Study On Reproductive Ecology Of Rhodiola Fastigiata A Psychrophyte In Tibet Plateau

Rhodiola fastigiata belongs to crassulaceae and Rhodiola L,which is perennial herbaceous with succulent root and rhizome .As its medicine use for Tonic Action, anti-senescence and so on ,it have been picked up a lot for commercial use, so it is in near danger state now and listed in《The red list of china species》(VOL.1). Four altitude bands were set at 100m interval between 4000m and 4400m, Quantitative characteristics, Breeding system, Flowering penology, reproductive potential, reproductive success, germination rate were all studied to illusrate the reproductive characteristics and factors that limit reproductivity and the theoretical base for protecting Rhodiola fastigiata will be laid. The results got were shown below:The density of reproductive genet is more during altitude 4300-4400m ,4000-4100m related with less vegetables and smaller canopy density, the density of reproductive genet is lest during altitude 4100-4300m for much more vegetables and intenser interspecific competition ,so the the reproductive genet's interspecific competition is weaker, The frequency of plot with hermaphroditic and gynoecy is more during altitude 400-4100m and 4300-4400,indiating that the distance between hermaphroditic and gynoecy is not a factor that effect pollination.In each altitude band, there exists no differences(p>0.05) between hermaphroditic floral parameter and that of pistillate except for pistil(p<0.05).The length of hermaphrodite's pistil is just1/2 of pistillate's, the length of stamen and that of pistil were different along the altitude at some extent(p<0.05). there are linear regression between number of flowers and diameter of inflorescence.Based on the results of hand outcross pollination and OCI, the breeding system of Rhodiola fastigiata is outcross and not self-compatible, not apomixes in hermaphroditic.Flower Life and stigma reactivity last long (hermaphroditic: 10-13d, Female: 18 or more), so the female's pollination chance and female fitness could be improved.The fitness of gynoecy is greater than that of hermaphroditic. In the wildfied investigation, two gynomonoecy was discovered, 90% of hermaphroditic aborted, just10% of hermaphroditic fruited successfully. There existed much difference between hermaphroditic and gynoecia: The number of ovule per pistil late(56)is much more than that of hermaphroditic(25).Fruit set per gynoecy,seed production per gynoecy,germination rate,the number of ovule per gynoecy were all much more than those of hermaphroditic,suggesting that the evolution of population's sex system was gynomonoecy→hermaphroditic→gynoecy and the evolution is not perfect now.Rhodiola fastigiata flowering season extended late June to later July. the flowering period was about 21~33 d, hermaphroditic flowers earlier than pistil late, flowering phonology dynamic is similar among four altitude bands, Two different patterns were observed in population: a unimodal flowering pattern and a bimodal flowering, The mean flowering duration of hermaphroditic was 9.29d (range from 2-21d), The mean flowering duration of gynoecy was 7.13 d (range from 1-16d), The flowering duration of a plant was affected by number of flowers, first flowering date. There no existed correlation between flowering synchrony and flowers, flowering duration, first flowering date. Flowering synchrony values obtained in each gynoecy pant mean that on an average day a plant can exchange genes with only12.5-77.3% of the population. There was no significant correlation between fruit success and flowering synchrony. flowering duration of Rhodiola fastigiata population was in the period which much precipitation and high temperature occurs in a year. No significant correlation result from air humidity, gene flow is probably very low as high air humidity and Outcrossing rate declined.Rhodiola fastigiata gynoecy plants have considerable reproductive potential but reproductive success . Mean number of buds and number of ovule per gynoecy was 38,2196respectively. reproductive success is limited by resource. There exists linear regression between number of flowers and number of inflorescence. Ovule per gynoecy is most in4180m and declined with altitude rising. The fruit per gynoecy declined with altitude rising. Seed production per gynoecy was different among four altitude bands.From buds to flowers, As for pollination limit, resource limit, pests and diseases. 22.9% of buds in a gynoecy was lost, from flower to fruit, 45.3% of flowers in a gynoecy aborted and just10.4% of ovules per gynoecy developed into seed. In all from buds to fruits, there were all57.8% of buds and 89.6% of ovules per gynoecy which were all lost.so the pollination and resource are main factors that limit Rhodiola fastigiata reproductive success.The mean numbers of seeds per fruit was 14.6(N =312), so the estimated mean seed production per plant was 228.6 seeds, indicating that the population size may be limited by seed production. The germination rate is 93.6%, suggesting that the quality of seed was not the factor for near danger.Soil and light are main ecological factors that affect frui and seed traits. There exists linear regression between number of seed and weight per fruit. so we can estimate number of seed per plant by weighting the fruit.