THE BIOSYNTHESIS OF INDOLEACETIC ACID IN MELAMPSORA LINI (PERS.) LEV.

Abstract

Mycelium of Melampsora was grown on flax cotyledons in tissue cultures. Mycelium and uredospores were incubated with DL-tryptophane-2-C¹⁴ and uredospores were incubated with L-tryptophane. Acid and neutral ether-soluble and aqueous fractions of the plant material and incubation medium were chromatographed and sprayed with chromogenic agents or radioautographed. Radioactive indoleacetic acid was produced in small amounts by both mycelium and spores (yield = 0.016% in 8 hours). The auxin was identified on the basis of its R_f values in two solvent systems, its reactions with Ehrlich and Salkowski reagents, and its ability to promote extension growth of Avena coleoptiles. Evidence for the formation of indoleacetaldehyde was also obtained. Several other radioactive and Ehrlich-positive products of tryptophane metabolism were detected but not identified. One of these could have been indolepyruvic acid. Tryptamine and indoleacetonitrile were not found. The results suggest that, in Melampsora, the synthesis of indoleacetic acid from tryptophane proceeds through indolepyruvic acid and indoleacetaldehyde.