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Cell Mother Cells: The stomatal guard cells in the grass Hor-deum vulgare are normally formed by a regular and predictable sequence of cell divisions. It was found, however, that it was possible to alter the direction of the mitotic spindles of the guard cell mother cells by administering 2-mer-captoethanol (a sulfur-containing derivative of ethyl alcohol) to the leaf sheath so that the cells were parallel to the leaf axis instead of transverse. Excision of the leaf sheaths also resulted in a few reoriented divisions. Both treatments presumably depressed nucleic acid synthesis in the guard cell mother cell. While the synthesis was depressed, the cell continued to elongate with the other cells until the oriented large molecules were irreversibly moved. The two methods were the result of efforts to explain cell polarity.
In fission the parent cell grows to approximately twice its original size and splits into two daughter cells. Plastic-walled cells, such is animal cells and protozoa, simply constrict in lie middle, and the two halves of the cell pull apart. Rigid-walled cells, such as plant cells, molds, and bacteria, divide by constructing a cross Wall and then separating. In both cases Ike cell constituents, which have doubled prior to division, are evenly divided between the two (laughter cells.
The grass leaf epidermis is made up of parallel rows of cells, including long cells and short cells. Some of the short cells contain silicon and may be linear, oblong, round, dumbbell-shaped, cross-shaped, or saddle-shaped. Pores bounded by two guard cells occur in the epidermis. The guard cells and the pore form a complex known as a stoma. Adjacent to each guard cell is another cell, called a subsidiary cell, which is variously shaped according to the kind of grass. Tiny 2-celled appendages (bicellular microhairs) are found on the leaf epidermis of most grasses; they also vary in length, shape, and thickness of cell walls.
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