Cytological Studies on Oedogonium cardiacum Wittrock and One Another Oedogonium sp.
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概要
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1. Cytological investigations as regards the morphology of the chromosomes during mitosis have been made out in two Oedogonium spp.2. The process of nuclear division during mitosis follows a normal course and the number of chromosomes has been estimated 19 in Oedogonium cardiacum from the counts of chromatids at anaphase and in another Oedogonium sp., the number of chromosomes has been estimated as approximately 41 during late prophase.3. The morphology of the chromosomes in regard to the position of the centromeres has been studied. Localised centromeres are easily recognisable as non staining regions at points of bending of chromatids during anaphase. As regards the positions of centromeres, the chromatids are found to be of three types, with median centromeres, sub-median centromeres and subterminal centromeres.4. The spiral structure of the chromosomes of various sizes is easily recognisable in mid-prophase and at telophase. Ohasi (1930) has reported about the spiral structure of the chromosomes in Oedogonium grande. Delicate spindle fibres appear to be present as pointed out by Ohasi (1930).5. The nucleus enlarges considerably during early prophase, the nuclear membrane becomes irregular and minute chromatin granules arranged in linear order, appear within whole nuclear cavity as observed by Kretschmer (1930) in Oedogonium pachyandrium. At about mid-prophase, long intertwined chromosome threads are visible, some of which are seen orientated lengthwise as pointed out by Kretschmer (1930).6. Chromatids are easily recognisable at pre-metaphase and at metaphase, the chromosomes appear short or long rod-shaped. Anaphase follows a normal course of division and the chromatids are seen more closely crowded at both ends of poles.7. The process of nuclear division and the structure of chromosomes of both spp. of Oedogonium appears similar to that of the higher plants.8. The method of staining by acetocarmine has been used throughout the investigation for cytological study.9. The sex organs were formed generally after three months in old cultures. But they were formed profusely and more rapidly within a week when they were grown in an atmosphere of carbon dioxide by placing the filaments in watch glasses enclosed in petri-dishes containing 5% sodium bicarbonate as reported by Starr (1955).10. After inoculation in fresh culture solutions, zoospores were produced within 4 days. The male and female filaments of Oedogonium cardiacum were inoculated singly in culture media and zoospores were seen to be produced from them.
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財団法人 日本メンデル協会 | 論文
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