Potassium Channels atCharaPlasmalemma
- 1 February 1985
- journal article
- research article
- Published by Oxford University Press (OUP) in Journal of Experimental Botany
- Vol. 36 (2) , 228-239
- https://doi.org/10.1093/jxb/36.2.228
Abstract
Exposure to high K+ medium transforms Chara plasmalemma into [K+]osensitive state (K+ state). The current-voltage (I/V)characteristics under such conditions display a negative conductance region. This feature results from the complex time and voltage dependence of K+ channel opening At potentials more negative than a threshold p.d. the channels are closed and the I/V characteristics become linear with a low slope conductance of ∼0.8 S m2 and only a weak dependence on [K+]o. Such behaviour is usually associated with a non-specific leak current The threshold level for K+ channel closing depends on [K+]o. In 2.0 mol m−3 and 5.0 mol m−3 K+ medium the membrane resting p.d. follows EK, but hyperpolarizes gradually if the [K+]o is lowered. The proton pump thus appears to be non-operative, while the cell is in the K+ state, and recovers slowly as the cell is returned to a low K+ medium. Excitation currents decline if the cells are kept in K+ state for some hours.Keywords
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