Highly-numbered Strands in Coleoptile as a Trait Characteristic to the Cool-region Type op Low-land Rice Plant

Abstract

The results of the present study led the author to the following conclusions. 1. Such cool-region-rice varieties as Soviet and Hokkaido groups have generally strands of larger number in their coleoptiles than those of Tohoku (a little warmer region) group. 2. From the experimental results obtained in the two common varieties Oou No. 191 and Tozo-mochi both suitable to be cultinated in Tohoku and Kanto Districts, Japan, it was found that the strand number in the coleoptile might be changed when the times of seeding or transplanting were shifted, and the increase in the number might be highly and positively correlated with the delay in heading of the mother plant. 3. Hence the author considers that the physiological internal condition of embryo during its earlier stage of development, when it takes place under a cool climate, may be very much similar to that in the case where heading delays under warmer climate, and that the occurrence of highly-numbered strands in coleoptiles of rice plants in cooler regions may be regarded as a result of physiological induction caused by the insufficient length of growth period for the mother plants.