Studies on chromosome arrangement in some higher plants. III. Haplopappus gracilis (2n=4) and Crepis capillaris (2n=6).

Mitotic spatial model: Arrangement of homologous chromosomes

“…Studies on radial metaphase arrangement by Ferrer and Lacadena (1977) in Crepis spp. and Tanaka ( 1981 ) in Crepis capillaris and Haplopappus gracilis are particularly more convincing.…”

“…In their studies, the adjacent and close positioning of the homologous chromosomes are clearly demonstrated. Tanaka (1981) also recorded that the spatial relationship of somatic chromosomes is maintained in the two adjacent daughter cells as well as in the two daughter nuclei in caffeine-induced binucleate cells.…”

“…This phenomenon is most common in mitotic metaphases of Drosophila, where it is termed 'somatic pairing'; however, it also occurs in several plants and animals (Brown & Stack, 1968;DuPraw, 1970;Heneen & Nichols, 1972;Juricek, 1975;Ferrer & Lacadena, 1977;Tanaka, 1981). Besides diploid cells, cases are on record where in tetraploid cells too, the four sets of chromosomes integrate themselves into a single somewhat larger metaphase ring, as in axolotl (see figs.…”

Low chromosome number angiosperms

“…The four chromosomes of this species can be divided in two pairs, the former shows V-shaped chromosomes and the latter J-shaped chromosomes (Jackson 1959;1962;Tanaka 1981). Tanaka (1967) evidenced an aceto-orcein banding pattern in H. Gracilis metaphase chromosomes.…”

“…Chromosome 1 (the V-shaped) possessed three heterochromatic regions due to the fusion of three chromosomes of H. ravenii with elimination of centromeres and loss of an euchromatic region, chromosome 2 (the satellited J-shaped) was presumed to be composed of both chromosomes 4 and an euchromatic segment translocated from chromosome 2. Sometimes light variation in the short arm of chromosome 2 are observed in strains collected in New Mexico (Jackson 1963) and the relationships between centromeric regions of chromosomes and nuclear envelop was analysed by Tanaka (1981). Sparvoli et al (1966) determined the duration of the mitotic cyle and its phases in the meristematic root cells by patterns of incorporation of 3 H-thymidine and the duration of perinuclear DNA replication was analysed too (Sparvoli et al 1977).…”