Any of a group of organic compounds which, when applied in low concentration, are able to promote elongation growth of plant shoots excised from a growing region of a young seedling. These substances were the first plant hormones to be studied, and were given the generic name auxins, indicating an increase, by F. Kögl and A. J. Haagen-Smit in 1931. The ability to increase the rate of shoot elongation is a key to the designation of a synthetic or naturally occurring compound as an auxin. However, auxins, and the other plant hormones, influence a variety of plant processes during various stages of plant development.