RESPIRATION STUDIES OF DEVELOPING JONATHAN APPLES

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Abstract
The Warburg apparatus employing the Barcroft differential manometer was used to study the course of respiration in developing Jonathan apples. This method has much to recommend it from the standpoint of sensitivity and accuracy for physiol. study of high plant materials, especially when plant parts can be used with little mutilation. Its greatest disadvantage is that only small amts. of plant material can be used for each determination. Jonathan apples, even when grown under very similar conditions, are variable in regard to their respiratory behavior. Each apple was measured separately in a respirometer vessel. The apples had attained such size by June 22 that whole apples could no longer be placed in the respirometer. A wedge-shaped slice cut to the center of the apple on the stem-calyx axis, as large as the vessel would accommodate, was used for each detn. after the fruits had attained this size. The rate of respiration was high during the period immediately following "fruit setting," and then decreased gradually for the remainder of the period. The increased surface and the effect of the wounding increased the rate of O2 consumption about 63% when sections of fruit were used for measurement. The R. Q. decreased from 0.84 May 23 to 0.46 June 28, at which time it began to increase, and on July 26 was 0.92. The R. Q. appeared to be little affected by the use of the wounded apple sections.