Methods of Auxin Application in Cutting Propagation: A Review of 70 Years of Scientific Discovery and Commercial Practice

Abstract The discovery of auxins as plant growth regulating chemicals in the 1930s and their ability to stimulate adventitious rooting in stem cuttings marked a major milestone in the modern history of plant propagation. Basic and applied research conducted during the past 70 years has provided information regarding absorption and translocation of auxin in cuttings, as well as the effects of timing of auxin application, methods of auxin application, type of auxin, and concentration of auxin on the rooting response of cuttings. The basal quick-dip method, the powder application method, and the dilute soak method have been the most commonly used methods for applying auxin to cuttings in commercial horticulture over the past 7 decades, with the first two methods still in common use today. In addition, a wide variety of other auxin application methods have been reported beginning in the 1930s and continuing to the present. Some of these methods remain primarily of historical interest, several find limited use...