Browsing by Author "Gebrekiristos, Samuel"

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    Chromosome Study of Some Species of Commelina L. and Tradescantia L. (Commelinaceae) From Ethiopia
    (Addis Ababa University, 2012-03) Gebrekiristos, Samuel; Dagne, Kifle (PhD); Kelbessa, Ensermu (Professor)
    Karyotypes and nucleolar number of four species of the genus Commelina L. and two species of the genus Tradescantia L. (Commelinaceae) which were collected from different localities of central and south-western part of Ethiopia (Addis Ababa, Ginchi, Sebeta, Entoto and Jimma), were analysed. Somatic chromosomes were prepared from root tips that emerged from the nodes of stem cuttings that were made to stand submerged in water. The roots were pretreated in 8-hydroxyquinelin 3-5 hrs followed by fixation in 3:1 ethanol: acetic acid for 1-24 hrs at 4OC. Air-dry slides were prepared following cellulase and pectinase maceration at 37OC, the preparation was stained in Giemsa stain (PH 6.4), rinsed and mounted. Nucleoli were stained in silver nitrate solution. Chromosome numbers and Karyotype formula of the six species were found as C. africana (A.A) 2n=2x=30 (12m + 10sm + 8st), C. africana (Sebeta) 2n=2x=30 (14m + 10sm + 6st), C. benghalensis 2n=6x=66 (36m + 24sm + 6st), C. diffusa (Entoto) 2n=2x=30 (16m + 6sm + 8st), C. diffusa (Ginchi) 2n=66 (28m +26sm + 12st), C. diffusa (Jimma) 2n=2x=30 (10m + 8sm + 12st), C. subulata 2n=2x=30 (18m +10sm + 2st), T. zebrina 2n=2x=24 (4m + 6st + 14t), T. fluminensis (green) 2n=60 (8m + 6sm + 22st + 24t) and T. fluminensis (variegated) 2n=60. According to Stebbins karyotype asymmetry, the karyotypes of C.africana (A.A), C. diffusa (Entoto), C. subulata were 2A type, while that of C. africana (Sebeta), C. benghalensis and C. diffusa (Ginchi) were 2B type. 3A asymmetry type was obtained for C. diffusa (Jimma) and 3B asymmetry type was also found for T. zebrina and T. fluminensis (green). Karotypes of Tradescantia were found to be bi-modal, while it is monomodal for the Commelina species of the studied plant materials. Satellites were observed for species C. africana, C. diffusa and T. zebrina with variation in number ranging from 2 to 6. The maxiumum number of nucleoli observed varies from two to four for Commelina, while, it is three for Tradescantia. This study reported karyotype and nucleoli of the Ethiopian Commelinaceae for the first time. The current investigation can be considered as an additional karyotype data to the earlier meiosis report for Ethiopian materials. Key words: Commelina L., Ethiopia, Karyotype, Nucleoli, Satellite, Tradescantia L.,