Browsing by Author "Kelbessa, Ensermu (Professor))"

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    Chromosome Study in Five Endemic Kniphofia Species (Asphodelaceae) of Ethiopia
    (Addis Ababa University, 2009-09) Gadissa, Fekadu; Dagne, Kifle (PhD); Kelbessa, Ensermu (Professor))
    The karyotype of five endemic Kniphofia species of Ethiopia were studied. The studied species are: K. foliosa, K. schimperi, K. hildebrandtii, K. isoetifolia, and K. insignis. Somatic chromosomes were prepared from the root tip meristem using colchicines, 8-hydroxyquinoline or ice-cold pretreatment, followed by fixation (3:1, ethanol:acetic acid) and then enzyme maceration in pectinase-cellulase solution at 37°C for about 1 hr. Air-dry slides were prepared and stained in Giemsa stain in Sorensons phosphate buffer (pH = 6.8). The karyotype analysis has shown that K. foliosa, K. schimperi, K. hildebrandtii and K. isoetifolia are diploid with 2n = 12, where as K. insignis has 2n = 22 chromosomes which is assumed to be a polyploid on the basis of x = 6 for the genus. Polyploidy is the first report for the species. Morphologically, the chromosomes showed a gradual decrease in size in all the species with only small differences between the longest and the shortest chromosomes of each species. The size differences are relatively more pronounced in K. insignis. The karyotype formula was found to be 2m + 8sm+ 2st in K. foliosa, K. schimperi and K. hildebrandtii; 2m + 2m/sm + 8sm for K. isoetifolia and 4m + 12sm + 1sm/st + 5st for K. insignis. Generally, there is only a minor degree of differentiation observed among the karyotypes of the diploid species. One pair of small satellites were observed on the tip of short arms in K. foliosa and K. hildebrandtii, two pairs in K. schimperii and K. isoetifolia and in K. insignis, the secondary constriction is located in the middle of the long arm of a pair of chromosomes and thus delineated two large satellites. Kniphofia foliosa from ‘Laga Shore’, about 10 kms from Gedo town, west of Addis Ababa, was found to have a B-chromosome. This is the first report of B-chromosome for the species as well as the genus. In spite of the fact that samples were collected from only a limited number of sites, the cytogenetical information reported here would create only the basis for further cytological investigation of Kniphofia species. It is, thus, recommended that further cytological and molecular studies including specimens from a wider geographic area should be carried out. Key words: B-chromosome, Chromosome, Endemic Kniphofia species, Ethiopia, Karyotype, Polyploidy.
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    Chromosome Study of Six Vernonia Species (Asteraceae) from Central Ethiopia
    (Addis Ababa University, 2009-09) Kumbi, Birhanu; Dagne, Kifle (PhD); Kelbessa, Ensermu (Professor))
    Chromosomes of six Vernonia species of the family Asteraceae collected from central part of Ethiopia were studied. The chromosomes were prepared from actively growing root tips by conventional air-dry technique and stained in Giemsa stain. Chromosome counts were made from well spread metaphase plates. All the counts are from somatic cells so that the chromosome numbers are 2n numbers. Chromosome counts of 2n = 20 for Vernonia amygdalina, Vernonia adoensis, Vernonia myriantha and Vernonia schimperi and 2n = 18 for Vernonia leopoldii and Vernonia galamensis were recorded. The karyotypes of the species are more of symmetrical with many median, some submedian chromosomes and only one pair of subterminal chromosomes in Vernonia myriantha. Prometaphase chromosome showed chromosomes with satellite (secondary constriction). The numbers of satellited chromosomes observed were one pair in Vernonia myriantha, Vernonia schimperi, Vernonia leopoldii and Vernonia galamensis and two in Vernonia amygdalina and Vernonia adoensis. The results of this study agree with most of the previous studies on the genus. Keywords: Chromosomes, Karyotype, Vernonia
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    Floristic Composition and Structural Analysis of Gedo Dry Evergreen Montane Forest, West Shewa Zone of Oromia National Regional State , Central Ethiopia
    (Addis Ababa University, 2010-06) Kebede, Birhanu; Kelbessa, Ensermu (Professor)); Soromessa, Teshome(PhD)
    This study was conducted on Gedo Dry Evergreen Montane Forest in West Shewa Zone of Oromia National Regional State, 182-196 km west of Addis Ababa (Finfinne). The objective of the study was to determine floristic composition and structural analysis of Gedo Forest. Systematic sampling method was used to collect vegetation data from 72 (20 m x 20 m) and subplots of 1 m x 1 m at the four corners and the center of the large quadrat for herbaceous plants. Vegetation classification was performed using PC-ORD software package. Sorensen’s similarity coefficient was used to detect similarities and dissimilarities among communities. Shannon - Wiener diversity index was applied to quantify species diversity and richness. All trees and shrubs with Diameter at Breast Height (DBH) 2 cm were measured for height and diameter. A total of two hundred thirty five specimens of plants (herbs, shrubs, lianas and trees) were recorded. One hundred and fourty of the species collected from sample plots were used for floristic and structural analysis. The rest, 95, were collected out of sample plots but from the forest and used to describe the complete floristic list. Asteraceae is the most dominant family with 36 species in 24 genera followed by Fabaceae with 16 species in 14 genera and Lamiaceae with 16 species and 13 genera. Out of the plants identified in this study, 25 were endemic species which have been included in the preliminary list assessed for IUCN Red Data List, of which 1 species is Critically Endangered, 18 species in Least Concern, 4 species Nearly Threatened, and 2 species vulnerable. The density of tree species in Gedo Forest decreases with increasing height and DBH classes. The forest is characterized by high density of trees in the lower class than in the higher. Three layers (lower, middle and upper) of tree were identified from the study of vertical stratification of Gedo Forest following the International Union for Forestry Research Organization (IUFRO) classification scheme. The regeneration status of selected woody species was assessed as well as the forest was compared with five dry evergreen forests of Ethiopia. Based on the result of the study, research on the soil seed bank, population dynamics, biology and ecology of endemic species and Ethnobotanical studies to explore the indigenous knowledge on the diverse uses of plants and its conservation, and Participatory management of the forest were recommended. Key words/Phrases: Dry evergreen montane forest, Endemic species, Gedo Forest, IUCN Red Data List, Phytogeographical comparison, vegetation structure