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  • 1
    Electronic Resource
    Electronic Resource
    Growth, membrane potential and endogenous ion currents of willow (Salix viminalis) roots are all affected by abscisic acid and spermine (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 99 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Growth measurements of hormone-treated roots from willow cuttings were combined with electrophysiological recordings to study hormone-induced changes in membrane potential and in endogenous ion currents. The mean growth rate of roots was 10 ± 2 μm min−1 in regular nutrient solution. It increased to 13 ± 2 μm min+1 after application of spermine and decreased to 0.07 ± 0.01 μm min−1 after treatment with abscisic acid (ABA). Transient depolarizations were elicited in root cortex cells by spermine, while ABA caused a transient hyperpolarization. All changes in membrane potential were accompanied by transient responses of the endogenous current. These responses suggest that first anions, then cations leave the root during spermine-induced depolarizations. From the changes of the endogenous current an apparent efflux of anions (presumably Cl−) and cations (presumably K+) of 200 to 700 pmol cm−2 per depolarization was calculated.To further investigate a possible relation between endogenous ion currents, growth and the growth regulators ABA and spermine, long-lasting extracellular vibrating-probe measurements were performed. Control roots showed an inward current of about 1.5 μA cm−2 at the apical elongation zone and an outward current with a maximum density of 1.3 μA cm−2 at the central and basal elongation zone. The addition of ABA and spermine (final concentration 0.1 mM) to the bathing medium affected the endogenous current in opposite ways: ABA caused a reduction of inward and outward current, while spermine stimulated both. Since protons are a major component of the endogenous current, and sucrose can be taken up by root cells from the apoplast via symport with H+, a role of the endogenous current in growth regulation is indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb05353.x
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  • 2
    Electronic Resource
    Electronic Resource
    Bioelectricity, gravity and plants (1997)
    Springer
    Planta 203 (1997), S. S98 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Electric current ; Gravity (root ; shoot ; single cell) ; Ion flux (H+ ; Ca2+) ; Membrane voltage (transmembrane potential) ; Surface potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. This brief review summarizes gravity-induced changes in bioelectric parameters and evaluates their contribution to our understanding of the sensing of gravity, and the transduction and transmission of the gravity stimulus in plants. During the last few decades, information has accumulated demonstrating gravity-induced changes in surface potentials, membrane voltages, endogenous electric currents and ion fluxes. These changes point to the plasma membrane as the site of perception and transduction of the gravity signal. To date, it is reasonable to assume that gravity affects the state of ion channels (in particular, Ca2+ channels) and the activity of ion pumps (in particular, the electrogenic H+-ATPase) in the plasma membrane leading to intracellular and apoplasmic changes in ion activities and in membrane voltages. The flow of H+ and Ca2+ currents is probably the means by which information about gravity is amplified and transmitted from sensing to responding cells. No data are available so far about the effect of microgravity on bioelectric parameters. However, it would be interesting to learn if plants become hypersensitive to gravity during a prolonged stay in microgravity. If so, such plants might fire action potentials after return to earth, because more Ca2+ channels than usual may be activated by 1 g in microgravity-adapted plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008122
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