Allelopathy Of Aqueous Extracts From Pine Needle And Isolation And Indentification Of Allelochemicals

Comparing with other plants, the plants under many pine trees is sparse and even not growth. Investigation also found that plant seedlings under pine trees grow not well and vegetation is difficult to regenerate, althought water and sunlight under trees are sufficient for vegetation to growth. The reason is that many pine trees have allelopathy highly and can produce allelochemicals to inhibite growth of neighbouring plants. In nature, allelopathy is a very common and important ecological phenomenon. The allelopathic effects of aqueous extracts of five pine needles (Pinus tabulaeformis, Pinus armandi, Cedrus deodara, Pinus bungeana, and Pinus sylvestnis var) on receptor seeds was studied, and the effect of different concentrations of extracts on the seeds germination and seedlings growth was determined. The aim is probing allelopathy of pine needles and competition between pine nddeles and weeds to found a safe and effective ecological method for the control of common weeds. The survey of separation and identification of potential allelochemicals can provide reference for the development of new biological herbicide. The results was showed as follows:1. Using solvent extraction to obtain 5 kinds of aqueous extract of pine needles, the effect of different concentrations of extracts on germination and seedlings growth of seeds was determined. Receptor seeds are Portulaca oleracea, Amaranthus retroflexus, white clover, lettuce, cucumber, sorghum, respectively. Test results showed that excepting effect on seedlings growth of Portulaca oleracea, allelopathic effect of 5 kinds of water extract on germination and seedlings growth of Portulaca oleracea, Amaranthus retroflexus, white clover and lettuce had different degree of inhibition. The inhibition inhanced when concentrations of water extract increased. But effect on cucumber and sorghum was not significant.2. Comparing with other pine extracts, the inhibitory effects of cedar extract on germination and seedlings growth of Portulaca oleracea, Amaranthus retroflexus, white clover and lettuce were strongest. The sensitive degree was Amaranthus retroflexus> white clover> lettuce> Portulaca oleracea> cucumber> sorghum, the mostest sensitive seed was Portulaca oleracea.3. The fractions of petroleum ether, dichlormethane, ethyl acete, butanol were obtained by extracting cedar extract. The allelopathic effects of every fraction on Portulaca oleracea were studied. The allelopathic activity of dichlormethane fraction showed strongest, and the inhibition gradually increased with the increase of concentrations. Inhibitory effects of dichlormethane fraction ongermination were higher than that on seedlings growth. The effects on seedling growth showed that low concentration promoted growth and high concentration inhibited growth.4. Allelochemicals of dichlormethane fraction were indentificated by GC-MS. Main allelochemicals were triethyl citrate,2-Cyclohexen-1-one, dihydroxanthin, diisooctyl phthalate,5,8,11-heptadecatriynoic acid methyl ester,2,2'-methylenebis[6-(1,1-dimethylethyl)-4-methyl]Phenol.5. Becaues of higher content in esters, triethyl citrate and diisooctyl phthalate were verificated. The effect of triethyl citrate showed low-high-low inhibition, and diisooctyl phthalate in higher concentrations inhibited germination and seedlings growth completely. The effects of diisooctyl phthalate on Portulaca oleraceas showed stronger than that of triethyl citrate.