﻿1016] APPLEMAN—REST PERIOD 273 



both lots of pulp were sampled for determinations of moisture, 

 starch, total sugar, reducing sugar, and diastase. 2 



The final carbohydrate results are calculated to original moisture 

 basis. It is thus possible to record results in percentage of wet 

 weight, as the possibility of apparent changes due to loss of water 

 by evaporation is excluded. Apparent changes due to this water 

 loss would also be excluded by calculating results to dry basis at 

 the time of analysis, but these results might still show changes due 

 to water taken up by hydrolysis, or to the accumulation of respira- 

 tory water, especially where evaporation is prevented. This 

 method, however, does not take into account loss in dry matter 

 through respiration. In the case of the vault-stored potatoes this 

 would be negligible, since respiration is very low at the vault tem- 

 perature. 



Failure of growth in the buds during the rest period is not due 

 to a lack of available sugar, since the percentage of both reducing 

 and total sugars in the greenhouse-stored tubers was no greater 

 when sprouting began than at the beginning of the rest period 

 (tables I-IV) ; besides, the seed end at the time of sprouting did 

 not contain a greater percentage of sugar than the stem end. The 

 carbohydrate transformations during the rest period are entirely 

 dependent upon changing temperature, and must, therefore, not be 

 considered after-ripening processes. 



Diastase. — Since the supply of soluble carbohydrates for the 

 growing buds is dependent upon the important enzyme diastase, a 

 gravimetric method was employed to determine the diastatic power 

 of the juice from the two ends at intervals during after-ripening 

 under greenhouse conditions. The determinations were made on 

 the same samples used for the carbohydrate analyses. 



The increase in. total sugar after incubation was considered an 

 index of the diastatic activity of the potato extract at the time of 

 analysis. It may indicate simply the excess of the hydrolytic 

 process over a simultaneously occurring synthetic process. On 

 either basis, the potato extract contained active diastase at all 

 times during the rest period. It was uniformly greater in the 



see Bull. no. 183. Maryland Agric. Exper. Sta. 



