Studies Of Trifolium Repens L.allelopathy On Weeds

The phenomenon-plants or microorganism has a direct or indirect, beneficial or bad affect on other plants or microorganism through releasing some special chemica(lallelochemical)into circumstance is called allelopathy. Allejopathy is a very common and important ecological mechanism existed in nature. The deep research on plant allelopathy has a important meaning on knowing the plant community and succession, logical application of agricultural cultivation system, exploitation of weeds-control by biology and new style pesticide.White clover(Trifolium repens L.)is a vivacious and leguminous plant, came from Europe, introduced in our country and planted far and wide. White clover has a strong reproduce ability and can be produced all year, now it is grown as a kind of grazing, green manure or lawn diffusely.The white clover can enhance the fertility, control weeds, enhance the ability of biological control when planted in orchard. Because it has the high ability of flexibility and revegetation, can form a thick grass layer, no matter being planted as pasture or lawn, can form the single community of white clover, and few weeds among them. This text studied the allelopathy of the white clover on weeds so as to supply the thinking ways of the logical application of allelopathy, exploitation of weeds-control by biology and new style herbicide. The research result as follows.1. The allelopathic effects of aqueous extract, volatile oil and root exudates of White clover (Trifolium repens L.) were studied on four crops: Abutilon theophrasti Medic., Echinochloa crusgalli L. ,Amaranthus retroflexux L. and Trifolium repens L.. The result showed that three different extracts inhibited the germination rate of seeds and inhibited the growth of seeding and young root. The experiment showed that White clover existed obvious allelopathy and autotoxidity effect.2. In order to ascertain the allelopathy of T.repens on weeds, the allelopathic effect of aqueous extract from the aerial part and root of T. repens. with different concentrations on the germination rate, physiological and biochemical mechanism of germinating seeds of Abutilon theophrasti Medic. and Echinochloa crusgalli L. were studied. The result showed that both of the aqueous extract from aerial part and root of T. repens inhibited the germination rate of weed seeds, root activity and respiratory rate , the activities of superoxide dismutase peroxidase and catalase of germinating seeds, enhanced the activity of peroxidase and the content of malondialdehyde. The germination rate reduced by 56% when barnyardgrass seed was dealt with 0.1 g/mL aqueous extract from the aerial part, the activities of superoxide dismutase peroxidase and catalase of germinating seeds were reduced by 40.63%,6.28%, the root activity and respiratory rate were reduced by 40.63%,36.28%, the activity of peroxidase and the content of malondialdehyde were enhanced by 32.30%,87.40% at the same time. The allelopathy became stronger along with the concentration of aqueous extract increasing, the allelopathy of aqueous extract from the aerial part of T. repens on two weeds is higher than the aqueous extract from the root of T. repens, the allelopathy on E. crusgalli is higher than on A. theophrasti.3. A preliminary analysis of allelochemicals showed there were plenty of o-hydroxybenzene and m-hydroxybenzene in white clover. As the age of white clover increasing, the allelopathic effects of aqueous extracts from the aerial part enhanced, the content of hydroxybenzene increasing and the activity of PAL showed the trend of increasing.4. It,s allelchemicals were isolated through extraction, thin-layer chromatography, and column chromatograpathy. After the white clover was infused in ethanol and evaporation, the leavings was dissolved by water. The aqueous extract was extracted by petroleum,chloroform, ethyl acetate and n-Butanol successively, and the bioassay showed that the chloroform phase has obvious inhibitory effect, the inhibitory rate was 44.32%,88.08% on Abutilon theophrasti M., seedling length and root length, 82.08%,92.16% on Echinochloa crusgalli L., seedling length and root length, and the Amaranthus retroflexux L., germination rate is 0, the secondly was ethyl acetate phase. The chloroform phase was isolated into 7 phases by column chromatograpathy, and the bioassy showed that the 1 phase has strong inhibitory effect, was 91.01% on Abutilon theophrasti M., root length, 51.35%,63.93%on Echinochloa crusgalli L, seedling length and root length, and the Amaranthus retroflexux L.,germination rate is 0, the secondly was 2 phase and 5 phas, and next we continued iaolated these two phases.