Occurrence and Metabolism of Indoleacetaldehyde in Certain Higher Plant Tissues Under Aseptic Conditions

Qualitative and quantitative evidence based on thin-layer chromatography and the Avena curvature test respectively, are presented for the normal and natural occurrence of indoleacetic acid (IAA), indoleacetaldehyde (IAAld) and tryptophol in the etiolated shoots of Pisum sativum, grown, harvested and extracted under aseptic conditions. Non-aseptic pea shoots contain much more IAA and IAAld than aseptic ones. Extraneous contribution to the indole pool of pea plants grown under non-sterile atmosphere, other than by the inherent agency of the plant itself, is therefore not excluded. Indoleacetaldehyde metabolizing activity of the tissues and cell-free preparations of etiolated Avena seedlings, leading to the production of IAA and tryplophol, is unaffected by the antibiotics actinomycin and streptomycin over a wide range of concentrations. Formation of IAA from IAAld is suppressed by a small degree (10 to 15 %) by chloramphenicol. But this antibiotic does not influence the concurrent production of tryptophol. It is deduced that epiphytic bacteria play little role in the transformation of IAAld to IAA and tryptophol by Avena tissues.