Operation of K+-channels in stomatal movement

The plasma membrane of guard cells contains two classes of voltage-sensitive K+-channels, one to catalyse K+-uptake, the other to catalyse K+-release. Recent progress in characterizing their biophysical properties and the regulatory mechanisms responsible for controlling their activation has provided extensive understanding of channel function. The activity of both channels is sensitive to membrane voltage and is modulated by the concentration of K+, Ca2+ and H+. Further regulation is accomplished by GTP-binding proteins and protein phosphorylation. It is now possible to understand how K+-channel gating underlies stomatal movement and how environmental and internal signals impact on this process.