Ion Channels in the Plasma Membrane of Plant Cells
Many types of ion channels have been characterised in the membranes of plant cells (Tester, 1990) but overall there is a lack of understanding of their physiological functions. The functions of plant ion channels need to be seen in context of the variable ionic environment to which plant cells are exposed. The mechanisms for acquisition of nutrients must cope with variable driving forces for uptake from low external concentrations yet simultaneously or subsequently be able to respond to excess concentrations. A proton pump energises the plasma membrane and due to a low membrane conductance and rather negative reversal potential of the pump, a large proportion of the electrochemical difference for protons (ΔµH+) is generated as an electrical potential difference (PD). Changes in the driving force due to variations in the external pH can be quickly compensated for by changes in PD. Ion channels are ideally suited to the control of the PD because large dissipative fluxes can occur through relatively few channels when they open.
KeywordsGuard Cell Anion Channel Single Channel Conductance Chara Corallina Subconductance State
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