CHANGES ACCOMPANYING BREAKING OF REST PERIOD 49 



In other words the later the date, and consequently the nearer the 

 end of the resting phase, the shorter was the period during which 

 respiration could be stimulated by the ether treatment. All twigs 

 were placed in the greenhouse. As before, where stimulation of CC>2 

 had been most marked, growth took place the quickest. 



It is known that enzymes soon become inactive if the products 

 of their work are not utilized. Also it is a matter of common 

 observation that the leaves of woody plants continue to elaborate 

 food in autumn for some time after length growth has ceased, 

 resulting, it is believed, in a great accumulation of carbohydrates, 

 thus greatly hindering the work of the ferments and perhaps causing 

 them to become wholly inactive. Believing that the secret of the 

 setting in of the rest period, as well as the breaking of the rest by 

 treatments, was to be found in a study of the workings of the en- 

 zymes in the tissues of dormant twigs, an investigation along this 

 line was made. The experiments were as follows: (1) With dia- 

 static activity; (2) presence and activity of proteolytic enzymes; 

 (3) fat splitting ferments; and (4) oxidizing enzymes. The agents 

 employed for breaking the rest period in the twigs used in these 

 studies were etherization, desiccation, warm water bath, alcohol 

 bath, hydrochloric acid bath, sodium nitrate spray and mechanical 

 injury. After treatment the cortex was scraped from the twigs and 

 ground into a fine pulp. The first test was for diastatic activity. 

 Potato starch was mixed with a portion of the cortex pulp and two 

 per cent toluene added to prevent bacterial growth. The material 

 was incubated at a temperature of 35 C. The tests for evidences 

 of the presence of diastase were dependent upon the well-known 

 color activity of iodine upon starch. If a starch-changing ferment 

 such as diastase acts upon starch for a time, the addition of iodine 

 does not produce a pure blue color, but instead a blue-purple or 

 violet, red-purple, red, red-brown, yellow-brown, or no color change 

 at all. Since the color reaction indicates the degree to which starch 

 has been changed, then the color obtained at the end of a definite 

 time serves as a basis for determining the enzyme activity. Practic- 

 ally all of the determinations made in this experiment were in dupli- 

 cate. 



To make the results of the tesr comparable, seven easily recog- 

 nized colors were taken as a stan/flard. Quite arbitrarily it was 

 considered that the J^^^||jMjjjjjgkter the color the less the 

 enzyme activity; conversely, t"5iSjffi tne c l r 



the more active the ferments. 



The control material for the experiment consisted of a quantity 

 of the cortex which had been heated in water to a temperature of 



4 



