Norstog, Knut, 1921-
M.S. (Master of Science)
Department of Biological Sciences
Barley; Plant cells and tissues
The triploid endosperm of barley follows the Nuclear pattern of development. Cellularization of the multinucleate endosperm is rapid and is completed in the first three days after anthesis. At one day post-anthesis the endosperm cytoplasm forms an attenuated layer lying on the periphery of the central cell. Nuclei are embedded at regular intervals within this peripheral layer of cytoplasm and appear to be metabolically active. Ingrowths, resembling those occurring in "transfer cells", appear to aid in transport of solutes across the central cell wall. The apparent source of these solutes is the actively dissolving cells of the inner nucellus. Freely growing cell wall channels, representing very early stages in cellularization, also project into the multinucleate, central cell cytoplasm from the bounding wall. Later in development, two to three days post-anthesis, these wall channels impinge upon the central cell vacuole; forming "partitions" between nuclei. In the three-dimensional aspect these partitions actually form a series of open-ended cylinders which may be referred to as "alveoli". The open ends of these partitions are occupied by thin sheets of cytoplasm which bridge the cell wall channel tips. As development continues, cross walls, without the apparent occurrence of karyokinesis, are formed in the median region of the alveoli, resulting in a peripheral layer of cells. As these cells are forming, the inwardly projecting cell wall channels continue to advance centripetally, producing a second layer of alveoli. This process persists until alveoli from the dorsal and ventral surfaces of the endosperm merge together, completing cellularization. Ultrastructurally, a cell wall channel tip is similar to a single edge of a phragmoplast of a forming cell plate. It is composed of a planar array of fusing vesicles. The origin of these vesicles is unknown; although dictyosomes and cisternae of the endoplasmic reticulum both seem to be involved in their production. Microtubules are arranged perpendicular to the plane of fusing vesicles and disappear as fusion of these vesicles becomes more complete. Cell wall material is laid down in these more advanced regions of vesicle fusion. A microtubule organizing center was not observed. Always present in the tip region are lipid droplets. Starch was absent at every stage of development.
Gruber, Chris M., "The cellularization of barley endosperm, the dorsal region" (1978). Graduate Research Theses & Dissertations. 5350.
Northern Illinois University
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