TY - JOUR A1 - Rudolph, Nicole A1 - Esser, Hanna G. A1 - Carminati, Andrea A1 - Moradi, Ahmad B. A1 - Hilger, Andre A1 - Kardjilov, Nikolay A1 - Nagl, Stefan A1 - Oswald, Sascha Eric T1 - Dynamic oxygen mapping in the root zone by fluorescence dye imaging combined with neutron radiography JF - Journal of soils and sediments : protection, risk assessment and remediation N2 - The rooted zone of a soil, more precisely the rhizosphere, is a very dynamic system. Some of the key processes are water uptake and root respiration. We have developed a novel method for measuring the real-time distribution of water and oxygen concentration in the rhizosphere as a biogeochemical interface in soil. This enables understanding where and when roots are active in respect to root respiration and water uptake and how the soil responds to it. We used glass containers (15 x 15 x 1 cm), which were filled with a quartz sand mixture. Sensor foils for fluorescence dye imaging of O-2 were installed on the inner side of the containers. A lupine plant was grown in each container for 2 weeks under controlled conditions. Then we took time series of fluorescence images for time-lapsed visualization of oxygen depletion caused by root respiration. Changing water content was mapped in parallel by non-invasive neutron radiography, which yields water content distributions in high spatial resolution. Also it can detect the root system of the lupine plants. By this combined imaging of the samples, a range of water contents and different oxygen concentration levels, both induced by root activities, could be assessed. We monitored the dynamics of these vital parameters induced by roots during a period of several hours. We observed that for high water saturation, the oxygen concentration decreased in parts of the container. The accompanying neutron radiographies gave us the information that these locations are spatially correlated to roots. Therefore, it can be concluded that the observed oxygen deficits close to the roots result from root respiration and show up while re-aeration from atmosphere by gas phase transport is restricted by the high water saturation. Our coupled imaging setup was able to monitor the spatial distribution and temporal dynamics of oxygen and water content in a night and day cycle. This reflects complex plant activities such as photosynthesis, transpiration, and metabolic activities impacting the root-soil interface. Our experimental setup provides the possibility to non-invasively visualize these parameters with high resolution. The particular oxygen imaging method as well as the combination with simultaneously mapping the water content by neutron radiography is a novelty. KW - Fluorescence imaging KW - Neutron radiography KW - Oxygen mapping KW - Rhizosphere KW - Root respiration KW - Water distribution Y1 - 2012 U6 - https://doi.org/10.1007/s11368-011-0407-7 SN - 1439-0108 VL - 12 IS - 1 SP - 63 EP - 74 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Rudolph, Nicole A1 - Voss, Sebastian A1 - Moradi, Ahmad B. A1 - Nagl, Stefan A1 - Oswald, Sascha Eric T1 - Spatio-temporal mapping of local soil pH changes induced by roots of lupin and soft-rush JF - Plant and soil N2 - The rhizosphere is a dynamic system strongly influenced by root activity. Roots modify the pH of their surrounding soil causing the soil pH to vary as a function of distance from root surface, location along root axes, and root maturity. Non-invasive imaging techniques provide the possibility to capture pH patterns around the roots as they develop. We developed a novel fluorescence imaging set up and applied to the root system of two lupin (Lupinus albus L., Lupinus angustifolius L.) and one soft-rush (Juncus effusus L.) species. We grew plants in glass containers filled with soil and equipped with fluorescence sensor foils on the container side walls. We gained highly-resolved data on the spatial distribution of H+ around the roots by taking time-lapse images of the samples over the course of several days. We showed how the soil pH in the vicinity of roots developed over time to different values from that of the original bulk soil. The soil pH in the immediate vicinity of the root surface varied greatly along the root length, with the most acidic point being at 0.56-3.36 mm behind the root tip. Indications were also found for temporal soil pH changes due to root maturity. In conclusion, this study shows that this novel optical fluorescence imaging set up is a powerful tool for studying pH developments around roots in situ. KW - Acidification KW - Alkalization KW - Exudates KW - Fluorescence imaging KW - Optical sensors KW - pH mapping KW - Rhizosphere Y1 - 2013 U6 - https://doi.org/10.1007/s11104-013-1775-0 SN - 0032-079X VL - 369 IS - 1-2 SP - 669 EP - 680 PB - Springer CY - Dordrecht ER -