Study On Reproductive Ecology Of The Invasive Plant Datura Stramonium,Lhasa

In recent years,as an invasive plant Datura stramonium has spreaded rapidly in Lhasa and its surrounding area,which reflects that its breeding system is more adaptable to the plateau environment.In order to study the reproduction characteristics and pollination mechanism of rapid spread of D.stramonium,this is study aims to clarify to the reproductive strategy of D.stramonium,an invasive plant distributed in Lhasa,through the study of its breeding system,so as to provide basic scientific basis for understanding the causes of rapid reproduction on the plateau.The pollination ecology of D.stramonium in three different habitats of Najin campus of Tibet University,the eastern suburb of Lhasa and the Lalu wetland National Park were studied by both field observation and laboratory experiment.Meanwhile,the reproductive allocation difference,seed germination rate and its influencing factors of D.stramonium population in two different habitats of the eastern suburb of Lhasa and the Lalu wetland were also studied.The results showd that:(1)the flowering period of D.stramonium is from June to the first ten days of October;the single flowering period is about one day.(2)The hybridization index(OCI)is 4.(3)The average pollen ovule ratio(P / O)of D.stramonium population in Najin campus of Tibet University is 285,in hillside of eastern suburb is 275,and in Lalu wetland is 300.The P / O ratio values of D.stramonium in three habitats indicate that its breeding system belongs to facultative outcrossing.(4)The results of four treatments in three habitats(emasculated bagging,natural bagging,emasculated label and corolla removal)show that the fruit setting rate of emasculated bagging is 0% in all three habitats,indicating that there is no parthenogenesis in D.stramonium.In the bagging treatment,the fruit setting rate is 100% in Najin campus of Tibet University,96% in the hillside of the eastern suburb and 84% in the Lalu wetland.In the treatment of removing male and without bagging,the fruit setting rate of D.stramonium in Nakin campus of Tibet University is 50%,in the eastern suburb is 8%,and in Lalu wetland is 72%,which indicates that pollen have different effects on the flower visiting attraction of insects in three habitats.In the treatment of removing the corolla,the fruit setting rate of D.stramonium in Najin campus of Tibet University is 96%,in the eastern suburb hillside is 96%,and in the Lalu wetland is 72%,indicating that the removal of the corolla have little effect on the its fruit setting rate.(5)Through the observations of flower visiting insects in three different habitats of D.stramonium,it is found that the main flower visiting insects of it are honeybee(Apis)and Syrphidae(Syrphidae).Among them,there are 2 species and 1 genus of bees,7 species and 4 genera of flies.It may be due to the large temperature difference between the seasons and the morning and evening,the time of insect visiting flowers is quite different.Most of the time of insect visiting flowers of D.stramonium in the habitat of Najin campus of Tibet University are concentrated in the morning and evening,the other two habitats are mostly concentrated around 11 a.m.The effective pollinators is identified as wasps.In addition,the number of bees of visiting flowers in the habitat of Najin campus of University of Tibet increased explosively in the evening;the visiting time of bees and flies in the hillside habitat of the eastern suburb of Lhasa is highly consistent,the total number of bees of visiting flowers in the wetland habitat of Lalu is small,and There is no obvious peak in it.The study on the reproduction allocation of D.stramonium in two habitats of the eastern suburb of Lhasa and the Lalu wetland shows that the average reproductive allocation of it in the eastern suburb of Lhasa is 17%,and in the Lalu wetland is 22%.There is no significant difference between them.Through the study of seed germination and its influencing factors of D.stramonium,it is found that the seed germination rate of it is only 2% at temperature 22?,but is 0% at temperature 15?,30 ? and treated with GA3 and placed at 20?,all these indicating that the seed germination rate of D.stramonium is very low,or there may be post-maturation of Datura seeds,which needs follow-up research.On the hillside of Lhasa,the average D.stramonium fruit yield per individual plant is 39,and the average of single fruit seed is 473;the D.stramonium fruit yield of Lalu wetland is 50,and the single fruit seed average is 409 capsules.It shows that in the relatively extreme environment of the plateau,D.stramonium may take on the strategy of increasing the number of seeds to achieve an increase its reproduction success rate,and tend to adopt r-ecological strategy.