Abstract:To understand the reproductive and ecological mechanisms of an endangered species Rhodiola fastigiata for protecting and restoring communities of this species, we have investigated the characteristics of flowering penology and reproductive success as well as controlling factors during the summer of 2007 in the Tibetan Plateau of China. The results showed that there are two breeding systems (hermaphroditic and female flower). Hermaphroditic flowers play the role of male′s functions only. Pollination of R. fastigiata mainly is wind-pollination. The flowering duration of R. fastigiata is about 30 days from late June to late July, when abundant precipitation and higher temperature occurred within a year. However, hermaphrodite individuals started to flower earlier and had a longer flowering duration (9.29 days) than male individuals. Two patterns of flowering dynamic curve, which are the unimodal flowering pattern and bimodal flowering pattern, were observed. The largest number of flower of hermaphrodite occurred later than that of female. Significant relationship among flowering duration, onset of flowering and number of flowers was observed, suggesting that plants with much flowers have a longer the flowering duration. Our results reveal that R. fastigiata has a great reproductive potential but poor reproductive ability. During the course of buds to flowers, a 16%-25% of buds was lost, and from flower to fruit, 36%-57% of flowers aborted that caused reproductive loss. Generally speaking, from buds to seed, about 82%-94% of ovules were lost and only 6%-16% of ovules developed into seed. The average number of seeds per fruit was estimated to be 14.6 (N =312) and the estimated average seed production per plant was 228.6 seeds. The high germination rate of R. fastigiata seed (93.6%) indicates that seed quality is not the factor driving the species into endangered situation. Therefore, the reproductive success of R. fastigiata could be greatly limited by pollen and seed production.