Tryptophan-dependent indoleacetic-acid biosynthesis from indole, demonstrated by double-labelling experiments.
(3)H-serine+(14)C-indole were administered to tips of sterily-grown pea seedlings and of non-sterile oat coleoptiles. The Try and IAA produced were extracted and purified by paper chromatography, and their (3)H/(14)C ratios were determined. The (3)H/(14)C ratio of IAA was lower than the (3)H/(14)C ratio of Try. However, the same decrease of the IAA (3)H/(14)C ratio was found when (3)H, (14)C-Try was supplied instead of (3)H-serine+(14)C-indole. This result supports the view that Try is the native IAA precursor and that no significant bypass from indole to IAA exists in the plant material used.
Sektion Biologie, Universität Rostock, Rostock, Germany.
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Erdmann
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Schiewer