Electrophoretic Isolation and Growth Activity of Indole-3-Acetic Acid Oxidation Products

Abstract

Indole-3-acetic acid (IAA) is oxidized by peroxidase enzymes. The physiological significance ascribed to this reaction is that it controls or regulates the biological activity of IAA. There are two views as to the function of auxin oxidases, one degradative and the other an activation role. The prevailing concept is that the oxidation of IAA represents a detoxification reaction considered necessary for plant to keep the level of IAA at an optimum for maximal physiological response (Galston and Davies 1969). Contrary to the concept of inactivation of IAA, it is proposed that the oxidative transformation of IAA also activates IAA (Meudt, 1965 and 1967). Furthermore, the function of an IAA oxidase, in a system other than for the inactivation of IAA, is suggested by our findings that binding of IAA, first shown by Siegel and Galston (1953), depends on prior oxidation of IAA (Meudt and Galston, 1962). It was suggested that the binding of IAA depended on at least two reactions; (1) enzymatic transformation of IAA by the IAA oxidase system followed by; (2) the binding of a primary oxidation product to RNA, (Galston, et al 1964). In 1967, Meudt and Gaines proposed that the binding involved an indolenine derivative conjectured to be an early oxidation product of IAA (Ray and Thimann, 1955 and Hinman and Lang, 1965). The IAA oxidase system thus assumes a new significance. The present paper collates data on the isolation, electrophoretic mobility, and biological activity of 3 oxidation products of IAA.