THE APPLICATION OF SIMS TO NUTRIENT TRACER STUDIES IN PLANT PHYSIOLOGY

Current controversies in root physiology relating to the uptake and tr anslocation of mineral nutrients are presented. The opportunities for a SIMS contribution to resolve these controversies are discussed for e ach of the stable isotope tracers relevant to plant nutrition. It is c oncluded that for all major nutrients except phosphorus there are prom ising stable isotope tracers. At the same time, there are challenges t o overcome in each case, with respect to background levels, peak inter ferences and sometimes sensitivity. Techniques of tissue preparation a nd handling are discussed in some detail, giving attention to the spec ial requirements of plant tissue preparation and analysis for diffusab le ions. It is suggested that adapting a preparation and transfer syst em, designed for production of bulk frozen-hydrated cryofractured spec imens, to a secondary ion mass spectrometer would permit easy, rapid p reparation. Additionally, this preparation minimizes several serious t echnical problems inherent to other preparative methods. Difficulties in quantitation are treated briefly, outlining some difficulties speci fic to plant tissue analysis. Prospects for future applications in pla nt mineral nutrition are evaluated, taking into account current instru mental developments.