558 Journal of Agricultural Research voi. v. No. 13 



DISCUSSION OF DATA 



If the results of these experiments are considered in a general way, it 

 is found that the rate of starch conversion varies with the temperature. 

 At 30° C. the process is rapid at first, but soon appears to approach a 

 point where no further conversion takes place. At 15.5°, if the second 

 experiment is regarded as typical, the rate of starch hydrolysis is less 

 rapid, but at this temperature also the process seems to approach a state 

 of completion. At 5° the process is distinctly retarded, but it continues 

 without decrease during the period covered by the experiments. 



The rate of accumulation of cane sugar also varies with the temper- 

 ature. At 30° the greater part of the cane sugar is formed during the 

 first 10 to 12 days after the roots have been severed from the vines, but 

 the rate of accumulation diminishes rapidly. At 5° very little cane sugar 

 is produced during the first 10 to 12 days, but subsequently the rate of 

 accumulation is considerably increased, as if there were a lag at first in 

 the formation of cane sugar at this temperature. 



The behavior of the reducing sugar is obscured by its utilization in 

 respiration. It is nevertheless evident from the data presented in this 

 paper and in former papers that at 30° C. the production of reducing 

 sugar is sufficiently rapid to provide all that is used in respiration and 

 still permit a considerable accumulation which, under normal condi- 

 tions, is not far behind that at 5°. At 15.5° (second experiment) and 

 at 5° there is a marked accumulation of reducing sugar at first, but at 

 these temperatures, as well as at 30°, there is very little further accumu- 

 ation, or even a slight subsequent loss. 



The apparent lag at first in the accumulation of cane sugar associated 

 with the marked accumulation of reducing sugar at low temperatures may 

 throw some light on the process of the formation of cane sugar from 

 starch. In the experiments at 5° C. reducing sugar was obviously 

 formed during the first period as a result of the conversion of starch. 

 The disappearance of starch continued at the same rate during the 

 second period. During this period there was, however, no further in- 

 crease in reducing sugar, but a large increase in cane sugar. Since it is not 

 likely that in the one instance reducing sugar resulted directly from the 

 conversion of starch, and in the other, cane sugar, it may be assumed that 

 the production of reducing sugar went on at a rate corresponding to the 

 loss of starch during both periods and that the excess which was pro- 

 duced during the second period was utilized in the formation of cane 

 sugar. In this connection it is worthy of note that the concentration of 

 reducing sugar always remains comparatively low. Even at low tempera- 

 tures, at which starch transformation goes on continuously and respira- 

 tion is reduced to a minimum, the reducing sugar content does not rise 

 above 2 to 2.5 per cent. It appears, therefore, that with the exception 

 of the quantity used for respiration the reducing sugar is transformed into 

 cane sugar as fast as it is formed from starch. Its rate of transformation 



