TY  - JOUR
A1  - Rudolph-Mohr, Nicole
A1  - Vontobel, Peter
A1  - Oswald, Sascha
T1  - A multi-imaging approach to study the root-soil interface
JF  - Annals of botany
N2  - Background and Aims Dynamic processes occurring at the soil-root interface crucially influence soil physical, chemical and biological properties at a local scale around the roots, and are technically challenging to capture in situ. This study presents a novel multi-imaging approach combining fluorescence and neutron radiography that is able to simultaneously monitor root growth, water content distribution, root respiration and root exudation.
 Methods Germinated seeds of white lupins (Lupinus albus) were planted in boron-free glass rhizotrons. After 11 d, the rhizotrons were wetted from the bottom and time series of fluorescence and neutron images were taken during the subsequent day and night cycles for 13 d. The following day (i.e. 25 d after planting) the rhizotrons were again wetted from the bottom and the measurements were repeated. Fluorescence sensor foils were attached to the inner sides of the glass and measurements of oxygen and pH were made on the basis of fluorescence intensity. The experimental set-up allowed for simultaneous fluorescence imaging and neutron radiography.
 Key Results The interrelated patterns of root growth and distribution in the soil, root respiration, exudation and water uptake could all be studied non-destructively and at high temporal and spatial resolution. The older parts of the root system with greater root-length density were associated with fast decreases of water content and rapid changes in oxygen concentration. pH values around the roots located in areas with low soil water content were significantly lower than the rest of the root system.
 Conclusions The results suggest that the combined imaging set-up developed here, incorporating fluorescence intensity measurements, is able to map important biogeochemical parameters in the soil around living plants with a spatial resolution that is sufficiently high enough to relate the patterns observed to the root system.
KW  - Roots
KW  - soil-root interaction
KW  - root distribution
KW  - Lupinus albus
KW  - lupin
KW  - pH dynamics
KW  - oxygen dynamics
KW  - soil water distribution
KW  - rhizosphere
KW  - fluorescence imaging
KW  - neutron radiography
Y1  - 2014
U6  - https://doi.org/10.1093/aob/mcu200
SN  - 0305-7364
SN  - 1095-8290
VL  - 114
IS  - 8
SP  - 1779
EP  - 1787
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
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  -