1981 Volume 19 Issue 2 Pages 69-72
The dynamics of the temperatures of adaxial and abaxial surfaces of a cotyledon were analyzed under controlled environments with reference to a physiological difference between those surfaces. The difference in temperature between those surfaces was clearly observed at the time of their lowest temperatures under the radiation; the temperature of the abaxial surface was 0.5°C lower than that of the adaxial one, when the cotyledon was radiated both on adaxial surface, and even on abaxial surface. In the case that the stomata closed by the treatment with ABA, there was scarcely any appreciable difference between the temperatures of both surfaces. In microscopical examination, the ratio of stomatal frequency on the adaxial surface to that on the abaxial one was found to be about 80% in the cotyledon used. From these results, it could be conceivable that the stomatal transpiration on the abaxial surface is higher than that on the adaxial one, and this function results in decrease in temperature on the abaxial surface under the radiation.
