title: Uptake and distribution of abscisic acid in Commelina leaf epidermis.
abstract: Closure of stomata by abscisic acid (ABA) was studied by floating leaf epidermal strips of Commelina communis L. in PIPES buffer (pH 6.8) containing a range of KCl concentrations. Control apertures were greatest at high concentrations of the salt, and the effects of ABA, in terms of closure, were most pronounced below 100 mol m(-3) KCl. Stomata opened on strips floated on buffer plus 50 mol m(-3) KCl and closed within 10 min when transferred to the same medium plus 0.1 mol m(-3) ABA. [2-(14)C]ABA was used to study uptake and distribution of the hormone by the epidermal strips. It was calculated that no more than 6 fmol ABA were present per stomatal complex at the time of closure, although uptake continued thereafter. Microautoradiography indicated that radioactivity from [2-(14)C]ABA accumulated in the stomatal complex at or near the guard cells within 20 min. TLC was used to examine the state of the label after 1 h incubation. Efflux of label from preincubated tissue appeared to occur in three phases (t1/2=7.2 s, 4.0 min, 35.2 min). Efflux was correlated with stomatal re-opening. The results confirm that ABA can accumulate in the epidermis of C. communis.
authors.affiliation: Botany Department, University of Glasgow, G12 8QQ, Glasgow, U.K..
authors.forename: J D
authors.initials: JD
authors.lastname: Weyers
authors.forename: J R
authors.initials: JR
authors.lastname: Hillman