Biosystematic Studies In The Genus Aster
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Biosystematic Studies In The Genus Aster
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Author : Charlotte J. Avers
language : en
Publisher:
Release Date : 1953
Biosystematic Studies In The Genus Aster written by Charlotte J. Avers and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1953 with Asters categories.
A Biosystematic Study In The Genus Aster Section Aster In Western North America
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Author : Milton Lee Dean
language : en
Publisher:
Release Date : 1966
A Biosystematic Study In The Genus Aster Section Aster In Western North America written by Milton Lee Dean and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1966 with Compositae categories.
A biosystematic investigation was undertaken in 15 species and three subspecies of the genus Aster, in western North America. Previous studies had been based entirely on external morphological features, and it was believed that much could be learned about the natural affinities of the taxa by exploring their cytological and genetical characteristics. More than 160 accessions were made during the course of the study. In the majority of cases, living rhizomes were transplanted in the greenhouse to provide material for making chromosome counts and hybridization experiments. Whenever possible, chromosomes were observed during meiotic divisions in microsporogenesis. One or more chromosome counts were made in 17 of the 18 taxa studied, 12 of which had not previously been examined cytologically. Ten taxa were found to include plants at two or more chromosome levels. The entire assemblage of species contains chromosome numbers on the basis of X = 8, with counts ranging from n = 8 to n = 48. Examples of aneuploidy, B-chromosomes, and meiotic irregularities were also discovered. A total of 383 artificial hybridizations was made among the species studied, resulting in the production of at least one fruit from 198 crosses. Most of the attempted crosses were interspecific, with the results indicating a striking lack of genetic incompatibility between the species at all polyploid levels. However, nearly all crosses involving diploid plants produced no fruits. First-generation hybrids of most species combinations were grown to maturity, and their potential fertility was estimated by observing the stainability of their pollen. The percent of pollen stainability in most of the hybrids was high enough to be judged partly or fully fertile. The polyploid complex composed of the species of Aster included in this study is comparable to certain other known complexes. Such complexes are similar in that the diploids are rather distinct morphologically and genetically, but they have contributed to the formation of a vast array of potentially interbreeding polyploids which lack sharp morphological definition. Most of the polyploids can be assigned to morphological categories that are more similar to related diploids than to other polyploids. Consequently, certain of the species have been delineated along vertical lines of relationship which may include several chromosome levels, In addition, some entities are retained as species which are known only as polypoids. which are relatively distinct and cannot be definitely donnested to a diploid species. This method is believed to be more indicative of relationship than would a system of grouping the entire polyploid assemblage in one highly polymorphic species, A phylogenetic chart of putative relationships among the taxa is presented, based largely on chromosome counts and morphology. The diploid entities are judged to be ancestral to, and thus more primitive than the polypoids, It was not possible to establish particular morphological traits as being more primitive or more advanced, Bathe it appears that evolution of morphological features has occurred at the diploid level, with subsequent polyploidy serving primarily to recombine the distinctive diploid features into various combinations. The information gained from the hybridization experiments contributed relative little to an understanding of natural affinities among these species, owing to the free crossability between the polyploids., Too few crosses were made involving diploids to determine accurately the degree of genetic incompatibility. Over 8000 herbarium specimens were examined in the process of delimiting species. The taxonomy section includes a key to the species, plus lists of synonyms, technical descriptions, citation of representative specimens, distribution maps, and brief discussions of the species. One new species, Aster idahoensis, is described in the thesis.
Biosystematics Of A Western North American Polyploid Complex In The Genus Aster
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Author : Geraldine Anne Allen Guppy
language : en
Publisher:
Release Date : 1980
Biosystematics Of A Western North American Polyploid Complex In The Genus Aster written by Geraldine Anne Allen Guppy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1980 with Asters categories.
Species relationships were investigated in a western North American polyploid complex in the genus Aster (Asteraceae). A combination of cytological, genetical, chemical, morphological and numerical approaches was employed. Fifteen presently recognized species were included in the study, and populations were sampled throughout most of the range of the group. Living plants from these populations were maintained in greenhouse and garden culture for studies of reproductive behavior, crossability, and flavonoid chemistry. A total of 232 chromosome counts were made from the sampled populations. Chromosomes were observed at meiosis in flower buds and in mitotic divisions in root-tip cells. The principal base chromosome number in the group is x = 8; six ploidy levels occur, ranging from n = 8 to n = 48. A few aneuploid numbers based on x = 9 were also recorded, and one species was found to have a base number of x = 13. Measurements of 35 morphological characters on 78 diploid specimens, followed by cluster analysis and discriminant analysis of the clusters, resolved seven phenotypic groups at the diploid level. These correspond to seven currently recognized taxa in six species. Three other taxa in which a diploid chromosome number was found failed to separate from these clusters; this may reflect the choice of characters used in the analysis, or an incorrect placement of these species by contemporary taxonomists. Morphological variation among the polyploids was greater than at the diploid level, and this variability included intermediates between certain diploid groups as well as forms not found among the extant diploids. Crossing experiments between diploids showed that in most cases the species are only partially interfertile. An exception was Aster greatai, a morphologically distinctive endemic taxon of southern California, which crosses readily with most of the other taxa. Several of the crosses yielded hybrid progeny; these had normal chromosome pairing at meiosis but lowered pollen viability. A preliminary investigation of flavonoid chemistry in 30 populations (representing seven taxa) was carried out using two-dimensional thin-layer chromatograms. Considerable chemical variation was found, which was not closely correlated with variation in external morphology. Detailed analysis of a clone of Aster eatonii revealed 11 flavones and flavonols, which were characterized and identified. A new finding was the common occurrence of diploid and tetraploid chromosome numbers based on x = 13 in the widespread species Aster ascendens. The karyotype of A. ascendens is distinctly asymmetrical, in contrast to the symmetrical karyotypes of the species based on x = 8. In view of the asymmetrical karyotype reported earlier for the related species A. ericoides (with n = 5), it seems likely that the genome of A. ascendens evolved from hybridization between a taxon with n = 5 and one (perhaps A. occidentalis) with n = 8. The complex is considered to contain approximately 14 species, of which nine contain some diploid populations. The present study extends the known morphological and geographical ranges of the diploid taxa, and improves understanding of species relationships and probable evolutionary lines within the group.
Studies In The Genetics And Cytology Of The Two Species In The Genus Aster And Their Polymorphy In Nature
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Author : Ralph Hartley Wetmore
language : en
Publisher:
Release Date : 1939
Studies In The Genetics And Cytology Of The Two Species In The Genus Aster And Their Polymorphy In Nature written by Ralph Hartley Wetmore and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1939 with categories.
Biosystematic Studies In Aster Subgenus Aster
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Author : Guy Richard Jelinek
language : en
Publisher:
Release Date : 1979
Biosystematic Studies In Aster Subgenus Aster written by Guy Richard Jelinek and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1979 with categories.
Biosystematic Studies In Aster
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Author : Charlotte F. Avers
language : en
Publisher:
Release Date :
Biosystematic Studies In Aster written by Charlotte F. Avers and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
Studies In The Genetics And Cytology Of Two Species In The Genus Aster And Their Polymorphy In Nature
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Author :
language : en
Publisher:
Release Date : 1939
Studies In The Genetics And Cytology Of Two Species In The Genus Aster And Their Polymorphy In Nature written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1939 with categories.
Biosystematic Studies In Hieracium Asteraceae Section Thyrsoidea
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Author : David Charles Deardorff
language : en
Publisher:
Release Date : 1977
Biosystematic Studies In Hieracium Asteraceae Section Thyrsoidea written by David Charles Deardorff and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with Hawkweeds categories.
A Monographic Study Of The Genus Aster In Oklahoma
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Author : Martha Virginia Flowers
language : en
Publisher:
Release Date : 1940
A Monographic Study Of The Genus Aster In Oklahoma written by Martha Virginia Flowers and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1940 with Asters categories.
A Biosystematic Study Of Machaeranthera Sect Psilactis And Selected Species Of Aster Compositae
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Author : Jon M. Stucky
language : en
Publisher:
Release Date : 1974
A Biosystematic Study Of Machaeranthera Sect Psilactis And Selected Species Of Aster Compositae written by Jon M. Stucky and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1974 with Asters categories.