The Nature of Root‐Promoting Substances in Lycopersicon esculentum Seedlings

Determination of the organ sites and chemical nature of root‐promoting substances in Lycopersicon esculentum seedlings was made. Results of organ excision indicated that the young cotyledons were the primary site of root‐promoting substances. As the cotyledon matured, its root‐promoting activity decreased while that of the developing plumular leaves increased. Application of 2,3,5‐triiodobenzoic acid (TIBA) at 10−3 M in lanolin to the hypocotyl below the cotyledonary node significantly prevented root formation. Bioassay, using a new tomato rooting test, of the basic, acidic and bound fractions of the cotyledon extracts after paper chromatography showed biological activities in all three fractions. Gas‐liquid chromatography of selected active regions of the paper chromatogram resulted in a partial tentative identification of indolepropionic acid, 5‐methylindole, 5‐hydroxy‐indole and 3‐indoleacetonitrile. The combined evidence indicated that the root‐promoting substances in tomato seedlings resemble auxin compounds.