Neutron radiography as a tool for revealing root development in soil: capabilities and limitations

Abstract

Neutron Radiography (NR) is a valuable non-invasive tool to study in situ root development in soil. However, there is a lacuna of quantitative information on its capabilities and limitations. We combined neutron radiography with image analysis techniques to quantify the neutron absorption coefficients (Σ) of various root-growth media for a range of water contents (θ) in the presence and absence of plant roots with various rooting systems. Plants were grown in aluminium containers (170×150×12 mm) and were imaged using NR, as well as X-Ray radiography and an optical scanner. Sandy soil was the best medium for NR because it supported plant growth at θ that gave a good contrast for root visualisation. After correction for neutron scattering, we obtained a linear correlation between Σ and soil θ. The minimum detectable root thickness in neutron radiographs was found to be 0.2 mm in these containers. Combining NR with X-Ray radiography could provide information on soil structure in addition to revealing root structure and development.

Recovering Root System Traits Using Image Analysis Exemplified by Two-Dimensional Neutron Radiography Images of Lupine

“…Neutron radiography is one of the few noninvasive and nondestructive techniques available for studying plant root systems in situ (Moradi et al, 2009). Although this technique is too time consuming for high-throughput screening of plants, it is capable of imaging plant root systems in opaque soil.…”

“…Plants were grown in a climate chamber at a humidity of 60% with a 16-h/8-h day/night cycle with 21°C/16°C temperature. The root system was visualized with neutron radiography at 12, 19, and 26 d after germination (at the Paul Scherrer Institute in Villigen, Switzerland), which is highly suitable to visualize roots and water in soil (Menon et al, 2007;Moradi et al, 2009). The field of view was 18 3 18 cm with a nominal resolution of 0.176 mm; thus, four scans per plant container were needed to record the whole sample.…”

“…A major advantage of NR as well as magnetic resonance imaging is the possibility to monitor water distribution and roots simultaneously (Menon et al, 2007;Oswald et al, 2008;Moradi et al, 2009;Carminati et al, 2010;Stingaciu et al, 2013). This is especially useful as water is a crucial factor ruling root allocation in soil (Hodge, 2010).…”

Quantitative 3D Analysis of Plant Roots Growing in Soil Using Magnetic Resonance Imaging

“…Computed tomography (CT; both x-ray and neutron) has been proposed to overcome the mentioned difficulties with studying roots in natural soil. CT has been successfully used to obtain high-resolution images of roots (Moradi et al, 2009;Flavel et al, 2012;Mooney et al, 2012). High resolution is necessary for segmenting roots due to a poor contrast between roots and soil (Jassogne et al, 2009;Mairhofer et al, 2012;Mairhofer et al, 2013).…”

Root distributions in a laboratory box evaluated using two different techniques (gravimetric and image processing) and their impact on root water uptake simulated with HYDRUS

“…thickness, transparency etc. ), roots can be either directly photographed or the neutron, x-ray computed tomography, NMR, 2D light transition imaging technique can be applied (de Dorlodot et al, 2007;Doussan et al, 2006;Garrigues et al, 2006;Moradi et al, 2009Moradi et al, , 2010Moradi et al, , 2013Moran et al, 2000;Oswald et al, 2008;Rudolph et al, 2012Rudolph et al, , 2013Rudolph-Mohr et al, 2014;Stingaciu et al, 2013). These techniques were mostly applied to analyze root development in the early stage of plant and roots growth.…”