Abstract:

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 about 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 outcrossing index of 4 bases. According to criteria of Dafni (1992), the breeding system is outcrossing with partial self-compatibility, needing pollinators. The pollen-ovule ratio (P/O) is about 700-1 000. Based on Cruden's criterion (1977), the breeding system is facultative xenogamy.

Key words: Rhodiola dumulosa, breeding system, outcrossing index, pollen-ovule ratio