. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). Metabolism and mode of action is generally considered to be a phenol reagent. Thus, we have tentatively concluded that the product may be a phenolic aminoacetophenone. Since neither OFA nor OAA is converted to the product, the hydroxylation step (presumably at the No. 5 or 6 position on the indole ring) must precede the ring cleavage between the No. 2 and 3 carbons {Figure 5). Our understanding of the physiolog
. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). Metabolism and mode of action is generally considered to be a phenol reagent. Thus, we have tentatively concluded that the product may be a phenolic aminoacetophenone. Since neither OFA nor OAA is converted to the product, the hydroxylation step (presumably at the No. 5 or 6 position on the indole ring) must precede the ring cleavage between the No. 2 and 3 carbons {Figure 5). Our understanding of the physiological significance of this conversion is limited to the observation that neither OAA, OFA, nor the authentic oxidation products appear to have any marked effects on growth in the pea epicotyl section test. Thus, lAA oxidase, if it is operative in tissue, results in the diminution of growth by the lowering of the effective auxin level. lAA Hydroxy-IAA <^^ Hydroxy-o-Formamido Benzoylacetic acid 0 II C-CHoâCOOH CH2âCOOH "N' H. â NH2 Hydroxy-OAA ^ ^ Hydroxy-OFA Figure 5. A possible scheme of oxidation oflAA and a possible product satisfying all experimental data. THE NATURE OF INDOLEACETIC ACID OXIDASE AND ITS INDUCTION BY lAA The enzyme complex which we refer to as indoleacetic acid oxidase was discovered by Tang and Bonner (1947) in etiolated peas and has since been shown to exist in other higher plants (Wagenknecht and Burris, 1950; Gortner and Kent, 1953; Jensen, 1955; Pilet and Galston, 1955) and in fungi (Sequeira and Steeves, 1954; Tonhazy and Pelczar, 1954). It appears certain that the enzyme differs from plant to plant and is absent from some tissues (Piatt, 1954); but we have limited ourselves to an attempt to understand its make-vip in one plant, Pisiim sativum, and in some closely related legumes. The essential facts which need to be considered in understanding the nature of the lAA oxidase system in peas, and the principal deductions to be drawn from them are
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