Reproductive Ecology of Iris ensata (Iridaceae)

By investigating and experimenting pollination pattern,reproduction mode,fruit and seed dispersal,seed dormancy and germination,characters of reproduction ecology of Iris ensata were researched in one nature population of Tianmu Mountain,Zhejiang Province from 2006 to 2008.Results were as follows.(1) The natural population of I.ensata was in the spatial pattern of aggregation distribution.Its population regeneration was almost built upon asexual reproduction with 0.756 percent contribution.(2) Artificial pollination indicated that the fruit set and seed set of self pollination were much lower than cross pollination (P0.05).The flower of I.ensata being covered by a mesh had no seed setting,and the fruit set rate of self-pollination between the same or different petal of the flower were 10% and 20% with 0 and 4±1(n=2) seed per fruit respectively.However,the fruit set rate of geitonogamy and xenogamy were 80% and 100% respectively,and seeds per fruit were 59±7(n=8) and 64±9 (n=10) respectively.The pollen-ovule ratio was 1277±270 (n=10),which further indicated that the pollination type of I.ensata was mainly xenogamy.(3) Apis mellifica was the effective pollinator with the frequency of 0.019 each flower in one minute,and the ratio of visiting the same flower was about 3.5%.(4) The seed number was estimated about 368 per square meter in nature.Fruits and seeds of I.ensata were persistent and the seed had no deep physiological dormancy.Light was needed during seed germination and the seed germination rate was 94.9±0.7% after 60 days cold moist stratification.(5) We concluded that I.ensata can adapt to the wet and cold mountain climates very well,and Tianmu Mountain may be one of origin and refuge places of this plant during the glacial epoch.The species of I.ensata takes the adaptation strategy of k type,and they possess the mechanisms of natural sustaining renovation in natural population.Some of those mechanisms are being disturbed more or less by human activities now.