{
    "abstract": "There is evidence for a role of increased cytoplasmic Ca2+ in the stomatal closure induced by abscisic acid (ABA), but two points of controversy remain the subject of vigorous debate--the universality of Ca2+ as a component of the signaling chain, and the source of the increased Ca2+, whether influx across the plasmalemma, or release from internal stores. We have addressed these questions by patch-clamp studies on guard cell protoplasts of Vicia faba, assessing the effects of ABA in the presence and absence of external Ca2+, and of internal Ca2+ buffers to control levels of cytoplasmic Ca2+. We show that ABA-induced reduction of the K+ inward rectifier can occur in the absence of external Ca2+, but is abolished when Ca2+ buffers are present inside the cell. Thus, some minimum level of cytoplasmic Ca2+ is a necessary component of the signaling chain by which ABA decreases the K+ inward rectifier in stomatal guard cells, thus preventing stomatal opening. Release of Ca2+ from internal stores is capable of mediating the response, in the absence of any Ca2+ influx from the extracellular medium. The work also shows that enhancement of the K+ outward rectifier by ABA is Ca2+ independent, and that other signaling mechanisms must be involved. A role for internal pH, as suggested by H.R. Irving, C.A. Gehring and R.W. Parish (Proc. Natl. Acad. Sci. USA 89:1790-1794, 1990) and M.R. Blatt (J. Gen. Physiol. 99:615-644, 1992), is an attractive working hypothesis.",
    "authors": [
        {
            "affiliation": "Department of Plant Sciences, University of Cambridge, United Kingdom.",
            "firstname": "F",
            "initials": "F",
            "lastname": "Lemtiri-Chlieh"
        },
        {
            "affiliation": null,
            "firstname": "E A",
            "initials": "EA",
            "lastname": "MacRobbie"
        }
    ],
    "conclusions": null,
    "copyrights": null,
    "doi": "10.1007/BF00233479",
    "journal": "The Journal of membrane biology",
    "keywords": [],
    "methods": null,
    "publication_date": "1994-01-01",
    "pubmed_id": "8006956\n6270629\n1534380\n24202027\n3235976\n2388697\n1534573\n2388696\n24186668\n11538499\n12297670\n1701140\n2174559\n24232888\n1375754\n1385219\n1501238\n16593851\n11607281\n12324599",
    "results": null,
    "title": "Role of calcium in the modulation of Vicia guard cell potassium channels by abscisic acid: a patch-clamp study.",
    "xml": "<Element 'PubmedArticle' at 0x788501e10130>"
}