Abstract: The diploid of Allium caeruleum，distributed in Tianchi，Tianshan Mountains，was observed as the research materials. The flowering process，the pollen viability and the stigma receptivity of A. caeruleum were recorded and detected，and the mating system was estimated by using emasculation，bagging and artificial pollination methods. The results showed that（1）the average diameter of umbel was（29.07 ± 1.17）mm；tepals were sky blue and flowering period was from June to August；bisexual florets was intensive and without bulbils，and the average quantity of florets was 205.67 ± 19.88；the floret experienced morphological changes of bullet，open mouth，spit anther，unfold，cohesion and wilting，which lasted 5–7 d；the anthers and the stigma existed spatial isolation in the process of floret opening and there were 12 dynamic changes that was from the first anther extending to all of six anthers shedding and from stigma elongation to wilting was needed 2–3 d，respectively；Under cloudy weather the anthers dehiscence were increased and the stigma wilting was delayed 0.5–1 d，respectively. The floral syndrome of A. caeruleum was protandry，dichogamy and herkogamy to prevent self-pollination.（2）The pollen viability was 79.23% ± 1.97% after the anther dehiscence 4 h. The pollen viability was within 36 h. A. caeruleum belonged to the short life pollen.（3）The stigma receptivity was detected by both the MTT and the benzidine hydrogen peroxide methods；when filaments equaled to the style the stigma receptivity was to be detected partially，and when filaments over passed the style the stigma receptivity was to be detected totally. The partial overlap of the stamens and pistils could prevent the failure of cross hybridization.（4）The single flower of A. caeruleum had 31 275 ± 3 651 pollens and six ovules；the ratio of pollen to ovule（P/O）was 5 212 ± 608 and the out-crossing index（OCI）was 5. The detection results of mating system showed that A. caeruleum has no spontaneous self-pollinating phenomenon and there was no wind pollination and apomixes. It tends to be outcrossing and selfing fertility. It has outcrossing and mixed mating system features and needs floral visits. The diploid A. caeruleum from Tianchi also take the seed dormancy and asexual propagation compensation strategies to ensure the population reproduction successfully.

Key words: Allium caeruleum, floral dynamic, pollen viability, stigma receptivity, pollen-ovule ratio（P/O）, out-crossing index, mating system