MRI for soil and plant research
Magnetic resonance imaging uses the nuclear magnetic resonance effect (NMR) for non-invasive, 3D high resolution imaging. Many atomic nuclei such as 1H, 23Na, 19F, which have a microscopic magnetic moment proportional to their spin, show this effect. They interact with an external magnetic field, in which they can be excited, they subsequently relax, and send a signal. This signal contains information about the content of the respective nucleus, e.g. 1H2O, but also about its physical and chemical environment. After analysis of the measurements, MRI maps water or NaCl contents, but also relaxation times which allow for conclusions on the properties of the porous medium. Spatial resolutions of 0.2 mm are routinely achievable.
In soil and plant research, we use MRI for imaging the development of root systems (Fig. 2), and their correlation with water of salt content. Furthermore, water flow and uptake pathways are visible by application of MRI sensitive tracer substances. An example is given in Fig. 3, where GdDTA tracer is enriched in certain zones around roots.