Date of Award


Document Type


Degree Name

Master of Science (M.S.)


Graduate Studies

First Advisor

Paul A. Richmond

First Committee Member

Dale W. McNeal

Second Committee Member

Alice S. Hunter


The actin fibrils found at the ectoplasm-endoplasm interface in Nitella internodal cells are a major component of the mechanism that is responsible for cytoplasmic streaming in these giant algal cells. The fibrils have been shown to attach to the inner surface of internodal chloroplasts which are embedded in long files within the stationary ectoplasm along the length of the cell. The existence of actin bundles at the ends of the cell, where chloroplast files are absent, has not been examined. Through the use of scanning and transmission electron microscopy, the present work shows that actin bundles are continuous throughout the cell and that those bundles in the chloroplast-free endwall region have a distinct distribution from those associated with chloroplast files. Additionally, the organization of regenerated actin bundles in blue light-irradiated areas of cells {in which an area of the cell cortex is stripped of its chloroplasts and associated actin fibrils) is compared to untreated regions of the cell. These morphological observations are quantified and discussed in terms of their implications towards the nature of actin bundle immobilization and bundle organization during cell ontogeny.



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