2017 ASHS Annual Conference

Ranunculus crucilobus H. Lev. is a perennial plant within the Ranunculaceae and is an endemic species on the Korean Peninsula. There are few reports on embryo development and seed germination of Ranunculus (Ranunculaceae) species. This study was conducted to determine the requirements for dormancy-break and germination, and to characterize the type of seed dormancy of R. crucilobus seeds. Ripe seeds (achenes) were collected between late May and early June. The seeds were sown in field soil in an experimental garden. Every 2 weeks, seeds were exhumed, and phenology of embryo growth, germination, and seedling emergence was observed. Temperature requirements for embryo growth and germination were also determined by incubating seeds under controlled laboratory conditions. Additionally, the effect of GA₃ on dormancy breaking was tested to characterize the type of seed dormancy. Seeds had underdeveloped embryos, which was about 16% of those of fully matured seed. When tested at the time of dispersal, seeds did not germinate during 8 weeks of incubation at 25/15^oC. Therefore, the seed dormancy type for R. crucilobus was morphophysiological. In natural conditions, embryos grew consistently at cold temperature during winter, and the embryos had reached the critical E:S ratio (0.83 ± 0.04) required for germination between 3 and 10 March 2013. On 31 March 2013, 90.9% of seed germination was observed. 91.7% of the seeds produced seedlings between 31 March and 14 April 2013. In the controlled laboratory experiment, the embryos grew to the critical length for germination at 5 ^oC. Thus, the seeds have complex type MPD. Cold stratification pretreatment was required for germination. After cold stratification at 5 ^oC for 0, 4, 8, or 12 weeks, the seeds germinated to 0%, 41.7%, 61.9%, or 83.8%, respectively, after 12 weeks of incubation at 25/15 ^oC. GA₃ treatment did not completely overcome the dormancy although the percentage germination increased with increasing the concentration of GA₃. The final germination proportions recorded at 0, 10, 100, and 1000 mg·L^-1 GA₃ were 1.7%, 4.2%, 3.3%, and 25.1%, respectively. Therefore, the seeds expressed deep complex morphophysiological dormancy (MPD).

(The results of this research were introduced at KSHS 2015 Annual Spring Conference through poster presentation.)