338 



Journal of Agricultural Research voi. in. no 4 



Table II. — Carbohydrate transformations in sweet potatoes in cold storage — Continued 



BIG STEM, SECOND LOT** 



SOUTHERN O^JEEN & 



Nov. 10. 



Dec. 8... 

 Dec. 33.. 



Oct. 23 

 Oct. 30 

 Nov. 6 

 Kov. 13 

 Nov. 20 

 Nov. 27 

 Dec. 4 

 Dec. II 

 Dec. 18 

 Dec. 25 



o The figures are all calculated for the original water content of the roots. 73.50 per cent. 

 *> The figures are all calculated for the original water content of the roots. 71.69 per cent. 



In these experiments three lots of potatoes were used. One lot of 

 the Big Stem and one of the Southern Queen were placed in cold storage 

 immediately after they had been cured. Another lot of the Big Stem 

 variety which had been kept in warm storage until March 27 was placed 

 in cold storage on that date. The cold-storage experiments were of 

 short duration, since the potatoes invariably rotted after having been 

 kept at the low temperature for about six weeks. 



These data show that at low temperatures the disappearance of 

 starch and the accumulation of sugar in sweet potatoes take place more 

 rapidly and proceed to a greater extent than at high temperatures. 

 As to the relative proportion of the individual sugars, the two types of 

 potatoes seem to differ somewhat. In both types the cane-sugar con- 

 tent is markedly higher in cold than in warm storage. In the Big Stem 

 sweet potatoes the invert-sugar content also is higher in cold storage, 

 but in the Southern Queen the invert-sugar content is no higher in cold 

 than in wann storage. In general, cane sugar is the chief product 

 which accumulates at low temperatures. The total carbohydrate con- 

 tent, with one exception, remains fairly constant, and the increase of 

 sugar accounts for the loss of starch. The exception mentioned is the 

 discrepancy between the loss of starch and the gain of sugar in the Big 

 Stem potatoes during the inten'al from December 9 to December 21. 

 The only explanations that can at present be suggested for this discrep- 

 ancy are either that after long exposure to low temperatures the various 

 phases in the process of the transformation of starch into sugar are 

 influenced in such a way that intermediate products which escape detec- 



