Harnessing the power of 11C-labelling and Positron Emission Tomography (PET) for investigating Phloem velocities above and belowground

The short-lived radioisotope 11C can be applied non-invasively to the plant as 11CO2 to follow the flow of recently fixed carbon. This method has allowed for many interesting findings on phloem flow in the past. The combination with PET detection and compartmental modelling has the potential to allow the imaging and quantification of phloem flow in complex 3D structures such as root system or branched shoots. However, this requires an experimental pipeline and facility to label and image plants in a reliable and consistent manner. We will show the key elements of the pipeline we have established in a plant-dedicated radiotracer lab for routine flow imaging along with discussing the advantages and limitation of the approach. Results will be presented on phloem flow velocities simultaneously measured in different root types of maize with statistically relevant numbers of individuals and other 3D examples. Furthermore, results will be presented on phloem flow in different parts of bean shoots and examples for other species

Monitoring spatial and temporal growth and carbon dynamics in roots by co-registration of Magnetic Resonance Imaging and Positron Emission Tomography

Individual plants vary in their ability to respond to environmental changes. The plastic response of a plant enhances its ability to avoid environmental constraints, and hence supports growth and reproduction, and evolutionary and agricultural success. Due to the opaque nature of soil, a direct observation of belowground processes is not possible. Major progress in the analysis of belowground processes on individual plants has been made by the application of non-invasive imaging methods including Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET). MRI allows for repetitive measurements of roots growing in soil and facilitates quantification of root system architecture traits in 3D. PET, on the other hand, opens a door to analyze dynamic physiological processes in plants such as long-distance carbon transport in a repeatable manner. Combining MRI with PET enables monitoring of carbon tracer allocation into active sink structures such as nodules. Further, co-registration of MRI and PET allows for innovative and image-based sampling strategies of rhizosphere microorganisms, such as bacteria, fungi and protists.We are convinced that this approach will help revealing novel traits demanded in ecological studies or breeding programs for future crops

Monitoring spatial and temporal carbon dynamics in the plant soil system by co-registration of Magnetic Resonance Imaging and Positron Emission Tomography for image guided sampling

Individual plants vary in their ability to respond to environmental changes. The plastic response of a plant enhances its ability to avoid environmental constraints, and hence supports growth, reproduction, and evolutionary and agricultural success.Major progress in the analysis of above- and belowground processes on individual plants has been made by the application of non-invasive imaging methods including Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET).MRI allows for repetitive measurements of roots growing in soil and facilitates quantification of root system architecture traits in 3D. PET, on the other hand, opens a door to analyze dynamic physiological processes in plants such as long-distance carbon transport in a repeatable manner. Combining MRI with PET enables monitoring of short livedCarbon tracer (11C) allocation along the transport paths (i.e. roots visualized by MRI) into active sink structures.To analyse the link between root-internal C allocation patterns and C metabolism in the rhizosphere, we are combining 11CO2 with stable 13CO2 labelling of plants. Isotope ratio mass spectrometry (IRMS) analyses of rhizosphere soil is applied to link root-internal C allocation patterns with distribution of 13C in the rhizosphere soil. The metabolically active rhizosphere organisms are subsequently identified based on DNA 13C stable isotope probing.In our presentation we will highlight our approaches for gathering quantitative data from both image-based technologies in combination with destructive analysis that provides insights into the functioning and dynamics of C transport processes in the plant-soil system

Linking root carbon partitioning to inter-kingdom microbial variation in the maize rhizosphere

As much as 20% of a crop’s photosynthetically fixed carbon is transported belowground where it is used for root growth, respirated or released into the rhizosphere. The excretion of plant derived carbon compounds into the rhizosphere is a substantial source of soil organic carbon. It supports the development of rhizosphere microorganisms and can thereby benefit plant performance. Meanwhile, little is known about the temporal and spatial distribution patterns of recently fixed carbon in roots and how it links to the rhizosphere microbial community structure. To address this point, we employed a combination of the two non-invasive imaging techniques magnetic resonance imaging (MRI) and positron emission tomography (PET) to visualize root carbon allocation over time. MRI allows 3D monitoring of root growth in soil, while PET uses the short-lived radioactive 11CO2 to trace recently fixed carbon within the root system. Maize plants were grown in a sandy loam for three weeks. Roots were scanned using MRI and PET at day 6, 13 and 21 after sowing. Monitoring of root growth and tracer allocation revealed an increased accumulation of recently assimilated carbon at root tips, particularly at young crown root tips. On day 21 after sowing, image-guided sampling based on co-registration of PET and MRI scans allowed us to sample the rhizosphere at high spatial resolution, whilst targeting areas with distinct patterns of recently assimilated carbon. We furthermore distinguished between all relevant root types and age classes to document small-scale differences in microbial community structure. Amplicon sequencing revealed that the community composition of bacteria, fungi and protists was significantly influenced by both, root carbon partitioning and the associated root type. During the congress, findings of bacterial, fungal and protist community analysis will be discussed, along with the associated tracer allocation patterns obtained by MRI/PET

Monitoring spatial and temporal growth and carbon dynamics in roots by co-registration of Magnetic Resonance Imaging and Positron Emission Tomography

Individual plants vary in their ability to respond to environmental changes. The plastic response of a plant enhances its ability to avoid environmental constraints, and hence supports growth and reproduction, and evolutionary and agricultural success. Due to the opaque nature of soil, a direct observation of belowground processes is not possible. Major progress in the analysis of belowground processes on individual plants has been made by the application of non-invasive imaging methods including Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET). MRI allows for repetitive measurements of roots growing in soil and facilitates quantification of root system architecture traits in 3D. PET, on the other hand, opens a door to analyze dynamic physiological processes in plants such as long-distance carbon transport in a repeatable manner. Combining MRI with PET enables monitoring of carbon tracer allocation along the transport paths (i.e. roots visualized by MRI) into active sink structures such as nodules. We will highlight our approaches for gathering quantitative data from both image-based technologies. In particular the combination of MRI and PET has high potential for gaining deeper insights into dynamics of root growth and, for example, interactions with microbes for revealing novel traits demanded in ecological studies or breeding programs for future crops