Dormancy-release and germination improvement of Korean bellflower (Campanula takesimana Nakai), a rare and endemic plant native to the Korean peninsula

Korean bellflower (Campanula takesimana Nakai) is a rare and perennial herb with medicinal and ornamental values, is endemic to the Ulleung Island of Korea. In this study, we investigated the dormancy-release and germination characteristics of C. takesimana (Campanulaceae) seeds by subjecting them to varying temperatures (5, 10, 15, 20, and 25 degrees C and diurnal/nocturnal temperatures of 15/6, 20/10, and 25/15 degrees C), cold stratification periods (0, 4, 8, or 12 weeks at 5 degrees C), and gibberellic acid (GA(3)) concentrations (0, 10, 100, or 1,000 mgL-1 at 15/6 degrees C and 25/15 degrees C) to identify the ideal seed propagation conditions. The seeds were stimulated to germinate (at 25 degrees C, 12-h photoperiod with fluorescent lamps at 40 +/- 10 mu mol center dot m(-2)center dot s(-1)) after cold stratification. To examine the germination characteristics, the seeds were tested for water imbibition and found to readily absorb water. The seeds exhibited underdeveloped embryos during dispersal, showed final germination of 37.00% +/- 4.43 at 25 degrees C and were not influenced by temperature. The seeds subjected to 0, 4, 8, or 12 weeks of cold stratification germinated at a success rate of 22.00% +/- 4.76, 87.00% +/- 6.80, 79.00% +/- 2.52, and 77.00% +/- 1.91, respectively. Additionally, the germination characteristics, which were based on final germination, mean germination time, and germination velocity (Timson index), were significantly greater in the seeds pretreated with 1,000 mgL-1 GA(3) at 25/15 degrees C than in seeds pretreated with 0 mgL-1 GA(3). Overall, the seeds broke dormancy with GA(3) and short-term cold stratification. Therefore, we concluded that C. takesimana seeds have non-deep, simple, morphophysiological dormancy, and pretreatment with cold stratification and GA(3) is required for effective seed propagation.

Automated summary

This study investigated the dormancy-release and germination characteristics of Korean bellflower seeds, and found that the use of GA(3) and short-term cold stratification can effectively propagate the seeds.