Über das Antherentapetum mit besonderer Berücksichtigung seiner Kernzahl

The tapetum: its form, function and possible phylogeny in Embryophyta

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.

Role of Polyploidy in Reproductive Organs and Tissues

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).

Physiology and cytology of anther developmeent

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

The tapetum in basal angiosperms: early diversity

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.

The origin and development of the compositæ.

Abstract: I the Compositas the mechanism involved in the presentation of pollen to the insect visitor includes both styles and stamens. These essential oi'gans ai-e discussed, therefore, in the present chapter, but for convenience the variation in structure of styles and stamens is described and discussed in separate sections, while their functions in the pollen-presenting mechanism is considered partly in section D of the present chapter and partly in Chapter III which deals with the irritability of the mechanism.

Ontogeny, genetics, and cytology of Nicotiana hybrids

Abstract: NICOTIANA SPECIES-CROSSES . . . . . . . . . . . . . 35 1. Crosses in which the pollen-tubes do not reach the ovary 36 2. Crosses in which the pollen-tubes reach the ovary, penetrate the micropyle, and induce parthenocarpy 38 3. Crosses in which the/ertilization occurs, but in which the embryos usually die in a very early stage . . . . 42 4. Crosses in which the seeds germinate, but the plants die in the seedling stage . . . . . . . . . . . . . . 44 5. Crosses/rom which mature hybrids are obtained . . . 45 I I I . T H E S L O W G R O W T H O F T H E H Y B R I D E M B R Y O S A N D T H E