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- Title
Guard cell cation channels are involved in Na+-induced stomatal closure in a halophyte.
- Authors
Véry, Anne‐Aliénor; Robinson, Michael F.; Mansfield, Terry A.; Sanders, Dale
- Abstract
SummaryThe halophyte Aster tripolium, unlike well‐studied non‐halophytic species, partially closes its stomata in response to high Na+ concentrations. Since A. tripolium possesses no specific morphological adaptation to salinity, this stomatal response, preventing excessive accumulation of Na+ within the shoot via control of the transpiration rate, is probably a principal feature of its salt tolerance within the shoot. The ionic basis of the stomatal response to Na+ was studied in guard cell protoplasts from A. tripolium and from a non‐halophytic relative, Aster amellus, which exhibits classical stomatal opening on Na+. Patch‐clamp studies revealed that plasma membrane K+ channels (inward and outward rectifiers) of the halophytic and the non‐halophytic species are highly selective for K+ against Na+, and are very similar with respect to unitary conductance and direct sensitivity to Na+. On the other hand, both species possess a significant permeability to Na+ through non‐rectifying cation channels activated by low (physiological) external Ca2+ concentrations. Finally, it appeared that the differential stomatal response between the two species is achieved, at least in part, by a Na+‐sensing system in the halophyte which downregulates K+ uptake. Thus, increases in guard cell cytosolic Na+ concentration in A. tripolium but not in A. amellus, lead to a delayed (20–30 min) and dramatic deactivation of the K+ inward rectifier. This deactivation is probably mediated by an increase in cytosolic Ca2+ since buffering it abolishes the response. The possible role of K+ inward rectifiers in the response of A. tripolium’s stomata to Na+, suggested by patch‐clamp studies, was confirmed by experiments demonstrating that...
- Subjects
PLANT cells &; tissues; HALOPHYTES; STOMATA; PLANT protoplasts
- Publication
Plant Journal, 1998, Vol 14, Issue 5, p509
- ISSN
0960-7412
- Publication type
Article
- DOI
10.1046/j.1365-313X.1998.00147.x