Induction of somatic embryogenesis in different explants from Ormosia henryi Prain

Abstract

An efficient in vitro plant regeneration method via somatic embryogenesis has been established in Ormosia henryi Prain, which is an important precious tree in the timber industry. Five types of explants, six types of basic media and different plant growth regulators (PGRs) were used for embryogenic callus (EC) initiation, EC proliferation, somatic embryo (SE) induction and SE germination. The EC and SE induction rates from mature zygotic embryos (MZE) were higher than those from stem segments, cotyledons, leaves and hypocotyls. MZE were used as explants, and the EC induction rate was greater than 30% on B5 medium supplemented with 1.0 mg/l 6-benzylaminopurine (BA) and 0.5 mg/l naphthaleneacetic acid (NAA) or 0.2 mg/l BA and 2.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D). The highest induction rate (22.83%) for SE was obtained with B5 medium supplemented with 0.5 mg/l kinetin (KT) and 1.0 mg/l 2,4-D. The EC proliferation rate and SE number in the suspension culture were increased compared to those in the solid culture. Fifty-four percent of SE developed to the cotyledonary stage on B5 medium supplemented with 0.5 mg/l BA and 0.2 mg/l NAA. The number of cotyledon embryos was the highest on medium supplemented with 0.5 mg/l thidiazuron (TDZ) and 0.2 mg/l NAA. Histological analysis confirmed the bipolar organization of the somatic embryos, which were comprised of shoot and root meristems, and showed that SE was characterized by globular, heart-shaped, torpedo-shaped and cotyledon stages in O. henryi, the developmental process of which was similar to that of zygotic embryos. An efficient in vitro plant regeneration method via somatic embryogenesis has been established in Ormosia henryi Prain using mature zygotic embryos as explant.