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| Home > Publications database > Diffusion and Flow Investigations innatural Porous Media by Nuclear Magnetic Resonance Imaging |
| Home > Publications database > Diffusion and Flow Investigations innatural Porous Media by Nuclear Magnetic Resonance Imaging |
| Dissertation / PhD Thesis/Book | PreJuSER-17290 |
2011
Foschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-89336-719
Abstract: Climate change and a growing global population impose severe pressure on securing the supply of nutrition to mankind. A crucial aspect thereby is the possibility to adopt the cultivation of crops to the changing climatic conditions. This is a strong motivation for being interested in root water uptake of plants. To obtain a better understanding of these mechanisms, analysis of water motion inside and towards plant roots in natural soil are essential. This work aims on the determination of water motion in natural porous media such as roots and soil using different techniques of nuclear magnetic resonance (NMR). NMR is known from medical diagnosis and allows non-invasive investigations of natural soil and intact plants. Therefore, NMR is best suited for investigating root water uptake processes. Since modeling of root water uptake processes requires an unambiguous three-dimensional reconstruction of the root skeleton, magnetic resonance imaging (MRI) is an appropriate technique for this challenge. From the spatial analysis of the answer of the sample to excitation with radio frequency (rf) pulses, the water distribution and motion inside the sample can be determined. This thesis shows how common imaging techniques introduce gaps in reconstructed roots due to susceptibility effects. To compensate for these effects, diffusion tensor imaging (DTI) was transformed to the requirements of plant roots and successfully applied for the first time. DTI is also an NMR-technique known from medical research, which detects local diffusive displacements of water molecules with high spatial resolution. Restrictions such as cell walls in plant roots limit the diffusion. If such restrictions are spatially dependent, diffusion is called anisotropic. This can be mathematically expressed by a tensor, describing the local anisotropy. DTI determines the diffusion tensors at different positions in the sample. Since DTI on plant roots shows typically a low signal to noise ratio (SNR), this work presents a new approach for data analyzing beside the common medical procedure. In the end, it was possible to visualize a single root of the root skeleton three-dimensionally by measuring diffusion tensors inside the root. [...]
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