COMPOSITION OF TUBERS, SKINS, AND SPROUTS OF 

 THREE VARIETIES OF POTATOES 



By F. C. Cook 



Physiological Chemist, Miscellaneous Division, Bureau of Chemistry, United States 



Department of Agriculture 



PREVIOUS INVESTIGATIONS 



The composition of the potato undoubtedly varies with the soil and 

 with the fertilizer used, as well as with other environmental and climatic 

 conditions. Since the sprouts depend for their growth on the tubers, the 

 composition of the tubers may influence that of the sprouts to no small 

 extent. 



The composition of tubers from different varieties of potato plants has 

 not been investigated, nor has any extended study been made of the 

 composition and growth changes of sprouts from the same or different 

 varieties of tubers. Buckner (j), 1 who has reported analyses of sprouts 

 skins, and tubers from one variety of potatoes for ash, phosphoric acid, 

 magnesium oxid, calcium oxid, and silica dioxid found a relatively high 

 percentage of ash in the sprouts. 



The cause and regulation of rest periods in plants have been studied 

 for years, several investigations having been devoted to the effect of 

 various chemicals on tubers, with a view to shortening the rest period. 

 Experiments at the Arizona Agricultural Experiment Station (5) have 

 shown that ethyl bromid, carbon tetrachlorid, ammonia, gasoline, 

 ethyl chlorid, and bromin are effective in bringing dormant tubers into 

 activity — that is, in stimulating the buds. Seed tubers treated with 

 manganese chlorid and ethyl ether showed no differences i-n the growth 

 of foliage but exhibited a pronounced increase of tuber formation. 

 Miiller (6) claims to have shortened the rest period of tubers by storing 

 them for one month at o° C. Appleman (1) has found an increase of 

 both total and reducing sugar in tubers stored at o° C. According to 

 this investigator, the carbohydrate transformation during the rest period 

 depends entirely on the changing temperature. He has separated also 

 the nitrogenous and the phosphorus compounds of tubers stored for 

 various periods. 



Schulze and Barbieri (9), in 1878, showed that potato sprouts con- 

 tained nonprotein nitrogen in addition to protein nitrogen and found 

 asparagin and solanin. It was shown that the potato contained 0.38 

 per cent nitrogen, practically one-half, or 0.18 per cent of which was in 



1 Reference is made by number (italic) to "Literature cited, " p. 634-635. 



Journal of Agricultural Research, Vol. XX, No. 8 



Washington, D. C Jan. 15, 1921 



wa Key No. E-15 



(62 3 ) 



