Effects of several factors on pollen germination in Platycodon grandiflorum

Pollen germination and its' viability in bellflower hybrid system are of great importance. The present study was conducted to investigate the several factors underlying the pollen germination of Platycodon grandiflorum and obtain the basic data for effective artificial pollination for the production of sound specifies. The pollens of Platycodon grandiflorum started germination from one hour after planting, and the germination was actively progressed as time dependent manner. For lighting conditions, the germination of pollens under the light was faster by more than twice than that without the light. Furthermore, the germination was better in the high temperature rather than in the low temperature. The germination rate was higher in the $30^{\circ}C$. For the carbon source, the germination rate was better at the concentration of 15% regardless of the kinds. In particular, the highest value was observed with glucose. The germination rate was decreased substantially as the increasing with the higher pH. The dynamic germination of pollens was observed at the pH 5. With respect to the growth regulator, the higher concentration of NAA induced the higher the germination rate. $GA_3$ showed a good germination rate in $0.05mg{\cdot}L^{-1}$. Meanwhile, for kinetin, lower concentration increased the germination rate, unlike NAA. The higher concentrations of boric acid degraded the germination rate, and the addition of boric acid of $10mg{\cdot}L^{-1}$ demonstrated higher germination rate than the addition of other growth regulators. Notably, the addition of asparaginic acid exhibited the similar results in all test sectors regardless of concentration, whereas a little higher result was observed in the high concentration sector. Taken together, the results concluded that the boric acid was considered as one of the essential minerals that played an important role on the germination of pollens.