Effects of Abscisic Acid on86Rb+Fluxes inCommelina communisL. Leaf Epidermis

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Abstract
86Rb+ was used as a tracer for K+ to study effects of abscisic acid (ABA) on ion fluxes in C. communis leaf epidermis tissue in relation to stomatal movements. The stomata had similar opening characteristics when floated on buffer solutions containing either KCl or RbCl. Net uptake of 86Rb+ was linearly related to stomatal opening, and microautoradiography showed that the tracer was taken up in the guard cell region. ABA, which caused stomatal closure in the system used, significantly decreased net uptake of the tracer after 80 min incubation, but not before. The hormone caused changes in the distribution of 86Rb+ within the epidermis as measured by quantitative microautoradiography. It also caused an increase in the efflux of tracer from epidermis transferred to ABA-containing solutions after 86Rb+ uptake. The results are discussed in relation to the mode of action of the hormone.