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  • 1
    ISSN: 1615-6102
    Keywords: Bean ; Elongation growth ; Osmiophilic particles ; Pea ; Spruce ; Sunflower
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence of elongation growth-related osmiophilic particles (OPs) was investigated in hypocotyls of sunflower, bean, and spruce as well as in pea epicotyls and in cress roots of intact seedlings. In all analyzed species, OPs were found to occur specifically within the periplasmic space between plasma membrane and the outer epidermal cell walls of elongating parts of hypocotyls, epicotyls, and roots, whereas cells of nonelongating parts were devoid of OPs. Auxin (IAA) markedly increased the number of OPs in epicotyl and hypocotyl segments. Treatment of pea epicotyl segments with the lectin concanavalin A inhibited their elongation growth in the presence of IAA. At a subcellular level this effect was characterized by the occurrence of a pronounced osmiophilic layer in the periplasmic space of the outer periclinal and the outer part of the anticlinal epidermal cell walls. Treatment of IAA-incubated segments with the secretion inhibitor brefeldin A inhibited both elongation growth and periplasmic occurrence of OPs. This effect was accompanied by complementary accumulation of OPs in the peripheral cytoplasm of epidermal cells. Together the results indicate that IAA-induced epidermis-specific secretion of OPs is closely related to cell elongation growth not only in organs of monocotyledonous species, but also in dicotyledonous angiosperms as well as in gymnosperms.
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  • 2
    ISSN: 1615-6102
    Keywords: Brefeldin A ; Gravitropism ; Osmiophilic particles ; Secretion inhibition ; Secale cereale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence of IAA-inducible osmiophilic particles (OPs) in the periplasmic space of epidermal cells in the upper and lower flank (UF, LF) of gravistimulated rye coleoptile segments was analyzed employing brefeldin A (BFA) as an inhibitor of secretion at the plasma membrane. A 2 h horizontal gravistimulation of untreated samples caused a duplication of OPs in the periplasmic space of epidermal cells at the growth-inhibited UF as compared to the LF of upward bending coleoptile segments. In contrast to this, the number of OPs within the cytoplasm close to the plasma membrane of epidermal cells was similar at both flanks. BFA caused an inhibition of graviresponsive growth and prevented the occurrence of OPs in the periplasmic space of the epidermal cells of the UF and the LF. Likewise, growth of vertically oriented coleoptile segments was inhibited by BFA. Growth inhibition of both gravistimulated and control segments was accompanied by a twofold increase of the occurrence of cytoplasmic OPs. The results illustrate that the occurrence of OPs within the periplasmic space of the epidermal cells depends on secretion processes. Furthermore they provide evidence that their increased occurrence in the growth-inhibited UF during gravistimulation is due to their inhibited infiltration into the cell walls. We suggest that thereby wall loosening is temporarily prevented.
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  • 3
    ISSN: 1432-2048
    Keywords: Filipin ; Lepidium ; Plasma membrane ; Root (membranes) ; Tonoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Membranes from roots of Lepidium sativum L. were investigated in situ and after fractionation by applying morphological and biochemical methods. After freeze-fracture combined with filipin labelling the tonoplast and the plasma membrane could be easily characterized by the frequency of intramembranous particles and the arrangement of filipin-induced lesions. On tonoplast vesicles, the filipin-induced lesions were arranged in clusters of different size whereas they were evenly distributed on plasma membrane vesicles. Enrichment of tonoplast and plasma membrane in different fractions was documented by filipin labelling, phosphotungstic acid staining and by the profiles of marker enzyme activities and ATP-dependent H+-transport. Additionally, the presence of rightside-out and inside-out vesicles of both tonoplast and plasma membrane could be demonstrated. It was found that filipin labelling used in combination with freeze-fracturing is suitable for quantitative determinations of the percentages of tonoplast and plasma membrane in membrane fractions, which have been found to be more than 40% for the tonoplast and about 40% for plasma membrane in the respective enriched fractions.
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  • 4
    ISSN: 1432-2048
    Keywords: Chara ; Graviperception ; Lepidium ; Microfilament ; Microgravity ; Statolith (reduced gravitational field)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During five rocket flights (TEXUS 18, 19, 21, 23 and 25), experiments were performed to investigate the behaviour of statoliths in rhizoids of the green alga Chara globularia Thuill. and in statocytes of cress (Lepidium sativum L.) roots, when the gravitational field changed to approx. 10−4 · g (i.e. microgravity) during the parabolic flight (lasting for 301–390 s) of the rockets. The position of statoliths was only slightly influenced by the conditions during launch, e.g. vibration, acceleration and rotation of the rocket. Within approx. 6 min of microgravity conditions the shape of the statolith complex in the rhizoids changed from a transversely oriented lens into a longitudinally oriented spindle. The center of the statolith complex moved approx. 14 μm and 3.6 μm in rhizoids and root statocytes, respectively, in the opposite direction to the originally acting gravity vector. The kinetics of statolith displacement in rhizoids demonstrate that the velocity was nearly constant under microgravity whereas it decreased remarkably after inversion of rhizoids on Earth. It can be concluded that on Earth the position of statoliths in both rhizoids and root statocytes depends on the balance of two forces, i.e. the gravitational force and the counteracting force mediated by microfilaments.
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  • 5
    ISSN: 1432-2048
    Keywords: Lepidium ; Membrane protein ; Monoclonal antibody TOP 71 ; Plasma membrane ; Tonoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Highly purified tonoplast and plasma-membrane vesicles isolated from roots of Lepidium sativum L. (garden cress) were used as a starting material for generating a monoclonal antibody against plant tonoplast. Tonoplast vesicles were isolated by discontinuous-sucrose-gradient centrifugation followed by free-flow electrophoresis. The deglycosylated tonoplast fraction was used to generate monoclonal antibodies by immunization of Balb/c-mice and by fusion of their β-lymphocytes with the mouse cell line X 63 Ag 8.653. Using plasma membrane purified by two-phase partitioning and freeflow electrophoresis to define the negative signal in screening, and purified tonoplast to define the positive signal in screening, a monoclonal antibody (TOP 71) was obtained which recognized a tonoplast protein of 71 kDa by immunoblotting in cress-root membrane fractions. Two-dimensional gel electrophoresis, affinoblotting and binding to concanavalin A showed that the TOP 71-antigen was a glycosylated protein and had an isoelectric point (pI) of 4.5. The TOP 71-antigen was found in the different tissues of organs of several higher plants (Glycine max L., Curcurbita pepo L., Zea mays L.) where it did not cross-react with the purified plasma-membrane fractions of these plants. Additionally, TOP 71 recognized its antigen in microsomal fractions of two lower plants (Chara globularis Thuili., Matteucia struthiopteris Tod.).
    Type of Medium: Electronic Resource
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