P3 - Plant Water

Emerging effects of root hairs and mucilage on plant scale soil water relations


The properties of the rhizosphere, which represents the soil volume enclosed and directly affected by plant roots, are shaped by a variety of factors. The underlying hypothesis of our project is that root hairs and mucilage secreted by roots are two key elements influencing these traits, especially in dry soils and at high transpiration rates. Our objective is to investigate the emerging role of root hairs and mucilage on two plant scale variables: transpiration and leaf water potential. Hence, we will compare two maize genotypes differing in the property of building root hairs and two cowpea lines that exudate different amounts of mucilage. We will measure how these rhizosphere traits influences the hydraulic conductance of the plant-soil system, and ultimately plant-soil water relations.
The project is structured into four work packages (WP). In WP1, we will use neutron radiography to test if different genotypes developed different root architectures to compensate for the lack of hairs or low mucilage production. By means of a root architecture model of water uptake (R-SWMS) we will inversely estimate the distribution of hydraulic conductances for the different plants. In WP2, we will measure the rhizosphere water dynamics and structure using neutron radiography and Synchrotron X-ray CT. By using Synchrotron X-ray CT, we will image root hair length and density. In WP3, we will study the effect of root hairs and mucilage on transpiration and RWU on the plant scale by means of a root pressure chamber. By means of a 3D model of RWU, we aim to derive the effective hydraulic conductance of the rhizosphere. In WP4, we plan to measure and model the effect of root hairs and soil texture on transpiration and leaf water potential in the field and over an entire cropping cycle (emerging properties at later stages). We will simultaneously monitor soil water potentials, root length distribution, sap flow and leaf water potentials. A macroscopic RWU model will be used to relate the distributions of the soil water potentials, the root density and the root-rhizosphere hydraulic conductances.
The outcome of this project is a mechanistic understanding of the role of root hairs and mucilage on transpiration and leaf water potential.

Link to English scientific abstract

Link to German scientific abstract