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Physical interaction between plant root growth and model granular soil - Evelyne Kolb

PMMH, UMR 7636, ESPCI ParisTech, France

The mechanical strength of a soil greatly affects the development of a plant root, which in turn affects the shoot development. In particular, plant roots growing in heterogeneous medium like sandy soils or cracked substrates have to adapt their morphology and exert radial and axial forces depending on the pore size between grains in which they penetrate or the mechanical obstacle they encounter.

To study such soil/root interactions we examine root penetration in model systems mimicking a granular soil and restricted to one pore between grains. We started with a single pore between solid constituents where a pivot root (chick-pea seeds, Cicer arietinum L.) of millimeter diameter had to grow in the constriction between two photoelastic disks in a two-dimensional (2D) cell. Recently we move to a new setup where the root experiences a localized and radial (3D) mechanical stress when growing in a polymeric tube mimicking the elasticity of a granular soil. By developing such simple experiments and by characterizing the mechanical behaviors of roots in different environments (in atmospheric conditions or in osmotic baths), we aim to identify the elementary mechanisms of responses of the root to a mechanical stress, providing experimental support to architectural modeling of root growth.


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