The application of SIMS to nutrient tracer studies in plant physiology

Current controversies in root physiology relating to the uptake and translocation of mineral nutrients are presented. The opportunities for a SIMS contribution to resolve these controversies are discussed for each of the stable isotope tracers relevant to plant nutrition. It is concluded that for all major nutrients except phosphorus there are promising stable isotope tracers. At the same time, there are challenges to overcome in each case, with respect to background levels, peak interferences and sometimes sensitivity. Techniques of tissue preparation and handling are discussed in some detail, giving attention to the special requirements of plant tissue preparation and analysis for diffusable ions. It is suggested that adapting a preparation and transfer system, designed for production of bulk frozen-hydrated cryofractured specimens, to a secondary ion mass spectrometer would permit easy, rapid preparation. Additionally, this preparation minimizes several serious technical problems inherent to other preparative methods. Difficulties in quantitation are treated briefly, outlining some difficulties specific to plant tissue analysis. Prospects for future applications in plant mineral nutrition are evaluated, taking into account current instrumental developments.