A Plant Growth Inhibitor and Plant Growth Inhibition

Abstract

There is an ether extractable substance in the cotyledons and leaves of several plants, particularly radish, that is capable of causing plant growth inhibition and positive Avena coleoptile curvatures. It is possible to analyse for this substance quantitatively by means of a bio-assay. With growth of radish leaves it was found that their inhibitor content decreased and was finally replaced by auxin. The inhibiting substance was found to be readily hydrolyzable into a growth promoting substance. Inhibitor has no polarity of movement in the radish or Avena plant in contrast to auxin. Auxin contaminating the crude extract may be removed by use of an inverse transport purification method. Inhibitor may be hydrolyzed at cut plant surfaces to form auxin. The inhibitor was found to be transported through the Avena coleoptile at approximately 11 mm. per hour, or at the same rate as auxin. Molecular weight determinations by the diffusion technique indicate that the auxin diffusing from radish cotyledons is possibly indoleacetic acid.