Abstract
While many studies concerning the changes in the components of sweet potatoes during storage have been investigated, the detailed distributions in the varied region of seed tuber are little understood. In the present paper, with a desire to obtain some further information on the physiological nature of seed tuber during the storage period, particular attention was paid to the variations of carbohydrate and nitrogen contents at the apex, center and tail both in the pith and cortex of seed tuber, using the variety "Gokokuimo" as material. The experimental results obtained are summarized as follows : 1. At the early stage of storage, the reducing sugar contents rose at the apex and center both in the pith and cortex, while those at the tail fell particularly in the pith. Moreover, the non-reducing sugar contents increased at all of the parts of tuber, and the starch contents declined at every part except the tail in the pith. 2. Being accompanied with the stage advanced, the reducing and non-reducing sugar contents were rich only at the tail in the pith, but poor at the other parts of tuber. And at the same time the starch contents were comparatively abundant at the apex and center, while those at the tail decreased both in the pith and cortex. 3. At the later stage of storage period, the reducing sugar consents declined at the apex, but they were considerably high at the center and tail both in the pith and cortex. Moreover, the non-reducing sugar contents were high at the apex and center, while those at the tail were low. On the other hand, the starch contents showed a striking contrast to the tendencies of non-reducing sugar contents in the pith and cortex. 4. Concerning nitrogen compounds, the soluble-N contents were generally high at the early and later stage, on the contrary the protein-N contents were abundant in the middle stage at all of the parts of tuber.
