13. Chemical and physiological studies on indoleacetic acid.


Previous work demonstrated the close interrelation of tryptophane and indoleacetic acid (IAA) in the developing corn kernel. Associated with these materials is a substance, now called auxin complex (AC), found to be present in large quantities in the kernel, and apparently capable af completely inactivating IAA for its usual role in the growth of the plant. In consideration of its probable importance in the growth and metabolism of the plant, work was begun on its isolation. Extensive solvent and chromotographic techniques were utilized to increase the AC concentration from 0.04 to 10%  on the basis of total IAA content.


Paper chromotography resolved the AC into two substances, both of which gave a color reaction for IAA and grovth activity after hydrolysis. Apparently, therefore, the AC is a mixture of two compounds both of which contain IAA ‑ possibly several isomers of the same substance exist.


Recent alkaline hydrolysis procedures on the AC concentrate indicate the release of at least three substances ‑ methyl anthranilate, IAA and a sugar. The interrelation of these substances, if any, remains to be established.


Mutants having a colored aleurone layer were utilized to help in establishing the site in the kernel for the production of the AC. Preliminary work that the gradient of AC concentration decreases from the aleurone layer inward into the endosperm as well as from the base to the top of the endosperm.


Extensive investigation to establish the presence of an enzyme system capable of transforming tryptophane to IAA was done using a dialysis technique to reduce the IAA and AC background. Results indicate that such a system does exist in the kernel, but is of very low activity.


Melvin Stehsel