酸素濃度

The writer (KOJIMA) has already shown in his observations of the young root of Vicia Faba cultured in tap water, that the richer the culture medium had oxygen, the higher were both the rate of elongation and the frequency of cell division in the root tip. In the present investigations the w riter wished to make clear whether or not the root, which was cultured in a medium lacking in oxygen, could be supplied with the needed oxygen indirectly through the aerial parts of the plant (leaves, stems etc.). The young root of . Vicia-seedlings were placed in water, from which oxygen was already excluded as far as possible by means of boiling, and the aerial part (cotyledons, young stem as well as leaves) of the seedlings were kept (1) in normal air, (2) in air from which oxygen was excluded by means of pyrogallol solution, or (3) in pure oxygen. The rates' of elongation in the roots of the three sets were very small and there was no remarkable difference among them ; the rates were about 10 % of that of control material, which was cultured in water, constantly bubbled with air and furthermore they were less than 10 % of that of another control material cultured in moist sawdust. The frequency of cell div i sion of the root was calculated by counting the number of mitotic figures in the sections of the root under the microscope. The frequencies of cell division of the roots in the three kinds of culture were also without exception very small; they were too small to note the difference among them ; compared with the frequency of cell division in the root of control plants cultured in moist sawdust, they were only about 2-3 %. Thus the rate of elongation as well as the frequency of cell division in the roots cultured in the medium of lack of oxygen was very low in any event whether the aerial part of the plant was in the normal air, or in pute oxygen, or in an oxygen-free atomosphere. This fact shows that the physiological function of the root tip is hardly influenced by the oxygen supplied by the atomosphere to the aerial part of plant.