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Polymorphism, sexual reproduction, meiosis and polyploidy and their implications for desmid taxonomy.


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Ling, Hau U 1977 , 'Polymorphism, sexual reproduction, meiosis and polyploidy and their implications for desmid taxonomy.', PhD thesis, University of Tasmania.

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Conjugation and zygospore germination are described for 6
Pleurotaenium, 2 Micrasterias and 1 Staurastrum species. Probable
chemotaxis is demonstrated in one Pleurotaenium species and selective
mating, where a plus clone actively chooses one of two minus clones,
Is shown to be common in the P. mamillatum complex.
The Pleurotaenium species show remarkable homogeneity in
conjugation features, possession of 5-walled smooth zygospores with
operculate exospores and mammillate mesospores and producing single
germination products. Zygospores of M. hardyi, A laticeps and
St. orbiculare var. ralfsii are spiny, 3-walled, but only the
Micrasterias zygospores are operculate. All three produce 2
germination products.
Meiosis is described in germinating zygospores from crosses
between various karyotypes and ploidy levels of the P. mamillatum
complex, between haploids and diploids and morphologically different
strains for other species of Pleurotaenium and the two Micrasterias
species. In the Pleurotaenium species meiosis is chiasmate,
conventional in character and the chromosomes have localized
centromeres. Sexual crossing, resulting in viable, fertile offspring,
occurs to a surprising degree between strains with widely
disparate chromosome numbers, ploidy levels and geographical
location. These strains form discrete groups that are reproductively
isolated from one another.
The implications that the results have for desmid taxonomy are

Item Type: Thesis - PhD
Authors/Creators:Ling, Hau U
Keywords: Zygnematales, Zygnematales
Copyright Holders: The Author
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Copyright 1977 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
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Thesis (Ph.D.)--University of Tasmania, 1978. 'Literature cited': l. 159-164

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