馬鈴薯の生理, 形態学的研究 : 第14報 馬薯鈴の炭水化物代謝に対する窒素と加里の相関々係に就いて

抄録

During the past decade much attention has been given by plant physiologists to the study of the role of the various plant-food elements in plant nutrition. Nitrogen and potassium are the two most important fertilizer elements needed plant growth. Supplying these elements at the optimum rates and in the proper ratios is an important nutritional problem. Especially with regard to potassium, it is essential to the normal growth of plants ; it has long been assumed that one reason for this is the connection of this element with the carbohydrate supply, either in its formation or in its translocation. In the present investigation, extending the work on carbohydrate metabolism of potato plants, particular attention was given to a study of the relation between the roles of nitrogen and potassium in the carbohydrate metabolism of potatoes during an entire growing period. In the present experiment, young seedlings of potatoes were transplanted from the nursery to Wagner pots filled with culture solutions. The culture solutions were so designed as to contain 9 varied levels of nitrogen and potassium in factorial combinations in each pot. Solutions of these 9 series were adjusted to an initial pH of 5.8 by the addition of sulfuric acid in each treatment and were renewed weekly. The experimental results obtained may be summarized as follows; 1. The amount of potassium was found to affect the number of tubers on each potato plant. The high level of potassium in the culture solution caused an increase in number of tubers per each potato plant. 2. With respect to the starch accumulation in the leaves, remarkable differences between the effects of varied levels of nitrogen and potassium supplies were recognized. The effects of nitrogen levels on the starch content in the leaves were more significant than those of potassium levels, but at the final harvest stage, the starch content in the tubers tended to decrease with higher levels of nitrogen. 3. When the potato plants did not receive adequate supplies of nitrogen and potassium at balanced levels in factorial combination, lowering of the accumulation and of the translocation of transitory starch resulted, which in turn caused decrease in the contents of storage starch in the new tubers and of the total yields of the tubers.