Allelopathy Of The Dominant Noxious Weed Ligularia Sagitta. In Psychro-grasslands

Ligularia sagitta mattf,a compositae noxious weed,distributed widely in psychro-grassland in the east of Qinghai-Tibet plateau of China.In retrogressive grassland,They formed monodominant species community.For contants toxinic succ-us and uneatable.Seriouslly hamful to pasture..In this thesis,allelopathy of L. sagitta mattf has been studied,The possible chemical relationship between the successful invasion of L.sagitta and the actuality of psychro-grasslands degeneration was investigated,We hope some anti-allelopathic pasture plants kinds can be selected. And the results will provide valuable information for recovery of retrogressive grassland.In our research,the donor material is aqueous extracts from different parts (root,leaf)of L.sagitta mattf and the receptors are 9 kinds of pasture plants.They are Elymus nutans,Festuca sinensis,Bromus magnus,Poa annua,Festuca ovina, Agropyron cristatum L,Bromas inermis.These seven kinds of plants distributed in the same area with L.sagitta,and Daclylis glomerate,Phieum pratense L cv 'Minshan'.These are distributed in the different area with L.sagitta.In these material the effect of L.sagitta on receptor seeds germination and seeding growth were studied. We want to find the possible chemical relationship between the successful invasion of L.sagitta and the actuality of psychro grasslands degeneration.Allelochemical of L. sagitta in root also have been isolated by silica chromatogram technique and identified with spectroscopy.The main results are as follows:The overrun of L.sagitta in retrogressive grassland is related to clone and allelopathy.The strong ability of clone makes the L.sagitta form monodominant species community.And allelopathic effect decrease the competition ability of pasture plants.Allelopathy,overpasture,drought and rats' destroy made the grasslands degeneration more serious,Then noxious weeds invaded into pasturage,New degeneration would began.Both seed germination and seedling growth of all tested pasture plants were inhibited to different extent by aqueous extracts from L.sagitta.Volatilization, eluviation and root system and rhizomes exudation were three ways which L.sagitta released allelochemicals to surroundings;The inhibitory effects of aqueous extracts of L.sagitta from underground part was stronger than from aerial part(leaves),which might be related to the competition of the underground resources in natural grassland;Seed germinative stage of tested plants was more obvious to be affected by the allelopathy of L.sagitta than seedling growth stage.During seed germination,the germination index was more sensitive to allelochemicals than germination rate.So the germination index may be the most sensitive criterion to judge allelopathy;Alleiopathy effect was concentration dependent,Inhibition effect decreased while the concentration of aqueous extracts decreased.Root development of tested seedings were also inhibited by L.sagitta,It showed the longth of root became shorter than normal,and the development of lateral root became slower.So the ability of absorption deceased too,and the growth of th tested plants be harmful.Different studied pasture plants has different sensitivity to aqueous extracts of L. sagitta.The inhibitory effects of aqueous extracts to germination from L.virgaurea on Agropyron cristatum.L,Elymus nutans,Daclylis glomerate,Poa annua,Festuca ovina was significant but on Phieum pratense L.cv 'Minshan',Festuca sinensis,Bromus magnus was not very sensitive.Accordingly,Phieum pratense L.cv 'Minshan',Festuca sinensis,Bromus magnus could be used as preference during vegetation recovery course of psychro-grasslands.From the root of L.sagitta.A kind of sesquiterpene compound has been isolated, spectroscopy identify showed it is 1-Hydroxy-13-nor-6,9-eremophiladiene-8,11-dione,F.M C₁₄H₁₈O₃.Accordly references,sagitta contents many kinds of penecompound,so it has great potentiality as bio-insecticide,bio-herbcide and folk medicine.