Budding reproduction

Perennial plants with shielded buds and vigorous asexual reproduction are relatively radioresistant. 

The implementation of animal test protocols in the 1980s has been accompanied by the development of a host of alternative methods to study adverse effects of chemicals on reproductive and developmental parameters. For example, rat whole embryo culture stems from the seventies (16), as does the rat limb bud organ culture (17) and rat limb bud and brain micromass was developed in the eighties (18). An elegant nonvertebrate alternative model used regeneration of polyps of Hydra atUnuata from dissociated cells (19). Animal-free in vitro alternatives include those employing the proliferation of a human embryonic palatal mesenchymal cell line (20), the attachment of a mouse ovarian tumor cell line (21), and the differentiation of a neuroblastoma cell line (22) and a embryonal carcinoma cell line (23). Various overviews of methods have been published over the years (24). The predictability of... 

Metamorphosis and budding inhibited reduction in pulsation rate Inhibited reproduction 60% died in 60 days 90% died in 30 days... 

The overall life cycle of a particular yeast Saccharomyces (S.) cerevisiae, is summarised in Fig. S.6 which shows how it is possible for the cells to fuse to form various cell and spore types. The figure shows the possible types of reproduction in yeast. Generally, industrial strains of S. cerevisiae, brewers yeast, reproduce by budding/ fission processes and only sporulate under specialised conditions. However, many strains of yeast are capable of cell fusion to form spores or cells with increased genetic complements. Such strains have many sets of chromosomes and are termed polyploid. Active fermentation of industrial strains involves growth by mitotic division and nutrient depletion which results in stationary cells with little or no spore formation. 

The Jerusalem artichoke can reproduce by two primary means. It can reproduce and colonize an area by the allocation of photosynthate and nutrients into both asexual (tubers and, to a lesser extent, rhizomes) and sexual (seed) reproductive organs. Flexibility in the amount of resources allocated between sexual and asexual means of reproduction confers a selective advantage in that conditions that inhibit or block sexual production (lack of pollen, herbivory of floral structures, undesirable weather) allow increased allocation to asexual reproduction. Artificially reduced allocation of resources to sexual reproduction, for example, results in a substantial increase in those allocated to asexual means. With flower bud removal, more (82 vs. 69) and larger (4.4 vs. 3.8 g) tubers were formed per plant than those with unlimited sexual reproduction (Wesdey, 1993). Total biomass was not altered, potentially indicating a relatively complete diversion of resources to asexual reproduction when sexual reproduction is blocked. From a reproductive standpoint, the risk of making it to the next season is high with sexual reproduction and relatively low with asexual reproduction. Increased investment in tubers increases the opportunity for sexual reproduction in the future. 

The molecular phylogeny and systematics of the fungi will be discussed elsewhere in this book [13]. A simple division of fungi with respect to clinical aspects is that into molds and yeasts, the former characterized by the formation of septate and nonseptate hyphae, the latter by an unicellular life cycle with reproduction mainly by budding. The so-called dimorphic fungi, such as Histoplasma... 

Thus, autocatalysis occurs in biology across various levels of structural and functional hierarchies, from a complete plant (or fungus, animal) over single cells down to such molecules which take part in metabolism and get doubled in cell budding and reproduction also. Both the... 

Gemmation or Budding.— This is the method of reproduction common among yeasts. The cell forms a protuberance called a bud which increases in size until it equals the size of the cell which formed it and then becomes detached, although frequently not until it has developed other buds and these still others. 

The ripened seed is the product of reproductive processes, and the starting point in the life of all Spermatophytes. The living part of the seed is the embryo, which, when developed, consists of four parts, the caulicle, or rudimentary stem, the lower end of which is the beginning of the root, or radicle. At the upper extremity of the stem are one, two, or several thickened bodies, closely resembling leaves, known as cotyledons, and between these a small bud or plumule. 

Inflorescence or Anthotaxy.—A typical flower consists of four whorls of leaves modified for the purpose of reproduction, and compactly placed on a stem. The terms Inflorescence and Anthotaxy are applied to the arrangement of the flowers and their position on the stem, both of which are governed by the same law which determines the arrangement of leaves. For this reason flower buds are always either terminal or axillary. In either case the bud may develop a solitary flower or a compound inflorescence consisting of several flowers. 

The general method of reproduction in Saccharomyces is that of gemmation or budding. A small protuberance of the cell wall com-... 

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