The use of PET/CT scanning technique for 3D visualization and quantification of real-time soil/plant interactions

Abstract

Aims Conventional methodology using destructive sampling, which is laborious and has poor spatial and temporal resolution, has limited our understanding of soil-plant interactions. New non-invasive tomographic techniques have the potential to significantly improve our knowledge. In this study we demonstrated the simultaneous use of PET (positron emission tomography) and CT (X-ray computed tomography) to (a) non-destructively image a whole plant growing in sand, and (b) to link the observed morphology with recently assimilated C. The PET scanner was used to detect and visualize the location of the short-lived radioisotope 11 C (with a half-life of 20.4 min) taken up by the plant through 11 C-labelled CO 2 . This provided information on carbon translocation and the metabolism of photo-assimilates in the plant as well as root structure. The CT scanners yielded data on soil and root structure. Methods A medical PET/CT scanner was used to scan a fodder radish plant growing in a pot with test soil composed of homogenous sand. We constructed an air-plant-soil controller system (APS) to control the environmental conditions, such as CO 2 , temperature and light during the experiment. The plant was allowed to assimilate 11 CO 2 for 90 min before PET scanning was initiated. We carried out PET scanning for 60 min. Subsequently, the aerial parts of the plant was cut off and the pot was rescanned using a micro-CT scanner to obtain more detailed information on structure of the root system and the growth medium structure. Results The acquired PET and CT images gave images clearly visualizing the architecture and morphology of root and soil. Using a CT scanner, we were able to detect the main taproot located at 0 to 30 mm depth. With the PET scanner, we were able to measure a signal down to 82 mm below the surface of the sand. We found the highest concentration of 11 C at the position of the main root. The PET images, at different time intervals, showed the translocation and metabolisation of photo-assimilates from top to root. Using the micro-CT scanner (voxel size of 90 μm), we were able to detect roots down to 100 mm depth. These findings correlated the PET signals measured down to 82 mm depth.

A Simple Method to Measure Key Parameters of Soil-root Structure Using Medical X-ray Tomography Scanning Technique

“…Nevertheless, scanning with a medical CT scanner yielded no information on the fine roots and the main taproot was distinguished from fine or lateral roots. The micro-CT scanner showed the presence of fine roots down to 100 mm depth, and the PET showed signal until a depth of 80 mm ) Garbout et al, 2011). The present study demonstrates the capability of medical CT scanning to supply datasets for non-destructive and non-invasive spatio-temporal studies on soil-plant interactions at high resolution.…”

“…The MRI is based on proton detection so that a sample contains a low amount of protons will not give a clear signal and the image resolution will be poor. With x-ray CT scan, it was not necessary to deal with such constraints ) Garbout et al, 2011). Using the medical CT scanner enables visualizing the main taproot and detecting it to 30 mm depth.…”

Challenges in imaging and predictive modeling of rhizosphere processes

“…However, these approaches only provide point information and not a complete 3D image. Garbout et al (2012) combined positron emission tomography (PET) with X-ray CT to observe the root system of a growing plant. This enabled them to link the observed morphology/structure with imaging of recently assimilated C. The PET scans were used to visualize 11 C taken up by the plant through 11 C-labelled CO 2 and emitted via the root system.…”

Plant-PET Scans: In Vivo Mapping of Xylem and Phloem Functioning

“…Voxel: the 3D counterpart of a pixel. may contribute significantly [25,[36][37][38][39][40][41][42][43] (Figure 2). This short-lived isotope can be widely used because of the presence of carbon in many plant molecules.…”