Open AccessSynergistic Effect of Light and Fusicoccin on Stomatal Opening
Author(s) -
Sarah M. Assmann,
Am Schwartz
Publication year - 1992
Publication title -
plant physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.98.4.1349
Subject(s) - fusicoccin , guard cell , molar concentration , biophysics , chemistry , vicia faba , patch clamp , darkness , membrane , atpase , biochemistry , botany , biology , enzyme , receptor , organic chemistry
Upon incubation of epidermal peels of Commelina communis in 1 millimolar KCl, a synergistic effect of light and low fusicoccin (FC) concentrations on stomatal opening is observed. In 1 millimolar KCl, stomata remain closed even in the light. However, addition of 0.1 micromolar FC results in opening up to 12 micrometers. The same FC concentration stimulates less than 5 micrometers of opening in darkness. The synergistic effect (a) decreases with increasing FC or KCl concentrations; (b) is dark-reversible; (c) like stomatal opening in high KCl concentrations (120 millimolar) is partially inhibited by the K(+) channel blocker, tetraethyl-ammonium(+) (20 millimolar). In whole-cell patch-clamp experiments with guard cell protoplasts of Vicia faba, FC (1 or 10 micromolar) stimulates an increase in outward current that is essentially voltage independent between - 100 and +60 millivolts, and occurs even when the membrane potential is held at a voltage (-60 millivolts) at which K(+) channels are inactivated. These results are indicative of FC activation of a H(+) pump. FC effects on the magnitude of inward and outward K(+) currents are not observed. Epidermal peel and patch clamp data are both consistent with the hypothesis that the plasma membrane H(+) ATPase of guard cells is a primary locus for the FC effect on stomatal apertures.