Abstract
In this paper there are given the results of a study of the relation of respiration to temperature, in seedlings of Vicia faba, and of the onset of geotropic response. It is shown that with due care and very accurate control of temperature constancy, one can get constant excretion of CO(2) even over fairly long periods. The treatment of the experimental data shows that the Q(10) ratio is of course a valueless "constant," as it is variable; but that the figure obtained for micro, the temperature characteristic (critical thermal increment), 16,250, is perfectly consistent with the values previously obtained for micro in respiratory oxidative processes in similar material. New data on the reaction time for the root of Vicia faba seedlings excited geotropically are given also. The study of the dependence of this time relation on temperature shows micro = 16,110, agreeing quantitatively with the value deduced previously from the relevant data of earlier investigators (Crozier, 1924). This points to the importance of some respiratory oxidative process as the agency controlling the onset of geotropic curvature.