Synergistic effect of light and fusicoccin on stomatal opening: Epidermal peel and patch clamp experiments

Sarah M. Assmann, Amnon Schwartz

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


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, tetraethylammonium+ (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.

Original languageEnglish (US)
Pages (from-to)1349-1355
Number of pages7
JournalPlant physiology
Issue number4
StatePublished - 1992

All Science Journal Classification (ASJC) codes

  • Physiology
  • Genetics
  • Plant Science


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