Dec. 27, 191S Carbohydrate Transformations in Sweet Potatoes 555 



further fact should be noted — viz, that the starch content of these pota- 

 toes at the beginning of the first period is comparable in general with 

 that of the potatoes at the beginning of the second period in the other 

 experiments, while the final starch is much lower than in the other two 

 groups. Similarly, the cane-sugar content at the beginning of the first 

 period is comparable with that of the other groups at the beginning of 

 the second period, but the final cane-sugar content is much higher than 

 in either of those. 



Here it is even more evident than in the corresponding experiment at 

 30° C. that the carbohydrate transformations were well under way at 

 the time when the sweet potatoes were dug and that the data given in 

 Table IV merely show the continuation of the processes which had 

 already been started in the ground. 



If the experiments at 5° are now summed up, it is found that whether 

 the potatoes had been dug while the vines were still active or some time 

 after the vines had been destroyed there was a fairly uniform loss of starch 

 during both periods. In the first two experiments only inconsiderable 

 quantities of cane sugar were formed during the first period, but during 

 the second period there was a marked accumulation of cane sugar. In 

 the third experiment the accumulation of cane sugar was marked during 

 both periods. In contrast to the cane sugar, there was a considerable 

 accumulation of reducing sugar during the first period in the first two 

 experiments and a slight loss during the second period. In the third ex- 

 periment there was little or no accumulation during either period. 



The results of the experiments at 15.5° C. (Table V) do not present the 

 same degree of uniformity as those at the other temperatures, but certain 

 definite tendencies are evident. In the first experiment the loss of 

 starch was large during the first period, but during the second the loss 

 was not so great. Correspondingly, there was a considerable quantity 

 of cane sugar formed during the first period and much less during the 

 second. Very little change in the reducing sugar is evident during the 

 first period, but during the second there is a distinct loss. It should be 

 recalled here that the halves used in this experiment lost a large amount 

 of water and that their behavior may have been influenced thereby, for 

 from the work of Lundegardh ^ it appears that the balance between oil 

 and starch and sugar and starch in seedlings is shifted with changes in 

 moisture content. The behavior of the roots in the second experiment 

 is probably more nearly normal. Here the loss of starch is lower during 

 the first period than at 30°, with no further loss during the second. 

 The accumulation of cane sugar is not as great at first as at 30°, but is 

 distinctly larger than during the second period. The increase in reducing 

 sugar during the first period was comparable to that observed at 5°. 

 During the second period there was a slight loss. 



1 Lundegardh, Henrik. Einige Bedingimgen dcr Bildung iind Auflosung der Starke. Ein Beitrag zu 

 Theorie des Kohlehydratstofivvechscls. In Jahrb. Wiss. Bot., Bd. 53, Heft 3, p. 421-463. 1914. 



