and

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