抄録
So far as the writers are aware, few detailed accounts seems to have been given, as yet, of the physiological nature of sweet potatoes. In the hope of catching sight of some fundamental informations for the improvement of its cultivation, the present investigation was undertaken with sweet potatoes of the variety"Gokoku". In the present paper are described the behavior of reserve carbohydrate contents, together with the variation of moisture contents, amylase activities, pH value of the pressed juice and the respiration rate of sweet potatoes during their growing season. Moreover, the progressive growing status of shoots and root tubers, in contrast to the inner physiological status, were also traced. The experimental results obtained may be summarized as follows: 1. At the early stage of growth, in spite of the rapid growth of the shoots, the growth of the root tuber was inconsiderable. Both the reducing and the non-reducing sugar contents, as well as the moisture, were rich at this stage, while the starch content was not prominent, and the pH value of the pressed juice was small. 2. In accordance with the vigorous growth of the shoots, the increase of the fresh weight of the root tuber was resulted, and at the same time a remarkable increase of starch content was recognized at the expense of a decrease of the reducing, non-reducing sugars and moisture contents. General weakening of the amylase activity and an evident decline of the respiration rate were ascertained, while the pH value of the pressed juice showed a little higher value than before. 3. By the reduction in the vital force of the shoots with the termination of the growing season, the growth rate of the root tuber progressively became less. Under such conditions, low content of the reducing sugar was recognized, while the non-reducing sugar and moisture contents showed higher value. The starch content decreased a little, but the amylase activity was also abundant. The pH value of the pressed juice was somewhat low and a rapid falling off in the rate of respiration was ascertained.
