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A slow anion channel in guard cells, activating at large hyperpolarization, may be principal for stomatal closing
Author(s) -
Linder Birgit,
Raschke Klaus
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)81176-m
Subject(s) - guard cell , biophysics , chemistry , depolarization , hyperpolarization (physics) , patch clamp , conductance , ion channel , membrane potential , repolarization , reversal potential , electrophysiology , biochemistry , stereochemistry , biology , physics , neuroscience , receptor , condensed matter physics , nuclear magnetic resonance spectroscopy
Slowly activating anion channel currents were discovered at micromolar ‘cytoplasmic’ Ca 2+ during patch‐clamp measurements on guard‐cell protoplasts of Vicia faba and Xanthium strumarium . They activated at potentials as low as −200 Mv, with time constants between 5 and 60 s, and no inactivation. The broad voltage dependence exhibited a current maximum near −40 mV. The single‐channel open time was in the order of seconds, and the unitary conductance was 33 ps, similar to that of the already described ‘quick’ anion channel of guard cells. Because of its activity at low potentials, the slow anion channel may be essential for the depolarization of the plasmalemma that is required for salt efflux during stomatal closing.