1 research outputs found
Mercury Localization and Speciation in Plants Grown Hydroponically or in a Natural Environment
Better
understanding of mercury (Hg) accumulation, distribution,
and speciation in plants is required to evaluate potential risks for
the environment and to optimize phytostabilization strategies for
Hg-contaminated soils. The behavior of Hg in alfalfa (<i>Medicago
sativa</i>) plants grown under controlled conditions in a hydroponic
system (30 μM HgCl<sub>2</sub>) was compared with that of naturally
occurring Horehound (<i>Marrubium vulgare</i>) plants collected
from a mining soil polluted with Hg (Almadenejos, Spain) to characterize
common mechanisms of tolerance. Synchrotron X-ray Fluorescence microprobe
(μ-SXRF) showed that Hg accumulated at the root apex of alfalfa
and was distributed through the vascular system to the leaves. Transmission
electron microscopy (TEM) implied association of Hg with cell walls,
accompanied by their structural changes, in alfalfa roots. Extended
X-ray absorption fine structure (EXAFS) determined that Hg was principally
bound to biothiols and/or proteins in <i>M. sativa</i> roots,
stems, and leaves. However, the major fraction of Hg detected in <i>M. vulgare</i> plants consisted of mineral species, possibly
associated with soil components. Interestingly, the fraction of Hg
bound to biothiols/proteins (i.e., metabolically processed Hg) in
leaves of both plants (alfalfa and <i>M. vulgare</i>) was
similar, in spite of the big difference in Hg accumulation in roots,
suggesting that some tolerance mechanisms might be shared