Aims Thallium hyperaccumulation has previously
been observed in the field but there are no laboratory
confirmations for Biscutella laevigata. Tolerance and
accumulation of thallium and its chemical analogue
caesium were compared in one non-metallicolous and
three metallicolous (calamine) populations of the candidate
Tl hyperaccumulator species, B. laevigata.
Methods Tolerance and accumulation were evaluated
in hydroponics. Moreover, Tl and Cs accumulation
were measured at different K concentrations in the
nutrient solution. Seedlings were also grown in Tl
contaminated calamine soil.
Results Estimated from their root growth response, all
the calamine populations showed hypertolerance to Tl,
although to very different degrees. Foliar Tl hyperaccumulation
from hydroponics and soil was apparent
in two populations. In one of them, it was a highaffinity
phenomenon, but it was only apparent at high
Tl exposure levels, and not associated with enhanced
root-to-shoot translocation in the other one. There was
no considerable inter-population variation in Cs tolerance
and accumulation, except that one population
showed a relatively low Cs retention in its roots under
low exposure.
Conclusions Tl hyperaccumulation and hypertolerance
are population-specific traits in B. laevigata. Cs
accumulation and tolerance are less variable and largely
uncorrelated with Tl accumulation and tolerance.
