Aspects of cell development in Micrasterias muricata (Desmidiaceae) revealed by cryofixation and freeze substitution
Micrasterias muricata (Bail.) Ralfs cells divided every third day under controlled culture conditions, development of an individual cell took 220 minutes. Fixation of M. muricata cells at different developmental stages by plunge freezing or high pressure freeze fixation followed by freeze substitution resulted in excellent preservation of the ultrastructure. During establishment of the highly symmetrical cell pattern which involves broadening of the primary wall forcell body formation and tip growth during lobe development, local deposition of primary wall material occurred by golgiderived vesicles which were similar to those described from other desmids. In addition, a new vesicle type was found in M. muricata. During the process of nuclear migration microtubules were observed adjacent to the nucleus and expanded in the lateral lobes.