Planta

, Volume 211, Issue 6, pp 894–898 | Cite as

Fast activation of a time-dependent outward current in protoplasts derived from coats of developing Phaseolus vulgaris seeds

  • Wen-Hao Zhang
  • N. Alan Walker
  • Stephen D. Tyerman
  • John W. Patrick
Rapid communication

Abstract.

An outward current that appeared to activate instantaneously in response to depolarising voltage pulses at low sampling frequencies predominated in the plasma membrane of ground-parenchyma protoplasts derived from coats of developing Phaseolus vulgaris L. (cv. Redland Pioneer) seeds. However, the outward current showed time-dependent activation when higher sampling frequencies were used to measure the current. Activation of the current was best described as a double-exponential time course with the fast and slow time constants being 1 and 20 ms, respectively. The current also exhibited a rapid deactivation that followed a double-exponential time course with time constants of approximately 2 and 30 ms, respectively. “Tail-current” analysis allowed us to show that this current exhibited a low selectivity between K+ and Cl (PK:Cl=1.8). Such a fast-activating current may account for some of the reports of time-independent, instantaneous currents that have been observed in plasma membranes of plant cells digitised at low sampling frequencies. Therefore, when “instantaneous” currents appear it is advisable to characterise these currents using higher sampling frequencies with correspondingly higher filtering frequency cut-offs.

Key words: Current activation (fast, time dependent) – Instantaneous current –Phaseolus (membrane current) – Plasma membrane current (activation) – Protoplast (patch-clamp) – Seed coat protoplasts 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Wen-Hao Zhang
    • 1
  • N. Alan Walker
    • 2
  • Stephen D. Tyerman
    • 1
  • John W. Patrick
    • 3
  1. 1.School of Biological Sciences, The Flinders University of South Australia, GPO Box 2100, Adelaide, SA 5001, AustraliaAU
  2. 2.Biophysics Department, School of Physics, The University of NSW, Kensington, NSW 2052, AustraliaAU
  3. 3.Department of Biological Sciences, The University of Newcastle, Newcastle, NSW 2308, AustraliaAU

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