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

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Abstract
Two methods of pretreating plant tissues in the field or laboratory for subsequent analyses of the expressed sap were studied; killing by heat and killing by freezing with solid CO2. The conc. of several of the mineral constituents in the expressed sap varied as a result of the pretreatment received. Ca and total S in the plant juices expressed from autoclaved cotton leaves were lower than the conc. in the plant juices pressed from similar leaf samples killed by freezing. The total S content of saps expressed from autoclaved tomato leaves and stalks was also lower than that from the frozen samples. Because of possible precipitation occurring during the heating process, killing of plant tissues by freezing is the preferable procedure.