Histological Reactions of Bean Plants to Indoleacetic Acid

Abstract

A mixture of 30 mg. of indoleacetic acid per gm. of pure lanolin was applied as a film to the cut surfaces of young bean stems. Tumors and tissue changes resulting after such application are descr. and figured in detail. The marked similarity of these changes and developments to those resulting from inoculations with Bacterium tumejaciens is pointed out. There is marked increase in meristematic activity of the cells of the endo-dermis, primary and secondary phloem, rays, and pith. Nuclear division frequently proceeds very rapidly, so that many cells are multinucleate for a time. Later wall formation follows. The cells derived from the meristematic activity of the various tissues may later differentiate into vascular strands or scattered elements in the endodermis, phloem, and pith, or erupt at the surface as small tumors variously distributed. The elements derived from the pith may continue development for many months and thus produce large complex tumors. Near the surface of application of the lanolin mixture adventitious roots are developed from the rays and flanking phloem tissue. Later roots may also differentiate from some of the proliferated endodermal and phloem cells at distances more than 5 cm. from the surface of application.