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The Aloineae

The Aloineae: A Biosystematic Survey

Herbert Parkes Riley
Shyamal K. Majumdar
Copyright Date: 1979
Pages: 192
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  • Book Info
    The Aloineae
    Book Description:

    The Aloineae, a tribe of several hundred species of succulent plants of the lily family, are ideal subjects for the study of karotypes and chromosome irregularities. This book brings together the major findings of a half-century of study of the Aloineae, with regard to polyploidy, aneuploidy, deletions, duplications, inversions, and translocations in the group.

    The possible evolutionary effects of ecological relationships, natural hybridization, and morphological changes during growth are also assessed. Illustrations include maps, diagrams, photographs, photomicrographs, and electron micrographs.

    eISBN: 978-0-8131-6522-6
    Subjects: Botany & Plant Sciences, General Science

Table of Contents

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  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. Preface
    (pp. vii-ix)
    Herbert Parkes Riley and Shyamal K. Majumdar
  4. Chapter One INTRODUCTION
    (pp. 1-6)

    The tribe Aloineae of the family Liliaceae is fundamentally a South African group, but some of the genera included in it are also found elsewhere. It is rather small and is variable, since not all authors include the same genera within it. As treated here the tribe will includeAloe, Gasteria, Haworthia, Astroloba (Apicra), Poellnitzia, Chamaealoe, Chortolirion, Lomatophyllum, Leptaloe,andGuillauminia.

    The Aloineae comprise a group of generally succulent plants characterized by having a loculicidal capsule and anthers with introrse dehiscence. The leaves are generally thick or fleshy and often toothed on the margins; they often have a bitter sap...

    (pp. 7-24)

    The Aloineae are a tribe almost exclusively of the southern and eastern hemispheres; onlyAloeis found outside those areas. A few species get above the equator in the eastern hemisphere, and in the western hemisphere one species has been introduced. The individual species differ considerably in the size of the regions they occupy; a few range rather widely within the confines of those hemispheres whereas many are very constricted and appear to consist of only a few small clumps. The species of this tribe are all succulent plants and therefore inhabit the drier parts of the country.

    The only...

    (pp. 25-33)

    Any study dealing with evolutionary problems in plants must consider the sources of the materials used – i.e., the places where and the conditions under which the plants forming the study were obtained. In considering the Aloineae two main sources of material have been used: collections growing in botanical gardens and collections made from the veld or natural regions where the plants are growing.

    With plants collected directly from the veld there are no particular problems of authenticity. Such plants are the end products of evolution to date and the raw materials of future evolution. They show the exact state of...

  7. Chapter Four KARYOTYPES
    (pp. 34-41)

    A useful and important device for studying cytogenetics, especially for comparing related species and genera to detect chromosome aberrations and evaluate phylogenetic relationships and evolutionary trends, is the karyotype. It is actually a picture of the chromosomal complement of an individual plant or animal or of a related group of such individuals as seen in somatic metaphase. It is important because it reveals clearly and in readily comprehended fashion the various attributes of the complement: the number of chromosomes; the absolute size of the chromosomes; the relative size of the different chromosomes of the same set; the position of the...

    (pp. 42-65)

    For nearly sixty years many observers have looked at and counted the chromosomes of the A1oineae. Ever since H. A. C. Müller (1912) pointed out that the sporophytic number was 14 inAloe striataHaw. (published as A. Hanburyana Naud.), many species ofAloe, Astroloba (Apricra),Chamaealoe, Gasteria, Haworthia, Lomatophyllum,andPoellnitziahave been studied. Most of the species have 14 sporophytic chromosomes, but there are some polyploid and some aneuploid plants, especially inHaworthia. From time to time lists of chromosome numbers have been compiled, such as those by Suto (1936), Kondo and Megata (1943), Snoad (1951a), and Riley...

  9. Chapter Six POLYPLOIDY
    (pp. 66-76)

    Soon after cytologists began to observe chromosome numbers in plants, they found some plants with a chromosome number that was a multiple of the haploid number found in other members of the species but a multiple higher than the normal diploid number. For example, the brilliant plant physiologist and geneticist Hugo de Vries had advanced his Mutationstheorie in 1901 and listed among his mutants ofOenothera lamarckianaagigas,or giant type, and asemi-gigas,a half-giant. A few years later Lutz (1907) and Gates (1909) examined the chromosomes and found that if the normal o.lamarckianaplant had 2n...

  10. Chapter Seven ANEUPLOIDY
    (pp. 77-82)

    Polyploids have somatic or sporophytic chromosome numbers that are multiples of the haploid number other than the diploid number. If the number in the haploid set is x (i.e., ifn=x), polyploid plants might have 3x, 4x, 5x, or some other multiple (i.e., 2n=3x, 4x, 5x, and so forth). Aneuploids resemble polyploids in that they also have extra or fewer whole chromosomes, but they differ in that their number is not an exact multiple. Thus their sporophytic numbers might be 2n+ 1 (trisomic), 2n+ 2 (tetrasomic), 2n+ 1 + 1 (double trisomic),2n...

    (pp. 83-96)

    Polyploids and aneuploids are aberrations that involve whole chromosomes. However, some chromosome aberrations involve only pieces of chromosomes; they belong to types known as deletions or deficiencies, duplications, inversions, and translocations.

    Deletions or deficiencies are aberrations in which one or more segments of a chromosome or chromosomes are missing. According to Rieger, Michaelis, and Green (1968), the term deficiency should be used if the missing piece is a terminal acentric segment of a chromosome, chromatid, or subchromatid, whereas deletion is properly applied only if the missing segment is intercalary. But this nice distinction is often ignored. Swanson (1957), for example,...

  12. Chapter Nine TRANSLOCATIONS
    (pp. 97-113)

    Among the more common and certainly more interesting chromosomal aberrations or chromosomal structural changes are translocations (also called interchanges). A translocation is an aberration in which pieces of chromosomes are transferred to new positions in the karyotype by a process other than normal crossing over.

    Translocations have frequently been classified into two types, simple and reciprocal. It was thought at one time that the simplest kind of translocation occurs when a piece of one chromosome breaks away and becomes attached to the end of another chromosome as a terminal translocation, but now it is known that this type of translocation...

    (pp. 114-134)

    In earlier chapters the number of chromosomes in a plant, the behavior of chromosomes in cell division, the various possible anomalies of chromosome behavior that can occur, and the various types of chromosomal aberrations that are seen in different plants have been discussed and have been considered as possible factors in plant evolution. However, in many species factors other than chromosomal have been operating and methods other than those of classical cytology have been used in studying evolution. Some of those factors and methods will be considered here, including meiotic pairing, self-incompatibility, fertility, biochemical profiles as revealed by paper chromatography,...

  14. Chapter Eleven HYBRIDIZATION
    (pp. 135-142)

    The possibility that natural hybridization occurs in the Aloineae has been suggested for almost a century. In Berger’s article inDas Pflanzenreich(1908) hybridization is discussed and a large number of putative hybrids are listed. They are supposedly hybrids that arose in nature, since the creation of hybrids by artificial pollination was not extensive then. The decision that a plant was or was not a hybrid was based on an analysis of its phenotypic characters and a comparison of them with those of other plants of the same genus. This method of comparative morphology demands a detailed understanding of all...

    (pp. 143-160)

    The previously discussed cytogenetic factors operating in the Aloineae are interesting in themselves and provide good material for laboratory exercises in courses in cytogenetics. A very fundamental problem is what role if any these cytogenetic factors as well as other factors play and have played in the evolution of the various taxa of the tribe.

    Basic to the question of evolution is the nature of genera, species, and other possible taxonomic categories. Before species can be compared they must be understood so they can be identified and recognized, especially since so much work is done in different countries. Faulty identification...

  16. Literature Cited
    (pp. 161-170)
  17. Index of Families, Genera, & Species
    (pp. 171-176)
  18. General Index
    (pp. 177-180)
  19. Back Matter
    (pp. 181-181)