Chapter 5: Root–Soil Interaction

Plant roots interact with and alter the properties of the surrounding soil in many ways. Understanding their mechanics and growth as well as their complex interplay with the soil properties at different spatial scales, from the sub-micron to the meter scales (cell wall, cell, tissue, root and root systems) requires multidisciplinary approaches and certainly offers a stimulating challenge for soft matter scientists. In this chapter we review the roles of the root and root systems in changing the physical, mechanical and hydric properties of the surrounding soil. We begin by describing the growth and mechanics of a primary root, whose complexity arises from its multicellularity and from the intriguing rheology of the cell wall surrounding the cell under turgor pressure. We continue by illustrating how the growth of a root is affected by the mechanical strength of the soil. Then we describe how an impeded root in a soil modifies the soil microstructure, either by a direct mechanical effect or by the secretion of a gel called mucilage. Finally, we extend to the root systems and their role in increasing the soil strength. Clearly it is crucial to understand the complex interplay between soil and root systems, as vegetation might be used as an ecologically friendly and sustainable alternative to more traditional hard engineering solutions for soil reinforcement.