Stimulation of Germination and Seedling Vigor in Dormant Seeds of African Juniper

Breaking of dormancy in african juniper (Juniperus procera) seeds is a challenge faced by nurseries attempting to grow large numbers of this plant for restoration projects. The purpose of this study was to develop a protocol for breaking dormancy and stimulating germination in african juniper. Seeds were presoaked in different concentrations (0, 1, 10, or 20 mg.L-1) of gibberellic acid (GA(3)), indole-3-butyric acid (IBA), and naphthalene acetic acid (NAA), and incubated under different air temperatures (10, 15, and 20 degrees C). The petri dishes were monitored daily for 84 days, to record germination percentage, rate, and uniformity, and the growth of shoots and roots, and biomass production. The highest germination percentages were obtained under 20 degrees C with a high concentration of NAA (20 mg.L-1). The greatest seedling growth was under 20 degrees C with IBA. The greatest seedling length was under 20 degrees C with a low concentration of IBA (1 mg.L-1). The greatest shoot fresh weight was under 20 degrees C with medium GA(3) concentration (1 mg.L-1). Compared with the control, almost all growth regulator treatments stimulated higher germination percentages and vigor indices with increased temperatures.