Comparison Of The Germinating And Growing Features Of Pokeweed Seeds Yielded From Native And Invaded Habitats

The invasion of alien species has not only reduced the diversity of native species in the ecosystem, but also caused serious harm to local society, economy and even human health. Pokeweed was initially introduced to our country as a medicinal plant,has now invaded many parts of our country rampantly, especially in the coastal areas of Shandong, causing serious reduction in the biodiversity of coastal protection forest.Concerning on the invasion of pokeweed, domestic scholars mainly concentrate on the study of reproduction, dispersal and allelopathy, researches on physiological and ecological mechanism are rare. This paper mainly explore the mechanism of invasion success of pokeweed, through comparison of the germinating and growing features of pokeweed seeds yielded from native and invaded habitats, as well as the provenances between different illumination conditions and levels of nitrogen application. The main research results for this study were as follows:(1) Under different pretreatment methods and different temperature, both the average germination rate of provenances and the average radicle of germinated seeds from pokeweed invasion place are higher than the species source in origin, which shows the strong reproductive capacity of pokeweed from invasion place. Meanwhile,through the analysis on effect of seed germination under different pretreatment methods and temperature, we discover that each kind of pretreatment method can improve the seeds to germinate in some extent. And the seeds average germination rate from invasion place is the highest by processing with 15% H2O2. In addition, under the variable temperature from both the average germination rate and radicles of pokeweed in origin and invasion places reach their highest level.(2) With the light and nitrogen treatments, two plants of different provenance possess significant plasticity. And, as the increasing of light and nitrogen, the plant height and biomass of two provenances have significant increases, while to the contrary the leaf area ratio and specific leaf area are reduced. In addition, the material distribution strategy of two provenances under the light and nitrogen are similar. The stem and root distribute more matters under a favorable environment and the leaf distribute more matters under a unfavorable environment, which presented theirstronger adaptability for external conditions. Furthermore, as the changes of light and nitrogen, photosynthetic performance, resource utilization and costs of two provenances have different changing trends, and overall they have the strongest growth on the condition of mid-light. However, contrasting with the plants in pokeweed ’ s origin, the plants of invasion places had no significant advantages on the aspects of biomass accumulation, biomass allocation, photosynthetic performance and resource utilization.(3) The index of forms and physiological plasticity of pokeweed provenances from invasion places are higher than the provenances of origin. It is illustrated that the plants from invasion places have stronger invasive adaptability, which benefit the success of invasion.In conclusion, comparing the provenances of seed origin, the provenances of pokeweed from invaded places show obvious invading power in terms of seed germination and phenotypic plasticity, but no stronger competitive power in terms of biomass accumulation, hpotosynthetic performance and resource utilization. These results showed that the successful invasion of pokeweed was not only related to its adaptability, but more dependent to the environment. This could be the major reason that pokeweed dispersed rampantly in coastal defense forest of Shandong. Further studies are still needed on this theme.