Propagation physiology of Juniperus phoenicea L. from Jordan using seeds and in vitro culture techniques: Baseline information for a conservation perspective
Seeds of Juniperus phoenicea L. collected from Shouback city, south of Jordan, were cold-moist stratified at 5°C for 1 and 3 months. Non-stratified seeds were used as the control. The recalcitrant nature of J. phoenicea was clear as shown by low germinability of seeds. The highest germination percentage was recorded for seeds stratified for three months. Germination bioassay of wheat grains indicated that stratification is a prerequisite for the germination of J. phoenicea seeds and that reduction in inhibitors found in mature seeds occurred with longer stratification periods. In a separate set of experiments, in vitro culture of J. phoenicea, using shoot tips with axillary buds from young seedlings and mature seeds from adult trees as explants was attempted. Explants were established on Murashige and Skoog (MS), and Rugni Olive (OM) media. The effects of kinetin (kin), 6-benzyl amino purine (BAP) and thidiazuron (TDZ) on the differentiation of axillary buds were tested at 0.5 mg/L and compared with that using plane media without hormones. Mature seeds were completely contaminated one month after culture establishment. The grooves along the surface of the seeds may have increased the chance for latent microbes to grow with prolonged culture time. In contrast, shoot tips with axillary buds responded better than seeds in vitro.
Keywords: Germination, in vitro culture, recalcitrance, seed morphology, thidiazuron (TDZ)