A cytotaxonomic study of some Australian species of Drosera L. (Droseraceae)

Abstract

KONDO, K. & LAVARACK, P. S., 1984. A cytotaxonomic study of some Australian species of Drosera L. (Droseraceae). Karyomorphological comparisons of 15 species of Australian Drosera are presented along with 11 new chromosome counts. In Australia the genus forms an extensive aneuploid series. The species which have chromosome numbers from n=10 to n= 19 show large chromosomes, while those which have chromosome numbers more than 20 show small chromosomes. Drosera paleacca shows the lowest chromosome number in the genus, 2n= 10, with 10 large chromosomes, indicating a new basic number, x = 5. The non‐staining gap between the chromatids of each chromosome is rather wide and their centromeric region is not seen throughout prophase, prometaphase, and metaphase. The C‐banding and silver‐staining analyses in Drosera petiolaris chromosomes suggest that Drosera chromosomes could have diffuse centromeres and simplified C‐segments. Some taxonomic implications are considered, notably the possible removal of Drosera banksii from Drosera section Ergaleium to Drosera section Lasiocephala and the reduction to synonymy of Drosera section Prolifera.

An evidence on diffused centromeres in Drosera chromosomes provided by scanning electron microscopy

“…This phenomenon supported those investigated by light microscopy (e.g., , Kondo and Olivier 1979, Kondo and Lavarack 1984, Kondo 1984, Kondo and Segawa 1988Sheikh and Kondo 1995;Hoshi and Kondo 1998a, b). Several small gaps interrupting the attachment of the two chromatids were seen.…”

“…Observations of C-banding and silver staining on chromosomes of Drosera petiolaris confirmed that the chromosome in the genus could have C-banding pattern and numerous silver-staining position segments suggesting multi-centromeres (Kondo and Lavarack 1984). Among the dicot genera, only Drosera chromosomes were concluded to have diffused centromeres (Kondo and Lavarack 1984). Later, Sheikh and Kondo (1995), Hoshi and Kondo (1998a, b) and Nontachaiyapoom et al (2000) supported Kondo's hypothesis on the "diffused-centromeres in Drosera chromosome".…”

“…suggested that it might be a case of polycentric (or diffused centromeric) chromosomes due to lack of single, localized centromere. Observations of C-banding and silver staining on chromosomes of Drosera petiolaris confirmed that the chromosome in the genus could have C-banding pattern and numerous silver-staining position segments suggesting multi-centromeres (Kondo and Lavarack 1984). Among the dicot genera, only Drosera chromosomes were concluded to have diffused centromeres (Kondo and Lavarack 1984).…”

“…The mitotic spindles were 60~90 nm diameter at many separate portions on a poleward side of prometaphase and metaphase chromosomes. During the course of investigations in a series of chromosome cytology in Drosera and its close relatives made by Kondo and his associates (Kondo 1966;1969, 1971, 1973, 1984, Kondo and Olivier 1979, Kondo and Lavarack 1984, Kondo and Segawa 1988, Kondo hypothesized that Drosera might have "Diffused centromeres" for the first time since their chromosomes showed commonly relatively wide nonstaining gap between the chromatids of chromosome and non-visible, localized centromeric-regions throughout mitotic prophase, prometaphase and metaphase. suggested that it might be a case of polycentric (or diffused centromeric) chromosomes due to lack of single, localized centromere.…”

Revisão taxonômica do clado tetraploide-brasileiro de Drosera L. (Droseraceae).

“…Com base na morfologia geral, em especial na presença ou ausência de órgãos de armazenamento (e.g. tubérculos ou raízes espessadas), folhas modificadas em propágulos para reprodução assexuada (gemas ou gêmulas) e estípulas, na divisão dos estiletes e nas novidades trazidas pela palinologia (Takahashi & Sohma, 1982), morfologia dos tricomas (Seine & Barthlott, 1993) e número cromossômico (Kondo, 1976), o gênero foi segregado em três subgêneros: D.…”