
%0 Journal Article
%A Beilby, Mary J. 
%A Shepherd, Virginia A. 
%T Modeling the current-voltage characteristics of charophyte membranes. III. K<emph type="7">+</emph> state of <emph type="2">Lamprothamnium</emph>
%J Functional Plant Biology
%D 2001/07/27
%V 28
%N 7
%P 541-550
%K hypotonic effect, I/V analysis, K + channels, Lamprothamnium, salt tolerance.
%R https://doi.org/10.1071/PP01032
%U https://www.publish.csiro.au/paper/PP01032 
%X The K + state of salt-tolerant charophyte Lamprothamnium papulosum (Wallr.) J. Gr., acclimated to 0.5 seawater (SW) containing 4.5 mM K + , was investigated by exposing the cells to a range of &#91;K + &rsqb; o from 0 to 45.0 mM . The current&#8211;voltage (I/V) characteristics were modeled as a sum of four different transporter currents: the large conductance K + channel current, inward and outward K + rectifier currents and linear background current. The first three transporters were fitted with the Goldmann-Hodgkin-Katz (GHK) model. The potential difference (PD) dependence of the population of open channels was simulated by Boltzmann probability distribution. The linear background current exhibited reversal PD independent of lsqb;K + &#93; o and the background conductance decreased as lsqb;K + &#93; o increased. The combined channel number and permeability parameter, N K P K , was in a similar range for all three K + transporters. The N K P K parameter of the large conductance K + channel reached a maximum at lsqb;K + &#93; o concentration of 9 mM , decreasing at 45 mM . The modeled large conductance K + channel revealed a strong asymmetry of the I/V profile in response to change of outside and inside K + concentrations. This behaviour was exploited to estimate the rise of cytoplasmic K + concentration at the time of the hypotonic effect. The cytoplasmic K + concentration range giving the best fit to the data in steady-state was 28&#8211;65 mM . 
