期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1987
卷号：84
期号：12
页码：4108-4112
DOI：10.1073/pnas.84.12.4108
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Stomatal pores in leaves enable plants to regulate the exchange of gases with their environment. Variations of the pore aperture are mediated by controlled changes of potassium salt concentrations in the surrounding guard cells. The voltage-dependent gating of K+-selective channels in the plasma membrane (plasmalemma) of cell-wall-free guard cells (protoplasts) was studied at the molecular level in order to investigate the regulation of K+ fluxes during stomatal movements. Inward and outward K+ currents across the plasmalemma of guard cells were identified by using the whole-cell configuration of the patch-clamp technique. Depolarizations of the membrane potential from a holding potential of -60 mV to values more positive than -40 mV produced outward currents that were shown to be carried by K+. Hyperpolarizations elicited inward K+ currents. Inward and outward currents were selective for K+ over Na+ and could be partially blocked by exposure to extracellular Ba2+. In cell-attached and excised membrane patches, previously identified K+-selective single channels in guard cells were studied. Averaging of single-channel currents during voltage pulses resulted in activation and deactivation kinetics that were similar to corresponding kinetics of inward and outward currents in whole cells, showing that K+-selective channels were the molecular pathways for the K+ currents recorded across the plasmalemma of single guard-cell protoplasts. Estimates demonstrate that K+ currents through the voltage-gated K+ channels recorded in whole guard cells can account for physiological K+ fluxes reported to occur during stomatal movements in leaves.
关键词：patch clamp ; K+ current ; ion channel ; rectifier ; stomata
