USING BULK MAGNETIC-SUSCEPTIBILITY TO RESOLVE INTERNAL AND EXTERNAL SIGNALS IN THE NMR-SPECTRA OF PLANT-TISSUES

Internal and external NMR signals from a variety of plant cells and pl ant tissues can be resolved by changing the bulk magnetic susceptibili ty (BMS) of the perfusing medium with [Gd (EDTA)](-) or Dy(DTPA-BMA). This separation is observed in samples consisting of cylindrical cells oriented along the Bo field, and is consistent with established theor etical predictions about BMS effects. Evidence is presented that the s hifted signals represent material outside the tissue as well as some c ontribution from intercellular spaces and cell walls, while intracellu lar signals are unshifted. The paramagnetic complexes used to separate the signals are shown to be nontoxic and to have no effect on a numbe r of transport processes. The method has been applied to roots, shoots , and giant algal cells, facilitating the interpretation of the in viv o spectra from a range of biologically important magnetic isotopes. Th e potential of the method for studies of transport is illustrated with experiments showing: (i) N-14/N-15 isotopic exchange of nitrate in ro ots; (ii) the influx of HDO into root and shoot segments; and (iii) th e use of saturation transfer to follow water movement into and out of plant cells. (C) 1997 Academic Press.