Regulation of Auxin Levels in Coleus blumei by Ethylene.

An investigation of the effects of ethylene pretreatment on several facets of auxin metabolism in Coleus blumei Benth "Scarlet Rainbow" revealed a number of changes presumably induced by the gas. Transport of indoleacetic acid-1-(14)C in excised segments of the uppermost internode was inhibited by about 50%. Decarboxylation of indoleacetic acid-1-(14)C by enzyme breis was not affected by the pretreatment. Levels of extractable native auxin in upper leaf and apical bud tissue of the pretreated plants were approximately one-half of those present in untreated plants. The rate of formation of auxin from tryptophan by enzyme breis from pretreated plants was approximately one-half that occurring in incubation mixtures containing the enzyme system from untreated plants. The conjugation of indoleacetic acid-1-(14)C in a form characterized chromatographically as indoleacetylaspartic acid was increased 2-fold in the upper stem region of plants pretreated with ethylene.