Metabolism of [(14)C]indole-3-acetic acid by the cortical and stelar tissues of Zea mays L. roots.

Reverse-phase high-performance liquid chromatography was used to analyse (14)C-labelled metabolites of indole-3-acetic acid (IAA) formed in the cortical and stelar tissues of Zea mays roots. After a 2-h incubation in [(14)C]IAA, stelar segments had metabolised between 1-6% of the methanol-extractable radioactivity compared with 91-92% by the cortical segments. The pattern of metabolites produced by cortical segments was similar to that produced by intact segments bathed in aqueous solutions of [(14)C]IAA. In contrast, when IAA was supplied in agar blocks to stelar tissue protruding from the basal ends of segments, negligible metabolism was evident. On the basis of its retention characteristics both before and after methylation, the major metabolite of [(14)C]IAA in Zea mays root segments was tentatively identified by high-performance liquid chromatography as oxindole-3-acetic acid.