Kristalloide im Plastidenstroma

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Abstract
The crystal-like structures in the plastid stroma of primary leaves of Phaseolus vulgaris, recently described by several authors, were studied with the electron microscope after different treatments: The crystal-like structures can be seen after fixation in glutaraldehyde followed by a post-fixation with osmium tetroxide as well as after osmium tetroxide fixation alone. They are not preserved by fixation in permanganate. After double-staining with uranyl acetate and lead citrate the electron-opacity of the filaments which compose the crystal-like body is selectively enhanced. This phenomenon does not occur after single-staining with lead citrate. When de-osmicated sections are treated with pepsin the substance of the crystal-like bodies is selectively digested, whereas this substance does not disappear after treatment with RNase. When pieces of leaves are kept floating on a sucrose solution the number of the crystal-like bodies is markedly increased. These results taken together seem to constitute evidence that the crystal-like bodies represent a store of protein. Some micrographs of small crystal-like bodies indicate that the straight filaments represent arrangements of globular subunits with diameters of about 5 nm. In a great many plastids some structures other than these crystal-like bodies are seen which seem to correspond to the “stromacentres” reported by Gunning (1965). Intermediates between this stromacentre-like type with curved filaments and the above mentioned crystal-like type with straight filaments can be observed. Die Stroma-Kristalloide in Primärblättern von Bohnen wurden elektronenmikroskopisch nach unterschiedlicher Behandlung der Ultradünnschnitte untersucht. Selektive Verdauung der Kristalloide mit Pepsin zeigt, daß es sich um Protein-Kristalloide handelt. Ihre Anzahl kann durch Saccharose-Fütterung erhöht werden. Die Befunde deuten darauf hin, daß diese Strukturen einen Proteinspeicher darstellen.