A Convenient Method for Determining the Effect of Abscisic Acid on the Stomatal Aperture of Rice (Oryza Sativa L.) by Feeding Solution to the Leaf Tip

We established a convenient method for determining the effect of abscisic acid (ABA) solution on the stomatal aperture in wilting-sensitive plants such as rice (Oryza staiva L.). Water or ABA solution in a small vial was fed into a leaf tip under field conditions. Stomatal conductance was decreased by concentrations of ABA from 10⁻³ to 10⁻⁸ mol L⁻¹ three hours after application. The amount of solution fed into the plant depended on the transpiration rate of the leaf. It was shown by the infiltration method that the stomata of an ABA-fed leaf closed first at the leaf edge and progressively toward the midrib. This heterogeneous stomatal closing may cause variance of stomatal conductance in the mid portion of the leaf in some cases. However if we can measure the stomatal conductance of portions of the leaf nearer to the tip, it may be possible to detect the stomatal response sooner and with less variation. We conclude that the assay method helps to define stomatal response to growth substances such as ABA of plants which suffer drought or any stress.