Abstract
In order to obtain fundamental information for cultivation, the experiments were performed to make clear the growing process of various parts of potato plant, by measuring the length of leaves and stems, the thickness of stems and their dry matter contents every 5 days. In this experiment Danshaku-imo (early variety) and Norin-No. I (medium-late variety) were used. And the crops were grown with a single stem per plant. The results obtained are summarized as follows: 1) Analogical growth is found among the individual leaves on the lower, middle and upper parts of the main stem under the first flower cluster, and the number of leaves in each part are 5. 5. 5 in Danshaku-imo and 6. 6. 3 in Norin No. I. The number of leaves of the lower or middle parts are equal to that of rhizome nodes and have a close relation to their leaf divergence. So, it may be deduced that the leaf divergence is different among varieties. 2) The elongation of stem length become vigorous since the time of bud formation and stops at the end of flowering time. The thickness of stem increases rapidly after the bud formation and shows the maximum at the last flowering of the first cluster. 3) Growth of primary stolon continues from the sprouting till 10 days after buds formation and that of secondary stolon continues from 5 days before buds formation till the end of the first cluster flowering. 4) The elongation of lateral stems and the growth of tubers begin at the same time, and also the increasing curves of their dry matter show the paralell figure. It seems that high temperature (over 28°C, the max. temp.) brings about abnormal growing of main stems, on the other hand, it disturbs the growth of lateral stems and tubers. 5) It may be said that the maturity of potato variety means the length of growing period which keeps pace with the growth of lateral stems and tubers. 6) The upper limit value of leaf area index of the potatoes under the normal condition may be found about 2.7 to 3.0.
