USE OF MAGNETIC-RESONANCE TECHNIQUES IN THE STUDY OF DISEASE AND SENESCENCE PROCESSES IN PLANTS

Some applications of NMR microimaging and EPR spectroscopy to the stud y of disease and senescence processes in plant organs are presented, w ith emphasis on the non-invasive nature of the techniques. A particula r strength of the use of NMR microimaging in research on live specimen s is its ability to perform repeated measurements on the same specimen . Images can be generated in either two or three spatial dimensions, d epending on the objectives and timescale of any particular experiment. Contrast is determined by a combination of mobile proton concentratio n and its physical and chemical properties, but at the present time on ly a very small amount of molecular information is generated. EPR spec troscopy produces information specifically on free radicals and parama gnetic metal-containing species on a whole sample basis. Biological sa mple volumes that can be used with most conventional spectrometers are extremely limited, however, due to a combination of the small physica l dimensions of microwave cavities and the fact that water strongly ab sorbs microwaves; the latter problem can be overcome to a large extent by freezing the specimen, but this is then at the expense of repeated measurements to obtain dynamic information. Both techniques largely a void the production of artifacts from sample preparation, which limits the validity of results obtained with destructive analytical techniqu es, where damage-induced responses may represent an appreciable and un avoidable complication.