Auxin-induced extension of the isolated epidermis of light-grown pea epicotyls

1. The effect of IAA and FC on the extension of isolated epidermisof light-grown Alaska pea epicotyls was studied under differentconditions with an extension apparatus. The following resultswere obtained.
2. The epidermis extended in response to low pHbuffer solutionof 1–10 mM, maximum extension being achievedat pH below5.5.
3. IAA, 5 mg/liter, caused, although not consistently,an extensionof epidermal strips in 1 mM buffer, but not at10 mM.
4. Consistent extension of the isolated epidermis dueto IAA wasobtained by addition of GTP, ATP, ITP or UTP (sodiumsalts),but not nucleosides, nitrogen bases or sugars.
5. A fungaltoxin, FC, at 10^–5 M induced extension of theepidermiswithout addition of the nucleoside triphosphates.
6. IAA andFC caused H⁺ extrusion in peeled epicotyl segments bothin thepresence and absence of GTP. IAA caused appreciable H⁺extrusionin the isolated epidermis only in the presence ofGTP, whereasH⁺ extrusion by the epidermis was induced by FCeven in theabsence of GTP.

From these results, we concluded that IAA induces extensionof the isolated epidermis under the above conditions throughthe mediation of H⁺ ions. (Received July 12, 1976; )