Factors affecting the dormancy and germination of bleeding heart [Lamprocapnos spectabilis (L.) Fukuhara] seeds.

Information on the optimal conditions to promote the germination of Lamprocapnos spectabilis (L.) Fukuhara seeds is limited; consequently, this study was conducted to establish the requirements to break their dormancy and promote germination. The selected seeds were morphophysiologically dormant and had not begun embryo development. To study the dormancy breaking and embryo development processes, seeds were subjected to constant or changing temperature treatments during moist stratification. High temperature and humidity conditions resulted in vigorous embryo growth, with the longest embryos occurring after a month of incubation at 20 ℃. At 4 ℃, the seeds required incubation period of at least three months to germinate. Embryo growth and germination were greater with changing high and low temperatures than under a constant temperature, and changing temperatures also considerably changed the endogenous hormone levels, embryo development, and germination. Bioactive gibberellin (GA) content was higher in the seeds incubated at 20 ℃ for one month, then at 4 ℃ for two months. The content of endogenous abscisic acid in the seeds subjected to the same treatment decreased by 97.6 %, compared with that of the untreated seeds. Embryo growth and seed germination require changing high and low temperatures; however, exogenous GA₃ could substitute for high temperatures, as it also causes accelerated germination. In this study, the seeds of L. spectabilis were identified as an intermediate simple type, a sub-level of morphophysiologically dormant seeds.