Study On The Allelopathic Activity Of Extract From Clausena Lansium Seeds

Allelopathy can produce natural herbicides that are good environmental compatibility,low toxicity,less residue,high safety,unique mode of action,high selectivity and so on.Many allelochemicals that have herbicidal activity,insecticide activity and antibacterial activity are isolated from the seed,flesh and foliage of Clausena lansium,which has a good development and application value.Therefore,it is important to isolate allelochemicals with herbicidal activity from Clausena lansiumseeds.In this paper,allelochemicals with herbicidal activity from Clausena lansium was isolated and identified with silica gel column chromatography and bioassay-guided method.And physiological activityof tested plants with treatment of allelochemicals was studied from the aspects of defensive enzymes and metabolic changes.The results were shown as following:1.Seed germination and seedling growth of 6 tested plants(monocotyledonous plants:Echinochloa crusgalli,Oryza sativa,Bromus inermis;dicotyledonous plants:Portulaca oleracea,Bidens pilosa,Brassica pekinensis were tested under different concentrations of methanol extract from the seeds of Clausena lansium.The results showed that the extracts of different concentrations had inhibition effects on seed germination and seedling growth of tested plants.And the inhibition rate was positively correlated with the treatment concentration.At concentration of 10 mg/mL,the inhibition rates of the seed germination of tested monocotyledon and dicotyledon were 30.25%~42.38%,4.17%~22.46%,respectively and the allelopathic index were-0.30~-0.42,-0.04~-0.22,respectively,which indicated that the inhibition effect of extract on seed germination of tested monocotyledon was greater than that of dicotyledon.The inhibition rates of stem length of dicotyledon and monocotyledon were 22.92%~43.73%,63.24%~72.86%,respectively.The allelopathic index were-0.23~-0.44,-0.63~-0.73,respectively,which suggested that inhibition effect of extract on stem length of tested dicotyledon was greater than that of monocotyledon.The inhibition rates of dicotyledon and monocotyledon were 92.62%~98.46%,93.13%~97.32%respectively,and the allelopathic index were-0.93~-0.98,-0.93~-0.97,respectively,which meant that inhibition effects of extract on root length of tested plants were significant.But the difference between them had no significant difference.2.The bioassay results of different extract phases on tested plants using the small glass method showed that the allelopathic effects of extracts on the tested plants were ethylacetate phase>petroleum ether phase>chloroform phase?n-butanol phase>water phase.Allelochemicals with herbicidal activity from the high-polarity extract phase(ethyl acetate phase)of the methanol extract fromClausena lansium had been isolated.In order to isolate the low-polarity allelochemicals with herbicidal activity from Clausena lansium,the low-polarity extract phase(petroleum ether phase)was chosen as the further separation phase.3.Fraction B2,C4 were isolated from petroleum ether phase after the silica gel column chromatography.The shoots of Portulaca oleracea all were withered after treatment with fraction B2 at concentration of 0.5 mg/mL.And the allelopathic index was-1.The inhibition rates of root length and stem length of Portulaca oleracea after treatment with fraction C4at concentration of 0.3mg/mL were 80.48%and 75.36%,respectively.And the allelopathic effect was significant.The results showed that fraction B2,C4 had the strongest inhibition effect on the tested plants.However,the content and purity of fraction C4 were lower.So the fraction B2 was regard as a main allelochemicals.4.Fraction B2 was identified as myristicin after purified.5.At at concentration of 0.01~5 mg/mL,the inhibition activity of myristicin on root lengths of bromus inermis,Oryza sativa,Portulaca oleracea and Bidens pilosa were 5.1,5.1,28.4 and 8.3 times that of atrazine,respectively.The inhibition activity of myristicin on stem lengths ofabove tested plants were 14.1,1.5,121.7 and 9.3 times that of atrazine,respectively.6.Physiological activities of four tested plants(monocotyledonous:Bromus inermis,Oryza sativa;dicotyledonous:Portulaca oleracea,Bidens pilosa)were tested under treatment with myristicin at different concentrations.The results showed that the activity of SOD,CAT and soluble sugar content in monocotyledon increased first and then decreased.The activity of SOD,CAT and soluble sugar content in dicotyledon decreased significantly.The activity of POD,root,chlorophyll content and soluble protein content in tested plants decreased significantly.And malondialdehyde content in tested plants inc reased.The root activity of tested plants increased first and then decreased.7.Optimum chromatographic conditions for detection of myristicin with high performance liquid chromatography:detection wavelength=210nm,mobile phase:methanol/water=50/50,flow rate=1.0 mL/min,column temperature:30?8.Herbicidal activity of residue substances from Clausena lansium seeds after extacted with methanol was studied.The results showed that residue substances had good inhibition effect on Rumex japonicas,Eleusine indica,Acalypha australis,Setaria viridis,Polygonum hydropiper after treatment with high application amount.And inhibition rates of root length,stem length,fresh weight and dry weight of Setaria viridis were 37.87%,16.81%,21.42%and 33.07%at application amount of 66.7kg/667m~2.And inhibition effect was significant.