Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-633
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
20 Dec 2016
Review status
This discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Water movement through plant roots: Exact solutions of the water flow equation in roots with varying hydraulic properties
Félicien Meunier1, Valentin Couvreur2, Xavier Draye2, Jan Vanderborght3,4, and Mathieu Javaux1,3 1Earth and Life Institute-Environment, Université catholique de Louvain, Louvain-la-Neuve, Belgium
2Earth and Life Institute-Agronomy, Université catholique de Louvain, Louvain-la-Neuve, Belgium
3Forschungszentrum Juelich GmbH, Agrosphere (IBG-3), Juelich, Germany
4Division of Soil and Water Management, KU Leuven, Leuven, Belgium
Abstract. In 1978, Landsberg and Fowkes presented a solution of the water flow equation inside a root with uniform hydraulic properties. These properties are root radial conductivity and intrinsic axial conductance, which control, respectively, the radial water flow between the root surface and the axial flow in the xylem. From the solution for the xylem water potential, functions that describe the radial and axial flow along the root axis were derived. In this paper, novel solutions of the water flow equation were developed for roots whose hydraulic properties vary along their axis, which is generally the case for most plants. Six arrangements of radial conductivity and intrinsic axial conductance varying linearly or exponentially with distance from the root tip were analysed. These solutions were subsequently combined to construct root branches with complex hydraulic property profiles. They produced flow distributions different from those in uniform roots. We used the obtained functions for evaluating the impact of root maturation versus root growth on water uptake which revealed very contrasted strategies for water uptake. In this study we also looked for optimal root traits that maximize water uptake under a carbon cost constraint. Optimal traits were shown to be highly dependent on the root hydraulic properties. These solutions lead to plant-scale parameters for root water uptake used in ecohydrological models and open consequently new avenues to look for optimal genotype x environment x management interactions.

Citation: Meunier, F., Couvreur, V., Draye, X., Vanderborght, J., and Javaux, M.: Water movement through plant roots: Exact solutions of the water flow equation in roots with varying hydraulic properties, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-633, in review, 2016.
Félicien Meunier et al.
Félicien Meunier et al.
Félicien Meunier et al.

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Short summary
To maintain its yield, a plant needs to transpire water that it acquires from the soil. A deep understanding of the mechanisms that lead to water uptake location and intensity is required to correctly simulate the water transfer in the soil to the atmosphere. This works present novel and general solutions of the water flow equation in roots that deeply affect the uptake pattern and the transpiration rate and can be used in ecohydrological models.
To maintain its yield, a plant needs to transpire water that it acquires from the soil. A deep...
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