Zusammenfassung
Wurzelstücke vonArmoracia rusticana wurden auf Agarmedien nachMurashige undSkoog 1962 mit Zusatz von 2,4 D kultiviert. Daraus entstanden Kallusgewebe mit zahlreichen Vegetationspunkten. Ohne Zusatz von Wuchsstoffen entwickelten sich Pflänzchen, die in Erde ausgesetzt zu groß en Individuen mit verschieden deformierten Blättern heranwuchsen. Diese, sowie steril gezogene Pflanzen und der Kallus wurden elektronenmikroskopisch untersucht.
Es fielen zweierlei Einschlüsse auf, schalenförmige, aufgebaut aus isometrischen Partikeln und spindelartige, bestehend aus fibrillären Partikeln. Die schalenförmigen Einschlüsse treten im Cytoplasma meristematischer Zellen des Kallus auf, die Partikeln sind ca. 20–22 nm groß. In allen übrigen untersuchten Geweben kommen die gleichen Aggregate nur in der Vakuole vor. Die Partikeln wurden auch in Plasmodesmen sämtlicher Gewebe gefunden. Sie liegen innerhalb eines Tubulus, der auf einer Seite der Zellwand ins Cytoplasma vorsteht. Desmotubuli kommen nur in partikelfreien Plasmodesmen vor. Zellwandvorstülpungen wurden nur in Kallusgewebe und Epidermiszellen der Blätter beobachtet. Innerhalb dieser sind ebenfalls Tubuli mit isometrischen Partikeln zu finden. Auffallend große Hohlräume in den Zellwänden der Kalluszellen, die in Verbindung mit Plasmodesmen stehen, enthalten viele zum Teil geordnete Partikeln. Es hat den Anschein, als würden sie in der Zellwand wie auch in der Vakuole abgelagert.
Die fibrillären Partikeln kommen selten gemeinsam mit den isometrischen in derselben Zelle vor. Man findet sie im Cytoplasma und im Zellkern meist in Form von Spindeln. Die Fibrillen haben einen Durchmesser von ca. 12 nm.
Das Thylakoidsystem der ausdifferenzierten Chloroplasten im Kallus und in den Blattzellen ist bogig gekrümmt, einzelne aufgetriebene Thylakoide liegen als Vesikeln im peripheren Stroma.
Da die Gewebe vonArmoracia- Pflanzen verschiedener Fundorte keine derartigen Einschlüsse und Piastidenveränderungen aufwiesen, kann angenommen werden, daß die für die Kultur verwendeten Wurzelstücke von zwei verschiedenen Viren infiziert waren. Eine Isolierung der Viren ist bisher nicht gelungen.
Summary
Root explants ofArmoracia rusticana were cultivatedin vitro on theMurashige, andSkoog 1962 nutrient medium with addition of 2,4 D (2,4-Dichlorophenoxyacetic acid). Under such conditions callus tissue containing several apical meristems developed. Without 2,4 D the explants were growing to aseptic small plants; when further cultivated in soil they developed into big plants showing leaves with different deformations. These leaves, aseptically cultivated plants and callus tissue were examined by light and electron microscopy.
There occured two types of inclusions consisting of isometric and elongated particles, respectively. Those of the isometric type were observed in the cytoplasm of meristematic cells of the callus; the isometric particles had a diameter of about 20–22 nm and were arranged hexagonally or in curvilinear arrays. In all other tissues that were examined such aggregates were to be seen only in vacuoles. Isometric particles were also found in plasmodesmata of all tissues examined. They lay in a tubulus which protrudes into the cytoplasm on one side of the cell wall.
Desmotubuli appeared only in particle-free plasmodesmata. Protrusions of the cell wall into the cytoplasm containing tubuli and isometric particles within were observed only in callus tissue and in epidermic cells of leaves. In the cell wall of callus cells, conspicuous cavities connected with the cytoplasm by plasmodesmata contained many particles which were arranged in hexagonal structures. It seemed as if they had been put away into the cell walls or into the vacuoles. The occurence of fibrillar inclusions together with those consisting of isometric particles in the same cell was extremely rare.
The fibrillar inclusions were observed in the cytoplasm and in the nucleus. The diameter of one fibril is about 12 nm.
The thylacoids in well differentiated chloroplasts in callus and in cells of leaves are curved; single swelled thylacoids lie as vesicles in peripheral stroma.
As tissues ofArmoracia rusticana plants from different localities do not contain such inclusions we assume that the root segment examined was infected with two different viruses. The isolation of the viruses has not yet been possible.
Footnotes
Wir danken dem Österreichischen Fonds zur Förderung der wissenschaftlichen Forschung für die Unterstützung der Arbeit.
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