Abstract:

Somatic embryos (SE) were induced from young zygotic embryos (ZE) of Sorbus pohuashanensis obtained after artificial pollination. The developmental process of ZE and SE was observed with paraffin section, scanning electron microscopy and transmission electron microscopy. The results showed that: 1) Somatic and zygotic embryogenesis underwent a similar course, by passing through globular, heart-shaped, torpedo-shaped stages and then reached mature stage; 2) SE derived from ZE cotyledons originated directly from single epidermis cell or indirectly occurred from single surface cell or inner cell of the embryogenic callus, but some of the indirectly occurred SE was possibly developed from multi-cell aggregates inside the embryogenic callus; 3) SE regenerated from single cells of ZE cotyledon epidermal and embryogenic callus surface had obvious suspensors during the early developmental stage, but they disappeared during torpedo-shaped stage; 4) There were no suspensors observed in SE regenerated inside embryogenic callus. 5) The first division of SE embryogenic cells was equally split, which was different from that of ZE; 6) Degradative cells around multicellular somatic preembryos displayed similar morphological patterns of programmed cell death.

Key words: Sorbus pohuashanensis, somatic embryogenesis, zygotic embryogenesis, embryo development