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  • 1
    ISSN: 1432-2048
    Keywords: Cell wall (pectin ring) ; Enforced growth fluctuation ; Intracellular free Ca2+ ; Lilium ; Pollentube ; Turgor pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Normally growing lily (Lilium longiflorum Thunb.) pollen tubes cultured in standard sucrose medium display a relatively steady tip-growth pattern and a rather even pectin sheath in the cell wall. In an attempt to better understand pulsatory growth, observed in some species, e.g., Petunia, and its possible role in causing the formation of thickened cell wall rings, we have imposed marked fluctuations in the growth-rate of lily pollen tubes. The appropriate growth-perturbing conditions were achieved by modulating the medium osmolarity or by applying caffeine, a non-turgor inhibitor, in a specially designed incubation chamber with a controlled medium flow. The relatively non-esterified pectin deposition in the wall of the growth-interrupted pollen tubes was detected by immunofluorescence microscopy using a monoclonal antibody, JIM 5. The observations show that the periods of slow or inhibited growth correspond to the times when the thickened walls are deposited. Since the growth fluctuations were induced by both turgor- and non-turgor-related means, the proposed endogenous regulatory role of turgor pressure is questioned. Other factors, such as the tip-focused Ca2+ gradient which was demonstrated by ratiometric ion imaging, and the alteration in the extensibility of the cell wall, which correlated with pectin esterification/de-esterification, emerge as candidates for the regulation of growth fluctuations.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Nicotiana tabacum ; Pollen ; Pollen tube ; Cell wall ; Immunogold localization ; Pectins ; Arabinogalactan proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The monoclonal antibodies JIM 5 (against unesterified pectin), JIM 7 (against methyl esterified pectin), MAC 207 (against arabinogalactan proteins, AGPs), and JIM 8 (against a subset of AGPs) were utilized singly or in combinations for immunogold labelling of germinated pollen grains and pollen tubes ofNicotiana tabacum. Pectins were localized in the inline of pollen grain, unesterified pectin being more abundant than the esterified one. AGPs were co-localized with pectin in the inline, but were present preferably close to the plasma membrane. In pollen tubes, AGPs, unesterified and esterified pectins were co-localized in the outer and middle layers of the cell wall. The density of the epitopes was not uniform along the length of the pollen tube, but showed alterations. In the pollen tube tip wall esterified pectin was abundantly present, but not AGPs. In the cytoplasm esterified pectin and AGPs were detected in Golgi derived vesicles, indicating their role in the pathway of the cell wall precursors. In the “cell wall” of generative cell only AGPs, but no pectins were localized. The co-localization of pectins and AGPs in the cell wall of pollen grain and pollen tube might play an important role, not only in maintenance of the cell shape, but also in cell-cell interaction during pollen tube growth and development.
    Type of Medium: Electronic Resource
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