X-ray absorption spectroscopy at the Ni-K edge in stackhousia tryonii bailey hyperaccumulator

Abstract

Young plants of Stackhousia tryonii Bailey were exposed to 34 mM Ni kg(-1) in the form of NiSO4 center dot 6H(2)O solution and grown under controlled glasshouse conditions fora 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. © 2008, Wiley-Blackwell.