HYPERNICKEL

 

Mobilisation of Nickel by hyperaccumulating plants

 

Funded by the Austrian Science Fund (https://fwf.ac.at)   

 

Partner Organisations:

 

1)  BOKU, Institute of Soil Research

2)  Montanuniversität Leoben, General and Analytical Chemistry

 

Aims:

 

Hyperaccumulation of metals in plants is a fascinating phenomenon. While some progress in the understanding of the physiological and molecular processes has been achieved, the mechanisms in the rhizosphere are still largely unknown. Contradicting results were reported on the potential mobilization of metals in the rhizosphere, e.g. by root exudates and/or associated microorganisms. The aim of this project is to clarify the Nickel mobilization processes in the rhizosphere of the nickel hyperaccumulator Odontarrhena chalcidica (syn. Alyssum murale). It is hypothesized that Ni mobilization processes depend on the bioavailability of both essential nutrients and nickel and that the activities of roots and associated microorganisms change Ni bioavailability. Changes in a) soil physico-chemical characteristics, b) nickel and iron stable isotope ratios, c) root exudation, and d) soil microbial characteristics in the rhizospere of O. chalcidica will be investigated for identifying the factors inducing Ni mobilizing processes as well as the extent and the effects of Ni mobilization in different substrates with varying Ni availability and Ni/Fe isotope ratios. Methods for accurate determination of Ni and Fe isotope ratios by multicollector-ICP-MS will be developed and applied as a novel tool in rhizosphere research. The assessment of changes in Ni and Fe isotope ratios in labile/extractable soil fractions as well as in the plant will reflect root-induced mobilization processes and reveal the contribution of primary vs. secondary soil minerals to Ni supply. Experiments including enriched stable isotopes of Ni and Fe as enriched tracers to identify sources and pathways of the two elements in green house experiments. Chemical imaging will reveal spatial gradients of labile Ni and associated elements in rhizosphere soil solution. Root exudates will be determined in rhizotest and rhizobox experiments. Soil microbial characteristics will be assessed in rhizosphere soils at defined distance from roots. The contribution of specific microbes (with a particular focus on root endophytes) to Ni accumulation in O. chalcidica will be assessed in an inoculation experiment. The results of this project will a) provide novel insights into rhizosphere processes involved in Ni hyperaccumulation, and b) contribute to the establishment of stable isotope research as a novel tool in rhizosphere biogeochemistry. The proposed work will be carried out by Markus Puschenreiter (BOKU, Vienna/Tulln, AT), Thomas Prohaska/Johanna Irrgeher (MUL Leoben, AT), Olivier Donard (IPREM UMR CNRS, Pau, FR), and Piotr Rozpądek (Małopolska Centre of Biotechnology, Jagiellonian University, Kraków, PL).