KARYOTYPES IN RUMEX ACETOSA L. AND THEIR GEOGRAPHICAL DISTRIBUTION

Abstract

Three new Karyotypes of Rumex acetosa were discovered. These are type VI (10i+2J), type VII (10i+2T) and type VIII (8i+2J+2T) (Table I., Fig. 1.). Accordingly the karyotypes of Rumex acetosa are 8 in all. The geographical distribution of the three karyotypes in Rumex acetosa has been studied. Type I was found to be distributed in the northern part of Japan proper, Corea, Kurile Islands and Formosa, and type II in the middle part and type III in the southern part of Japan proper. Owing to the scanty materials the distribution of the remaining karyotypes (types IV-VIII) can not easily be determined (Fig. 2.).
Meiosis in some hybrids between these karyotypes was studied; some of these showed rather irregular divisions while others were quite normal.
The author has arrived at the following conclusions on the origin of the different karyotypes in Rumex acetosa:-
I. The existence of many triploid intersexes in wild and in cultivated plants plays an important part about the origin of karyotypes. Meiosis is more irregular in the triploid intersex than in the triploid male plant or in other autotriploid plants.
II. Consequently new shapes of chromosomes which were not found in the mother plant were found in the progenies of triploid intersexes (Fig. 3-1).
III. Plants with several fragments of chromosomes were often found in the wild. Usually we observed some large J-or V-shaped chromosomes in these plants (Fig. 3-2). Fragmentation of chromosomes was often observed in the course of PMC divisions of some hetero- as well as euploid plants of this species.
IV. Two plants in which the segmental interchange of chromosomes and simple translocation had occured were found. Both are female so that I could not study the ring of four expected. But judging from the shape of somatic chromosomes I can easily decide which chromosomes have changed. The interchanged chromosomes are shown in dots (Fig. 3-3 F' C', 3-4 B' D').
V. The chromosomes of new shape whose origin is undetermined are labelled with question marks in figures. These chromosomes may be explained as the results of complicated changes of chromosomes in the progenies of triploid intersexes. These structural changes in chromosomes perhaps give rise to the differentiation of karyotypes.