Auxin

Article By:

Cohen, Jerry D. Department of Horticultural Science, University of Minnesota, Saint Paul, Minnesota.

Baldi, Bruce G. Plant Hormone Laboratory, U.S. Department of Agriculture, Beltsville, Maryland.

Armitage, Lynne Department of Biology, University of York, York, United Kingdom.

Leyser, Ottoline Department of Biology, University of York, York, United Kingdom.

Last reviewed:March 2021

DOI:https://doi.org/10.1036/1097-8542.065500

Any of a class of plant growth substances (phytohormones or plant hormones) that have an essential role in coordination of many growth and developmental processes during the life cycle of plants, especially the ability to increase the rate of shoot elongation. Auxins are important phytohormones (plant hormones). They have been defined collectively as a group of organic compounds (Fig. 1) that, 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 they were given the generic name auxins in 1931 by Fritz Kögl and Arie Jan Haagen-Smit because they increase growth (Greek auxein, meaning to increase or grow). From the very early research, it was known that the role for this signal in plant development was profound and included regulation and coordination of organ formation, development, directional growth in response to light and gravity, and normal cell elongation and growth. A unique aspect of auxin is its ability to move directionally from the apical meristem, thus establishing a shoot–root polarity that is maintained throughout the life of the plant. Findings have shown that auxin signaling involves a soluble receptor that initiates the degradation of proteins that otherwise inhibit expression of auxin-responsive genes. See also: Apical meristem; Plant development; Plant growth; Plant hormone; Plant hormone receptors; Plant movement; Plant physiology

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