Speaker
Description
Adaptations of Phaseolus vulgaris crop root exudate release to U(VI) in hydroponic environment
Julia Marie Mätzkow*, Robin Steudtner, Frank Bok, Thorsten Stumpf, Susanne Sachs
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany
* j.maetzkow@hzdr.de
A crucial aspect of radioecology is assessing the risk of environmental contamination by radionuclides in order to protect life from ionizing radiation. Radionuclides released into the groundwater can be transported in soil and absorbed by crops. The ability of radionuclide to enter the food chain rises health concerns for humans. While non-essential for plants, depending on chemical speciation, radionuclides are taken up by them and induce morphological adaptations at multiple developmental stages, as well as changes in metabolic pathways and root exudate release patterns. Root exudates contribute to alterations in bacterial community composition within the rhizosphere and enhance nutrient absorption capacity. Given the capacity of root exudates to influence radionuclide speciation and mobility, they must also be considered when modelling radionuclide bioavailability in the environment. The purpose of this study is dual: first, to identify root exudates released into the rhizosphere in the presence of radionuclides, and second, to investigate radionuclide speciation.
This study analyzes the interaction between uranium (U) and the Phaseolus vulgaris crop in a hydroponic medium (phosphate-reduced, half-concentrated Hoagland) as a function of U concentration, pH, and exposure time. U bioassociation was determined by inductively coupled plasma-mass spectrometry. Modifications in U speciation in hydroponic culture were measured using time-resolved laser-induced fluorescence spectroscopy. Changes in root exudate release profiles were identified by high-performance liquid chromatography and non-target screening analysis in collaboration with the company AFIN-TS GmbH.
Both U bioassociation and phenotypic adaptations of the plant depend on exposure time, U concentration, and pH. Spectroscopic analysis revealed variations in the U speciation in hydroponic solution and were supported by thermodynamic calculations. The initial U speciation is characterized by various species, including sulfate, hydroxo, and carbonate complexes. Three main U(VI) species were detected (UO2(CO3)34-, (UO2)x(OH)y2x-y, uranyl(VI) malate) during plant U exposure. The uranyl(VI) malate complex, whose proportion rises with exposure time, is formed with malate as a well-documented root exudate. However, malate is not the sole root exudate released. Our investigation revealed elevated concentrations of organic acids and amino acids in U presence being able to modify bioavailability of U in the environment.
This study contributes to a better understanding of the interaction of U with plants, which is crucial for improving radioecological models assessing the behavior of radionuclides in the environment.
This research is part of the TRAVARIS project, funded by the German Federal Ministry of Research, Technology and Space under the contract number 15S9437C.