Polyethylene Glycols as Carriers for Growth-Regulating Substances

1. Addition of Carbowax compounds to aqueous solutions of 2,4-dichlorophenoxyacetic acid increased the effectiveness of the acid in bringing about growth responses and form changes in kidney bean plants as measured on a quantitative basis. 2. Marked form changes occurred in roots, hypocotyl, first internode, and terminal and lateral buds as the result of application of 4 γ of the acid to one primary leaf of seedling bean plants. Application of 1 γ of the acid in a like manner resulted in greatly inhibited bud growth. 3. A 0.5% solution of Carbowax 1500 was found to be nontoxic to several kinds of crop plants. 4. Application of relatively high concentrations of 2,4-dichlorophenoxyacetic acid in solution with Carbowax killed the bean plants when applied either to the soil or above-ground portions. The possibility of using this compound, and various others together with Carbowax, as selective herbicides is suggested. 5. A relatively simple quantitative method of measuring the effectiveness of growth-regulating compounds in bringing about growth responses is described. It is based on the application of exact amounts of the substance to a bean leaf and the subsequent measurement of the growth changes in the stem and buds.