Abstract: [Objective] In this article, we aimed to establish large scale propagation methodologies for Liriodendron sino-americanum (hybrid Liriodendron) and to this end we investigated how various combined treatments with the plant hormones abscisic acid(ABA)and zeatin(ZT)affect its somatic embryogenesis and development.[Method] We successfully induced somatic embryos using the embryogenic callus of L. sino-americanum genotype 15-5202. We tested how adding either ABA alone or ABA and ZT together to the differentiation medium affected somatic embryogenesis. Our differentiation medium induced somatic embryos with a high frequency and was screened by counting the number of somatic embryos and observing their growth and development.[Result] 1) The addition of ABA to the medium showed positive effect on the induction and maturation of somatic embryos. 0.5-1.5 mg·L^-1 ABA in the medium accelerated the development of somatic embryos with largely normal morphology. When adding 2.0-2.5 mg·L^-1 ABA, the differentiation rate of somatic embryos increased significantly, but the proportion of abnormal embryos increased. After 30 days of treatment with low-concentration ABA, somatic embryos matured with an additional 2 weeks of culture in light. By contrast, on medium without ABA, somatic embryos were white and not fully matured with pale yellow cotyledon. 2) Adding ABA together with ZT to the medium significantly increased the differentiation rate and development of somatic embryos. Treatment with 2.0 mg·L^-1 ABA combined with 0.2-0.4 mg·L^-1 ZT induced somatic embryos with normal morphology, clearly showing green cotyledons and a radicle after 2 weeks light culture, while the growth and development of somatic embryos was noticeably slower without ZT treatment. Adding ZT concentration of higher than 0.6 mg·L^-1 inhibited growth and development of somatic embryos and was unfavorable to their induction and maturation.[Conclusion] A differentiation medium containing 2.0 mg·L^-1 ABA and 0.2-0.4 mg·L^-1 ZT, significantly increases the efficiency of L. sino-americanum somatic embryogenesis and promotes normal development of somatic embryos.

Key words: Liriodendron sino-americanum, somatic embryogenesis, ABA, ZT