Sn. Whiting et al., Zinc accumulation by Thlaspi caerulescens from soils with different Zn availability: a pot study, PLANT SOIL, 236(1), 2001, pp. 11-18
The role of Zn bioavailability in soil on Zn hyperaccumulation by Thlaspi c
aerulescens was investigated. Thlaspi caerulescens from Prayon, Belgium, an
d Clough Wood, UK, were grown in pots containing unenriched soil (35 mug Zn
g(-)1), or five treatments enriched with Zn compounds of different solubil
ity (ZnS, Zn-3(PO4)(2), ZnO, ZnCO3, and ZnSO7. 7H(2)O). The Zn-enriched tre
atments had similar total Zn contents (1000 mug Zn g(-)1), but differed gre
atly in their concentrations of extractable-Zn. In the treatments with litt
le extractable-Zn (unenriched and ZnS-enriched) T. caerulescens accessed Zn
fractions that were not initially soluble; the mass of Zn accumulated in t
he shoots on Day 90 was greater than the mass of ammonium nitrate extractab
le-Zn in the soil on Day 0. Moreover, the decrease in ammonium nitrate extr
actable-Zn in the unenriched treatment after growth accounted for only 50 a
nd 24% of the Zn accumulated by plants of the Clough Wood and Prayon popula
tions, respectively. Despite accumulation of Zn from the previously non-lab
ile fraction in soil, Zn hyperaccumulation from the unenriched and ZnS-enri
ched treatments was less than from the four treatments with highly extracta
ble-Zn. The mechanisms involved in the solubilization of Zn were therefore
not strong. The dissolution of Zn in the soil might have resulted from the
very high root density in the pots either enhancing weak mobilization mecha
nisms, and/or highly efficient uptake in to the roots coupled with replenis
hment of the Zn taken up through the soil buffering capacity.