Auxin and hydrogen ion actions on light-grown pea epicotyl segments I. Tissue specificity of auxin and hydrogen ion actions

摘要

Growth responses to added auxin and hydrogen ions of differently prepared tissue segments excised from 5th internodes of light-grown Alaska peas were studied. Unpeeled segments extended in response to auxin but not to hydrogen ions. Peeled segments elongated well in response to hydrogen ions but much less when exposed to auxin. Hollow-cylinder (central part removed) and infiltrated (by reduced pressure) unpeeled segments significantly elongated in response to hydrogen ions as well as to auxin. Outward curvature of split segments was enhanced by buffer solution at pH lower than 5.0. Peeled segments secreted hydrogen ions into an incubation medium containing auxin or a fungal toxin, FC. Unpeeled segments and the isolated epimermis secreted much less hydrogen ions in response to these agents. Hydrogen ions generated by the action of auxin thus seem to accumulate in the region adjacent to the cuticle, that is, epidermal cells. The significance of the epidermis in auxin and hydrogen ion actions is discussed.