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Semin Cell Biol. 1993 Apr;4(2):113-22.

Ca2+ and cell signalling in guard cells.

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Department of Plant Sciences, University of Cambridge, UK.


Abscisic acid (ABA)-induced stomatal closure involves two different signalling chains, only one of which is Ca(2+)-dependent. ABA induces deactivation of the inward K+ channel and activation of an inward 'background' current, changes also produced by high cytoplasmic Ca2+ or injection of inositol 1,4,5-trisphosphate. It is argued that ABA produces local increases in Ca2+, which are obligatory for the response, even where global increases are not observed with present methodology. Deactivation of the inward K+ channel is abolished in the presence of internal Ca2+ chelator, but not by external Ca2+ chelator, arguing for release from internal stores. ABA-induced turnover in the polyphosphoinositide cycle occurs within 30 s, and may precede the electrical changes. Activation of the outward K+ channel is Ca(2+)-independent; changes in cytoplasmic pH, of unknown origin, may be responsible.

[Indexed for MEDLINE]

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