Degree Name

Master of Science (MS)

Semester of Degree Completion

1977

Thesis Director

Richard L. Smith

Abstract

Eremosphaera viridis de Bary was studied with light microscope techniques to determine the method of cytokinesis and to explain the ontogeny of the membranous ring separating the mature daughter cells in the intact sporangium.

It is proposed that cytokinesis in this organism is phylogenetically advanced and that the separation of mature daughter cells involves the sequential deposition of two cell walls. The first wall develops centripetally by the addition of membrane subunits. The resulting cleavage furrow is oriented by transverse microtubules found along the cell division plane. The newly formed walls separate the two daughter cells and give rise to two sporangial plates. The second wall develops after the initial cytokinesis, also by membrane addition, fo llowed by the deposition of the cell wall proper. The second wall, however, forms simultaneously along the entire surface of each daughter cell. Hence, it redefines the shape of the daughter cells i.e. they change from hemispherical to spherical while within the sporangium.

A furrow-phycoplast method of cytokinesis has been proposed for E. viridis with the distinctions: (1) that initial wall formation occurs centripetally, (2) that the transversely oriented microtubules serve to orient the plane of wall formation i.e. cleavage during the original cytokineses, and (3) that the formation of two separate and distinct walls is involved in the development of mature daughter cells of this organism.

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