Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/2004
Publication Date: 9/12/2004
Citation: Tappero, R., Peltier, E., Mcnear, D.H., Chaney, R.L., Sparks, D.L. 2004. Metal interaction and localization in nickel hyperaccumulator alyssum murale: a synchrotron-based micro-xrf and tomography study [abstract]. International Congress Rhizosphere 2004-Perspectives and Challenges. p. 276. Interpretive Summary: Summary.
Technical Abstract: Unique metal-accumulating plants (i.e. hyperaccumulators) have the ability to absorb, translocate, and compartmentalize about 100 times more metals in their shoots than crop plants. These rare plants can be used to extract metals from contaminated sites (i.e., phytoextraction) or to mine metal-rich soils (i.e., phytomining). Industrial sites contaminated with Ni often have co-contaminants present, which can compete with Ni and perhaps alter the extraction efficiency of hyperaccumulators such as A. murale. We investigated the effect of competing metals (Co and Zn) on Ni accumulation by A. murale and observed metal localization and associations in various root and shoot tissues using synchrotron- based micro-XRF and tomography. Plants were grown in perlite media and exposed to nutrient solution via an ebb and flow method. The modified 1/4-strength Hoagland's solutions contained elevated (50 uM) levels of Ni, Co, and/or Zn (i.e. Ni, Ni+ Co, Ni+Zn, and Ni+Co+Zn), and were buffered at pH 6.2 with 2 mM MES. After six weeks exposure, plants were harvested (root and shoot material), weighed, dried, digested (EPA 3050 B), and analyzed for total metal content (and nutrients) by ICP. Shoot biomass was not significantly affected by the metal treatments. Nickel shoot concentration was highest for plants exposed to cobalt (Ni+Co treatment), although differences in shoot Ni concentration between the treatments were not statistically significant. Likewise, elevated Co or Zn concentrations in solution did not significantly affect Ni accumulation by A. murale. The plants exposed to all three metals had the highest Co concentration (2065 mg/kg) and Co accumulation (13.2 mg/plant), suggesting Zn had a synergistic effect on Co uptake. Cobalt in the leaves of A. murale was preferentially localized at the leaf tips and margins (especially older leaves). Nickel was distributed relatively evenly throughout the leaves, although slightly elevated at the leaf tips and basal portion of leaf trichomes. Zinc was ubiquitous in the leaves and did not appear to compartmentalize at the tissue level. X-ray fluorescence microtomography of A. murale roots revealed Ni and Co localized within the vascular region near root tips, while older root tissue had these metals predominately within the epidermal region. These preliminary results shed light on metal localization and partitioning in A. murale, and suggest aqueous Co and Zn have little influence on Ni accumulation.