Monitoring root water uptake processes by the novel combination of magnetic resonance- and neutron imaging.

点击翻译按钮获取中文摘要

The soil in direct vicinity of the roots, the so called rhizosphere, is heavily modified by the activity of roots, compared to bulk soil, e.g. in respect to microbiology and soil chemistry. In recent time it has turned out that the rhizosphere, though small in size, also plays a decisive role in the hydraulics controlling the water flow from bulk soil into the roots. The most promising tool for the non-invasive investigation of water dynamics, water flow and solute transport is the combination of the two imaging techniques magnetic resonance imaging (MRI) and neutron imaging (NI). Both methods are complementary: NI maps the total proton density which corresponds to total water content, and is able to detect changes and spatial patterns with high resolution. On the other side, NMR relaxation times reflect the interaction between fluid and matrix. Therefore MRI is additionally capable of classifying different water pools via their relaxation times in terms of structural water,bound water, and mobile water. In this project both methods will be combined for the first time for the detailed, three-dimensional imaging of the system root-rhizosphere-bulk soil. In order to avoid alterations of this sensitive zone by long range transport, additionally to a conventional high-field MRI device, a movable MRI system will be used that allows 3D imaging on-site at the neutron imaging facility. Investigated systems are young lupin and maize plants in fine sandy and sandy loam soils under steady state conditions, but also during desiccation - rewetting cycles.As main results we expect for the first project phase the characterization of the root, rhizosphere and surrounding bulk soil by water content (NI) and water dynamics (MRI) ending up in a classification of water fractions in the rhizosphere. After the steady state conditions in the second project phase flux processes from soil to roots are mapped by tracer tracking under stationary and rewetting cycles, respectively. The overall aim is to calculate uptake rates for different compartments and conclude on changes in conductivities.