The breaking of seed dormancy of guayule (Parthenium argentatum Gray.) by treatment with gibberellic acid and smoke water solution
Guayule seed exhibits poor germination due to natural dormancy that can last from six- to twelve months after seedset. In an attempt to stimulate seed germination, four guayule seed lines (AZ101, AZ-3, N565 and 11591) were treated with smoke water as well as gibberellic acid, both separately and in combination. The split-plot analyses of variance showed no significant interaction between cultivar and treatment factors (P = 0.71), but when the time factor was included interaction was highly significant (P < 0.0001), indicating that some treatments influenced the rate of germination. Seeds of cultivar AZ-3 treated with the smoke water-gibberellic acid mixture required the shortest number of days for maximum germination to occur. However, treatment of seeds with gibberellic acid resulted in the highest germination of seeds of all four cultivars. These results showed that guayule seed can be stimulated to germinate faster and better by treatment with gibberellic acid and/or smoke water solutions.