| Flaveria bidentis (Asteraceae), a native of South America, has its first record of China in Henshui, Hebei, China in 2001. Since then, the weedy species has been spread over more than 47 counties and cities of Hebei Province as well as 6 districts of Tianjin Municipality. Upon the invasion of the weedy species, the action of control is immediate in demand. This paper deal with the Flaveria bidentis could be suppressed by applying vegetation replacement in the long run. To test the hypothesis, experiments have been conducted in greenhouse and in field using several candidate plants alone or combinations of them for replacement. The performances of F. bidentis competing with Helianthus annuus and Medicago sativa were further investigated to estimate the competition between the target plant and the plants used for replacement.1. Seeds of 14 plant species are treated with the aqueous extracts of F. bidentis to evaluate the potential allelopathy of the invasive species on the germination of the test species. Only one of them was affected significantly by the treatment, compared with by application of H2O as control. Therefore, all other 13 species, namely Helianthus annuus, Medicago sativa, Lolium perenne, Festuca arundinacea, Astragalus adsurgens, Euchlaena Mexicana, Amorpha fruticosa, Amararanthus paniculatus, Lolium multiflorum, Poa pratensis, Coronilla varial, Indigofera pseudotinctoria, and Lespedeza bicolor, were eligible for in-field assays.2. In field, F. bidentis were planted and sided with eligible species above or some of them combined, with 16 schemes in totoal. Height, node numbers, biomass, and amount of soluble proteins and peroxidase (POD) of F. bidentis were measured in aim to screen the schemes that were potential for the weed control in the future. 5 schemes have shown to be most promising. The numbers were 3,7,13,14,15 and they were M. sativa, A. paniculatus, H. annuus + L. perenne, H. annuus + F. arundinacea, and H. annuus + M. sativa. Three others, L. bicolor, A. adsurgens, and A. fruticosa of the numbers 6,8,11, also indicated certain potential.3. Germination of F. bidentis seeds treated with aqueous extracts of M. sativa was evaluated to investigate the suppression of M. sativa upon F. bidentis. The seeds were geminated in 32% at the concentration of 0.1g/mL of the extracts. Further investigation revealed that radicle development of the seeds had been reduced by 69.2% when treated with 0.05 g/mL of the extracts. Actually, reduction of node numbers (by 77.7%) and height (by 46.4%) of F. bidentis has been found in field when M. sativa was planted aside in even very low density. The occurrence density of F. bidentis accompanied by M. sativa was 26% lower than that of mono-cultivated, although biomass of F. bidentis individual showed no significant difference between those were mono-cultivated and mixed-cultivated.4. Greenhouse experiments were designed according to de Wit's methods to evaluate the interspecific and intraspecific competition between/among F. bidentis and M. sativa, as well as the effect of density and composition of the cultivation on the competitions. The data showed that F. bidentis was suppressed most when the ratio of H. annuus and F. bidentis was 3:1, in terms of height, node numbers and biomass. Relative yield (RY) of F. bidentis was significantly lower than 1, only except when cultivated in lowest density. Accordingly, RY of H. annuus were mostly far above 1 with few exceptions. The result implied that the effect of intraspecific competition was larger than interspecific competition for F. bidentis when cultivated with H. annuus. In medium and high density, the relative yield total (RYT) of both vegetations was not significantly away from 1, indicating that the recourse they required for development were basically equivalent under such conditions. In the later phase of competition, amount of soluble proteins of F. bidentis was reduced due to strong effect of the competition, while activity of POD was increased when density of the cultivation became higher.
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