Ecological studies of diploid and autotetraploid rice plants.

Abstract

1. To make clear ecologicai characteristics of auto-tetraploid in rice plant, diploid plants of six varieties and the auto-tetraploid ones induced artificially from each of them were used. They were exposed to various environmental conditions, i. e. natural conditions, short day, Ioilg day, high Lem-perature, early sowing, and iate sowing. Gtowth, date of heading, and fertility were investigated to corxipare the tetraploids with the diploids. 2. There was a tendency that tetraploids were. superior to diploids in the elongation of their heiaht from tillering stage to the booting stage. But as fbr the height of plant after he.ding.", the tetraploid were c, .earfy lower than diploids. The cause of this seems to lie in the fact that the d.iploids are very superior to the tetraploids in the length of the first interriode Sust Jender the ear. 3. In bomparison with diploids, the date of heading of the tetraploids was little later or nearly equal in the Japanese late varieties. This tehdency was more clear in Java N0.28. On the contrary Aikoku (middle variety) and P.hiiippine No. 5, were hastened. 4. Between the diploid and tetraploid of Philippine No. 5, there was a difference in photoperiodic resonse. The heading of the tetraploids was earlier than the diploids in aH the other treatments except short day treatment in which the former was later than the latter. Ear formatiori of diploids did not occur under the long day condition but in the tetra-plaids, it was perfectly indifferent to this condition. 5. These-facts will furnish same new valuable data on the problems of adaptation and geographical distribution of polyploid plants.