Association and distribution of meiotic chromosomes in a haploid of Ricinus communis L.

Abstract

In a haploid of Ricinus communis L., the ten chromosomes are unpaired at pachytene but they frequently display end-to-end association. This kind of association is also common in diplotene.At diakinesis, there is considerable variation among PMC's in number of chromosomes involved and in frequency of different associations in each association. Associations involving only two chromosomes do not appear as genuine bivalents and associations of more than two chromosomes often resemble chains.Chromosome distribution at metaphase I is as follows: in 78.2% of the PMC's (N=238), all ten univalents are scattered haphazardly; in 16% of the PMC's, some or all of the univalents are oriented at the equatorial plate; and in 5.8% of the PMC's, the univalents are found in 2 polar groupings.This study does not support the hypothesis of polyploid origin of Ricinus as proposed by Narain and Singh (1968).