[Evidence for catalase activity in peroxisomes of Micrasterias fimbriata (Ralfs)].
By ultrastructural methods, cytology, and cytochemistry it is shown that peroxysomes are present during all stages of the life cycle of the green unicellular alga Micrasterias fimbriata, cultivated on mineral medium. These organelles, surrounded by a single membrane, are in connection with endoplasmic reticulum. In full-grown cells, they are preferentially situated near chloroplasts and cell walls. The number of peroxisomes increase before cellular division and the organelles flow into the young bulge in front of the chloroplast.Application of a modified Graham and Karnosky's medium using DAB at pH 9 shows that an important activity of catalase is present not only at the level of peroxisomes but also at the level of the cell walls and certain Golgi vesicles.The topographic relations of peroxisomes with different cellular organelles and their possible functions in cell wall or mucus synthesis are discussed.
Cytophysiologie de la Photosynthèse, C. N. R. S., Gif sur Yvette, France.
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