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

与散装土壤相比，直接靠近根系的土壤，即所谓的根际，受到根系活动的严重影响，例如在微生物学和土壤化学方面。近年来已经证明，根际虽然很小，但在控制水从大块土壤流向根的水力学中也起着决定性的作用。磁共振成像（MRI）和中子成像（NI）这两种成像技术的结合，是对水动力学、水流和溶质输运进行无创研究最有前途的工具。这两种方法是互补的：NI绘制与总含水量相对应的总质子密度图，并且能够以高分辨率检测变化和空间模式。另一方面，核磁共振弛豫时间反映了流体与基质之间的相互作用。因此，MRI还能够根据结构水、结合水和流动水的松弛时间对不同的水池进行分类。在这个项目中，这两种方法将首次结合起来，对系统的根-根际-散装土壤进行详细的三维成像。为了避免远程传输对敏感区域的改变，除了传统的高场MRI设备外，还将使用可移动的MRI系统，该系统可以在中子成像设施现场进行3D成像。所研究的系统是在稳定状态下的细砂和砂壤土中幼小的卢平和玉米植物，以及在干燥-再湿润循环中的系统。作为项目第一阶段的主要成果，我们期望通过含水量（NI）和水动力学（MRI）对根、根际和周围散装土壤进行表征，最终得到根际水组分的分类。在第二个项目阶段的稳态条件下，通过示踪剂跟踪分别绘制了固定循环和再湿润循环下从土壤到根系的通量过程。总体目标是计算不同隔室的吸收率，并得出电导率变化的结论。

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.