Studies In The Genetics And Cytology Of The Two Species In The Genus Aster And Their Polymorphy In Nature

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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.

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 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.

Hybrid Zones And The Evolutionary Process

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Author : Richard Gerald Harrison
language : en
Publisher: Oxford University Press, USA
Release Date : 1993

Hybrid Zones And The Evolutionary Process written by Richard Gerald Harrison and has been published by Oxford University Press, USA this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with Evolution (Biology) categories.

Hybrid zones--geographical areas in which the hybrids of two races are found--have attracted the attention of evolutionary biologists for many years, both because they are windows on the evolutionary process and because the patterns of animals and plant variation seen in hybrid zones do notfit the traditional classification schemes of taxonomists. Hybrid zones provide insights into the nature of the species, the way barriers to gene exchange function, the genetic basis of those barriers, the dynamics of the speciation process. Hybrid Zones and the Evolutionary Process synthesizes theextensive research literature in this field and points to new directions in research. It will be read with interest by evolutionary biologists, geneticists, and biogeographers.

Canadian Journal Of Genetics And Cytology

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Author :
language : en
Publisher:
Release Date : 1976

Canadian Journal Of Genetics And Cytology written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1976 with Cytology categories.

Plant Science Literature

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Author : United States. Bureau of Plant Industry. Library
language : en
Publisher:
Release Date : 1939

Plant Science Literature written by United States. Bureau of Plant Industry. Library 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.

Cytotaxonomic Studies In Michigan Asters

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Author : Paul Van Faasen
language : en
Publisher:
Release Date : 1962

Cytotaxonomic Studies In Michigan Asters written by Paul Van Faasen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1962 with Asters categories.

Publications

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Author :
language : en
Publisher:
Release Date :

Publications written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with Botany categories.

Consists of offprints from various publications.

Biographical Memoirs

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Author : National Academy of Sciences
language : en
Publisher: National Academies Press
Release Date : 1994-02-01

Biographical Memoirs written by National Academy of Sciences and has been published by National Academies Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994-02-01 with Biography & Autobiography categories.

Biographic Memoirs: Volume 64 contains the biographies of deceased members of the National Academy of Sciences and bibliographies of their published works. Each biographical essay was written by a member of the Academy familiar with the professional career of the deceased. For historical and bibliographical purposes, these volumes are worth returning to time and again.