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Iron Lung: How Rice Roots Induce Iron Redox Changes in the Rhizosphere and Create Niches for Microaerophilic Fe(II)-Oxidizing Bacteria
journal contribution
posted on 2019-08-23, 12:08 authored by Markus Maisch, Ulf Lueder, Andreas Kappler, Caroline SchmidtAlthough water-logged rice paddies
are characterized by anoxic
conditions, radial oxygen loss (ROL) from rice roots temporarily oxygenates
the soil rhizosphere. ROL not only triggers the abiotic oxidation
of ferrous iron (Fe(II)) but also provides the electron acceptor for
microaerophilic Fe(II)-oxidizing bacteria (microFeOx). Both processes
contribute to the formation of ferric (Fe(III)) iron plaque on root
surfaces. Redox interactions at single roots have been studied intensively.
However, temporally resolved spatial changes of ROL in the entire
rhizosphere and the impact on redoximorphic biogeochemistry are currently
poorly understood. Here, we show how ROL spatiotemporally evolves
and correlates with Fe-redox transformations. Applying noninvasive
measurements in a transparent artificial soil, we were able to visualize
opposing O2 and Fe(II) gradients that extend from the root
surface 10–25 mm into the rhizosphere. The microoxic zone expanded
exponentially in size throughout the entire rhizosphere creating niches
for microFeOx. Following iron mineral formation and pH, we show that
root-related ROL induces iron redox transformations on and around
roots and correlates with rhizosphere acidification. These findings
highlight the dynamic nature of roots in the rice plant rhizosphere,
and our approach spatiotemporally resolved their impact on iron redox
chemistry and microbial niche formation in the rice plant rhizosphere.
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Keywords
ferrous ironFe-redox transformationsanoxic conditionswater-logged rice paddiesmicrooxic zonerice plant rhizosphereiron redox chemistryroot surfacesrhizosphere acidificationapproach spatiotemporallyelectron acceptorniche formationnoninvasive measurementsiron Lungredoximorphic biogeochemistryRedox interactionsROL spatiotemporallyO 2root-related ROLiron redox transformationsoxygen lossabiotic oxidationRice Roots Induce Iron Redox Changesrice rootssoil rhizosphereiron mineral formation
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