Continuous somatic embryogenesis in Japanese maple (Acer palmatum Thunb.)

Somatic embryogenesis was induced in immature zygotic embryos of Japanese maple (Acer palmatum Thunb.) cultured on modified Murashige and Skoog medium supplemented with different combinations of 2,4-D and BAP. The most effective combinations were 10.0 mu mol/L BAP and 0.1 mu mol/L 2,4-D and/or 5.0 mu mol/L BAP without 2,4-D. The presence of BAP proved essential for somatic embryogenesis. Somatic embryos were formed directly on zygotic embryos or on developed calluses. Continuous somatic embryogenesis was achieved after transfer of cultured tissues on MS medium with 0.05 mu mol/L BAP and 0.5 mu mol/L NAA. New somatic embryos developed directly on somatic embryos (secondary somatic embryogenesis), from a microcallus formed on the root tip of a somatic embryo or from an embryogenic callus. Somatic embryos with normal and also aberrant: morphology developed, matured and converted into plantlets on the same medium. The conversion continued after transfer onto half strength MS medium without growth regulators. The rooted plants were grown in a greenhouse. The selected cultures of Japanese maple were able to produce somatic embryos continuously and this ability has not been declining for more than 2 years.