Interplay of chelating and reducing root exudates in plant iron acquisition

Biogeochemistry

Iron (Fe) is an essential micronutrients for plants that often limits their growth and reproduction. Despite its high abundance, biologically available Fe is restricted by the low solubility and the slow dissolution kinetics of Fe-oxides, in particular at alkaline pH conditions such as calcareous soil. To cope this, plants under such conditions exudate protons, reductants and Fe-binding ligands to increase Fe availability. Co-exudation of reductants and ligands also has been observed under Fe deficient soil environments. In the presence of both a reductant and a ligand, synergistic Fe mobilizations from Fe-oxide have been shown in single Fe(III) (hydr)oxide minerals and calcareous soil. One of the proposed hypotheses of synergistic Fe mobilization is reductant-induced surface labilization catalyzes ligand-controlled Fe-oxide dissolution processes.

Recently it has been observed Fe-deficient Arabidopsis plants exudate coumarin-types compounds as root exudates which can reduce Fe(III) (low solubility) to Fe(II) (high solubility) as well as chelate both Fe(II) and Fe(III). However, identifications of coumarin-type root exudates, functional groups of the compounds regarding Fe reduction and chelation, and chemical mechanisms of Fe-oxide dissolution processes by coumarins have not been elucidated so far.  

The goals of this project are identifying of coumarin-type compounds with specific Fe-related functions such as the chelation and/or reduction, and elucidating Fe-oxide dissolution mechanisms by coumarins in particular with regards to synergism between reductive and ligand-controlled dissolution.

This research is funded by the Austrian Science Fund (FWF, Grant No.: I2865-N34).

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