Somatic Embryogenesis and Plantlet Formation from a Rare and Endangered Tree Species, Oplopanax elatus

We tested the possibility of plantlet formation via somatic embryogenesis with leaf segments and mature zygotic embryos from a rare and endangered tree species, Oplopanax elatus. To induce calli, explants were cultured under darkness in a solid MS medium containing 3% sucrose, $1g\;L^{-1}$ glutamine, and 0.3% gel rite. Treatment supplements included 2,4-D alone or in combination with thidiazuron. Generally, callus induction and growth were good from leaf explants, whereas embryogenic calli could be induced only from zygotic embryos. These embryogenic calli were white or pale yellow and very friable. ABA and activated charcoal appeared to be important factors when inducing somatic embryos, with optimum levels being $0.1mg\;L^{-1}$ and 0.02%, respectively. Many somatic embryos showed abnormalities during their development on the germination medium, but 35% could be converted if placed on a medium containing gibberellic acid $(GA_3)$. The germinating embryos sometimes formed secondary embryos at the lower portion of the hypocotyls. Normal or converted plantlets were acclimatized in an artificial soil mixture; their survival was about 60% after two months. This culturing system provides a feasible approach for regenerating plants, via somatic embryogenesis, from mature zygotic embryos.