AN APPLICATION OF NMR MICROIMAGING TO INVESTIGATE NITROGEN-FIXING ROOT-NODULES

Various techniques to obtain high-resolution NMR images (voxel size do wn to 39 x 39 x 250 mu m) of nitrogen-fixing root nodules from soybean [Glycine max (Merr.)] and peanut (Arachis hypogaea L.) are compared. We describe the artefacts arising from changes in the magnetic suscept ibility throughout the sample and how these can be minimised, A series of T-1 (TR = 220 to 3020 ms) and T-2 (TE = 9.3 to 33.6 ms) weighted i mages are presented. From these it has been possible to locate the oxy gen diffusion barrier, A possible interpretation in terms of nodule bi ochemistry and physiology are given. The data and parameters presented are shown to serve as a basis for more extensive investigations of ro ot nodules (e.g., the oxygen diffusion barrier or the mechanisms drivi ng the regulation of the oxygen concentration in the infected zone by leghemoglobin) by NMR microimaging. (C) 1997 Elsevier Science Inc.