[Occurrence and metabolism of auxin in multicellular algae of the Baltic sea].

1. Unsterile and sterile green algae (2 species tested) and red algae (3 species) were able to hydrolize indole-3-acetonitrile (IAN) to indole-3-acetic acid (IES). Indole-3-acetamide (IAAm), detected together with IES, seemed to be an intermediate. Brown algae (3 species) incubated with IAN could produce neither IES nor IAAm. All algae oxidized IAN to indole-3-carboxaldehyde (IA) and indole-3-carboxylic acid (ICS). 2. IES destruction by living algae was mainly due to the activity of marine microorganisms. Sterile algae showed low activity; but sea-water previously incubated with unsterile algae, was active. IA and ICS, together with unidentified substances, were products of the IES-destruction. 3. All but one tested species of algae showed peroxidase activity in vivo. Enzyme preparations made of red and brown algae possessed neither peroxidase nor IES-oxidase activity, but preparations of 5 species of green algae (with one exception: Cladophora rupestris) showed peroxidase and IES-oxidase activity. IES-oxidase of these algae was active only in the presence of the cofactors Mn(++) and 2.4-dichlorophenol. Natural inhibitors of IES-oxidase were present in the enzyme preparations made of several (but not all) red and brown algae; they were absent in all green algae preparations.