Abstract: In in vitro culture , Platycodon grandiflorus was treated with colchicine at different concentration and time duration. It showed that the induction rate could reach 50% with colchicine at 0.1% for 40 h. Compared with the normal
diploid plants, the polyploid plants had thicker leaves and larger leaves, darker leaf color , stronger stems with longer length per stem stalk, larger stomata and fewer stomata per unit area. Cytological observation showed the chromosome number of variant plants is 2n=4x=36, while that of normal diploid plant is 2n=2x=18, x=9. Therefore, the variant plants (2n= 4x=36) belong to tetraploid plants. Karyotype formula of the former is 2n=2x=14m+ 20sm+ 2st, and that of the latter is 2n=4x=7m+10sm+1st. Both of the karyotype belong to Stebbins’s 2B type. It was also found that a few induced plants were aneuploid .

Key words: Platycodon grandiflorus