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 plant tissues can be resolved by changing the bulk magnetic susceptibility (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 theoretical predictions about BMS effects. Evidence is presented that the shifted signals represent material outside the tissue as well as some contribution from intercellular spaces and cell walls, while intracellular signals are unshifted. The paramagnetic complexes used to separate the signals are shown to be nontoxic and to have no effect on a number of transport processes. The method has been applied to roots, shoots, and giant algal cells, facilitating the interpretation of the in vivo spectra from a range of biologically important magnetic isotopes. The potential of the method for studies of transport is illustrated with experiments showing: (i) N-14/N-15 isotopic exchange of nitrate in roots; (ii) the influx of HDO into root and shoot segments; and (iii) the use of saturation transfer to follow water movement into and out of plant cells. (C) 1997 Academic Press.