The Ecological Adaptive Significance Of Protandry And Pollen Gradual Presentation In Silene Olgiana

Silene olgiana is an early-spring ephemeroid herb. It has the characteristics of protandry, dichogamy and pollen gradual presentation. The paper studies S.olgiana on the floral syndromes, pollination syndromes, reproductive system and so on, which distribute in the fix and semi-fix dune near Chepaizi oil field (44°55′18.6″N, 84°56′35.9″E, alt. 300m) at the Guerbantonggut Desert, Xinjiang, China, so that we can understand how does this species get reproductive success in the cruel environment and the ecological adaptive significance of protandry, herkogamy and pollen gradual presentation. We measured the floral syndrome, observed the visitors and did the mating experiment of S. olgiana between 2007 and 2008. The main result are as follows:(1) The individual plant flowering lasts for 19-30d, the inflorescence lasts for 11-19d and the individual flower lasts for 3-4d. Its flowers ususlly open at about 19:00 that the flowers opened and the white sepals stretch out. The flowers open not only in the night but also in the day, and they keep secreting nectar to attract visitors.(2) The species has the characteristics of asynchronous protandry, movement herkogamy, pollen gradual presentation at the same time. They avoid self-pollination and interference between male and female function, which can improve the fitness and get the reproductive success.(3) In the population, the ratio between male phase flowers and female's is about 2:1. The two whorls of stamen have the similar ontogenetic development and so do the viability of the two whorls of pollen. The different is just that there is a time gap about 24h between the two whorls of pollen presentation. It is useful to provide the high pollen viability and attract the visitors. The stigma has been receptive during 48-96h after the flowers open and its peek is during the 48 h to 72h, after 96h it is not receptive. It is well matched with the pollen viability and will promote the reproductive success.(4) The P/O ratios of the flowers is 512±97, OCI>4, it is probability facultative out-crossing, and pollinators are needed during the process of pollination. There are no anemophily (wind pollination), apomixis and autogamy. Although control, geitonogamy and cross-pollination both get the seed, the latter produces the most, which indicates pollinators are needed for the reproductive success of S. olgiana.(5) The visitors of S. olgiana were hymenoptera and lepidoptera. Four species of main insects are as follows: Tetralonia macroglossa, Halictus pollens, Halictus malachurus, and Halictus nigripes. During the process of pollination, the pollinators'behaviors are affected by the varies between temperature and humidity. There are kinds of Lepidoptera to visit the flower for the nectar in the night, but not contact with the sexy organ, so they are considered as nectar-thieves in the paper.