Tissues213-page14 - meristems protoderm cells become...

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Plant Tissues - 14 Controlling Cell Growth and Development Before we leave the discussion of tissues, you have learned that cell division in plants occurs in meristems and that plant cells in general have great genetic "plasticity", which is a way of saying they retain genetic competency (totipotency) after specialization of cells. Molecular biologists are studying the mechanisms of cell growth, expansion, morphogenesis and differentiation at the gene level, particularly with the small Arabidopsis thaliana , for its genome has less than 30,000 protein-coding genes. Its small size and rapid life history, with as many as 5000 seeds per plant make it ideal for such studies, just as the fruit fly was ideal for early studies on inheritance patterns. Cell division in meristems increases the number of cells; cell expansion, following division, increases the plant's mass. We have already stated that plant development is substantially determined by a cell's position in the derivative
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Unformatted text preview: meristems: protoderm cells become epidermis, ground meristem cells become ground tissues and procambium cells differentiate into vascular tissues. Position of cells during mitosis is one of the determinants of growth. The symmetry of cell division is also important. Role of Microtubules in Cell Orientation As presented in Biology 211, the plane (or direction) of plant cell division is determined in late interphase. A set of microtubules located in the outer cytoplasm of a cell about to divide orients into a ring called the preprophase band. The preprophase band "imprints" the cell actin microfilaments to its plane of division. During mitosis, the microtubules disperse, but the microfilaments orient the nucleus of the cell until the spindle complex has arranged the chromosomes for metaphase. The imprinted actin microfilaments also determine the vesicle alignment for the cell plate formation....
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