Neutron computed laminography yields 3D root system architecture and complements investigations of spatiotemporal rhizosphere patterns

Purpose Root growth, respiration, water uptake as well as root exudation induce biogeochemical patterns in the rhizosphere that can change dynamically over time. Our aim is to develop a method that provides complementary information on 3D root system architecture and biogeochemical gradients around the roots needed for the quantitative description of rhizosphere processes. Methods We captured for the first time the root system architecture of maize plants grown in rectangular rhizotrons in 3D using neutron computed laminography (NCL). Simultaneously, we measured pH and oxygen concentration using fluorescent optodes and the 2D soil water distribution by means of neutron radiography. We co-registered the 3D laminography data with the 2D oxygen and pH maps to analyze the sensor signal as a function of the distance between the roots and the optode. Results The 3D root system architecture was successfully segmented from the laminographic data. We found that exudation of roots in up to 2 mm distance to the pH optode induced patterns of local acidification or alkalization. Over time, oxygen gradients in the rhizosphere emerged for roots up to a distance of 7.5 mm. Conclusion Neutron computed laminography allows for a three-dimensional investigation of root systems grown in laterally extended rhizotrons as the ones designed for 2D optode imaging studies. The 3D information on root position within the rhizotrons derived by NCL explained measured 2D oxygen and pH distribution. The presented new combination of 3D and 2D imaging methods facilitates systematical investigations of a wide range of dynamic processes in the rhizosphere.

Modern 2D & 3D X-ray Technologies for Testing and Failure Analysis

Modern 2D and 3D X-ray technologies are among the most useful non-destructive testing methods that enable the inspection of an object's internal features without cutting or disassembling the sample. This paper discusses the basic operating principle, advantages, and disadvantages of 2D and 3D X-ray based approaches for testing and failure analysis and describes how these different methods have practical application for failure analysis and dimensional metrology. The techniques discussed are radiography, classical laminography, computed tomography, and computed laminography.