Figure 3
Localised spectroscopy in in-situ root nodule reveals sugar differences in pre- and post-granule onset regions. (a) FLASH reference with PRESS Region of Interest (ROI), numbered one through five. Roman numerals indicate nodule zones: Meristem (I), Infection zone (II), Nitrogen fixation zone (III). Grey dotted boxes show ROI shift of Betaine due to Chemical Shift Displacement Error (CDSE). Pulse excitation was centred around 4.0 ppm. (b) PRESS spectra captured from Regions of Interest (ROI) shown in a, for Nodule Meristem (1), (early) Nitrogen fixation zone (2), Nitrogen fixation zone (3 & 4), Basal region (5). PRESS voxel sizes were 200 × 350 × 350 µm3. Spectra were aligned to the betaine peak at 3.3 ppm. Water peak region at 4.7 ppm has been omitted for ease of viewing. Intensities of the spectra have not been normalised, reflecting the strength of the signal recorded. This means that for the meristem little information can be discerned. Line broadening 10 Hz. (c) Co-registration of Optical Microscopy confirms the presence of bacteroids in the active nitrogen fixation region. Toluidine blue staining 10x magnification. Abbreviations: nc, nodule cortex; vb, vascular bundle; m, meristem; ra, root attachment area. Scale bars 200 µm.
