Objective  To seek means for improvement on crossbreeding the appealing, long flowering, widely adaptable bell clematis by overcoming the long dormancy and high embryo abortion in seed germination.

  Method  Seeds of Dream King clematis (Clematis texensis) collected 45 d after pollination were cultured in vitro on various media to optimize the conditions for embryo rescue and dormancy breaking. An orthogonal experiment of 12 treatments consisting of additions of 6-BA and/or NAA in various concentrations as well as exposures to temperatures and daylight was conducted to observe the resulting seed germination and seedling survival.

  Result  The addition of 0.5 mg·L⁻¹ 6-BA and 0.05 mg·L⁻¹ NAA to the MS basic medium improved the seed germination rate to 54%, with 47% of the seedlings reached maturation. When 10% of coconut milk was added to the medium, both seed germination and seedling survival rate were significantly raised to reach 62%. Exposure of the seeds to low temperature and day 25℃/night 15℃ promoted the germination. And, the presence of either 50 mg·L⁻¹ ​​​​​​GA or 30 mg·L⁻¹ 6-BA in the medium facilitated breaking the seed dormancy.

  Conclusion  Embryos of clematis could be rescued in vitro to mitigate premature abortion caused by high temperature. The growth hormone addition could significantly shorten dormancy and promote germination of the bell clematis seeds.