Pharmacological study of two potential Ca 2+ signalling pathways within stomatal closing in response to abscisic acid in Commelina communis L.

Abstract

It has been previously suggested that, depending on its applied concentration, abscisic acid (ABA) induces stomatal closing through one of two potential Ca 2+-dependent transduction pathways. This hypothesis was worked further in Commelina communis by comparing the stomatal responses to 10 nM ABA (ABA 10) and 100 nM ABA (ABA 100) on the basis of a pharmacological dissection of implicated Ca 2+ signalling. Compared to the ABA 10 response, the response to ABA 100 was differentially affected by the putative plant modulators of Ca 2+ fluxes caffeine, ruthenium red, procaine, SDZ-202 791 S(+), S-(−)-BAY K8644 and SDZ-202 791 R(−). Furthermore, the ABA 100 response specifically displayed positive interactions between the plant Ca 2+ buffer 1,2-bis( o-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid (BAPTA) and the anion channel blockers anthracene-9-carboxylic acid, [(6,7-dichloro-2-cyclopentenyl-2,3-dihydro-2-methyl-1-oxo-1H-inden-5-yl)oxy]acetic acid or 2-(α,α,α-trifluoro- m-toluidine)-pyridine-3-carboxylic acid, whereas the anion channel blocker 5-nitro-2,3-phenylpropyllamine benzoic acid positively interacted with BAPTA to prevent both the ABA 10 and ABA 100 responses. Together, these results might support indirectly that stomatal closing in a graded response to increasing concentrations of exogenous ABA proceeds from different Ca 2+ signalling pathways.