title: Effects of abscisic acid on K+ channels in Vicia faba guard cell protoplasts.
abstract: Potassium channels were resolved in Vicia faba guard cell protoplasts by patch voltage-clamp. Whole-cell currents and single K+ channels had linear instantaneous current-voltage relations, reversing at the calculated Nernst potential for K+. Whole cell K+ currents activated exponentially during step depolarizations, with half-activation times of 400-450 msec at +80 mV and 90-110 msec at +150 mV. Single K+ channel conductance was 65 +/- 5 pS with a mean open time of 1.25 +/- 0.30 msec at 150 mV. Potassium channels were blocked by internal Cs+ and by external TEA+, but they were insensitive to external 4-aminopyridine. Application of 10 microM abscisic acid increased mean open time and caused long-lasting bursts of channel openings. Since internal and external composition can be controlled, patch-clamped protoplasts are ideal systems for studying the role of ion channels in plant physiology.
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology*; D007887:Fabaceae; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D010944:Plants / Q000187:drug effects / Q000378:metabolism*; D010946:Plants, Medicinal; D011188:Potassium / Q000378:metabolism*; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism
chemical_list: D003509:Cyclohexanecarboxylic Acids; D007473:Ion Channels; D000040:Abscisic Acid; D011188:Potassium