Studies on the Growth of Tobacco Roots : IX. On the respiratory character of root apex

Abstract

For the purpose of finding some data on the physiological mechanism of root elongation, the influence of external and internal conditions on the respiration of root apex was studied. The results obtained were summarized as follows. 1. Oxygen uptake of roots in the buffer solution ranging from pH 4.53 to 8.30 showed a conspicuous difference. The optimum range was found at pH 7 order and the uptake decreased in the acidic side below pH 6 and basic side beyond pH 8. 2. Root apex grown under low temperature showed higher respiration than that grown under high temperature. Oxygen uptake of roots was highest in the medium of high oxygen concentration. 3. Respiratory rate of root was highest at the apex and decreased toward the base of the root. Respiration in the youog or fine roots was hihher than in the old or big ones. 4. The optimum Mol density for respirtory rate of glucose and fructose was 0.24, whereas that of sucrose 0.12. 5. Addition of malic acid and succinic acid solution to root apex increased root respiration, TCA cycle is supposed to be connected with the progress or root respiration.