Über das Antherentapetum mit besonderer Berücksichtigung seiner Kernzahl
01 Feb 1954-Vol. 101, Iss: 1, pp 1-63
TL;DR: In der vorliegenden Arbeit wurden zur Prufung der jungst aufgeworfenen Frage, ob dem Vorkommen des einkernigen Tapetums eine gewisse systematischen Bedeutung zukame, nicht nur die Angaben uber das Einkernige Tapetum (vgl. die Zusammenstellung S. 15−17) kritisch gesichtet, sondern auch alle Angabens uber e
Abstract: Da in den letzten Jahren die Beobachtungen uber ein einkerniges Tapetum weiter zugenommen haben, liegt die Vermutung nahe, das dieses eine weitere Verbreitung hat, als bisher angenommen wurde. In der vorliegenden Arbeit wurden zur Prufung der jungst aufgeworfenen Frage, ob dem Vorkommen des einkernigen Tapetums eine gewisse systematische Bedeutung zukame, nicht nur die Angaben uber das einkernige Tapetum (vgl. die Zusammenstellung S. 15–17) kritisch gesichtet, sondern auch alle Angaben uber ein mehrkerniges Tapetum gesammelt und beide Vorkommen einander gegenubergestellt (vgl. den systematischen Teil). Es schien auch angezeigt, auf die verschiedenartigen Abweichungen von der normalen Tapetumentwicklung hinzuweisen, da in einzelnen solchen Fallen (bei weiblichen Pflanzen und pollensterilen Apomikten) ein Unterbleiben oder Verzogern von Kernteilungen in den Tapetumzellen beobachtet werden konnte, wodurch eine Einkernigkeit vorgetauscht sein kann. — Das Vorhandensein sowohl eines inneren als auch eines mehrschichtigen Tapetums ist in den vorliegenden Fallen nicht an eine bestimmte Kernzahl geknupft.
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TL;DR: A hypothetical phylogenesis of the tapetum is proposed on the basis of its morphological appearance and of the nutritional relations with meiocytes/spores, and the evolutionary trends of thetapeta tend towards a more and more intimate and increasingly greater contact with the spores/pollen grains.
Abstract: It appears that the tapetum is universally present in land plants, even though it is sometimes difficult to recognize, because it serves mostly as a tissue for meiocyte/spore nutrition. In addition to this main function, the tapetum has other functions, namely the production of the locular fluid, the production and release of callase, the conveying of P.A.S. positive material towards the loculus, the formation of exine precursors, viscin threads and orbicules (= Ubisch bodies), the production of sporophytic proteins and enzymes, and of pollenkitt/tryphine. Not all these functions are present in all land plants:Embryophyta. Two main tapetal types are usually distinguished in theSpermatophyta: the secretory or parietal type and the amoeboid or periplasmodial type; in lower groups, however, other types may be recognized, with greater or lesser differences. A hypothetical phylogenesis of the tapetum is proposed on the basis of its morphological appearance and of the nutritional relations with meiocytes/spores. The evolutionary trends of the tapeta tend towards a more and more intimate and increasingly greater contact with the spores/pollen grains. Three evolutionary trends can be recognized: 1) an intrusion of the tapetal cells between the spores, 2) a loss of tapetal cell walls, and 3) increasing nutrition through direct contact in narrow anthers.
346 citations
01 Jan 1984
TL;DR: After more than 30 years of research on the nuclear cytology of differentiated tissues, it is now clear that the “supernumerary chromonemal reproduction” at interphase, better called “chromosome endoreduplication” (Levan and Hauschka 1953), is the commonest and most widespread process of cell polyploidization in both plants and animals.
Abstract: In the older literature on angiosperm morphology many examples of very large cells with giant or “hypertrophied” nuclei within differentiated tissues, including reproductive tissues, have been reported, and the connection between nuclear size and trophic activity of the cell has been stressed (references in Schnarf 1929, Tischler 1944, Maheshwari 1950). Goldstein (1928) even attempted to establish a correlation between nuclear form and functional activities of normal and pathological cells. In the absence of adequate knowledge of the mechanisms responsible for the multiplication of the genome, the large size and the variable form (irregular, crenate, lobate, constricted, furrowed, etc.) of nuclei were generally assumed to result from fusion of nuclei and/or amitosis. The significance of restitutional mitosis as a mechanism of doubling the chromosome number was not realized, and was generally regarded as a pathological process. The situation began to change in the late 1930’s—early 1940’s following the discovery of endomitosis in Homoptera, e.g., the pondskaters of the genus Gerris (Geitler 1939), and the proposition that the tetraploid mitoses “with paired chromosomes” (now called “diplochromosomes”) in poly somatic root tips of Spinacia oleracea are due to a double chromosome reproduction at interphase (Berger 1941). After more than 30 years of research on the nuclear cytology of differentiated tissues, it is now clear that the “supernumerary chromonemal reproduction” at interphase (Lorz 1947), better called “chromosome endoreduplication” (Levan and Hauschka 1953), is the commonest and most widespread process of cell polyploidization in both plants and animals (Brodsky and Uryvaeva 1977, D’Amato 1977 a, Nagl 1978).
178 citations
TL;DR: This article is restricted to a summary, discussion and evaluation of the knowledge of the physiology and cytology of anther development, particularly the role of tapetum and the development of pollen grains.
Abstract: An understanding of the morphology and physiology of the angiosperm flower and its component parts is of considerable importance in programmes for the development of new agricultural and horticultural varieties, in the elucidation of various hereditary processes and their control, and for an insight into various problems of cell biology, cell division and the physiology and control of reproduction. A great deal of work has been produced since the days of Amici (1824) and Hofmeister (I 848) regarding the developmental aspects of reproductive parts of the angiosperm flower, fertilization and the development of endosperm and embryo leading to the formation of a mature seed. Much of this work is summarized in the books by Schnarf (1929, 1931), and Maheshwari (1950, 1963). Unfortunately, very little effort, if any, has been made to understand the physiology of the reproductive organs of the angiosperm flower, particularly the chemical and cytochemical changes involved in the initiation and control of these processes (Vasil, 1965). The ultrastructural studies made by Rosen, Gawlik, Dashek & Siegesmung (1964) and by Sassen (1964) of the pollen tubes, by Heslop-Harrison (1962, 1963b, 1964) of the developing anther, and by Jensen (1963) of the embryo sac, fertilization and embryogenesis are, therefore, especially welcome. Some work has also been done recently on the histochemical and biochemical aspects of reproduction in higher plants (Linskens, 1 9 6 4 ~ ) . In order to limit the field of discussion and because of my own interest and familiarity with the angiosperm anther, this article is restricted to a summary, discussion and evaluation of our knowledge of the physiology and cytology of anther development, particularly the role of tapetum and the development of pollen grains." Discussion of the various aspects of the physiology of pollen grains after dehiscence is excluded as
123 citations
111 citations
TL;DR: The distribution of tapetal types in basal angiosperms is reviewed both from the literature and new observations in the context of recent phylogenetic analyses, finding apparent plasticity for a relatively brief but critical time in angiosperm evolution.
Abstract: The distribution of tapetal types in basal angiosperms is reviewed both from the literature and new observations in the context of recent phylogenetic analyses. Secretory tapeta predominate among land plants. The majority of basal angiosperms share a secretory tapetum with their anthophyte ancestors. Plasmodial and invasive tapeta are relatively rare in eudicots but have evolved several times among early‐branching angiosperms, especially in monocotyledons, in which they have evolved three or more times. The invasive tapetum has evolved at least four other times independently in basal angiosperms: in Nymphaeaceae, Annonaceae, Monimiaceae, and Winteraceae. Plasmodial tapeta are mostly found in monocotyledons but have evolved at least twice in basal angiosperms, in Annonaceae, and in Hernandiaceae/Lauraceae. This apparent plasticity for a relatively brief but critical time in angiosperm evolution may reflect the early evolution of highly specific pollination syndromes.
82 citations
References
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TL;DR: The subterranean vertical rhizome of Peltandra virginica is built up sympodially from branches arising in the axils of the penultimate leaves of continuation shoots of successively higher rank, and evidence for the occurrence of cross-pollination was found.
Abstract: 1. The subterranean vertical rhizome of Peltandra virginica is built up sympodially from branches arising in the axils of the penultimate leaves of continuation shoots of successively higher rank. Each continuation shoot, as well as the primary axis, terminates in a spadix. A second spadix arises in the axil of the ultimate leaf. 2. Usually vegetative buds, which sometimes result in vegetative multiplication of the plant, arise in the axils of only the antepenultimate leaves. 3. There is a tendency to limit the number of foliage leaves formed on a continuation shoot. The minimum number was three. 4. Leaves and inflorescences appear to be initiated about 20 months before they actually emerge from the terminal bud. 5. Development of the staminate flowers differs from that of the pistillate in that the latter alone show a distinct segmentation of the floral primordia. 6. A "bouquet" stage was found in early meiosis. The haploid number of chromosomes was 56. 7. Periplasmodium formation was found in the micros...
22 citations
TL;DR: It seems clear that this type of embryo is characteristic of this family of aroids, where the male nuclei are not surrounded by a definite cytoplasmic envelope, and the division producing them is often delayed until dehiscence or later.
Abstract: 1. The development of the archesporium in aroids follows no uniform rule. In one species studied, the primary archesporial cell produces two megaspores, the outer one of which functions; in two cases there are four megaspores, the outermost one of which functions; in one case the primary cell produces two cells, one of which may be a tapetal cell; one species develops four megaspores in the same horizontal plane, and the functioning one then develops a tapetal cell at its upper end; one species develops four megaspores, the innermost of which functions; and in one case the primary sporogenous cell develops directly into an embryo sac. 2. The number of antipodals varies from 3 to 11, four species having regularly more than 3. This is a relatively primitive feature, and occurs in other primitive orders. 3. Previous to the work here reported, embryos of the spherical type lacking a suspensor had been reported by Campbell in Pistia, Dieffenbachia, and Lysichiton. The writer has confirmed Campbell'S observatio...
22 citations
TL;DR: Riassunto L'A.
Abstract: Riassunto L'A. stabilisce che in Euphorbia Paralias L., in E. falcata L. var. acuminata (Lam.) Fior, E. pubescens Vahl ed E. Pithyusa L. var. ovalifolia Fiori lo sviluppo del gametofito femminile e di tipo Normale S-nucleato; in Euphorbia Characias L. il gametofito femminile puo svilupparsi secondo il tipo Normale e il tipo Scilla con una frequenza di sviluppo del primo rispetto al secendo del valore approssimativo percentuale del 7%; in Euphorbia amygdaloides L. il gametofito si sviluppa sempre secondo lo schema del tipo Scilla. Stabilisce inoltre che il numero aploide dei cromosomi e n=S in Euphorbia Paralias L., n = 18 in E. falcala var. acuminata (Lam.) Fiori, n = 7 in E. pubescens Vahl, n = 18 in E. Pithyusa L. var. ovalifolia Fiori, n = 10 in E. Characias L. ed n = 9 in E. amygdaloides L. Fenomeni di associazione secondaria dei cromosomi del corredo aploide potrebbero indicare che il numero aploide n = 7 di Euphorbia pubcscens Vahl sia derivato dal numero aploide 6. Si prospetta quindi la possibilit...
21 citations
TL;DR: The ovule is anatropous and has two integuments, and the mature anther shows well-defined endothecia three or four cells in thickness and disintegration of the stomium.
Abstract: 1. Origin of the floral organs of Agave lechuguilla is acropetal, sepals appearing first and carpels last. 2. The flower is epigynous. Its vascular anatomy is simple, being a direct divergence of vascular bundles into the separate organs. All vascular bundles ending in either sepal or petal structures are derived from bundles differentiated early in connection with these floral parts. 3. The ovule is anatropous and has two integuments. Placentation is axial. 4. Megasporogenesis starts with differentiation of a single hypodermal archesporial cell and ends with formation of a tetrad of megaspores arranged usually in linear fashion. Two variations in megaspore arrangement were noted. 5. Periclinal division of the archesporial cell gives rise to a primary parietal cell and to a single primary sporogenous cell which enlarges and becomes the megaspore mother cell. Development of the megagametophyte follows the so-called normal type. 6. A single parietal layer is present in the ovule, disintegrating when the meg...
21 citations