TY - JOUR A1 - Moradi, Ahmad B. A1 - Carminati, Andrea A1 - Vetterlein, Doris A1 - Vontobel, Peter A1 - Lehmann, Eberhard A1 - Weller, Ulrich A1 - Hopmans, Jan W. A1 - Vogel, Hans-Jörg A1 - Oswald, Sascha T1 - Three-dimensional visualization and quantification of water content in the rhizosphere JF - New phytologist : international journal of plant science N2 - Despite the importance of rhizosphere properties for water flow from soil to roots, there is limited quantitative information on the distribution of water in the rhizosphere of plants. Here, we used neutron tomography to quantify and visualize the water content in the rhizosphere of the plant species chickpea (Cicer arietinum), white lupin (Lupinus albus), and maize (Zea mays) 12 d after planting. We clearly observed increasing soil water contents (h) towards the root surface for all three plant species, as opposed to the usual assumption of decreasing water content. This was true for tap roots and lateral roots of both upper and lower parts of the root system. Furthermore, water gradients around the lower part of the roots were smaller and extended further into bulk soil compared with the upper part, where the gradients in water content were steeper. Incorporating the hydraulic conductivity and water retention parameters of the rhizosphere into our model, we could simulate the gradual changes of h towards the root surface, in agreement with the observations. The modelling result suggests that roots in their rhizosphere may modify the hydraulic properties of soil in a way that improves uptake under dry conditions. KW - extent of rhizosphere KW - modelling KW - neutron tomography KW - rhizosphere hydraulic properties KW - root water uptake KW - soil moisture profile KW - water distribution Y1 - 2011 U6 - https://doi.org/10.1111/j.1469-8137.2011.03826.x SN - 0028-646X VL - 192 IS - 3 SP - 653 EP - 663 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Moradi, Ahmad B. A1 - Carminati, Andrea A1 - Lamparter, Axel A1 - Woche, Susanne K. A1 - Bachmann, Jörg A1 - Vetterlein, Doris A1 - Vogel, Hans-Jörg A1 - Oswald, Sascha T1 - Is the rhizosphere temporarily water repellent? JF - Vadose zone journal N2 - The rhizosphere has a controlling role in the flow of water and nutrients from soil to plant roots; however, its hydraulic properties are not well understood. As roots grow, they change the pore size distribution of the surrounding soil. Roots release polymeric substances such as mucilage into their rhizosphere. Microorganisms living in the rhizosphere feed on these organic materials and release other polymeric substances into the rhizosphere. The presence of these organic materials might affect the water retention properties and the hydraulic conductivity of the rhizosphere soil during drying and rewetting. We used neutron radiography to monitor the dynamics of water distribution in the rhizosphere of lupin (Lupinus albus L.) plants during a period of drying and rewetting. The rhizosphere was shown to have a higher water content than the bulk soil during the drying period but a lower one during the subsequent rewetting. We evaluated the wettability of the bulk soil and the rhizosphere soil by measuring the contact angle of water in the soil. We found significantly higher contact angles for the rhizosphere soil than the bulk soil after drying, which indicates slight water repellency in the rhizosphere. This explains the lower soil water content in the rhizosphere than the bulk soil after rewetting. Our results suggest that the water holding capacity of the rhizosphere is dynamic and might shift toward higher or lower values than those of the surrounding bulk soil, not affected by roots, depending on the history of drying and rewetting cycles. Y1 - 2012 U6 - https://doi.org/10.2136/vzj2011.0120 SN - 1539-1663 VL - 11 IS - 3 PB - Soil Science Society of America CY - Madison ER - TY - JOUR A1 - Carminati, Andrea A1 - Schneider, Christoph L. A1 - Moradi, Ahmad B. A1 - Zarebanadkouki, Mohsen A1 - Vetterlein, Doris A1 - Vogel, Hans-Jörg A1 - Hildebrandt, Anke A1 - Weller, Ulrich A1 - Schüler, Lennart A1 - Oswald, Sascha T1 - How the rhizosphere may favor water availability to roots JF - Vadose zone journal N2 - Recent studies have shown that rhizosphere hydraulic properties may differ from those of the bulk soil. Specifically, mucilage at the root-soil interface may increase the rhizosphere water holding capacity and hydraulic conductivity during drying. The goal of this study was to point out the implications of such altered rhizosphere hydraulic properties for soil-plant water relations. We addressed this problem through modeling based on a steady-rate approach. We calculated the water flow toward a single root assuming that the rhizosphere and bulk soil were two concentric cylinders having different hydraulic properties. Based on our previous experimental results, we assumed that the rhizosphere had higher water holding capacity and unsaturated conductivity than the bulk soil. The results showed that the water potential gradients in the rhizosphere were much smaller than in the bulk soil. The consequence is that the rhizosphere attenuated and delayed the drop in water potential in the vicinity of the root surface when the soil dried. This led to increased water availability to plants, as well as to higher effective conductivity under unsaturated conditions. The reasons were two: (i) thanks to the high unsaturated conductivity of the rhizosphere, the radius of water uptake was extended from the root to the rhizosphere surface; and (ii) thanks to the high soil water capacity of the rhizosphere, the water depletion in the bulk soil was compensated by water depletion in the rhizosphere. We conclude that under the assumed conditions, the rhizosphere works as an optimal hydraulic conductor and as a reservoir of water that can be taken up when water in the bulk soil becomes limiting. Y1 - 2011 U6 - https://doi.org/10.2136/vzj2010.0113 SN - 1539-1663 VL - 10 IS - 3 SP - 988 EP - 998 PB - Soil Science Society of America CY - Madison ER - TY - JOUR A1 - Schulz, K. A1 - Seppelt, Ralf A1 - Zehe, Erwin A1 - Vogel, Hans-Jörg A1 - Attinger, Sabine T1 - Importance of spatial structures in advancing hydrological sciences N2 - [1] Spatial patterns of land surface and subsurface characteristics often exert significant control over hydrological processes at many scales. Recognition of the dominant controls at the watershed scale, which is a prerequisite to successful prediction of system responses, will require significant progress in many different research areas. The development and improvement of techniques for mapping structures and spatiotemporal patterns using geophysical and remote sensing techniques would greatly benefit watershed science but still requires a significant synthesis effort. Effective descriptions of hydrological systems will also significantly benefit from new scaling and averaging techniques, from new mathematical description for spatial pattern/structures and their dynamics, and also from an understanding and quantification of structure and pattern-building processes in different compartments ( soils, rocks, and land surface) and at different scales. The advances that are needed to tackle these complex challenges could be greatly facilitated through the development of an interdisciplinary research framework that explores instrumentation, theory, and simulation components and that is implemented in a coordinated manner Y1 - 2006 UR - http://www.mendeley.com/research/importance-of-spatial-structures-in-advancing-hydrological-sciences/ #page-1 U6 - https://doi.org/10.1029/2005wr004301 ER -