﻿APPLEMAN—REST PERIOD 



Butkewitsch (4) showed that the stored starch in the cortex 

 and wood can be dissolved by the action of toluol and chloroform, 

 and also by high temperature. He thinks the action is similar to 

 cold and consists in a weakening of the plastids. 



Gruss (9) investigated the chemical changes set up in the cells 

 around the wound in potatoes, and found an increase in the oxidiz- 

 ing enzymes and in the diastase activity. There was some sugar 

 accumulation in the subphellogen. Muller-Thurgau (19) was 

 probably the first to observe the accumulation of sugar in potatoes 

 stored at low temperatures. 



Fisher (8) studied the changes in the starch content of trees 

 during the rest period. He found the maximum of starch from 

 leaf fall to the beginning of November. Starch solution began 

 in November and reduced the starch content to the minimum 

 in the winter. Starch synthesis began in March and reached 

 the maximum again in April, after which hydrolysis began and 

 brought the starch content to the minimum during the latter 

 part of May, or the time of the beginning of vegetative activity. 

 Storage of starch occurred of course during the summer. 



Biochemical 



It is obvious from the foregoing survey of the literature that 

 there is little exact experimental data on the chemical and physical 

 situation in stems which forces the growing cells into a period of 

 rest. The same is true of the changes in the resting tissue or its 

 immediate environment which are essential to the release of the 

 growth processes at the end of the rest period . These latter changes 

 will be spoken of as after-ripening, using the term in its broadest 



It is a well known fact that under normal conditions potato 

 tubers will not sprout for several weeks after harvest. Rehobeth 

 potatoes harvested on July 17 and planted immediately in the same 

 field did not sprout until October, although good growing conditions 

 prevailed during the entire period. McCormick potatoes harvested 

 on November 11, and kept constantly under favorable growing 

 conditions in the greenhouse, did not sprout until January 24; 

 general sprouting did not occur until February. It has been gen- 



