馬鈴薯の生理形態学的研究 : 第12報 生育期間中に於ける葉部のアスコルビン酸含量の消長と塊莖の形成に就いて

抄録

It has generally been known that ascorbic acid occurs more abundantly in all green leaves than in non-green tissues of the plants. with regard to the ascorbic acid content of the potato plants, Sugawara (1946) and Demers (1951) are of the same opinion, and also some investigators have good reasons to assume that the synthesis of ascorbic acid is concerned with the process of photosynthesis. In the preceding numbers of this series (1951, a, b) the authors have reported that there is a close relation between the accumulation of starch and the variation of ascorbic acid content in potato tubers during the stage of their development. In the present investigation, extending the work on the influence of ascorbic acid on the accumulation of starch in the tubers, particular attention was paid to the physiological correlation between the contents of ascorbic acid, reducing sugar and chlorophyll (a+b) in the green leaves of potato during the growing period, with a desire to obtain further knowledge upon the mechanism of tuberizition of potatoes. The experimental results obtained may be summarized as follows : (1) At the early stage of growth, the total ascorbic acid content in the potato leaves increased after the sprouts emerged from the soil and this rise continued until immediately after the flowering stage. At the same time, the contents of reducing sugar and chlorophyll (a+b) in the potato leaves increased keeping pace with the increase of ascorbic acid content. Data obtained with regard to the increase of ascorbic acid content in the potato leaves indicate that the sprouts became gradually independent of the mother tuber after they emerged from the soil and concomitant with an accumulation of reducing sugar in the leaves due to the vigorous awakening of photosynthesis of leaves, certain favorable conditions for the formation of ascorbic acid resulted. (2) At the tuber maturing stage, the lowering of the contents of ascorbic acid and reducing sugar in the leaves due to their translocation into the new tubers was recognized. As reported in the previous paper (1952) the authors have ascertained that the content of ascorbic acid in the new tuber increased in proportion to the progressive maturity of the tuber. The experimental data at hand indicating that the time of rapid lowering of ascorbic acid content in the potato leaves coincides with the time of its striking increase in the newly developing tubers shortly after the flowering stage, may add further confirmatory support to our previous assumption that the ascorbic acid in the potato plants may be concerned with the formation of the tuber, especially with the accumulation of starch in the new tuber.