Pollen Vigor in Blooming Period and Seed Setting of Platycodon grandiflorum

Platycodon grandiflorum is a herbaceous plant,its pollen vigor change during blooming period was evaluated by pollen germination in vitro,and fructification rate of dissimilar ageing pollens was estimate by emasculation,bagging and artificial pollinating.The result showed that the pollen germination was better at 25℃～40℃,and it was the best at 30℃ for 1.5 hours.Germination ratio of pollen in the bud and fresh flower was lower,its tubes length were shorter.With pollen growth after flowering its viability was enhance rapidly,pollen viability is the relatively highest in 6 hours after blooming,its germination rate and tubes length can reach to 92.2% and 602.9 μm respectively,and begins to decline on 8th hour.The pollen germination were 63.1% in 120 hours after blooming.However,its tube length was just 287.0 μm.Within 24 hours after blooming.The fructification rate of the pollen was the highest,and begins to decline on 2nd day and completely losing its fructification ability on 3rd day.In field environment,the life span of the pollen was about 5 days.However,its fructification ability was only 2 days.It was the reason of losing fructification ability of pollen on 3 days after blooming that pollen tube grows slowly.