-This study aimed to get the basic data on the breeding of good varieties in Hypericum patulum Thunberg. The optimum materials, concentration and soaking time were examined to identify the effective approach to induce tetraploid plant by colchicine treatment to cultivate the varieties. For the seed germination rate of seed by colchicine treatment, the higher colchicine concentration was and the longer soaking time was, the more the germination rate decreased. While individuals were germinated in 16 test groups except control group (no treatment group), all the plants were diploid and no tetraploid was induced. For the plant regeneration rate by colchicine treatment on the explant of Hypericum patulum Thunberg that was under in vitro culture, the higher the colchicine concentration increased, the ress the regeneration rate. While total 147 individuals were regenerated in all treatment, when the explant was soaking treatment in more than 0.05% for over 6 hours, tetraploid could be obtained. In the soaking treatment of 0.05% for over 6 hours, tetraploid could be obtained. In particular, for the soaking treatment in 0.05% for 12 hours, 8 tetraploids were induced, which was about 47.1% of the number of plant regenerated. In accordance with the observation on doubling of DNA contents in leaf in order to identify polyploidy, the peak DNA content of G1 phase was 94.5 for diploid and 192.5 for tetraploid. It confirmed doubling of DNA content. Furthermore, the number of chloroplasts per guard cell depending on polyploid was around 10 in diploid and 17 to 19 in tetraploid, which were around 1.7 to 1.9 times as much as diploid.

-This study was carried out to determine the optimal medium composition and growth regulators for the micropropagation of Platycodon grandiflorum (Jacq.) A. DC. Nodes containing yellow green petals were used as plant materials to execute the study. The best performance of adventitious root development was found in 1/4 strength of MS basal salt and the growth was satisfactory in the concentration of 1/2 MS medium. The best condition for adventitious root development and growth was observed in the higher concentration (5%) of sucrose and activated charcoal free 1/4MS medium respectively. Adventitious roots were developed at the controlled culture medium at pH 4.8 with a tendency of suppression with higher levels of pH. However, it was prevailed that the development and growth depended on the concentration of agar. The lower concentration of agar (0.4%) was performed better than that of higher concentration (1.2%), whereas the agar concentration (0.4%) showed the best performance for the development and growth of adventitious roots. For the development of shoots containing node, BA combined with IAA was more effective than kinetin with IAA or NAA. The highest shoot development (3.9 shoots per explant) was performed on MS medium supplemented with 0.1 ㎎/L BA and 0.5 ㎎/L IAA.