1Global Institute for Food Security, 421 Downey Rd, Saskatoon, SK, S7N 4L8, Canada
2Sylvia Fedoruk Canadian Centre for Nuclear Innovation, 303-111 Research Drive, Saskatoon, SK, S7N 3R2, Canada
| Received 16 Jul 2024 |
Accepted 09 Mar 2025 |
Published 14 Mar 2025 |
The real-time and non-invasive visualization and quantification of symbiotic nitrogen fixation (SNF) in nodulated roots of soybean plants using Positron Emission Tomography (PET) imaging, coupled with the application of [13N]N2 gas as a PET radiotracer, has been explored in only a few studies. In these studies, [13N]N2 was delivered to nodulated soybean roots suspended in air within gas-tight acrylic boxes, followed by two-dimensional (2D) PET imaging to visualize the assimilated [13N]N2 in the air-suspended root nodules. In this paper, we introduce the In-Media Plant PET Root Imaging System (IMP2RIS), a novel gas delivery system designed and constructed in-house. Unlike the previous methods, IMP2RIS allows for non-intrusive delivery and exposure of [13N]N2 gas to the nodulated roots of soybean plants grown in a clay-rich, soil-like and visually opaque growth medium. This advancement enabled in-soil, three-dimensional (3D) visualization of SNF in soybean root nodules using Sofie, a preclinical PET scanner. Equipped with automated controls, IMP2RIS ensures ease of operation and operator safety during the [13N]N2 delivery process. We describe the components and functionalities of IMP2RIS, supported by experimental results showcasing its successful application in efficient delivery and exposure of [13N]N2 gas to nodulated roots of three soybean plant cultivars that vary in rates of N2 fixation. The in-soil quantitative PET imaging of SNF, aided by IMP2RIS, holds promise for enhancing the integration of SNF as a functional phenotypic trait into breeding programs, aiming to enhance SNF efficiency by identifying breeding materials with high SNF capacities.
