X-ray absorption spectroscopy at the Ni-K edge in Stackhousia tryonii Bailey hyperaccumulator Page: 1 of 6
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
X-ray absorption spectroscopy at the Ni-K edge in
Stackhousia tryonii Bailey hyperaccumulator
M. lonescu,'* N. P. Bhatia,' D. D. Cohen,' A. Kachenko,2 R. Siegele,' M. A. Marcus,3
S. Fakra3 and G. Foran4
1 Australian Nuclear Science and Technology Organisation, Sydney, Australia
2 Faculty of Agriculture, Food and Natural Resources, The University of Sydney, Sydney, Australia
s Advanced Light Source, Lawrence Berkeley National Laboratory, California, USA
4 Australian National Beamline Facility, Tsukuba, Japan
Young plants of Stackhousia tryonii Bailey were exposed to 34 mm Ni kg-1 in the form of NiSO4 6H20
solution and grown under controlled glasshouse conditions for a period of 20 days. Fresh leaf, stem and root
samples were analysed in vivo by micro x-ray absorption spectroscopy (XAS) at the Ni-K edge. Both x-ray
absorption near edge structure and extended x-ray absorption fine structure spectra were analysed, and the
resulting spectra were compared with spectra obtained from nine biologically important Ni-containing
model compounds. The results revealed that the majority of leaf, stem and root Ni in the hyperaccumulator
was chelated by citrate. Our results also suggest that in leaves Ni is complexed by phosphate and histidine,
and in stems and roots, phytate and histidine. The XAS results provide an important physiological insight
into transport, detoxification and storage of Ni in S. tryonii plants. Copyright @ 2008 John Wiley & Sons,
Ltd.INTRODUCTION
Stackhousia tryonii Bailey (Stackhousiaceae) is an Australian
rare perennial shrub, native of north-eastern Aus-
tralia, and one of three reported Ni hyperaccumulating
(>1000 mg Ni kg-1 dry weight (DW) in any above-ground
tissue) plants from the Australian continent.1 This herba-
ceous plant has been reported to hyperaccumulate nickel in
excess of 4% DW in leaf tissues, with no adverse effects on
the plant physiology.2 So far, over 320-Ni hyperaccumula-
tors have been identified with the majority of these species
located within tropical environments.3 More recently, sev-
eral additional examples of Ni hyperaccumulation have been
found from the ultramafic soils in western and central regions
of Turkey.4
Hyperaccumulation appears to be a genetic trait,
as inferred by studies of hyperaccumulator and non-
accumulator plants belonging to the same species.5 Boyd and
Martens6 proposed five hypotheses that could potentially
explain the evolutionary significance of the metal hyperac-
cumulating trait. These included (1) chemical defense against
herbivores or pathogens; (2) drought resistance; (3) metal tol-
erance or disposal; (4) interference with neighbouring plants
and (5) inadvertent uptake. The first explanation, termed the
'defense hypothesis' has been tested in great detail with
the majority of studies demonstrating that the accumulated
metal can account for the deterrent effect.78 Studies inves-
tigating the remaining hypotheses are scarce and warrant
further investigation.
*Correspondence to: M. Ionescu, Australian Nuclear Science and
Technology Organisation, Australia.
E-mail: Mihail.Ionescu@ansto.gov.auThe ability of S. tryonii to absorb, transport and store Ni
in above-ground biomass has raised a number of questions
currently being debated in the scientific literature. One such
question is the chemical associations between Ni and ligands
including oxygen, nitrogen or sulphur donors during uptake
and translocation from the roots to leaves. Recently, it was
suggested that malic acid was the dominant organic acid
present in leaf extracts of S. tryonii following exposure to
Ni; however, a precise physiological explanation was not
determined.9 In this way, Ni atoms may be chelated, and
once fixed by these macro-molecules, may be prevented from
further reacting and thus manifesting its known toxicity.
Here we employed in situ x-ray absorption spectroscopy
(XAS) to further elucidate the presence of Ni-complexes
in living tissues of S. tryonii. Synchrotron-based XAS
has previously been usedo-12 to probe the coordination
environment in several hyperaccumulator species as it
requires minimal sample preparation, thus preserving the
true elemental distribution within whole plant tissues
without the need for abrasive pre-treatments.
In this report, we present results which suggest that
Ni absorption and sequestration in various tissues of S.
tryonii is achieved not by one unique Ni-complex, but by a
combination of Ni-complexes, specific for roots, stems and
leaves.
EXPERIMENTAL
Young S. tryonii plants were collected from the tropical
region of north-eastern Australia, as described elsewhere,13
and grown in a controlled glasshouse environment.
Plants were exposed to Ni concentration of 34 mM kg1
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Ionescu, Mihail; Bhatia, Naveen P.; Cohen , David D.; Siegele, R.; Marcus, Matthew A.; Fakra, Sirine C. et al. X-ray absorption spectroscopy at the Ni-K edge in Stackhousia tryonii Bailey hyperaccumulator, article, October 8, 2007; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc933428/m1/1/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.