7本および8本のaccessory染色体を有するライ麦の細胞学的研究〔英文〕

概要

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The cytological behavior of accessory chromosomes in the plants with seven and eight accessories was investigated in meiosis. The results are summarized as follows:1. Notwithstanding the fact that both of the plants have a large number of accessory chromosomes, the accessory chromosomes pair very well with each other and form many radial multivalents. In the radial multivalent of even valency two types were distinguished; that is, the one is symmertical and the other asymmetrical. The mode of configurations in the 7acc. plant was 1IV++1II+1I followed by 3II+1I; and in the 8acc. plant 1IV+2II followed by 1VIII.2. The disjunction of accessory chromosomes at anaphase I was not unusual, being determined by the type of metaphase I configuration. That is, in most of cells 3-4 and 5-2 distributions were observed in the 7acc. plant; and 4-4 and 5-3 in the 8acc. plant. The cells with one or two laggards of accessory chromosomes were considerably observed, but the number of micronuclei in tetrads was a very few. This indicates that the meiotic elimination of accessory chromosomes is suprisingly low.3. The cytological behavior in different species with many accessory chromosomes and the numerical limit of accessory chromosomes contained per plant were dicussed.
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