The characterization of apomictic reproduction in Cenchrus echinatus
| Autor: | Shi-Ying Wang, 王世英 |
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| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 Apomixis is an asexual reproductive mode through seeds, and it is classified in three types based on the developmental differences: apospory, diplospory and adventitious embryony. Previous apomixis studies in Taiwan are focus on Paniceae species. In this thesis, we established the basic characteristics of apomictic mode in Cenchrus echinatus through the observations of embryo sacs, flow cytometric seed screening (FCSS), and chromosome counts. Both apomictic and sexual C. echinatus plants showed similar embryo sacs of Polygonum type, which the 8-nucleated embryo sac composes of one egg cell、two synergid cells、one central cell of two polar nuclei and three antipodals. Both apomictic and sexual plants have anatropous ovules. Multiple embryo sacs, however, were observed in one ovule in apomictic individuals. This observation is a typical character of apospory. In addition, an alternative oriented embryo sac was found in our studies. This embryo sac developed perpendicularly to the axis of chalazal and micropylar ends, and there is no passage between this embryo sac and the micropyle. Depending on the observations of multiple embryo sacs and the different oriented embryo sac, we speculate the apomictic type of C. echinatus is apospory. While counting the chromosome numbers of somatic cells from root tips, both apomictic and sexual C. echinatus cells are plants tetraploid which possess 68 chromosomes (2n = 4x = 68). The results from single-seed FCSS and bulk-seed FCSS revealed the apomictic seeds built of a tetraploid embryo and an octoploid endosperm autonomously without fertilization. Facultative apomictic plants produce both apomictic and sexual seeds in same maternal individuals. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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