J Integr Plant Biol. ›› 1958, Vol. 7 ›› Issue (1): -.

• Research Articles •    

Intercellular Migration of Nucleus in Somatic Tissues

S. H. Wu   

Abstract: In the present paper, a brief review is given to the recently published literatures dealing with the phenomenon of intercellular migration of nucleus in reproductive and vegetative organs of the lower plants as well as the higher plants and to the modern interpretations for such a phenomenon. The materials and methods employed in general for studying the phenomenon concerned were described rather in details. For the present study, the materials used were the vegetative organs of bulb plants (Allium) and the somatic tissues of the ovules of some cereal plants (Triticum, Avena and Hordeum). The present report was chiefly based upon the studies of paraffin sections. Preparations of total mounts were also made for supplement. According to the paraffin sections, it is evident that the nuclear migration not only takes place in the epidermal tissues, in the underlying parenchymal tissues, but also occurs in the elements of the vascular tissues of the rapidly growing leaf sheath, young bud sheath, scale and clove sheath of the garlic plant. It is especially interesting to note that the nuclear material has pressed on the outer surface of the vessel and protruded via the unthickened portions of the wall into the vessel. In the same material, enormous or extraordinarily long nuclei, which sometimes take a zigzag form, have usually been observed in the elements, including vessels, of the vascular bundles. These phenomena may have an important bearing on the views of the mechanism of translocation of organic materials in plants. As the leaf sheath or young bud sheath begins to wither and its inclusions is being withdrawn, the intercellular migration of nucleus again makes its appearance in the epidermis, underlying parenchyma and the vascular tissuer. The nucleus, however, migrates in a different manner. It generally tends to tranverse the side wall of the cell and moves toward the vascular bundle. After fertilization, the antipodal cells of Triticum, Avena and Hordeum plants multiply and increase a great deal in size. In the course of development of the embryo sac, the nucellar tissue gradually disorganize. Their nuclei deform, loose their normal structure and migrate to the neighborhood of the embryo sac, where they eventurely disappear. Nuclear migration has sometimes been observed in the undisorganized cells of the nucellar tissue. At the time when the endosperm develops into a cellular structure, the antipodal cells, which usually occupy a lateral position and attach to the ventral surface of the endosperm, begin to disorganize. Their inclusions form irregular and darkly stained lumps, which disintegrate and disappear completely within 2 or 3 days. The nuclei of endosperm cells next to the disorganized antipodal tissue become stained more deeply and given strongly positive reaction to Feulgen stain. Their cytoplasm also shows more or less the same reaction. Evidently this phenomenon indicates that the disintegrated nuclear matter of the antipodal tissue enters the endosperm cells. In the course of disorganization of antipodal tissue, intercellular migration of nucleus occurs at first in endosperm cells next to the disorganized antipodal tissue and laterly it appears in the portion of endosperm surrounding the proembryo where an accumulation of nuclear material has been made. The same phenomenon also occasionally takes place in proembryo cells. The various events observed in the course of development of the embryo sac of Triticum, Avena and Hordeum plants offer another excellent example as garlic plant in support of the view that the nuclear migration is associated with the process of translocation and redistribution of organic materials from the senescent tissue to the newly grown. Based upon the studies of preparations made by a variety of microtechnical and physiological methods in our earlier works in comparisi on with the present studies of paraffin sections, the migrating nucleus is characterized by its high chromaticity, homogeneites and strong reaction to Feulgen stain. It almost invariably takes up an excentric position in the cell. Its extruded portions typically assume the form of dense, homogeneous bodies in adjoining cell, at the same time retaining a connection with the parent nucleus. The phenomenon observed in vegetative organs of bulb plants is evidently very similar to that observed in the somatic tissues of ovules of cereal plants mentioned above. A somewhat different phenomenon has also been observed in a few cases (parenchyma of leaf sheath of garlic), chromatin bodies are budded off from the nucleus into the cytoplasm of the same cell instead of into that of another cell. These bodies vary considerably in size and number. Great difficulty was experienced in following the subsequent destiny of these bodies. Though they sometimes also migrate through the cell wall, the events thereafter are not quite clear.

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