Studies Upon the Isolation and Identification of Auxins in Plant Materials

1. A survey was made of plant materials in search of a suitable new source material for auxin isolation. 2. The existing methods of isolation were considered as to their usefulness and point of application in the procedure. An alkali acetone purification and an exhaustive ligroin extraction were introduced. 3. It was found that indole-3-acetic acid rendered uncertain the interpretations of separations made in the final isolation steps. Heretofore, it has been considered that all of the indole-3-acetic acid is completely destroyed by the esterification procedure preliminary to high-vacuum distillation. This has been shown not to be the case. 4. The phenomenon of the increased yield of auxin from wheat and corn by alkali treatment was investigated by isolation. Both pseudo-auxin-a and indole-3-acetic acid were isolated and identified, which marks the first time that this last substance has been found in a higher plant material. The evidence obtained indicates that about 90% of the increased amount of auxin obtained by the alkali hydrolysis is due to indole-3-acetic acid. 5. A substance giving a positive curvature in the Avena test was discovered. This substance is a growth inhibitor.