40 BULLETIN" *79, U. S. DEPARTMENT OF AGRICULTURE. 



plays an important r61e. This translocation, which constitutes the 

 essential physiological difference in the two methods of curing, 

 involves the transfer into the stalk of the amid and amido com- 

 pounds derived from the protein, ammonia and a portion of the 

 mineral constituents, nitrate and, doubtless, a portion of the carbo- 

 hydrates. The picked leaves after curing contain, therefore, much 

 larger quantities of amid and amido compounds, and ammonia and 

 somewhat larger quantities of mineral matter and nitrate than the 

 leaves cured on the stalk. 



The physiological processes characteristic of tobacco curing indi- 

 cate the presence of diastatic, proteolytic, and deamidizing enzyms, 

 and probably also of oxidases. The process of starvation to which 

 the leaves are subjected leads to an increased secretion of diastase 

 during the progress of the curing. 



Temperature has a very marked effect on the rate of curing. The 

 rate of curing increases very rapidly with rise in temperature up to 

 the killing point of the protoplasm (about 130° F.). The moderate 

 use of artificial heat in air curing does not materially affect the final 

 result in curing so far as measured by the ordinary methods of 

 chemical analysis, provided other conditions remain favorable in 

 both cases. 



Thorough wilting in the initial stages of the curing promotes the 

 progress of the process, provided the further drying of the leaf is not 

 allowed to proceed too rapidly. 



o 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914 



