Indole acetic acid and its metabolism in the stem nodules of a leguminous emergent hydrophyte, Aeschynomene aspera

Mature stem nodules of Aeschynomene aspera Linn., an economic leguminous em ergent hydrophyte, contain high amount (2.54 mu g/g fresh weight) of indole acetic acid (IAA). A big tryptophan pool (2890.5 mu g/g fresh weight) pres ent in the stem nodules might serve as a source of IAA production. Metaboli sm of IAA in the stem nodules was evidenced by the presence of IAA metaboli zing enzymes, IAA oxidase and peroxidase. The symbiont, Azorhizobium caulin odans produced high amount of IAA in L-tryptophan supplemented medium. The possible role of the nodular IAA in the legume - Azorhizobium symbiosis of stem nodules is discussed.