A PHYSIOLOGICAL AND ULTRASTRUCTURAL STUDY OF CELLULASE IN TOBACCO ABSCISSION CELLS.
Item
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Title
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A PHYSIOLOGICAL AND ULTRASTRUCTURAL STUDY OF CELLULASE IN TOBACCO ABSCISSION CELLS.
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Identifier
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AAI8409407
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identifier
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8409407
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Creator
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LIEBERMAN, STEVEN J.
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Contributor
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Jack G. Valdovinos
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Date
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1984
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Plant Physiology
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Abstract
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A study was conducted to determine if cellulase is involved in cell wall degradative processes leading to abscission in tobacco flower pedicels. A cytochemical method was utilized for ultrastructural localization of cellulase. Deposition of a copper precipitate was utilized to detect cellulase activity in the cells. Copper precipitate was observed principally in the middle lamella region of the cell wall during advanced stages of abscission where pollination was prevented, and in ethylene-treated tissue. In these studies, break-strengths of pedicels decreased prior to increases in cellulase activity. Morphometric analysis was utilized to measure quantiative ultrastructural changes during abscission. An increase in surface area of the rough ER was found with ethylene treatment. Cellulase enzymes were also characterized by a viscometric assay following biochemical extraction procedures. The most significant increases in buffer-soluble cellulase activity were observed during advanced stages of abscission where pollination was prevented. Flower pedicels initially broke before enzyme levels had increased dramatically. No significant increase in salt-soluble cellulase activity was observed. Both exo- and endocellular fractions were assayed to differentiate between cellulase activity found within the cellular free space and in the cell. The most dramatic increase in exocellulase activity was found in capped tissue harvested at 5 days after anthesis. Pedicels initially broke before the exocellulase activity had increased to a high level. The most significant increase in endocellulase activity was observed in capped tissue harvested at 4 days after anthesis. Upon electrophoresis of the exocellular fraction, a protein band was isolated (band 4) which contained exocellulase activity and was observed only in gels of capped tissue harvested at 5 and 6 days after anthesis. Band 4-exocellulase activity was found at a relatively high level in tissue harvested at these stages of the time-course. Pedicel break-strengths were decreasing when the increase in enzyme activity was first observed. This study suggests that cellulase may have an important role during abscission, after initial break-strength decreases have already begun. Results of a study for localizing peroxidases in gels, indicated that they were secreted into the wall during abscission.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biology
