Inaug.-Dis.--Rostock. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 80-82).

Call number: LD2668 .T4 1937 H32

Thesis (Ph. D.)--University of Michigan, 1924. / Cover title. "Reprinted from the American journal of botany, XI ... December, 1924." Bibliography: p. 645-646.

The question investigated in this study was whether or not somatic recombination can occur in Ustilago hordei whilst it is in the parasitic phase on barley. The investigation was carried out in two parts. In the first and major part, barley seeds were inoculated artificially with mixtures of nutritionally deficient mutants of U. hordei. This was done in such a way that infection of the mature plants could only occur if at least one recombination event had taken place asexually, between at least two infective dikaryons, prior to teliospore formation. One smutted plant was found. Detailed analysis of the teliospores from this infection was carried out. The second part of the study was designed to demonstrate that more than one infective dikaryon can simultaneously occupy the host. Again, mixtures of nutritionally deficient mutants were used to inoculate barley seeds but this time so that the origin of teliospores from any infection could be traced back to the parental types in the infective dikaryon. It was concluded that somatic recombination can in fact occur whilst the fungus occupies the host tissue. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 44-48). Also available via the Internet.

Call number: LD2668 .T4 1948 S34 / Master of Science

No description available.

A comparative light and electron microscope technique has been used to study the cytological changes accompanying teliospore (i.e. probasidium) germination in Ustilago hordei (Pers.) Lagerh. Special emphasis has been placed on determining the ultrastructural events involved in karyokinesls, especially meiosis, and cytokinesis. The thesis is divided into five parts, of which the first is concerned with pre-germinal differentiation. The great increase in microanatomical complexity which occurs during the pre-germinal stages is due largely to an increase in the amount of endoplasmic reticulum (ER) and to the formation of "primary hydration vacuoles." Evidently the nuclear envelope gives rise to the new ER which in turn dilates to form the vacuoles. This is accompanied by an increase in mitochondrial size and the development of patches of patches of "flocculent cytoplasm." Part II concerns the initiation and subsequent extension of the metabasidium (i.e. promycelium). Initiation involves the localized degradation of the inner spore wall, and deposition of new wall material. The ER and spherosome-like bodies seem to be associated with these activities. Once spore wall rupture has occurred the structural basis of promycelial extension is unknown but changes in the number, size, and distribution of the spherosome-like organelles appear to have profound effects on the differentiation of the organism. Septation, knee-joint formation, and budding are discussed in part III. Elaborate membrane complexes are associated with cross wall initiation. A membranous plate is completed across the cell before septal wall thickening begins. The initiation of sporidia (i.e. basidiospores) involves a localized plasti-cization of the promyoelial wall followed by degradation of the old wall and subsequent synthesis of new wall material. Bridge-formation results when two adjacent cells give rise to bud-like processes which grow together and subsequently fuse to produce a protoplasmic bridge. The structure and activities of the metabasidial nuclei and their associated structures are discussed in part IV, Both meiosis and mitosis are unusual in that the two chromatin bodies apparently remain attached to the centriolar-kinetochore-equivalent and at least one of the chromatin bodies in attached to the nucleolus throughout the division cycle. The results are compatible with Brown and Stack's (1971) model for somatic nuclear division in some fungi. Membrane complexes, resembling those which Initiate septa, form in association with prophase nuclei and maintain a specific relation with the nucleus throughout division. In part V the suggestion is made that these complexes form part of a mechanism controlling the positional relationships of nuclear and cell divisions in the promycelium. / Science, Faculty of / Botany, Department of / Graduate

published_or_final_version / Botany / Doctoral / Doctor of Philosophy