アルファルファの生理的特性に関する研究 : 第3報 アルファルファにおける地上部各器官および根の生育経過と生育に伴う3要素含量の推移について

抄録

This experiment was conducted to study the growth conditions of alfalfa free from the cutting treatment, as well as the changes taking place in the content of three essential nutrient elements in the course of its growth. The main results obtained were as follows: (1) The plant height, the number of nodes and the number of stems reached their maximum at the stage of full bloom, whereas the root diameter continued to increase almost rectilinearly until the experiment came to an end. (2) Both the leafiness and the T/R ratio decreased with the growth of the plant. The T/R ratio, in particular, began to decrease drastically at the start of the tap-root growing stage due to the sudden increase in the weight of the roots. (3) With regard to the distribution of oven dry weight among various organs of the plant, the roots occupied the greater part of the weight in question, accounting for more than 50 per cent of the total weight after the flowering time. The oven dry weight of the stem part increased by degrees with the growth of the plant (from 21 to 31 per cent), whereas that of the leaves gradually decreased (from 50 to 11 per cent). The oven dry weight of the flowers occupied only 2 per cent of the total weight, constituting a very small part in the weight distribution. (4) As to the hay producing rate dried in a forced draught oven at 70°C, both the tops and the roots attained the highest rate during the period from the stage of buds to that of early bloom. (5) The percentage of N, P and K contained in the plant body was relatively high in the early stage of growth, and tended to decrease with the growth of the plant. The percentage of N contained was the highest in the leaves, and the flowers, the roots and the stems followed in that order. In fact, the leaves were found to contain twice as much amount of N as that of the stems. On the other hand, the percentage of K contained was the highest in the leaves, and the stems, flowers and roots followed in that order. (6) The absolute amount of N, P and K absorbed in the plant body differed greatly accrding to the change in the dry matter weight. The amount in question gradually increased with the growth of the plant. The maximum amount differed depending on the essential nutrient elements and the variety of the organs, although it began to deccease at a certain period of time. (7) The greater part of N contained in the plant distributed over the leaves at the early stage of growth, but later, 50 per cent of the N content were concentrated in the roots. The percentage in regard to P was similar to that of N, but, in the stage of ripe pod, about 60 per cent of the entire P content gathered in the roots, exceeding the corresponding value of N. The greater part part of K distributed in the upper part of the plants, particularly in the stem.