COMPARISON OF THE CALCIUM AND SULPHUR CONTENT OF PLANT FLUIDS EXPRESSED FROM TISSUES KILLED BY AUTOCLAVING AND BY FREEZING WITH SOLID CARBON DIOXIDE

Sap analysis in combination with analysis of the complete tissue is particularly useful in gaining information concerning the distribution of elements between fluids and solids of a given tissue and the relative availability of elements for conditioning metabolic processes of the plant. Two methods, killing by heat and killing by freezing with solid carbon dioxide, are readily adapted to the pretreatment of plant tissues in the field for subsequent studies on the expressed sap. Both procedures have been used but few comparisons of results of mineral analyses of sap obtained by the two methods have been published. Results reported in this paper are intended to call to the attention of investigators of plant tissues the possibility of obtaining expressed fluids of different composition depending upon the methods of pretreating the materials. Particular emphasis is placed on the calcium and total sulphur of such saps because these two constituents showed the greatest change as a result of the type of pretreatment for the plants and elements studied. With other plants, other constituents may differ.