PRODUCTION OF INDOLE ACETIC-ACID IN ROOT-NODULES AND CULTURE BY A RHIZOBIUM SPECIES FROM ROOT-NODULES OF THE FODDER LEGUME MELILOTUS-ALBA DESR

The root nodules of Melilotus alba DESR., a fodder legume, contained h igh amounts of IAA. A tryptophan pool present in the nodule might serv e as a source of IAA production. Presence of IAA oxidase and peroxidas e in the nodules indicated the metabolism of IAA, at least in part, in the nodules. The Rhizobium species isolated from the root nodules pro duced a high amount of IAA (190 mu g/ml) from L-tryptophan supplemente d basal medium. IAA production and microbial growth were coincident. T he production of IAA by the Rhizobium sp. was increased by 315% when t he medium was supplemented with lactose (1%), NiCl2 (10 mu g/ml), cety l pyridinium chloride (0.5 mu g/ml) and glutamic acid (0.4%), in addit ion to L-tryptophan (3 mg/ml). The possible role of the rhizobial prod uction of IAA on the rhizobia-legume symbiosis is discussed.