Cytoplasmic Ca2+ has No Effect on the Excitability of Chara Plasmalemma |
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Authors: | L?hring Hinrich; Tazawa Masashi |
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Institution: | Department of Botany, Faculty of Science, University of Tokyo Hongo, Tokyo 113, Japan |
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Abstract: | Internodal cells of Chara australis were subjected to two consecutiveintracellular perfusions with a Ca2+-free EGTA medium whichdisintegrated the tonoplast within about 10 minutes and thenwith a Ca2+-buffered medium. All perfusion media usually contained1 mM ATP. To stop the electrogenic pump, the internode was depletedof intracellular ATP. The excitability of the plasmalemma wasnot significantly influenced by intracellular free Ca2+ concentrationsup to 104 M. To trigger action potentials, minimum currentdensities of 1 to 2 µA cm2 had to be applied atall tested Ca2+ concentrations. In the absence of cytoplasmicATP, excitability was completely lost at all Ca2+ concentrations.
1 Present address: Botanisches Institut der Universit?t Bonn,Venusbergweg 22, D-5300 Bonn, FRG. (Received September 22, 1984; Accepted March 6, 1985) |
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