Abstract: Immature embryos of 10 weeks after pollination of Carya cathayensis were selected as explants. The factors which affect embryogenic calli formation and somatic embryogenesis including basal medium，plant growth regulators（PGRs）and desiccation length of somatic embryos were tested. Cytohistological observations of anatomical structure change during embryogenic callus formation and somatic embryos production were also made. Embryogenic callus percentage was significantly higher on the medium 1/2 MS than other treatments，reached 45.3%. Somatic embryogenesis percentage was significantly higher on DW medium than other media，reached 16.7%. Global embryo，heart-shaped embryo，embryos and cotyledonary embryos were easily observed under microscope. The highest embryogenic callus percentage was obtained on the medium with 1.0 mg · L-1 6-BA and 0.01 mg · L-1 picloram reached 48.6%. The highest somatic embryogenesis percentage was obtained on the medium with 1.0 mg · L-1 6-BA and 0.001 mg · L-1 picloram，reached 23.6%. The formation and development of somatic embryogenesis is indirect somatic embryogenesis which goes through callus phase. Subsequent desiccation for 3 d with saturated Ca(NO3)2 · 4H2O resulted in 39.03% germination. Non-desiccated somatic embryos failed to germinate. Germinated somatic embryos developed into plantlets with 3 to 4 leaves 10 weeks after they were transferred to WPM basal medium under light condition. 　

Key words: Carya cathayensis, somatic embryo, indirect somatic embryogenesis, plant regeneration, cytohistological observation