The helical motions of roots are linked to avoidance of particle forces in soil

Adalvan Martins (1, 2) , Felicity O’callaghan (1) , a Glyn Glyn Bengough (1, 3) , Kenneth Loades (1) , Moacir Pasqual (2) , Evelyne Kolb (4) , Lionel Dupuy (1)

1 The James Hutton Institute
2 UFLA - Universidade Federal de Lavras = Federal University of Lavras
3 University of Dundee
4 PMMH - Physique et mécanique des milieux hétérogenes (UMR 7636)

Limitation to root growth results from forces required to overcome soil resistance to deformation. The variations in individual particle forces affects root development and often deflects the growth trajectory. We have developed Transparent Soil and Optical Projection Tomography microscopy systems where measurements of growth trajectory and particle forces can be acquired in a granular medium at a range of confining pressures. We developed image processing pipelines to analyse patterns in root trajectories and a stochastic‐mechanical theory to establish how root deflections relate to particle forces and thickening of the root. Root thickening compensates for the increase in mean particle forces but does not prevent deflections from 5% of most extreme individual particle forces causing root deflection. The magnitude of deflections increases with pressure but assemble into helices of conserved wavelength in a response linked to gravitropism. The study revealed mechanisms for the understanding of root growth in mechanically impeding soil conditions and provides insights relevant to breeding of drought‐resistant crops.

Mots clés: Transparent Soil; Biophysics; root; granular; mechanical stress; deflection

Domaines: Botanique; Biomécanique [physics.med-ph]

Adalvan Martins, Felicity O’callaghan, a Glyn Glyn Bengough, Kenneth Loades, Moacir Pasqual, et al.. The helical motions of roots are linked to avoidance of particle forces in soil. New Phytologist, In press, ⟨10.1111/nph.16312⟩. ⟨hal-02361859⟩