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  • 1
    ISSN: 1573-5036
    Keywords: cation exchange capacity ; gypsum ; lime ; Quercus petraea ; sessile oak
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a former 45 to 50 year old sessile oak ( Quercus petraea (M.) Liebl.) coppice mixed with birch (Betula pubescens Ehrh.) and rowan (Sorbus aucuparia L.) on a poor acidic forest soil at la Croix-Scaille in the French Ardennes, several liming amendments were applied in 1990 and 1994. Data on soil and soil solution composition, as well as stand growth and foliar composition were collected between 1994 and 1997. All treatments, containing 1.4 t ha-1 equivalent of CaO supplied as lime, gypsum or a mixture of the two, resulted in an increase of cation exchange capacity and base saturation down to 15 cm and for CaSO4 treatments down to 30 to 45 cm, increases of soil pH and Ca concentration at the surface and a decrease of Al concentration in the soil and soil solution in the surface layers. No negative effects like increased nitrate or cation leaching were observed. Although Mg nutrition was not improved by the treatments (not containing Mg), a relative and maintained gain of radial increment of sessile oak in the order of 40% for both lime and gypsum applied, was observed immediately from the first year on, after the application (1991).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 194 (1978), S. 303-313 
    ISSN: 1432-0878
    Keywords: Cement gland ; Xenopus laevis ; Secretion ; Mucus ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cement gland was studied from stage 17, when the anlage is established, to stage 49, shortly before its disappearance. At early stages, the apical membrane is covered by small microvilli that are more abundant than in the surrounding epiblast cells. Vesicular protrusions along the cell boundaries are also more numerous in the gland cells. When the gland reaches maturity, the apical membranes of gland cells differentiate into two regions. In the cranial, kidney-shaped region, the membranes are very narrow and protrude above the level of cell boundaries. Long and slender villi raise from the surface adjacent to cell boundaries. Apical surfaces in the caudal portion are larger and flattened. Cell boundaries are lined with shorter and thicker surface projections. At these stages, the bordering cells are covered with secretion vesicles. During involution the number of cells is progressively reduced. The area of the caudal portion increases relative to the area of the cranial portion. Apical surfaces become more flattened. Surface projections become much shorter and invade the whole of the apical surface. Bordering cells lose their secretion vesicles and their apical surface becomes ruffled with numerous short wrinkles. The significance of the apical structures and their evolution is discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 148 (1976), S. 193-207 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To establish a morphological baseline for experimental studies of differentiation using the cement gland as a model, the following observations are added to those on record. The elongated cells of Xenopus laevis cement glands have an internal organization displaying five distinct zones differing in structure and specialized function. The apical zone contains packed secretion vesicles apparently belonging to two different types. The transit zone appears to be devoid of major biosynthetic activity and contains secretion vesicles migrating toward the surface. The zone of biosynthesis is typically organized in concentric regions. The very elongated nucleus lies in the next zone. Finally, the storage zone is characterized by lipid droplets and yolk platelets.Only quantitative differences are observed between cells of young and mature cement glands. Though all cells have the same general organization they may probably be divided into two subtypes according to the structure of their cytoplasm. The epithelial cells surrounding the gland differ according to their position along lateral or basal borders.
    Type of Medium: Electronic Resource
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