Measurement of the Rates of Oxindole-3-Acetic Acid Turnover, and Indole-3-Acetic Acid Oxidation inZea maysSeedlings

Abstract

Nonhcbcl, H. M. 1986. Measurement of the rates of oxindole-3-acetic acid turnover and indole-3-acetic acid oxidation in Zea mays seedlings.—J. exp. Bat. 37: 1691–1697. Oxindole-3-acetic acid is the pnncipal catabolite of indole-3-acetic acid in Zea mays seedlings. In this paper measurements of the turnover of oxindole-3-acetic acid are presented and used to calculate the rate of indole-3-acetic acid oxidation. [³H]Oxindolc-3-acetic acid was applied to the endosperm of Zea mays seedlings and allowed to equilibrate for 24 h before the start of the experiment. The subsequent decrease in its specific activity was used to calculate the turnover rate. The average half-life of oxindole-3-acetic acid in the shoots was found to be 30 h while that in the kernels had an average half-life of 35 h. Using previously published values of the pool sizes of oxindole-3-acetic acid in shoots and kernels from seedlings of the same age and variety, and grown under the same conditions, the rate of indole-3-acetic acid oxidation was calculated to be I-I pmol plant⁻¹ h⁻¹ in the shoots and 7·1 pmol plant⁻¹ h⁻¹ in the kernels.