Developing Biological Characteristics And Somatic Embryogenesis Associated With Immature Embryos Of Torreya Grandi S ’Merrillii’

Embryos of Torreya grandis ‘Merrillii’ were used as explants for the induction of somatic embryos.The effects of different basal medium,organic additives,carbon sources and plant growth regulators（PGRs）for the initiation of primary calli were tested. The optimal PGRs for the induction andproliferation of embryogenic tissue were analyzed. The preliminary study on somatic embryosinduction、germination and development characters of immature embryos was also carried out.。The main results obtained are presented as follows:1.Schenk and Hildebrandt (SH) was selected as the best basal medium and3%sucrose was theoptimal carbon source. The callus initiation frequency was significantly higher（P＜0.05）on the SHmedium that supplied with glutamine than other treatments， reached50.1%.Initiation mediumcontaining low concentration of2,4-dichlorophenoxyacetic acid（2,4-D）or a-naphthaleneacetic acid(NAA) was found to be efficient in improving primary calli induction. The medium supplied with0.1mg/L NAA had a significantly higher（P＜0.05） callus induction frequency than other treatments.Optimal concentration of NAA for the initiation、proliferation of embryogenic tissue was0.05mg/L.Somatic embryos were produced when calli were inoculated onto SH medium supplemented with ABAand PEG6000. Exposure of somatic embryos to1200lx light had a better germination quality than in thedark.2. The embryo development of Torreya grandis ‘Merrillii’ has polyembryonic phenomenon duringearly seed development. Competition intensifies among early embryos until a dominant embryoemerges.Dominant embryo goes through globular, clavate, heart-shaped, torpedo and cotyledonaryphases. The changes of endogenous hormones(ABA,IAA,ZR﹠GA) in the immature embryos wasintricate, while the rate of GA/ABA and ABA/(IAA+ZR+GA) appeared regularly changing. For Torreyagrandis ‘Merrillii’ immature embryos, the dedifferentiation capacity was closely related with the explantage. When the development of embryo age (EA) increased the induction proportion of embryogenictissue (ET) decreased. The ET was easily derived from embryo collected on july8, which had asignificantly higher callus induction frequency, reached70.4%. The way and place of ET formation wasdramatically affected by the explant age. Embryo collected on july2to july15derived ET from thehead of embryo or the whole embryo directly, while the late embryo derived from hypocotyl orsuspensor. The proliferation activity of ET varied with the place of ET formation, that was the wholeembryo＞the head of embryo＞suspensor.