On the Effect of Temperature upon the Division and Elongation of Cells in the Root of Rice Plant

Abstract

Experiments were carried out to investigate the effect of temperature upon the division and elongation of cells in the seminal root of rice plant. The results obtained are as follows : 1) We could find no dividing cells in the root tips of the seedling kept under 40° and 43°C, as results of changes in protoplasm : vacuolation of cytoplasm, deformation of nucleolus and others. Under 25°C treatment, the intensity of cell division was most flourishing. The number of dividing cells decreased in proportion to the decline from 25°C as in Fig. 1. 2) The primary maxima of the frequency of cell division occurred at 10 A.M. and 10 P.M. with the smaller secondary maxima at 4 A.M. and 6 P.M., and this periodicity proceeded in a similar rhythmic fashion without distiniction of difference of temperatures as to be seen in Fig. 2. 3) The degree of the elongation of cortical cells were most conspicuous under 30°C treatment, and those cells were shortened according as temperature rose or fell from that point. Furthermore, we recognized that the effect of temperature on the elongation of the root was almost the same as the results obtained in the elongation of cortical cells above mentioned. 4) As the optimum temperature for cell division differed from that for cell elongation in root tip, it may be considered that in accordance with changes of temperature the inner morphological state of roots became unlike, even if the growth of roots was same.