The present study aimed to compare and investigate the morphological characteristics and yield components according to ploidy level of diploid and tetraploid Platycodon grandiflorum under vinyl-greenhouse and open field conditions. Plant height of diploid and tetraploid P. grandiflorum was 51.3 ㎝, 54.0 ㎝, respectively. The results revealed that the plants grown in the vinyl-greenhouse showed significantly higher growth compared to those grown in the open field. Regardless of the growing place, diploid and tetraploid of P. grandiflorum showed the rapid elongation of internodes after 4 and 3 internodes respectively and elongation tends to be decreased as entering the flower-bud differentiation period. The starting day of flowering in vinyl-greenhouse cultivation was found to be faster than that of the open field cultivation by 2∼ 3 days and tended to be delayed by about 5∼6 days in tetraploid P. grandiflorum compared to diploid. Fresh weight of roots from the vinyl-greenhouse cultivation showed a high quantity as 34.2g and 49.4g in diploid and tetraploid P. grandiflorum, respectively and especially tetraploid P. grandiflorum was found to be increased by approximately 44.4% compared to other plots.

The present study was performed to compare the morpho-physiological characteristics of the tetraploid and diploid varieties of Platycodon grandiflorum and to obtain basic data for cultivating a tetraploid variety with high yield and content of functional substances. The plant height of the tetraploid variety (54.0 cm) was slightly higher than that of the diploid variety. The leaf length and width of the tetraploid variety were 10.2 cm and 7.3 cm, respectively. The results obtained from the present study revealed that the form of the leaf changed from lanceolate to ovate, and the chlorophyll content in the tetraploid variety (16.7) was slightly higher than that in the diploid variety. The photosynthetic rate significantly increased (24%) to 13.4 μmol CO2·m -2 ·s -1 in the tetraploid variety from that of the diploid variety. The pollen viability of the tetraploid variety was decreased by approximately 33% with respect to that of the diploid variety, but this did not have a significant adverse effect on seed production. The fresh weight of tetraploid P. grandiflorum was 49.4 g, which was approximately 44% higher than that of the diploid variety.