Indole-3-acetic Acid Catabolism by Soybean Bacteroids

Abstract

SUMMARY: Bacteroid preparations from nodules of soybean were able to destroy aerobically substantial quantities of indole-3-acetic acid (IAA). Kinetic studies indicate the involvement of two processes. The supernatant derived during preparation of bacteroids had an active IAA oxidation during the first 30 min. Successive washings of bacteroids still retained some activity although it was reduced. A high level of IAA destruction was always observed with washed bacteriods and the reaction proceeded linearly for at least 4 h. Glucose gave a slight stimulation but succinate, pyruvate and fumarate at low concentrations (approx. 25 mm) were strong inhibitors. No IAA catabolism occurred with washed bacteroids at a PO2 of 30 mmHg or less, but it increasingly occurred with further increase in oxygen partial pressure up to 150 mmHg. No difference was observed between bacteroids with or without active nitrogenase.