Physiological effects of promotion and inhibition of ethylene biosynthesis on branch abscission in Azolla.
Item
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Title
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Physiological effects of promotion and inhibition of ethylene biosynthesis on branch abscission in Azolla.
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Identifier
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AAI9405530
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identifier
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9405530
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Creator
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Gillen, John Joseph.
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Contributor
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Adviser: Dominick V. Basile
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Date
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1993
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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, Botany | Biology, Plant Physiology
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Abstract
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The phenomenon of abscission has been largely neglected in the non-flowering plants. A very small aquatic fern, Azolla Lam., which reproduces mainly through branch abscission was used to study anatomical and physiological aspects of abscission. Light and electron microscopy were used to establish that separation occurs between two layers of cells, beginning at the periphery and proceeding inward along the middle lamellae. Separation leaves intact cortical cell faces at both the proximal and distal sides of the abscission zone; stelar cells break mechanically. The abscission zone cells, while highly vacuolated, contain organelles found in flowering plant abscission zone cells.;The physiological effects of promotion and inhibition of ethylene biosynthesis on branch abscission were measured by adding ethylene inhibitors and/or promoters to water in which a known number of Azolla plants were growing, and counting the number of plants after a period of incubation followed by vigorous agitation on a mechanical shaker. 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene in higher plants, and napthaleneacetic acid (NAA), an auxin known to promote the enzymatic conversion of S-adenosylmethionine (SAM) to ACC, significantly increased (p {dollar}\le{dollar} 0.05) the amount of abscission. Inhibition of branch abscission significant at p {dollar}\le{dollar} 0.05 was observed with amino-oxyacetic acid (AOA), an inhibitor of ethylene biosynthesis, and with silver ion, an inhibitor of ethylene action. Adding NAA together with aminoethoxyvinylglycine, an inhibitor of ethylene biosynthesis, produces significantly less (p {dollar}<{dollar} 0.05) branch abscission than was observed with NAA alone. Abscission of branches of the smallest size (1.0 mm or less) was significantly increased by ACC and by AOA.;This is the first evidence that ethylene plays a role in abscission in a pteridophyte, and provides indirect evidence supporting the hypothesis that ethylene may be produced via the same biosynthetic pathway used by higher plants.
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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.
