Factors influencing the induction and viability of somatic embryos of Quercus robur L.

To induce somatic embryogenesis in Quercus robur L. immature zygotic embryo s at different developmental stages were collected in weekly intervals from June until September in three consecutive years from four open pollinated trees at two Vienna sites. Acorns were surface sterilised and cultured firs tly on P24 medium with 5 mu M 2.4-dichlorophenoxyacetic acid (2,4-D) and 0. 5 mu M 6-benzylaminopurine (BAP) or on hormone-free P24 medium and secondly on P24 medium with 0.9 mu M BAP. The formation of white-yellow globular st ructures of somatic embryos started during the fourth week after the induct ion treatment. High induction frequencies of 30 - 80 % were achieved on 2,4 -D/BAP medium, whereas rates on hormone-free medium were below 20 %. The in itiation of somatic embryogenesis was favoured in the heartshaped and early cotyledonary stage of the zygotic embryo in all three years and lasted unt il the acorns reached maximum size in August.