Does root architecture matter in the quest of more efficient capture of soil water by plant roots?

The magnitude and distribution of root water uptake is controlled by the distribution of soil, rhizosphere and root hydraulic properties and how these are connected to each other. Therefore, estimating the ability of a root system to extract water depends not only on the root system architecture and hydraulics but also on the environmental conditions. While experimental tools exist to characterize soil, rhizosphere and root segment hydraulic properties, how the combination of soil/plant local properties relate to the whole plant hydraulic behavior is still an open question.

Today, modeling tools exist that simulate the soil-root system hydraulics at local and plant scales. Based on physical laws these multiscale models integrate the impact of the plant regulation on internal resistances and the control of the soil and of the rhizosphere on water stream. They have also been used to estimate root hydraulic properties by inverse modeling. Yet, simplified, upscaled models are needed, which estimate plant behavior at lower computational costs.

Here, we present an analytic pipeline based on mathematical models, which allow one to estimate root scale macroscopic properties based on specific root and rhizosphere traits, without the need of solving of the full water equations in a 3D root system. This allow us to quantitatively estimate the sensitivity of root system conductance to local traits. It can also be used to investigate how combinations of plant traits will lead to conservative or risky water uptake strategies. Finally, we can identify optimal strategies as a function of environmental constraints. These tools allow us to define the concept of “eco-ideotypes”, i.e. ideal combination of local root traits that optimize their water capture over their crop cycle in a particular environment. These new tools were compared to a FSPM model to validate their performance.