Promotion of Adventitious Roots in Chrysanthemum Cuttings by Soaking in Ozonated Water

To examine the effect of soaking in ozonated water (OW) on development of adventitious roots, basal ends of chrysanthemum cuttings (Chrysanthemum morifolium Ramat.) were soaked in 1, 3 or 5 mg L-1 OW, in an indol-3-butyric acid (IBA) solution prepared from a commercial root promoting agent or in distilled water (DW). At 20 day after transplanting (DAT), a significant increase in adventitious root number (ARN) was observed in the IBA-treated cuttings but early root elongation was delayed. When soaked in the 5 mg L-1 OW, ARN and total root length (TRL) grown over 40 mm were increased with a decrease in soaking duration (from 50 to 5 min). Lateral root number (LRN) of the cuttings soaked in the 3 mg L-1 OW for 1 h showed four times higher than that of the DW treatment at 19 DAT. Optimal combination of dissolved ozone concentration and soaking duration can promote early root elongation and LRN of chrysanthemum cuttings. From a comprehensive standpoint, a high DOC of OW with a short soaking duration (3 mg L-1 1 h and 5 mg L-1 5 min) worked as well as IBA for adventitious rooting of chrysanthemum cuttings. These findings indicate that ozonated water can be an alternative to root promotion agents for adventitious rooting of chrysanthemum cuttings.