Abstract:

Allelopathy is the important intrinsic factor in forming plants community, deciding the plants categories on plants community and causing the plants community to evolve, and it is also the important mechanism in the successfully invading of invasive plants.To produce and release the allelochemicals and the strength of its effect of plants largely depend on their living environment besides their inherent characteristics. Wedelia chinensis Merr., which was proved to have allelopathy, has spread throughout the agroecosystem and wilderness in Liaoning, Jiangsu, Zhejiang, shouth China etc. Herbicide, a stronger environmental factor for most weeds, was widely used in the prevention of C. chinensis. But if herbicide will affect its exudation and change the allelopathic effect eventually? The present research was projected to answer it. In this study three different categories of herbicides, Paraquat, Glyphosate and Fluazifop-butyl，were selected and sprayed to the C. chinensis populations in field at three different concentrations (one fourths of recommend dosage, half of dosage and recommend dosage). The C. chinensis was sampled every 10 days after sprayed herbicides. Cabbage seeds were used to test the allelopathic trends. The results demonstrated: (1) Within 40 days after sprayed herbicides, the variation range of allelopathy from sprayed C. chinensis population was wider than contrasting ones, but this characteristic only appeared apparently at 0.5g/ml; (2) Three different categories of herbicides resulting in a same peak allelopathy time, the 20th day; (3) Allelopathy of C. chinensis stressed by herbicides almost rebounded to contrasting samples after certain fluctuation; (4) Significant differences of allelopathy appeared at the same concentration extracts stressed by the same leve(one fourths of recommend dosage, half of dosage and recommend dosage) of different categories of herbicides, it maybe have relations with the mechanism and intensity of the herbicides; (5) The components of allelochemicals did not change with the herbicide, the concentrations of herbicide and the stage of plants. All the above indicate chemical herbicides strengthen the allelopathy of C. chinensis within some period and make its invasive potential strengthen.