The term auxin is applied to the indole-3-acetic acid (IAA) and to other natural and synthetic compounds having certain growth regulating properties.
NAA (Naphthalene Acetic Acid) and 2,4-D (2,4- dichlorophenoxy acetic acid) are synthetic auxins.
IAA and IBA (Indole Butyric Acid) have been isolated from plants. All these auxins have been used extensively in agricultural and horticultural practices.