Mapping soil deformation around plant roots using in vivo 4D X-ray computed tomography and digital volume correlation

• Published in: Journal of biomechanics Vol. 49; no. 9; pp. 1802 - 1811
• Main Authors: Keyes, S.D, Gillard, F, Soper, N, Mavrogordato, M.N, Sinclair, I, Roose, T
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 14-06-2016; Elsevier Limited
• Subjects: Biomechanics; Computation; Computational biology; Computed tomography; Correlation; Deformation; Digital Volume Correlation; Four-Dimensional Computed Tomography; Fourier transforms; Funding; Granular media; Imaging techniques; Mechanical Phenomena; Medical imaging; Physical Medicine and Rehabilitation; Plant roots; Plant Roots - growth & development; Professional relationships; Roots; Sensors; Soil; Soil (material); Studies; Surface layer; Texture; X-ray Computed Tomography; Zea mays - growth & development; Biomechanics; Plant Roots; Digital Volume Correlation; Computational Biology; Soil; Computed Tomography; X-ray Computed Tomography; Granular Media; Computed tomography; Granular media; Plant roots; Computational biology
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2016.04.023

Abstract The mechanical impedance of soils inhibits the growth of plant roots, often being the most significant physical limitation to root system development. Non-invasive imaging techniques have recently been used to investigate the development of root system architecture over time, but the relationship with soil deformation is usually neglected. Correlative mapping approaches parameterised using 2D and 3D image data have recently gained prominence for quantifying physical deformation in composite materials including fibre-reinforced polymers and trabecular bone. Digital Image Correlation (DIC) and Digital Volume Correlation (DVC) are computational techniques which use the inherent material texture of surfaces and volumes, captured using imaging techniques, to map full-field deformation components in samples during physical loading. Here we develop an experimental assay and methodology for four-dimensional, in vivo X-ray Computed Tomography (XCT) and apply a Digital Volume Correlation (DVC) approach to the data to quantify deformation. The method is validated for a field-derived soil under conditions of uniaxial compression, and a calibration study is used to quantify thresholds of displacement and strain measurement. The validated and calibrated approach is then demonstrated for an in vivo test case in which an extending maize root in field-derived soil was imaged hourly using XCT over a growth period of 19 h. This allowed full-field soil deformation data and 3D root tip dynamics to be quantified in parallel for the first time. This method paves the way for comparative studies of contrasting soils and plant genotypes, improving our understanding of the fundamental mechanical processes which influence root system development.