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  • 1
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Cell-lineage ; Cereal tissue culture ; Somatic embryogenesis ; Sorghum bicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Immature leaf explants ofSorghum bicolor (L.) Moench can be stimulatedin vitro to form roots, shoots or embryos. When the cultures were maintained with the high 2,4-D level which was essential for optimal culture initiation, the organs or embryos proliferated as suppressed primordia, but they could always be identified by simple histological means. Perivascular cells of comparatively old but still immature leaf sheath regions appeared to be strongly determined to form adventitious roots or root-type “callus” cultures. We have evidence that the embryogenic tissue, and ultimately the embryos, are of multicellular origin. This ontogeny of the embryos appears to be contradictory to the often stated view that somatic embryos generally arise from single “committed” cells. The implications of these findings for basic and applied research on cereal tissue culture are discussed.
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  • 3
    ISSN: 1615-6102
    Keywords: Shoot meristems ; 2,4-Dichlorophenoxyacetic acid ; Teratoma ; Somatic embryogenesis ; Cereal tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tissue cultures capable of plant regeneration were successfully initiated from extremely immature shoot meristems of 21 randomly selected genotypes of wheat on nutrient media containing 2,4-dichlorophenoxyacetic acid (2,4-D). By means of scanning electron microscopy it was demonstrated that cultures consisted of teratomatous primordia, which were kept in a proliferating budding state by the 2,4-D. These are characteristic of cereal tissue cultures. Release of the primordia and outgrowth of normal shoots and roots occurred when the cultures were no longer exposed to 2,4-D. Shoot primordia which were clearly identifiable were always associated with root primordia in a quasi-bipolar fashion. Sometimes regions assumed the shape of zygotic embryos, but the transition from apparently normal embryos with scutellum to abnormal configurations with shoot and root regions was gradual. The differences between genotypes in shoot regeneration potential was minimal compared to cultures derived from explants which were taken from regions temporally and spatially more distant from the shoot apex. It is concluded that the ability to give rise to cultures capable of shoot regeneration was lost within a fraction of a millimeter distance from the apical meristem in many genotypes. The proliferating tissues were subcultured at regular intervals over a period of one year and the regeneration potential was monitored. Areas capable of shoot regeneration tended to deteriorate more or less rapidly and were overgrown by root-type tissue in a number of genotypes. The results are discussed in the context of the frequently observed, but largely unexplained, variability in the regeneration potential of cereal tissue cultures.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 153 (1990), S. 141-148 
    ISSN: 1615-6102
    Keywords: Cell shaping ; Cell wall ; Immunofluorescence ; Mesophyll ; Microtubules ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Differentiated mesophyll cells ofTriticum aestivum (cv. Star) exhibit a lobed outline resembling tube-shaped balloons with almost regularly spaced constrictions. It was shown that these constrictions are probably the result of hoops of wall reinforcements laid down during early stages of cell expansion. It appears that these hoops prevent expansion in the corresponding regions and thus give rise to the peculiar cell shape. The comparatively thin cell walls of the bulges are uniformly reinforced after the lobed shape is established. By using immunofluorescence techniques a change in the pattern of cortical microtubule arrangement was observed which corresponded to the pattern of cell wall deposition. Discrete bands of microtubules were found beneath the sites of hoop reinforcement. These bands disintegrated during late stages of cell expansion with microtubules fanning out into the almost empty regions of the bulges.
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  • 5
    ISSN: 1615-6102
    Keywords: Carrot ; Embryogenesis ; Immunofluorescence ; Preprophase band of microtubles ; Suspension culture ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To date it has been accepted that preprophase bands of microtubules (PPBs) either do not precede cell division or do so inconsistently in suspension cultures, the assumption being that such cultures proliferate in an “unorganized” state in which placement of cell plates is not regulated by the PPB system that is widespread in organized tissues. Using indirect immunofluorescence microscopy with antitubulin, the relative frequency of occurrence of PPBs in enzymatically separated cells from root tips and suspension cultures of carrot and tobacco, was quantified by taking the ratio of the number of PPBs: phragmoplast. This ratio was termed the “PPB index”. One carrot suspension culture proliferated in a medium containing 2,4-Dichlorophenoxyacetic acid (2,4-D), and recognizable stages in somatic embryogenesis formed when 2,4-D was removed from the medium. Another carrot suspension culture was nonembryogenic and removal of 2,4-D resulted in a reduction of cell division and increase in cell elongation. The tobacco culture was a cytokinin habituated cell line and also required 2,4-D to maintain cell division. It ceased proliferation, and cell elongation took place if 2,4-D was removed. The PPB index in the root tips from both species, and in both types of carrot suspension culture was approximately the same but was approx. 15-fold lower in the tobacco suspension. PPBs in the tobacco suspension were atypical in structure as well as sparse in numbers. The PPB index allows quantitative comparisons between different tissues to be made. The low PPB index and the irregular PPBs in the tobacco suspension correlates with its inability to undergo organized morphogenesis and generate spatially defined cell lineages upon 2,4-D removal. In contrast, the high PPB index in the carrot suspension cultures correlates with their potential for organized embryo formation, whether or not that potential is realized by withdrawal of 2,4-D. However, their high PPB index is not obligatorily coupled to embryogenesis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 173 (1993), S. 8-12 
    ISSN: 1615-6102
    Keywords: Nigella damascena ; Mesophyll ; Arm-palisade ; Microtubules ; Wall deposition ; Cell shaping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cell shaping in the mesophyll ofNigella damascena was investigated with the aim of determining the origin of the arm-like protrusions, which are characteristic of, e.g., arm-palisade cells. It was found that hoops of cell wall were deposited during the early stages of cell expansion. The hoops were interconnected, thus embracing the cells with a wide-meshed net of local wall reinforcement. The pattern of wall deposition in the extra-cellular matrix correlated with a pattern of bands of microtubules in the cortical cytoplasm of the cells. During lateral expansion bulges were forced through the comparatively thin walls of spaces between the meshes, giving rise to the arm-like protrusions. After establishing the cell shape the bands of microtubules disintegrated and cell wall was uniformly deposited. The results are discussed in the context of the mode of cell shaping observed in the mesophyll of other systems and of a previous, classical hypothesis on the origin of arms in mesophyll cells.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5044
    Keywords: Lolium multiflorum ; ryegrass ; tissue culture ; somatic embryogenesis ; inflorescence ; node
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When cultured on agar-solidified media (based on Murashige and Skoog's formula), immature inflorescences and nodes ofLolium multiflorum underwent several different pathways of morphogenesis. The pathway expressed was dependent upon the type of explant, its age and the composition of the culture medium. Immature inflorescences generally produced either leaves and roots or embryoids whereas nodes produced axillary shoots or embryoids. Embryogenesis from both explant sources occurred from a firm, white, opaque, proliferating tissue. The embryoids could be cultured individually and induced to produce plantlets capable of transfer to soil. Generally the plantlets formed from newly isolated tissues were green, but chlorophyll-deficient plantlets arose infrequently (up to about 5%). However, this frequency increased as the embryoid-producing tissues were propagated by subculture.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1615-6102
    Keywords: Cereal tissue culture ; Sorghum bicolor ; 2,4-D auxinherbicide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In this paper we present further studies on the generation of tissue cultures from leaves of the cerealSorghum bicolor (L.) Moench. It could be shown that during differentiation the leaf tissue rapidly loses the ability to respond to conventional tissue culture techniques. This was probably related to a loss of sensitivity towards 2,4-D, an otherwise most potent growth regulator in tissue culture. The immature tissue which proved to be sensitive proliferated over a wide range of concentration with a broad optimum of about 0.6–6 mg 1−1 2,4-D. This concentration range appears to be only slightly higher than that described for many dicotyledonous tissue cultures. The relevance of these findings is discussed with reference to the well known dual function of 2,4-D, namely as a selective herbicide and a potent artificial auxin. The implications of these attributes to the practical application of cereal tissue culture is stressed.
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  • 9
    ISSN: 1615-6102
    Keywords: Cereal tissue culture ; Inflorescence ; Somatic embryogenesis ; Sorghum bicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A method for reproducibly initiating tissue cultures from immature sorghum inflorescences is described. The cultures are maintained through the proliferation of embryo-like structures and shoot primordia, which under appropriate conditions grow further to form plants. Evidence is presented that these structures develop from a tissue similar to that found in the scutellum of immature embryos, which arises from superficial cells of the inflorescence expiants. Possible applications of such a system are discussed.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2048
    Keywords: Leaf development ; Mesophyll (cells, protoplasts) ; Microtubule (patterns, density) ; Nicotiana ; Tissue culture (in vitro competence) ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the density of microtubular mesh-works were analysed in mesophyll cells and mesophyll derived protoplasts of Nicotiana tabacum L. and Triticum aestivum L. during leaf development. The main purpose of this study was to test whether the low density, if not lack, of microtubular networks recently described in protoplasts that had been isolated from fully differentiated mesophyll cells happened during protoplast isolation or whether the loss of microtubules actually occurred during differentiation of the leaf tissue. Immunofluorescence microscopy showed that the density of the microtubular cytoskeleton in the leaf tissue decreased steadily after cessation of cell growth in both species. Nevertheless, in Triticum microtubule disappearance was swifter and occurred along a gradient from the base to tip of the leaf, a phenomenon reflecting the differences in the ontogeny between the dicotyledonous Nicotiana and the mono-cotyledonous Triticum leaves. Protein extraction from leaf tissues and Western blot analysis indicated that in both species the disappearance of microtubules was the result of a degradation of tubulin and not only due to a depolymerisation into tubulin subunits. When the cell walls were removed from live cells and the protoplasts released, the original patterns of the microtubules became obscured and, particularly in differentiated cells, the integrity and density of the microtubule strands deteriorated. The potential application of the density of the microtubular cytoskeleton as a marker in studies on differentiation and dedifferentiation in mesophyll cells and protoplasts is discussed.
    Type of Medium: Electronic Resource
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