The effect of benzo‐18‐crown‐6, a synthetic ionophore, on stomatal opening and its interaction with abscisic acid

Treatment of tomato seedlings with 5 mM benzo‐18‐crown‐6, a potassium ionophore, produced a reduction in transpiration of 40%. Treatments of epidermal strips of Commelina communis with ben‐zo‐18‐crown‐6 (1‐l0mM) inhibited stomatal opening, and this effect was shown to be reversible. An antagonistic interaction between abscisic acid (10 −7 M) and benzo‐18‐crown‐6 (4 × 10 −3 M) was also observed.