Browsing by Author "Wiencke, Christian"
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Item Morphogenesis of the brown alga Desmarestia antarctica cultivated under seasonally fluctuating Antarctic daylegths(1991) Wiencke, Christian; Stolpe, Ute; Lehmann, HeinerThe development of Desmarestia antarctica has been studied under seasonally daylenghts mimicking the daylength conditions on King George Island (Antarctica). Under June conditions the sporophytes were uniseriate. Primary laterals developed in July, secondary laterals were observed in September. Cortication of the main axis and primary laterals started in October and November, respectively. Shedding of uncorticated parts was observed in the entire growth period of the sporophyte. In February all uncorticated filaments were shed. The main axis of October - November developmental stages consists of several layers of small outer cortical cells, larger inner cortical cells, into which smaller cells are interspersed, and the axial cell row. Around the axial cells a trasitory pericentral caviry is developed, which is filled in the later stages by small cells forming a sheath. Cells of the axial filament show the characteristics of trumpet cells, which imply a tansport function. Occlusions of their lumen apparent in sections of chemically fixed cells are artefacts since they were not found in clyofixed plants. X-ray microanalyses revealed considerably higher concentrations of K+ and CL- in cortical compared to axial cells, pointing to the presence of organic translocates in the axial cells. The vegetative structure of the gametophytes varies depending ont he light conditions. Gametogenesis was observed al temperatures < 5ºCItem Notes on the Development of some Benthic Marine Macroalgae of King George Island, Antarctica(1988) Wiencke, ChristianFrom a total number of 29 species of Antarctic macroalgae in 26 species reproductive tissue was found, release of viable spores or gametes was observed in 21 species during two expeditions to King George Island in January/ February 1986 and 1987. Germination and further development has been monitored in laboratory cultures under varied light conditions. Within one year of culture adult plants developed in Gigartina papillosa, Iridaea obovata, Leptosomia simplex, Adenocystis utricularis and Enteromorpha bulbosa. In the latter two species spore release was observed after one year. In the former perennial species formation of reproductive tissue started after one year, maturation, however, is very slow and presumably may take additional five months or more. Growth in some developmental stages is light saturated at very low photon flux densities, total darkness is tolerated for several months. The gamethopyte of Leptosomia simplex, which previously was unknown, is described and microscopic evidence of the mating and fusion process of Aseoseira mirabilis gametes, which previously were regarded as spores, is given.Item Techniques and equipment for culturing antarctic benthic marine algae, and for preparing specimens for electron microscopy(1986) Clayton, Margaret; Wiencke, Christian