2D Kinematic Quantification of Soil Particles around Growing Plant Root based on Optical Mechanics

Wenbin Wu,Jian Zhao

doi:10.3844/ajbbsp.2020.494.506

Abstract

The quantitative kinematic description of the surrounding soil particles during root growth is a technical challenge and biologically important. In this study, a two-dimensional camera-based imaging system was used to observe micro scale interactions between plant roots and soil particles. Maize root tip was imaged during ingress into the soils. This produced a series of two-dimensional images that represent temporal resolution of the geometric soil and root configurations at the micrometer scale. These images were used as inputs for full-field kinematic quantification methods, which enabled the analysis of two-dimensional deformation of the soils around elongating root. Correlation-based discrete object tracking and contour updating were used to track the shapes and the locations of soil particles and soil aggregates, while incremental digital image correlation was proposed to extract deformation and strain field within soil particle and soil aggregate. These techniques allowed the full-field displacements and strains of the soil to be quantified and the changes in shapes of soil particles to be visualized. Experimental results show that the presented shape tracking scheme, incremental digital image correlation and the research findings will be useful for the measurement and quantification of soil particle kinematics of soil-root physical interactions.

Highlights

The root system is the dynamic interface between soil and plant
The root passing through the soil directly changes the soil pore space and induces the soil particle displacement, which mainly occurs in the axial displacement in front of the root and the radial displacement near the root (Meurer et al, 2020)
A series of soil particles and aggregates initially located at the lateral of the initial position of the root tip are translated to form a compacted structure by large displacements that are essentially aligned to the direction of root growth

Summary

Introduction

The root system is the dynamic interface between soil and plant. The interactions between roots and soils is important for a better understanding of how plants interact with their environment (Keyes et al, 2017; 2016; Bengough et al, 2011). The quantification of the mechanical process of soil deformation around roots remains a methodological challenge. This task is difficult due to the obvious facts that direct observation and dynamic data acquisition of root and soil is obstructed by opaque soil. In order to visualize soil particle displacement and strain and to develop method of proper analysis for shape tracking during soil penetration by plant roots, coarse soil (Ruiz et al, 2017) packed at a bulk density of 1500 to 1700 kg/m3 was used.

Methods

Results

Conclusion