Effects of phenolic substances on metabolism of exogenous indole-3-acetic acid in maize stems [p-Coumaric acid; Ferulic acid; 4-Methylumbelliferone; p-Hydrozybenzoic acid; Caffeic acid; Protocatechuic acid; 2.3-Dihydro-2,2-dimethyl-7-benzofuranol; IAA]
1980
Lee, T.T. (Agriculture Canada Univ. Sub P.O., London, Ontario. Research Inst.)
Four-day-old stem segments of Zea mays L. cv. Seneca 60 were treated sequentially with phenolic substance and indole-3-acetic [2-('14)C] acid ([2-('14)C]IAA). Formation of bound IAA was rapid, but a pretreatment with p-coumaric acid, ferulic acid or 4-methylumbelliferone decreased the level of bound IAA. The decrease is not likely related to the effect of the phenolics on enzymic oxidation of IAA, since the level of free IAA was not limiting and the activity of ferulic acid in enzymic oxidation of IAA is different from that of p-coumaric acid and 4-methylumbelliferone. Apparently these compounds inhibited the formation of bound IAA and consequently caused an accumulation of free IAA. In contrast, caffeic acid, protocatechuic acid and 2,3-dihydro-2,2-dimethyl-7-benzofuranol had little effect. After the uptake of IAA there was slow but steady incorporation of the radioactivity into the 80% ethanol-insoluble, 1 M NaOH-soluble fraction. Phenolic substances also affected this process. The compounds which are cofactors of IAA-oxidase increased the incorporation while those which are inhibitors of IAA-oxidase decreased the incorporation. Results suggest that the phenolics also affected the enzyme oxidation of IAA in vivo in the same way as in vitro
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