Aerial Seed Bank Dynamics And Xerochasy Characteristics Of The Infructescence Of Onopordum Acanthium

Onopordum acanthium seeds were wrapped in the infructescence which matured from July to August.Infructescence gradually dehisced and most seeds retained in the infructescence, by the xerochasymovement of infructescence, it gradually spreaded out over time and dispersed, included hygroscopicclosing and dry dehiscence processes. Onopordum acanthium had an aerial seed bank characteristics. Thisexperiment investigated aerial seed bank size and duration of Onopordum acanthium populations inUrumqi and Qapqal, combined with seed vigor test and germination in the laboratory. Manually simulatedthe precipitation (13.6mm,.6mm,4.2mm) and temperature (35celsius,24celsius,19celsius) gradient,effect of precipitation and temperature on the xerochasy movement of infructescence has beed studied andcome to conclusions as following:1. Onopordum acanthium aerial seed bank duration was less than one year, as seasonal aerial seed bank.Seeds persistent proportion of different populations affected by the climate condition with seasonaldifferences. From September2012to January of next year, persistent proportion of aerial seed bank ofOnopordum acanthium in Qapqal was significantly higher than in Urumqi (P＜0.05) or (P＜0.01).From February to April in2013, the persistent proportion of aerial seed bank of Onopordum acanthiumwas insignificantly (P＞0.05) among the two populations.2. Matured seeds of Onopordum acanthium could keep vigor for a long time. Among diffenent populations,dispersal time and state significantly affected the seed vigor (P＜0.01). Seed vigor of Onopordumacanthium in Qapqal was higher than in Urumqi. Both retained and dispersed seed vigor decreased overtimes, furthermore, vigor of retained seed was higher than dispersed. Germination rate of seeds fromdifferent populations varied significantly (P＜0.01) over times, and seed germination rate of Onopordumacanthium in Qapqal was higher than in Urumqi. Both retained and dispersed seed germination ratedecreased over times, Germination rate of retained seeds was significantly higher than dispersed seeds (P＜0.01). Seeds, which matured from the hot summer of these two populations, could germinate rapidlywith suitable conditions of water and heat, besides, characterized a high germination rate.3. The infructescences of Onopordum acanthium had a rapid closing mechanism caused by precipitation. Single rainfall amount was the leading factor that affected the speed of the infructescence hygroscopicclosing process. Temperature was the most important factor affected the infructescence dry dehiscenceprocess. The precipitation affected water content rate of closed infructescences, which was the watercontent rate of infructescences at the state of dry dehiscence started. Under the same condition, thehigher the tempperature,the shorter the time required of dry dehiscence process, and the faster themoisture loss.