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Side view (a) and top view (b) slice from the low‐field magnetic resonance imaging (LF‐MRI) 3‐D image set collected from a sorghum plant grown under field conditions in a Belk clay soil in the summer of 2020
Source publication
Root phenotyping provides critical information to plant breeders for developing varieties with improved drought tolerance, greater root biomass, and greater nutrient use efficiency. Phenotyping roots in the natural environment is important for understanding the effect of the soil environment on root genotypic expressions. The goal of this work was...
Citations
... As lightweight magnets must be used, the magnetic field strengths of portable devices are generally lower than 1 T, commonly referred to as lowfield devices. The spatial resolution of such devices can range from ~ 100 μm [10,12] to a couple of millimeters [13], while the temporal resolution can range from minutes to a few hours, depending upon the experiment. The balance between spatial and temporal resolution depends largely on the SNR, which is lower in portable devices due to the lower magnetic field strength. ...
... It has also been demonstrated that portable MRI is capable of measuring the water content of leaves, as well as studying how leaf water content evolves diurnally and in the context of hydric stress [37]. At the level of underground plant organs, the difference in relaxation times between the soil and the roots permitted the direct imaging of roots within intact soil and to observe their distribution [13,38]. Figure 2 shows how proton density measurements and T 2 relaxation times can be used to create weighted images, and these images are comparable to what can be obtained with microscopy. ...
... These methods enable a spatially resolved study of root water uptake. Recently, Bagnall et al. demonstrated with a lowfield MRI device that roots can be detected and imaged in natural soils, helping to better understand root morphology, architecture, and development [13,38]. But, as far as we know, spatially resolved root water uptake has not yet been studied with portable MRI. ...
Plant physiology and structure are constantly changing according to internal and external factors. The study of plant water dynamics can give information on these changes, as they are linked to numerous plant functions. Currently, most of the methods used to study plant water dynamics are either invasive, destructive, or not easily accessible. Portable magnetic resonance imaging (MRI) is a field undergoing rapid expansion and which presents substantial advantages in the plant sciences. MRI permits the non-invasive study of plant water content, flow, structure, stress response, and other physiological processes, as a multitude of information can be obtained using the method, and portable devices make it possible to take these measurements in situ, in a plant’s natural environment. In this work, we review the use of such devices applied to plants in climate chambers, greenhouses or in their natural environments. We also compare the use of portable MRI to other methods to obtain the same information and outline its advantages and disadvantages.
... Without the siting limitations of high field MR systems, low field systems allow magnetic resonance to be taken outside of a controlled laboratory or radiology suite and used for a broader range of applications. Low field MR can be used to image the roots of plants in soil [1,2], detect spoilage of food products [3][4][5], identify explosives [6] or for emergency room use and bedside patient diagnosis [7][8][9]. Taking an MR system out of the laboratory or radiology suite removes many environmental controls, such as temperature and noise levels, which can result in measurement variation [1,4,5]. ...
... Low field MR can be used to image the roots of plants in soil [1,2], detect spoilage of food products [3][4][5], identify explosives [6] or for emergency room use and bedside patient diagnosis [7][8][9]. Taking an MR system out of the laboratory or radiology suite removes many environmental controls, such as temperature and noise levels, which can result in measurement variation [1,4,5]. To ensure a system is functioning properly and that accurate measurements are being recorded, there is a need for reference materials that are characterized over a wide range of magnetic fields and temperatures. ...
Objective:
Temperature controlled T1 and T2 relaxation times are measured on NiCl2 and MnCl2 solutions from the ISMRM/NIST system phantom at low magnetic field strengths of 6.5 mT, 64 mT and 550 mT.
Materials and methods:
The T1 and T2 were measured of five samples with increasing concentrations of NiCl2 and five samples with increasing concentrations of MnCl2. All samples were scanned at 6.5 mT, 64 mT and 550 mT, at sample temperatures ranging from 10 °C to 37 °C.
Results:
The NiCl2 solutions showed little change in T1 and T2 with magnetic field strength, and both relaxation times decreased with increasing temperature. The MnCl2 solutions showed an increase in T1 and a decrease in T2 with increasing magnetic field strength, and both T1 and T2 increased with increasing temperature.
Discussion:
The low field relaxation rates of the NiCl2 and MnCl2 arrays in the ISMRM/NIST system phantom are investigated and compared to results from clinical field strengths of 1.5 T and 3.0 T. The measurements can be used as a benchmark for MRI system functionality and stability, especially when MRI systems are taken out of the radiology suite or laboratory and into less traditional environments.
... Extending field results to imaging, Bagnall and colleagues built and deployed an MRI system to phenotype sorghum roots in the field (Bagnall et al., 2022). By using weak or low field magnets, they avoided challenges with the weight of conventional and interaction with magnetic particles that prevent the use of MRI in field settings or with cores for many realistic soils. ...
The Plant Phenome Journal is excited to present 10 papers that were submitted in a special section on belowground phenotyping. Plant roots and their environment are important for crop resilience and resource efficiency. To meet growing productivity challenges, breeders will benefit from tools that are developed to optimize belowground traits.
The root system is vital for anchorage, mobilizing water and nutrients and symbiosis with soil microbes, which influence adaptation and crop performance. However, root traits are not widely used in crop variety development because root phenotyping is difficult and there is limited understanding of the genetics of root traits. The available genetic variation and emerging root phenotyping and genotyping technologies present opportunities for integrating root traits in breeding. Selection efficiency for root traits can be enhanced by integrating shovelomics, digital imaging, crop modelling and gene sequencing systems. Therefore, the objectives of this review are to discuss critical root traits and their vital functions, genetic variation present for root traits, opportunities and challenges in root phenotyping and integration of genomic tools in breeding for improved root systems. The information presented in the paper will guide crop breeders in developing a new generation of crop varieties with desirable yield and root traits.
A simple spatial filter for 2D projection MR imaging is introduced. It works in the third (unresolved) direction to eliminate uniform or slowly varying interfering background signals. A constant amplitude gradient pulse in the unresolved direction is applied at the same time as the usual phase encode gradient during 2D acquisition. The filter is demonstrated for root imaging in soil, where background soil water signals can be troublesome. The filter suppresses the soil water signal while preserving the desired signal of plant roots. Fundamental to the operation of the filter is that the roots are sparse in the image domain, meaning there are relatively few pixels with multiple roots present. The performance of the through-plane filter is demonstrated and compares favorably to more conventional in-plane spatial filtering.
