In vivo monitoring of legume root and nodule development

Abstract

Quantitative non-invasive measurement of structural and functional development of plant organs allows for deep phenotyping and dynamic investigation of plant performance under stress. While this can be done straightforward for leaves or stems other plant parts, such as seeds enclosed in pods or roots and nodules hidden in soil are more difficult to investigate. Their development however is critical for yield and performance under stress and direct observations in conjunction with genetic and metabolomics approaches may hint on the underlying mechanisms. Here, we apply a set of three non-invasive techniques for studying such developmental processes: 1) Low field nuclear magnetic resonance relaxometry with portable devices (pNMR) is used to study dry matter and water content in pods over periods of several weeks. 2) Magnetic Resonance Imaging (MRI) is used to study the structural development of roots and nodules in soil filled pots over several weeks. 3) Positron Emission Tomography (PET) with the short-lived radiotracer 11C is used to monitor the partitioning of photoassimilates and its dynamics among roots and nodules. We show the application of all three techniques to pea and bean plants grown in soil. We also discuss their potential to provide a direct view on the effects of genotype or rhizobial strain on plant performance under stress and on biological nitrogen fixation