Measurement of micro-scale soil deformation around roots using 4D synchrotron tomography and image correlation

Abstract

This study applied time lapse (4D) synchrotron X-ray computed tomography (SRXCT) to observe micro-scale interactions between plant roots and soil. Functionally contrasting maize root tips were repeatedly imaged during ingress into soil columns of varying water content and compaction. This yielded sequences of 3D densiometric data, representing time –resolved geometric soil and root configurations at the micron-scale. These data were used as inputs for two full-field kinematic quantification methods, which enabled the analysis of 3D soil deformation around elongating roots. Discrete object tracking was used to track rigid mineral grains, whilst continuum Digital Volume Correlation (DVC) was used to track grey-level patterns within local sub-volumes. These techniques both allowed full-field soil displacements to be quantified at an intra-rhizosphere spatial sampling scale of <300 µm. Significant differences in deformation mechanisms were identified around different phenotypes under different soil conditions. A uniquely strong contrast was observed between intact and de-capped roots grown in dry, compacted soil. This provides evidence that functional traits of the root cap significantly reduce the amount of soil disturbance per unit of root elongation, with this effect being particularly significant in drier soil.

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Identifiers

ORCID for Samuel Keyes: orcid.org/0000-0002-4129-2228

ORCID for Laura Cooper: orcid.org/0000-0003-0198-7591

ORCID for Tiina Roose: orcid.org/0000-0001-8710-1063

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