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  • 1
    ISSN: 1615-6102
    Keywords: Betula pendula ; Histochemistry ; Pollen wall ; Dormancy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Anthers ofBetula pendula were collected at regular intervals during the dormancy period until anthesis. Ultrathin sections of maturing pollen grains were especially stained for polysaccharides and proteins and examined with TEM to determine whether structural or/and chemical changes in the pollen wall occur during the dormancy period of the plant life cycle. At the beginning of the dormancy period, the microspore wall consists of a well developed tectum, columellae and a foot layer. Spinules and supratectal elements are prominent. Microchannels are present in the tectum but not obvious in the foot layer. Some of the columellae are not clearly connected with the foot layer, but some connections are evident. Pores are filled with a thick fibrillar network “flocculent material”. The cytoplasm is packed with starch grains and lipid globules. The stainability for acidic and neutral polysaccharides and protein was tested, and variations in the pollen wall are illustrated. As temperature increased towards the end of dormancy and before anthesis there is obvious differentiation in the morphology of the pollen wall. The granular fibrillar layer beneath the pore and the Zwischenkörper are the most variable part of the wall. Different histochemical reactions observed in different layers at the aperture sites indicate different functions of these layers.
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  • 2
    ISSN: 1615-6102
    Keywords: Allergens ; Allergy ; Betula pendula ; Immunolabelling ; Pollen grains ; Tapetum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Although intact pollen grains are assumed to be the primary carrier of pollen allergens, specific immunoreactive components have been found in other aerosol fractions, e.g., starch grains and remains of tapetal cells Cryo-scanning-electron-microscopy results demonstrate the presence of a clear network of strands connecting the tapetum with the microspores. The distribution of protein in tapetal orbicules, pollen wall, and pollen cytoplasm was tested by histochemical stains for light microscopy and transmission electron microscopy. The protein is mainly localized at the apertures and starch grains in the cytoplasm of pollen and in the core and on the surface of tapetal orbicules. Monoclonal antibodies Bv-10, BIP3, and BIP4 have been used to locate the cellular sites of pollen and tapetal allergens inBetula pendula (syn.B. verrucosa). The application of rapid-freeze fixation prevented relocation of allergens from their native sites. The allergens are predominantly found in the starch grains and to lesser extent in the exine. We also tested interactions between mature birch pollen and human fluids: saliva, nostrils fluid, and eyes solution. The aim was to mimic more closely the in vivo situation during allergenic response. In all cases we observed several pollen grains that were burst and had released their cytoplasmic contents. In the nose the allergens are released from the pollen within minutes. In rhinitis, nasal pH is increased from the normal pH 6.0 to 8.0. When we used nasal fluid at pH 8.0, the number of ruptured pollen grains increased. The mechanism that might induce formation of small allergen-bearing particles from living plant cells is discussed.
    Type of Medium: Electronic Resource
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