ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES FACULITY OF LIFE SCIENCES Chromosome Study of Some Species of Commelina L. and Tradescantia L. (Commelinaceae) From Ethiopia By Samuel Gebrekiristos A Thesis Submitted to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Biology (Applied Genetics) March 2012 ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES FACULITY OF LIFE SCIENCES Chromosome Study of Some Species of Commelina L. and Tradescantia L. (Commelinaceae) From Ethiopia By Samuel Gebrekiristos A Thesis Submitted to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Biology (Applied Genetics) Table of Contents Pages List of Tables ................................................................................................................................. iv List of Figures ................................................................................................................................. v List of Appendices ........................................................................................................................ vii Abbreviations ................................................................................................................................. ix Acknowledgements ......................................................................................................................... x Abstract .......................................................................................................................................... xi 1. Introduction ................................................................................................................................. 1 2. Literature Review........................................................................................................................ 3 2.1 Taxonomic description of Commelinaceae ........................................................................... 3 2.2 Geographic distribution ......................................................................................................... 4 2.3 Botanical description of the study species ............................................................................ 4 2.3.1 Commelina benghalensis L. ........................................................................................... 4 2.3.2 Commelina africana L. ................................................................................................... 5 2.3.3 Commelina diffusa Burm. f. ........................................................................................... 6 2.3.4 Commelina subulata Roth .............................................................................................. 6 2.3.5 Tradescantia zebrina Hort. ex Bosse ............................................................................. 7 2.3.6 Tradescantia fluminensis Vell. ....................................................................................... 7 2.4 Uses of the study plant .......................................................................................................... 8 2.4.1 Folk medicine ................................................................................................................. 8 2.4.2 Modern medicine (pharmaceuticals) .............................................................................. 9 2.4.3 Ornamental and other values .......................................................................................... 9 2.4.4 Food and fodder ............................................................................................................ 10 2.5 Cytogenetics of Commelinaceae ......................................................................................... 10 2.5.1 Commelina .................................................................................................................... 11 2.5.2 Tradescantia ................................................................................................................. 13 2.6 Implication of cytological study in karyosystematics ......................................................... 14 2.7. Karyotype ........................................................................................................................... 15 i 2.8. Constituents of karyotype................................................................................................... 15 2.8.1 Chromosome number ................................................................................................... 17 2.8.2 Centromere ................................................................................................................... 19 2.8.3 Secondary constriction ................................................................................................. 20 2.8.4 Telomere ....................................................................................................................... 21 2.8.5 Chromosome size ......................................................................................................... 21 2.8.6 Heterochromatin ........................................................................................................... 22 2.9. Chromosome staining ......................................................................................................... 23 2.9.1 Silver staining ............................................................................................................... 24 2.9.2 Giemsa staining ............................................................................................................ 25 2.10. Genome size ..................................................................................................................... 25 2.11. Mechanisms of chromosomal polymorphism .................................................................. 26 2.11.1 Inversion ..................................................................................................................... 26 2.11.2 Deletion, duplication and translocation ...................................................................... 27 2.11.3 Robertsonian fusion and centric fission ...................................................................... 28 2.12 Karyotype evolution .......................................................................................................... 29 3. Objectives of the Study ............................................................................................................. 30 3.1 General objectives ............................................................................................................... 30 3.2 Specific objectives............................................................................................................... 30 4. Materials and Methods .............................................................................................................. 31 4.1 Plant material....................................................................................................................... 31 4.2 Cytogenetic analysis ............................................................................................................ 34 4.2.1 Somatic chromosome preparation ................................................................................ 34 4.2.2 Silver staining ............................................................................................................... 36 4.2.3 Karyotype analysis ....................................................................................................... 37 5. Results ....................................................................................................................................... 39 5.1 Commelina africana ............................................................................................................ 43 5.1.1 C. africana from Addis Ababa ..................................................................................... 43 ii 5.1.2 C. africana from Sebeta................................................................................................ 45 5.2 Commelina benghalensis .................................................................................................... 47 5.3 Karyotype description of Commelina diffusa...................................................................... 49 5.3.1 C. diffusa from Entoto .................................................................................................. 49 5.3.2 C. diffusa from Ginchi .................................................................................................. 51 5.3.3 C. diffusa from Jimma .................................................................................................. 52 5.4 Commelina subulata ............................................................................................................ 54 5.5 Tradescantia fluminensis (green) ........................................................................................ 56 5.6 Tradescantia fluminensis (Variegated) ............................................................................... 58 5.7 Tradescantia zebrina ........................................................................................................... 58 6. Discussion ................................................................................................................................