Diploid-Bud Formation in a Haploid Oryza with Some Remarks on the Behaviour of Nucleolus in Mitosis
1941 年 11 巻 4 号 p. 515-525
詳細
1941 年 11 巻 4 号 p. 515-525
1. A fertile diplosporophyte derived from a haplosporophyte by bud-variation was separated as a clone from the mother stock. The root tip cells in the mother stock had 12 chromosomes and those in the fertile diplosporophyte had the doubled chromosome complement.
2. There appeared several culms on which the panicles had fei tle grains mixed with some abortive flowers. Some adventitious roots from such culms consisted of haploid cells only, but others had completely diploid cells, and in other cases the root showed the constitution of a sectorial chimera of haploid and diploid tissue in longitudinal rows. A comparison in the sizes of the cells and the thickness of these roots was made and it was concluded that the sizes of the cells in respective tissue are firstly determined by the chromosome complements, but the propagation of the cells in the respective tissue is much influenced by other factors.
The ratio of the cell volume of the haploid cells to that of the diploid cells is ca. 1:1.26 which is very near to 3√2, in other words the 2x-cells have about 2 times the volume of 1x-cells.
3. As the cause of the bud variation in the present case an over-heating of the water of the culture pot in the sprouting period is suggested. The 2x-sporophytes propagate more rapidly and grow more vigorously than 1x-sporophyte and overhelm the latter. So we can easily see that in nature haplosporophytes produced in some perennial plant, may survive until when the 2x-bud variation appeared among them, an event which proved fatal to the 1x-plants.
4. In early period of the mitosis, probably all the chromosomes are attached to the nucleolus either with their special points or with their end. The former are the naked or very thinly covered parts of the chromonemata, and not the surface of the hyalonema (the chromosome matrix). The nucleolar substance is probably concerned in the various stages of the chromosome cycle for all chromosomes, and not limited to particular ones such as the nucleolar or SAT-chromosomes. The latter kinds of chromosomes have longer naked or thinly covered chromonema neck, so that they are attached snore closely to the nucleolus.
Here the writer wishes to express her thanks to Prof. K. Fujii for his kind advice in the course of this investigation. Her thanks are also due to the authorities of the Konosu Branch of the Imp. Agric. Exper. Station for the supply of the material.
