Changes in Soil Water Content Resulting fromRicinusRoot Uptake Monitored by Magnetic Resonance Imaging

Abstract

Magnetic resonance imaging (MRI) was used to study the soil water content changes caused by root water uptake. A 4‐wk‐old Ricinus communis carmencita with a highly developed root system was planted in a cylindrical container filled with a model soil (99.5% fine sand, 0.5% clay), fully water saturated. The bottom and surface of the container were sealed so that water loss by factors other than transpiration via the leaves could be neglected. The water content of the soil was monitored for 3 wk using the MRI sequence SPRITE at an isotropic spatial resolution of 6.3 mm. In contrast to conventionally used MRI sequences, the T2* relaxation was monitored, temporally resolved, and extrapolated to zero. This procedure is a better measure of water content than a single signal at a given time point since it eliminates varying MRI relaxation times during soil desiccation. A linear correlation between the MRI‐determined and gravimetrically measured total water content proves the correctness of the monitoring and data evaluation procedure. Simultaneously, the root architecture was also imaged at 0.6 mm isotropic resolution by the MRI sequence constructive interference in steady state (CISS), which yielded a good contrast between soil and roots. The coregistration of both types of imaging (water content and root architecture) indicates that greater changes in water content took place in the bottom region and near the surface, where the highest root densities were found.

A simple three-dimensional macroscopic root water uptake model based on the hydraulic architecture approach

“…Yet, root architecture and hydraulic properties are more difficult to derive from in situ measurements of plant roots than rRLD. However, this type of information can be obtained from root growth models calibrated on root profile measurements (as done in this study) or from noninvasive methods like MRI (Pohlmeier et al, 2008), X-ray or neutron tomography (Menon et al, 2007). The sensitivity of SSF to the root architecture type should be characterised in the future.…”

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

“…Imaging techniques for the visualization of soilgrown root systems in two and three dimensions include x-ray computed tomography (Heeraman et al, 1997;Tracy et al, 2010;Mooney et al, 2012), neutron radiography (NR; Oswald et al, 2008), and magnetic resonance imaging (Pohlmeier et al, 2008). NR is one of the most suitable techniques to investigate roots grown in soil, because it allows a high throughput, provides a strong contrast between roots and soil, and therefore requires little effort for image processing.…”

Developing X-ray Computed Tomography to non-invasively image 3-D root systems architecture in soil

“…A number of other imaging techniques have been developed to visualise and quantify root properties in situ, including Nuclear Magnetic Resonance (NMR) (Rogers and Bottomley 1987;Jennette et al 2001), Magnetic Resonance Imaging (MRI) (Pohlmeier et al 2008), Thermal Neutron Tomography (Tumlinson et al 2008) and Neutron Radiography . Like X-ray CT, each approach has a number of merits and some limitations when used to visualise root systems architecture, and particularly root systems architecture in soil.…”