Physical root–soil interactions

Abstract

Abstract. Plant root system development is highly modulated by the physical properties of the soil and especially by its mechanical resistance to penetration. The interplay between the mechanical stresses exerted by the soil and root growth is of particular interest for many communities, in agronomy and soil science as well as in biomechanics and plant morphogenesis. In contrast to aerial organs, roots apices must exert a growth pressure to penetrate strong soils and reorient their growth trajectory to cope with obstacles like stones or hardpans or to follow the tortuous paths of the soil porosity. In this review, we present the main macroscopic investigations of soil-root physical interactions in the field and combine them with simple mechanistic modeling derived from model experiments at the scale of the individual root apex.2

Root-restricting layers in German agricultural soils. Part I: extent and cause

“…The root architecture of cultivated plants is genetically controlled (Lynch and Wojciechowski 2015), for example dicotyledonous plants such as alfalfa (Medicago sativa L.) tend to develop a deeper root system than monocotyledon (Materechera et al 1992). However, root growth is highly responsive to its environment (Kolb et al 2017). Therefore, the developmental plasticity of roots is considerable in soils.…”

“…Seasonal changes in soil water content also exhibit a great influence on soil strength. Dry soils tend to be hard because capillary bridges between soil particles induce tensile forces (Bengough et al 2011;Kolb et al 2017;Lynch et al 2012). This explains why soil strength can change drastically across both space and time.…”

Elasticity and stability of shape-shifting structures

“…Another interesting area may lie at the interface between elastic structures and granular or colloidal materials, so-called elastogranular interactions. Research in this regard is beginning to lay out the fundamental behavior of bending and packing of elastic rods within grains [286,287,288], which is clearly relevant in the form and function of growing plant roots [289,290,291], and is beginning to show promise for programmable, reversible architecture [292,293,294]. Finally, in my opinion the biggest limitation in achieving the next generation of shape-shifting structures is the absence of simple to fabricate and robust materials that are highly responsive to stimulii.e.…”

The cap size and shape of Arabidopsis thaliana primary roots impact the root responses to an increase in medium strength

“…Root growth against the interface generates an increasing compression reaction force on the root (Kolb et al ., 2017). If the compression force reaches a critical value while the root is still in contact with the obstacle, Euler’s buckling can occur (Bizet et al ., 2016).…”

“…The force needed to penetrate soil, provided by root growth, is determined by soil strength. In natural conditions, soil strength – commonly estimated by penetrometer measurements – is in the range of 1MPa (Jin et al ., 2013; Kolb et al ., 2017). Soil heterogeneities may be overcome with soil compaction or soil drying, which results in an increase in soil strength.…”