Chromosome Cytology of Some Species of the Lamiaceae Family from Ethiopia
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Date
2007-07
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Addis Ababa University
Abstract
Chromosome numbers are reported here for 11 species of the Lamiaceae
belonging to 6 genera. Two of the species, Satureja paradoxa and Thymus
schimperi, are endemic to Ethiopia. Chromosome preparations were made
from root tip cells after pretreatment with colchicine or 8-hydroxyquinoline
or cold treatment in ice water. Maceration was done in 4% cellulase + 4%
pectinase solution at 36-370C for about one hour which was followed by
airdry slide preparation. Chromosomes were stained with Giemsa in
Sorensen’s phosphate buffer (pH=6.8). The following 2n chromosome
numbers were observed for the studied eleven species: Ajuga integrifolia,
2n=64; Ocimum basilicum var. basilicum, 2n=50; O. lamiifolium, 2n=42;
Plectranthus caninus, 2n=30; P. ornatus, 2n=30; P. punctatus, 2n=56; P.
pseudomarrubioides, 2n=64; Salvia nilotica, 2n=32; Satureja paradoxa,
2n=32; S. simensis, 2n=22; and Thymus schimperi, 2n=30. The
chromosome numbers were determined from somatic mitotic chromosomes
at early prophase to metaphase stages. Polyploidy is evident in most of the
species. Variable basic chromosome numbers for species of the same genus
were observed. Detailed studies of chromosome morphology were not
possible because of the small size of the chromosomes. Notes on the
taxonomy and distribution of each of the genera and species under this
study are provided. It was recommended that further cytogenetical studies
of many species of the family occurring in Ethiopia are required for better
understanding of the phylogenetic and evolutionary relationships of the genera and species.
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Biology