QUANTITATIVE X-RAY-MICROANALYSIS OF SOLUTES IN INDIVIDUAL PLANT-CELLS- A COMPARISON OF MICRODROPLET AND IN-SITU FROZEN-HYDRATED DATA

Two different approaches to X-ray microanalysis were tested and compar ed. These were the analysis of sap droplets extracted from individual cells (plants grown and analysed in Banger, U.K.), and the analysis of cells in situ in frozen tissue (plants grown and analysed in Hannover , Germany). The data suggest that both these methods can produce quant itative data accurately reflecting in vivo concentrations in cereal le af epidermal cells. The relative merits of the two procedures are disc ussed with reference to possible sources of error and their applicatio n to other cell types. Bulk wheat leaf tissue concentrations of K and Cl did not differ significantly between the two locations, but Ca conc entration was significantly higher in the plants grown in Hannover. Mi crodroplet analysis invariably yielded linear responses in the range o f concentrations found in plant tissue (r(2) for Ca > 0.97, r(2) for K , Cl > 0.99), and interference of other components of the sap was mini mal. The calibration curves for the frozen-hydrated material were typi cally linear in the same range of concentrations (r(2) for K, Ca, Cl > 0.95), and the results for K and Cl concentration in these samples we re highly consistent with those measured in the microdroplet experimen ts. In wheat, for example, the cellular Cl concentration varied betwee n 12 mM and 119 mM, but no significant differences were found between the two techniques of measurement, The results for cellular Ca differe d in a manner which might be predicted from the results of the bulk ti ssue analyses.