Somatic Embryogenesis From Mature and Immature Sweetgum Tree Tissues, 1997 Biological Sciences Symposium Proceedings

Most forest tree embryogenic culture systems described to date rely on cloning zygotic embryos via direct embryogenesis. The full power of somatic embryogenesis for clonal propagation of forest trees could be realized if tissues from mature trees could be used as explants to initiate high-frequency embryogenic cultures. Certain tissues from mature trees may provide a source of cells with the flexibility to undergo indirect embryogenesis. We initiated cultures from staminate inflorescence and floral tissues of sweetgum as well as from seeds from the same trees. Inflorescences were collected at various stages of elongation, and seeds were collected at different stages of maturity. Somatic embryos were produced from both anthers and axes of staminate inflorescences that had just begun to elongate within the bud following dormancy. Continuous culture on medium containing thidiazuron gave the highest frequency of embryogenic response. Some of these cultures became repetitively embryogenic, in some cases producing proembryogenic masses (PEMs). Immature seeds given a 2- week pulse or cultured continuously on medium with 2,4-D also produced repetitively embryogenic cultures, some of which proliferated as PEMs. PEMs of both inflorescence and seed origin produced somatic embryos following transfer to basal medium and embryos from both sources germinated to produce plantlets.