THE NATURE OF THE AUXIN IN TOMATO STEM TIPS

It is of considerable importance to know the chemical identity of the naturally occurring growth hormone or auxin. However, the natural auxin occurs in such small amounts in the plant that chemical isolation is difficult if not impossible. To overcome the difficulty of the low concentration plant materials have been sought which contained an exceptionally high auxin concentration. As such, corn oil and malt (K?gl, Erxleben and Haagen-Smit, ? and 7 ; Haagen-Smit et al., 4) or immature corn kernels (Avery, Berger and Shalucha, 2, 3) have been chosen as materials for isolation. From the work of van Overbeek (15) it must be concluded, however, that the auxin in the kernels is not involved in growth of the mesocotyl and coleoptile. Whenever auxin has been extracted from growing organs the concentration was found to be very low (well below 0.1 mg./kg.). With such small concentrations and with limited amounts of tissue only indirect methods of identification of the auxin are possible. These indirect methods include : 1. Determination of the diffusion coefficient