Abstract
3102
Introduction: Much of the world's agricultural land is already impacted by saltwater intrusion in ground water and from seawater often driven by climate change. A way to combat this is to utilise saline water sources or partial desalination (much more energy efficient than full desalination). In order to utilise saline water, research is needed to learn basic information about how plants transport sodium, where it gets stored and how potential genetic differences alter sodium transport in plants. Traditionally Na22 has been used but mainly through single time point well-counting. Limited Na22 plant micro-PET scanning has also been performed previously 1 2 3 4,5. We postulated that the use of a Human PET/CT in continuous multiday dynamic mode for full size plants may yield new information.
Objectives: 1. Examine the impact of nutrition levels and sodium inhibition on sodium transport using multiday PET/CT imaging of barley. 2. Examine diurnal variation in sodium transport of barley.
Methods: This research was conducted in two separate experiments, using a Na22 radiotracer and Siemens MCT 128 PET/CT scanner. Timed synthetic lighting was used to create diurnal cyclical conditions. Four nutrient treatments in the hydroponic solutions were used in the experiments. High nutrient without inhibitor, high nutrient with the inhibitor, low nutrient without the inhibitor and low nutrient with the inhibitor. All was enclosed in a custom hydroponic rig with artificial timed lighting and contamination protection. Approx. 2 mbq of Na22 was administered into each plant hydroponic solutions. PET images were analysed using MATLAB. ROI’s were generated around the plant’s roots and leaves. A reference activity vial was used to normalise drift over the days of PET imaging.
Results: The pattern of sodium influx was consistent across the two experiments, with increased Na22 transport in low nutrient plants and the dose modulated effectiveness of the sodium inhibitor. The diurnal pattern of sodium metabolism was evident, with the plants anticipating the onset of darkness and dawn.
Conclusions: Despite the technical challenges of partial volume effect with thin leaves and the stability of scanning over many days, useful results were obtained, and further experiments are planned with gene mutants to understand gene function in the context of Na transport. 1. Ariño-Estrada, G., et al. Imaging Salt Transport in Plants Using PET: A Feasibility Study. in 2017 IEEE NSS/MIC, 1-2 (2017). 2. Partelová, D., et al. Application of positron emission tomography and 2-[18F]fluoro-2-deoxy-d-glucose for visualization and quantification of solute transport in plant tissues. Chemical Papers 68, 1463-1473 (2014). 3. Beer, S., et al. Design and initial performance of PlanTIS: a high-resolution positron emission tomograph for plants. Physics in Medicine and Biology 55, 635-646 (2010). 4. McKay R.M.L., Palmer, G.R., Ma, X.P., Layzell, D.B. & McKee, B.T.A. The use of positron emission tomography for studies of long-distance transport in plants: uptake and transport of 18F. Plant, Cell & Environment 11, 851-861 (1988). 5. Ariño-Estrada, G., et al. Imaging Salt Uptake Dynamics in Plants Using PET. Scientific Reports 9, 18626 (2019). Figure 1: Inhibitor effect on the Na22 uptake. Dark shading indicates night times. Low nutrient roots: A) Radioactivity ratio without (blue) and with (green) the inhibitor. B) Rate of change of radioactivity ratio without (blue) and with (green) the inhibitor. Low nutrient leaves: C) Radioactivity ratio without (blue) and with (green) the inhibitor. D) Rate of change of the radioactivity ratio without (blue) and with (green) the inhibitor. High nutrient roots: E) Radioactivity ratio without (red) and with (purple) the inhibitor. F) Rate of change of the radioactivity ratio without (red) and with (purple) the inhibitor. High nutrient leaves: G) Radioactivity ratio without (red) and with (purple) the inhibitor. H) Rate of change of the radioactivity ratio without (red) and with (purple) the inhibitor.
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