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Kunihiro Kasamo, Effect of Abscisic Acid on the K+ Efflux and Membrane Potential of Nicotiana tabacum L. Leaf Cells, Plant and Cell Physiology, Volume 22, Issue 7, November 1981, Pages 1257–1267, https://doi.org/10.1093/oxfordjournals.pcp.a076278
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Abstract
K+ efflux from tobacco (Nicotiana tabacum L, cv. Samsun NN) leaf discs into the external medium was increased and the membrane potential (Em) changed in the positive direction with a change in pH from 8.0 to 4.0. Em was affected by the external concentration of KCl, greatly decreasing with a change in concentration from 1 mM to 100 mM. The equilibrium potential of the membrane for K+ (Ek) was decreased in a Nernst fashion with increasing external concentrations of KCl. Ek is more positive than Em above ca. 50 μM KCl. Most of the experiments were carried out under conditions in which the difference between the electrochemical potential for K+ on the inside to the outside of the cell (∇μk is positive. Thus, K+ may passively flow to the outside of the cells accompanied by the depolarization of the membrane.
Abscisic acid (ABA) increased the K+ efflux under conditions of passive transport. K+ efflux was accelerated with an increasing concentration of ABA, being maximal at 10−4M−10−3M. This acceleration was due to the enhancement of the potassium motive force (∇μk/F) which is the force causing the net passive transport of K+. The membrane potential was decreased from −205 mV to −170 mV by 2 × 10−4M ABA within 10 min. The depolarization was not transient, being lost for at least 3 hr.
These results show that ABA accelerated passive K+ efflux, which accompanied depolarization of the membrane.
