Experiments with Locust and Willow Diffusates on Rooting Cuttings

Abstract

Aqueous diffusates of either Salix erythroflexus (contorted willow) or Robinia pseudoacacia (black locust) were tested as a root-promoting substance on woody plants and Vigna radiata (mung bean). On 8 July 1995 water diffusates were prepared from fresh chopped terminal stems of either willow or locust (680 g) that were steeped in 4 liters of water for 24 hours. Semihardwood cuttings of Chionanthus retusus were double wounded, steeped in either willow, locust, or water for 24 hours followed by a treatment with 3.0% IBA in talc. One additional group of cuttings was treated with 3.0% IBA only. After 75 days, cuttings treated with willow diffusate and IBA produced the greatest number of roots, followed by the locust diffusate and IBA treatments. A similar test using willow diffusate and IBA on softwood cuttings of Chionanthus virginicus resulted in an 80% success rate. A modified mung bean bioassay was used to partially characterize and verify the effects of the diffusates. Diffusates were made from chopped frozen locust or willow terminal stems (10 g/300 ml H2O), stirred for 24 hours. Mung bean cuttings treated with either locust or willow diffusate (5 ml/10 ml H2O) plus 80 ppm IBA produced more roots than IBA or either diffusate alone. A dose response test showed a significant increase in rooting as concentrations increased (H2O,10%, 50%, 75%, and 100%) for both diffusates. Ethyl acetate extractions of each diffusate at pH 3.0 produced more roots than extracts at pH 7.0. A thermal stability test (20 min at 100 °C) on the diffusates showed willow maintained its root-promoting activity, while locust did not.