AN APPROACH TOWARD UNDERSTANDING SOME OF THE MORPHOGENETIC BASES OF PHYLOGENY OF STREPTOCARPUS (GESNERIACEAE).
Item
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Title
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AN APPROACH TOWARD UNDERSTANDING SOME OF THE MORPHOGENETIC BASES OF PHYLOGENY OF STREPTOCARPUS (GESNERIACEAE).
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Identifier
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AAI8203319
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identifier
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8203319
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Creator
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ROSENBLUM, IRWIN MURRAY.
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Contributor
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Prof. Dominick V. Basile
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Date
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1981
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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
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Abstract
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By utilizing an experimental approach, phenovariants of Streptocarpus (Gesneriaceae) species expressing ancestral morphological features have been induced. Since these phenovariants resulted from use of plant growth regulators, a beginning has been made toward understanding phylogeny (evolutionary diversification) of this taxon in chemical terms.;Two morphogenetic patterns have been critically involved in speciation within the Gesneriaceae. Subfamily Cyrtandroideae is characterized by accrescence of one of the two cotyledons as a result of continued activity of basal intercalary meristems, accompanied by suppression of growth of the second cotyledon.;In the second pattern, sustained growth of the accrescent cotyledon accompanied by suppression of the displaced shoot apical meristem gives rise to an acaulescent, dorsiventral vegetative plant body (phyllomorph) which characterizes species of subgenus Streptocarpus and also several other genera within Cyrtandroideae.;Exogenous plant growth regulators were applied to several species in subgenus Streptocarpus, especially S. prolixus (gracilis) at critical stages under three sets of experimental conditions. These were axenic plantlets regenerated from lamina discs, axenically grown seedlings, and pot grown seedlings. In all instances, the growth regulators were present at time of initiation of regenerants, or at time of or within two days of germination.;Gibberellin A(,3) at levels of 10('-5)M and higher caused suppression of cotyledonary accrescence and early activity of the shoot apical meristem, with production of a plumule. Sustained application of GA(,3) resulted in caulescent plants with radial symmetry.;Similar isocotylous, caulescent seedlings were induced by application of the auxin antagonist 2,3,5-triiodobenzoic acid. Such seedlings also resulted from coating upper cotyledonary surfaces with a variety of pastes two days after germination; a possible role for ethylene was indicated.;A single exogenous application to germinating seedlings of the cytokinin benzyladenine at 10('-6)M and higher caused desuppression of the second (micro-) cotyledon, resulting in accrescence of both cotyledons and growth of bi-phyllomorphic acaulescent plants.;Since these phenovariants were induced by exogenous application of growth regulators, there is strong indication that endogenous growth regulators control the unusual morphogenetic patterns found in subgenus Streptocarpus and elsewhere in subfamily Cyrtandroideae. Phylogenetic changes in balances among the regulators at critical stages in ontogeny probably account for evolutionary diversification within the Gesneriaceae.;A preliminary hypothesis regarding roles of phytohormones in controlling morphogenesis in subgenus Streptocarpus is offered. Further experimentation can expand understanding in this area and may lead to isolation of substances and processes at the molecular level which are mediated by the regulators.
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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
