对稀有物种生物学特征及繁育系统的研究将有利于我们对稀有物种的保育。该文通过野外定位观测稀有植物小丛红景天(Rhodiola dumulosa)的花部综合特征，并运用杂交指数、花粉-胚珠比的方法首次对其繁育系统进行初步测定。结果表明：该物种单花花期一般为5～6 d，开花过程中花柱逐渐伸长并向外弯曲，子房开裂并逐渐伸长，花药散粉具有先后顺序，一般外轮对萼花药先散粉，其后1 d左右对瓣花药开始散粉。单花花期依照其形态和散粉时间可分为6个阶段：花蕾期、内轮散粉期、内轮散粉末期、外轮散粉期、外轮散粉末期和凋谢期。而种群花期一般可持续30 d以上，不同海拔观测地点有所不同，海拔2 202 m处的观测地点B开花物候最为滞后。由于其杂交指数不小于4，花粉-胚珠比在700～1 000之间，根据Dafni(1992)和Cruden(1977)的标准，初步判定该物种的繁育系统属于异交为主，部分自交亲和，传粉过程需要传粉者。
Aims Knowledge of floral syndrome and breeding system is important for understanding reproduction and population dynamics of plants, especially rare plants. Our objective was to determine the floral syndrome, flowering course and dynamics and functional floral morphology of the rare plant Rhodiola dumulosa in Dongling Mountain, Beijing, China, to determine its breeding system.
Methods For individual flower, flowering lasted 5 to 6 days, the flowering process for one flower of this species can be divided into 6 periods according to the flower morphology and anther dehiscence: “Budding period"—petals are visible but not open, two rings of anthers are red and no dehiscence; “Inside-dehiscence "—petals are open in a way, and the inside anthers dehisce; “Post-inside-dehiscence"—after 1-2 days of flowering, the inside anthers over the pollen exposure and the color changes to black; “Outside-dehiscence"—the outside anthers dehisce, ovary becomes bigger and then split, stigma stretches out; “Post-outside-dehiscence"—petals are open well, all anthers over the pollen exposure and the color changes to black or brown; “Withering period"—after 5-6 days of flowering, the color of filaments and ovary changes to red, petals start wilting.
Important findings In the process of flowering, styles become long and curved slowly. The anthers dehisce in order of priority. The inside anthers accounting for 50% of whole anthers whose dehiscence pattern is longitudinal always dehisce first, followed by the outside others. The flowering span among populations is a bout 30-40 days. The flowering course of every observation plots is different, the observation plot B whose altitude is 2 202 m lagged behind other observation plots, and we presume that different weather condition of every observation plot and disturbances of tourists should be the great factors. The species is protandrous with an out crossing index of 4 bases. According to criteria of Dafni (1992), the breeding system is out crossing with partial self-compatibility, needing pollinator s. The pollen-ovule ratio (P/O) is about 700-1 000. Based on Cruden’s criterion (1977), the breeding system is facultative xenogamy.