CRYOSCOPY OF SMALL AMOUNTS OF EXPRESSED TISSUE SAP

Abstract

Apparatus and procedure are descr. whereby osmotic pressure values of 0.5 to 1 ml. of sap, expressed from small blocks of tissue, may be obtained. While designed for beet root, the method is applicable to other plant juices. Freezing points are detd. by use of an Anschutz type thermometer with a small bulb, calibrated in 0.01 [degree]C. Crystallization is initiated at [long dash] 2[degree] by inserting an ice-filled glass capillary into the soln. Simultaneous correction for both supercooling and heat capacity effects is accomplished by standardizing the apparatus with pure sucrose solns. and comparing values obtained with accepted correct values. Freezing-time curves prove the validity of such correction. The method permits up to 6 detns. in an hr.