Study On Fruit Morphology And Mechanical Analysis Of Bidens L. In Beijing

Bidens L. belongs to Trib. Heliantheae of Compositae, there are nine species and two varietas in China, seven species in Beijing. On the one hand, Bidens L. has a value in use, we can use some species as medicines; on the other hand,the fruits of the genus have barbs and barbed spine as special structure to spread. Some have been as invasive species, and have been malignant weed, and people have to father them. The distribution of all species in Bidens L. and macro morphological characters between species have overlap, meanwhile the concept and entity have chaos, that have difficulties in use prevention and cure.The paper used advanced stereomicroscope and scanning electron microscope(SEM) to have a paired observation study on seven species ofBidens L. in Beijing, in order to provide some new materials and evidences to plant taxonomy and identification. Meanwhile, based on the length and other parameters of fruits,barbs and barbed spines, there is a measurement, building a mathematic model, and in order to provide some evidences to prevent and cure the plant, there is a mechanical analysis about spreading. The main conclusions are:(1) The shape of achene,the number of edge,the way and the position which barbed spines have on the barbs and other characters of the seven species of Bidens L. can be used as the main morphologic evidences in identifying.(2) In respect of micromorphology, the patterns of sculpture of pericarps of seven species have obvious differences and have their own specialties. And the conclusions in affiliation is in accord with the results from the shape of leaf,geographic distribution and molecule which researchers studied, that implies the significance in taxonomy. (3) On the basis of the patterns of sculpture of pericarps and the epidermic cells and other characters, the seven species can be divided into two categories:one has typical, rugose or scalariform sculptures,the other pattern has striate network or portrait sculpture.(4) The mathematical model and the mechanical analysis showed that,B. pilosa can endure the most force, B. biternata is opposite. B. pilosa has the most possibility to diffuse,so the correlative departments shoule pay more attention on it.