Rooting responses of guayule (Parthenium argentatum Gray) cuttings to hormone solutions
Vegetative propagation of selected guayule (Parthenium argentatum Gray), with elite qualities of vigorous growth and high latex yield, was investigated. Rooting responses of guayule cuttings to treatment solutions of indole butyric acid (IBA), naphthalene acetamide (NA) and naphthalene acetic acid (NAA) were determined. Specific concentrations of hormone solutions were applied to guayule cuttings, cultivar AZ-3, and rooting response was determined in terms of rooting percentage, root length and root dry weight. Naphthalene acetic acid treatment rooted the highest percentage of cuttings (52.38%) at a concentration of 60 mg l-1. Indole butyric acid treatment produced the longest roots (147.83 mm) at a concentration of 120 mg l-1. Naphthalene acetamide contributed the heaviest root dry mass (1.8 g) at a concentration of 120 mg l-1. Results indicated that all three hormones were concentration specific in improving root formation, root length and root weight when compared to the controls.