2018 ASHS Annual Conference

An indole-3-butyric acid (IBA) dose response study was conducted on a model cycad species, Zamia furfuracea L.f.. Stem cuttings were subjected to one of five IBA concentrations within the range of 0 to 30,000 ppm in order to determine the IBA dosage that would induce adventitious root formation in the shortest amount of time. Stem cuttings were planted in perlite within clear containers, and the bottom surface of each container was checked daily until the first sign of root contact for each cutting. Less than two months were required to reach 50% rooting success. Cuttings receiving IBA dosages between 3,000 and 16,000 ppm developed roots more quickly than the control cuttings. In contrast, cuttings receiving IBA of 30,000 ppm developed roots more slowly than the control plants. The results suggest that IBA between 16,000 and 30,000 ppm would be optimum for inducing adventitious roots most rapidly for this species. Published IBA dose response studies have been conducted on various angiosperm and a few gymnosperm species. To our knowledge, this is the first IBA dose response study for any cycad species. This information will inform cycad horticultural practices and add to an important conservation agenda, as cycads are the most threatened group of plants worldwide.