A study of tuberization in the potato plant. : V. A relation of the mother tuber to the plant growth and tuberization with plant growth.

Abstract

Seed tuber in the potato plant relates very greatly in its growth and yield. Here the author observed a periodical relation of mother tuber to plant growth and tuberization. The experiments were carried out during 1947, 1948 and 1949 years. The results observed are as follows. 1. The growth of serial part (shoot and leaf weights) and the process of tuberization were observed upon the material plants used of each year. The growth curves of aerial part were expressed as Robertson's formula and the changing points of growth-rate were about the 20 th day after sprouting and the stage of the maximal development was about the 40 th day after sprouting. The process of tuberization could be distinguished in 4 periods as already reported, namely stolon elongation period, tuber formtion p., tuber enlargement p. and tuber completion p. A stage of transition from the stolon elongation p. to the tuber tormation p. began at a direct stage after the changing point of growth-rate. 2. Morphological changes of the mother tuber with plant growth were observed by 5 classified degenerating-grades. The first degeneration was seen at the stage of about the 30 th or the 35 th day after sprouting and afterthat the degeneration advanced qualitatively and quantitatively. 3. The nucellus and the cytoplasma in the cell of mother tuber were seen clearly at the stage before collape of tissue in mother tuber, but the cytoplasm was only a thin layer. A characteristic fact of the collapse was a separation of each cell. YASUI (1946) has reported that the collapse of tissue in mother tuber probably causes by an unbalance of anabolism and catabolism in the mother tuber. The first part of collapse of tissue was mostly the inside of vascullar bundle, namely outernal medulla and in this part dead reaction of the tissue was observed firstly. 4. Starch grain in the mother tuber could be scarcely seen at about the 20 th day after sprouting (Fig. 1), and various abnormal forms which probably showed degenerating processes of the starch grain were observed during the process of numerical decrease of it. 5. Dry matter and water contents of mother tuber at each stage of plant growth before the 40 th day after sprouting were observed on percentage to fresh material at every stages and the comparative value aginst seed tuber before bedding. The dry matter content decreased rapidly before about the 20 th day after sprouting and afterwards its change became very little. Change of water content expressed as percentage of fresh material was opposite to it of dry matter, but the comparative value of water content increased rapidly after sprouting to about 130% by water absorption and afterthat the value did not changed with a constant tendency. 6. Changes of main compositions expressed as percentage of fresh material were observed. The contents of total carbohydrate and total nitrogen decreased rapidly before about the 20 th or the 30 th day after sprouting and afterthat these changes were a little. The contents of total and reducing sugars increased before the 10 th day after sprouting and afterthat decreased more or less. 7. At last the author considered a periodical relation of mother tuber to plant growth and tuberization in potato plant on the ground of the observations described above. The mother tuber in potato plant relates of very great to first growth of aerial part till a stage of changing point of growth-rate and before tuber enlargement period, and afterthat the mother tuber stores water till its collapse, but the water storage is supposed to be only a phenomena with a secondary significance among roles of mother tuber.