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  • Pelvetia  (2)
  • Ionophore gradient  (1)
  • Springer  (3)
  • 1975-1979  (3)
  • 1940-1944
  • 1
    Electronic Resource
    Electronic Resource
    Forced calcium entry and polarized growth of Funaria spores (1979)
    Springer
    Planta 144 (1979), S. 401-406 
    Details
    ISSN: 1432-2048
    Keywords: A23187 gradients ; Calcium ; Germination (moss spores) ; Electric fields-Funaria ; Ionophore gradient ; Moss spores-Polarization ; Spores (moss)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used both steady electric fields, and gradients of the divalent ionophore, A23187, to control the point at which rhizoids emerge from spores of the common moss Funaria hygrometrica. The spores were grown in a medium containing calcium nitrate as the only major salt. Spores tend to form rhizoids towards the positive electrode, with a half maximal response to a difference of 4–8 mV across each cell. They also tend to form rhizoids towards the end of higher ionophore concentration in response to A23187 gradients. Both of these responses are the same at pH 5.5 and 8.0. Our tentative explanation is that Funaria spores tend to form rhizoids where most calcium enters. However, the point of chloronema emergence is scarcely affected by steady fields of up to 45 mV/cell. Moreover, when steady fields are applied across already developed rhizoids or chloronemata, their subsequent growth is directed towards the negative electrode in both cases, with rhizoids giving a 50% response at only 3—5 mV/cell, and chloronemata being less responsive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380114
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  • 2
    Electronic Resource
    Electronic Resource
    Cell-wall formation in Pelvetia embryos. A freeze-fracture study (1976)
    Springer
    Planta 133 (1976), S. 57-71 
    Details
    ISSN: 1432-2048
    Keywords: Cell-wall formation ; Fucoid eggs ; Pelvetia ; Fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cell-wall formation in the egg of Pelvetia fastigiata (J.G. Agardh) DeToni (Fucaceae) was studied with freeze-fracture. 1. The wall is lamellated with microfibrils approximately parallel in each lamella. The average orientation of microfibrils turns about 35° in each subsequent lamella. This slow turn gives rise to bow-shaped arcs when the wall is obliquely cross fractured. 2. The organization of the fibrils in the innermost lamellae is visualized by their imprints on the plasma membrane. These imprints are the result of both turgor pressure and adhesion of fibrils to the membrane. 3. Strings of membrane particles appear on the plasma membrane shortly after fertilization. They seem to be formed by a fertilization-induced aggregation of isolated membrane particles. Later each string comes to lie under a fibril and along its imprint. Peculiar lateral rips indicate that some strings are tightly bound to a fibril and may be involved in its orientation. 4. Wall formation in Pelvetia is marked by pronounced secretory activities. Following fertilization, the fusion of cortical vesicles and other vesicles make numerous loci in the plasma membrane. In older embryos, fibril-free patches in the plasma membrane mark the position of microfibril elongation centers in the wall matrix. Prior to germination, these elongation centers and their corresponding membrane patches reach a high density at the presumptive rhizoid end.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386007
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of membrane potential on calcium fluxes of Pelvetia eggs (1978)
    Springer
    Planta 140 (1978), S. 63-67 
    Details
    ISSN: 1432-2048
    Keywords: Calcium fluxes ; Fucoid eggs ; Ion fluxes ; Membrane potential ; Pelvetia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 45Ca2+ fluxes across the plasma membrane of zygotes of the fucoid alga, Pelvetia fastagiata (J. Ag.) De Toni, were studied in artificial sea waters of various potassium concentrations. Except for two cases, hyperpolarization of the cell membrane (with low [K+]) increases, and depolarization (with high [K+]) decreases the influx of Ca2+ over the range of [K+] studied (1–100 mM). The fractional increases of influx during hyperpolarization are close to the fractional increases in membrane potential but the decreases during depolarization are much smaller than those in membrane potential. In two anomalous cases, the influxes of 45Ca2+ at a potassium concentration of 30 mM were about 20% higher than the control value instead of being 10% lower. The effluxes of 45Ca2+ are increased by both hyperpolarization and by depolarization. On balance (and excepting the two anomalous cases) the net result of hyperpolarization should be to increase and that of depolarization to decrease intracellular [Ca2+].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389381
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