Investigating belowground dynamics with MRI and PET

Development of a root system and management of its various functions suited for the local dynamic resource situation and environmental conditions is critical for plant survival, performance and yield. For “Root Crops” where the yield-relevant organ is developing belowground, the processes leading to amount and quality of the product at harvest also happen among the plants hidden half. Unfortunately, the opaque nature of soil prevents observation of such processes by simple means and while a number of approaches for observing 2D root development such as rhizotrons have been applied successfully, roots naturally develop interacting with their 3D soil environment and form complex 3D structures. Therefore the ability to deep-phenotype the 3D structure and function of roots and other belowground structures non-invasively yields a high potential for gaining new insights into root development, its regulation and responses to stress. Magnetic resonance imaging (MRI) is a technique that allows for non-invasive visualization and quantification of root system architecture traits in soil such as root length and mass, as well as internal structures of belowground storage organs. Positron emission tomography (PET) using short-lived radiotracer 11CO2 provides additional imaging of the distribution of newly fixed photoassimilates. Also Photoassimilate flow characteristics can be extracted from PET data with a model-based analysis. We show here application of both techniques for visualization and quantification of root system architecture, anatomy and photoassimilate allocation on a range of species and developmental stages including barley, maize, sugar beet and pea