@article{HaberPohlmeierToetzkeLehmannetal.2019,
  author    = {Haber-Pohlmeier, Sabina and T{\"o}tzke, Christian and Lehmann, E. and Kardjilov, Nikolay and Pohlmeier, A. and Oswald, Sascha},
  title     = {Combination of magnetic resonance imaging and neutron computed tomography for three-dimensional rhizosphere imaging},
  series = {Vadose zone journal},
  volume    = {18},
  journal   = {Vadose zone journal},
  number    = {1},
  publisher = {Soil Science Society of America},
  address   = {Madison},
  issn      = {1539-1663},
  doi       = {10.2136/vzj2018.09.0166},
  pages     = {11},
  year      = {2019},
  abstract  = {Core Ideas 3D MRI relaxation time maps reflect water mobility in root, rhizosphere, and soil. 3D NCT water content maps of the same plant complement relaxation time maps. The relaxation time T1 decreases from soil to root, whereas water content increases. Parameters together indicate modification of rhizosphere pore space by gel phase. The zone of reduced T1 corresponds to the zone remaining dry after rewetting. In situ investigations of the rhizosphere require high-resolution imaging techniques, which allow a look into the optically opaque soil compartment. We present the novel combination of magnetic resonance imaging (MRI) and neutron computed tomography (NCT) to achieve synergistic information such as water mobility in terms of three-dimensional (3D) relaxation time maps and total water content maps. Besides a stationary MRI scanner for relaxation time mapping, we used a transportable MRI system on site in the NCT facility to capture rhizosphere properties before desiccation and after subsequent rewetting. First, we addressed two questions using water-filled test capillaries between 0.1 and 5 mm: which root diameters can still be detected by both methods, and to what extent are defined interfaces blurred by these imaging techniques? Going to real root system architecture, we demonstrated the sensitivity of the transportable MRI device by co-registration with NCT and additional validation using X-ray computed tomography. Under saturated conditions, we observed for the rhizosphere in situ a zone with shorter T1 relaxation time across a distance of about 1 mm that was not caused by reduced water content, as proven by successive NCT measurements. We conclude that the effective pore size in the pore network had changed, induced by a gel phase. After rewetting, NCT images showed a dry zone persisting while the MRI intensity inside the root increased considerably, indicating water uptake from the surrounding bulk soil through the still hydrophobic rhizosphere. Overall, combining NCT and MRI allows a more detailed analysis of the rhizosphere's functioning.},
  language  = {en}
}
@article{HaberPohlmeierToetzkeOswaldetal.2017,
  author    = {Haber-Pohlmeier, Sabina and T{\"o}tzke, Christian and Oswald, Sascha and Lehmann, Eberhard and Bl{\"u}mich, Bernhard and Pohlmeier, Andreas},
  title     = {Imaging of root zone processes using MRI T-1 mapping},
  series = {Microporous and mesoporous materials : zeolites, clays, carbons and related materials},
  volume    = {269},
  journal   = {Microporous and mesoporous materials : zeolites, clays, carbons and related materials},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1387-1811},
  doi       = {10.1016/j.micromeso.2017.10.046},
  pages     = {43 -- 46},
  year      = {2017},
  abstract  = {Noninvasive imaging in the root soil compartment is mandatory for improving knowledge about root soil interactions and uptake processes which eventually control crop growth and productivity. Here we propose a method of MRI T-1 relaxation mapping to investigate water uptake patterns, and as second example, in combination with neutron tomography (NT), property changes in the rhizosphere. The first part demonstrates quantification of solute enrichment by advective transport to the roots due to water uptake. This accumulation is counterbalanced by net downward flow and dispersive spreading. One can furthermore discriminate between zones of high accumulation patterns and zones with much less enrichment. This behavior persists over days. The second part presents the novel combination of MRI with neutron tomography to couple static, proton density information of roots and their interface to the surrounding soil with information about the local water dynamics, reflected by NMR relaxation times. The root soil interface of a broad bean plant is characterized by slightly increasing MRI and NT signal intensity but decreasing T-1 relaxation time indicating locally changed soil properties.},
  language  = {en}
}