Phytohormones, Rhizobium mutants, and nodulation in legumes. IV. Auxin metabolites in pea root nodules

High specific activity [³H]indole-3-acetic acid (IAA) was applied directly to root nodules of intact pea plants. After 24 h, radioactivity was detected in all plant tissues. In nodule and root tissue, only 2-3% of³H remained as IAA, and analysis by thin layer chromatography suggested that indole-3-acetyl-L-aspartic acid (IAAsp) was a major metabolite. The occurrence of IAAsp in pea root and nodule tissue was confirmed unequivocally by gas chromatography-mass spectrometry (GC-MS). The following endogenous indole compounds were also unequivocally identified in pea root nodules by GC-MS: IAA, indole-3-pyruvic acid, indole-3-lactic acid, indole-3-propionic acid, indole-3-butyric acid, and indole-3-carboxylic acid. Evidence of the occurrence of indole-3-methanol was also obtained. With the exception of IAA and indole-3-propionic acid, these compounds have not previously been unequivocally identified in a higher plant tissue.