Localization an speciation of Zn in mycorrhized roots by SXRF and EXAFS

Abstract
Mycorrhizae are symbiotic associations between soil fungi and plant mots, which enhance mineral nutrition for the plant, and might play an important role in metals acquisition and accumulation. The processes allowing metals mobilizaiion in the soil, absorption by the root and/or the fungus, transfert or bioaccumulation we still poorly understood. However, the properties of mycorrhizal fungi could be used for phytoremediation, a soft technique using plants for the clean-up of metal polluted soils. In this work, mycorrhized roots of tomato plants grown in a Zn-contaminated sail were investigated. The distribution of metals and the speciation of Zn were studied at the micron scale using micro synchrotron-based X-ray fluorescence ( SXRF) and micro X-ray absorption spectroscopy ( EXAFS). Zn associated to the root was Zn malate and/or Zn citrate, and Zn associated to the fungus was Zn phyllosilicate. This study illustrates the great potential of X-ray microbeams for the study of biological samples containing various amounts of metals.