title: A multi-imaging approach to study the root-soil interface.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany nrudolph@uni-potsdam.de.
authors.forename: Nicole
authors.initials: N
authors.lastname: Rudolph-Mohr
authors.affiliation: Paul Scherrer Institute, 5232 Villigen, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Vontobel
authors.affiliation: Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany.
authors.forename: Sascha E
authors.initials: SE
authors.lastname: Oswald
mesh_terms: D002138:Calibration; D006863:Hydrogen-Ion Concentration; D021621:Imaging, Three-Dimensional / Q000379:methods*; D031297:Lupinus / Q000033:anatomy & histology* / Q000502:physiology*; D064847:Multimodal Imaging; D009502:Neutrons; D010100:Oxygen / Q000032:analysis; D018517:Plant Roots / Q000033:anatomy & histology* / Q000502:physiology*; D012987:Soil; D013997:Time Factors
chemical_list: D012987:Soil; D010100:Oxygen
keywords: Lupinus albus; Roots; fluorescence imaging; lupin; neutron radiography; oxygen dynamics; pH dynamics; rhizosphere; root distribution; soil water distribution; soil–root interaction