Three-Dimensional Positron Emission Tomography/Computed Tomography Analysis Of (No3-)-N-13 Uptake And N-13 Distribution In Growing Kohlrabi

We report the application of three-dimensional positron emission tomography/computed tomography (PET/CT) for the analysis of (NO3-)-N-13 uptake and N-13 distribution in growing kohlrabi. The analytical procedures, equipment parameters, and image reconstruction mode for plant imaging were tested and selected. N-13 in growing kohlrabi plants was imaged versus time using both PET movies and PET/CT tomograms. The (NO3-)-N-13 transport velocity in kohlrabi from root to petiole was estimated to be 1.0 cm/min. The appearance of shell-shaped (NO3-)-N-13 transport pathways, corresponding to the kohlrabi,corm, suggests the existence of special routes with higher efficiency for (NO3-)-N-13 transport, which tends to have the shortest distances to the leaves or buds. Standardized uptake values (SUVs), used as the representative figures for describing N-13 distribution, were quantified versus time at some putative sites of interest. For multiple analysis of the same-plant, N-13 distribution in kohlrabi under normal conditions, methionine sulfoximine (MSX) stress, and recovery from MSX stress was examined. The N-13 distribution variation studies were also done under the above three growth conditions. Our results suggest a significant downregulation of nitrate uptake in kohlrabi in the presence of MSX.