Study On Allelochemical 4,8-DHT For Woodland Weed Control

4,8-Dihydroxy-1-tetralone(4,8-DHT)is an allelochemical of Carya cathayensis exocarp,which has been proven to have herbicidal activity and has not been verified in the field.In order to determine the herbicidal activity of 4,8-DHT in woodland and its effect on the physiological and biochemical indexes of weeds,the experiment was set up according to the Pesticide for the field efficacy trials(1)(GB/17980.48-2000).Water and 2458 g ai/ha glyphosate isopropylamine salt were used as negative and positive controls respectively.The weed number,coverage and plant control effect were selected to compare the effect of 4,8-DHT in woodland.The seed germination,biomass,physiological and biochemical indicators were selected to analyze the effect of 4,8-DHT on woodland weeds in laboratory.The results were as follows:(1)The herbicidal activity of 4,8-DHT presented weeds selectivity in weed control.4,8-DHT with concentration of 1920 g ai/ha had 100%control effect on L.procumbens,G.affine,P.asiatica,C.hirsuta and G.pensylvanicum in C.yedoensis woodland,and had 100%control effect on H.auricularia in L.indica woodland.(2)266.7 g ai/ha 4,8-DHT could reduce the germination potential of five tested weeds,up to 0%,and significantly inhibited the germination rate of F.miliaceae,E.indica and H.auricularia(P<0.05).4,8-DHT had the strongest inhibitory effect on the apparent biological indicators of L.procumbens.The inhibition rate on root length,stem length,root fresh weight and total fresh weight of L.procumbens were 77.6%,47.8%,100.0%and 30.1%,respectively.(3)Under the treatment of 266.7 g ai/ha 4,8-DHT,the water content of H.auricularia leaves decreased by 17.7%,the amount of chlorophyll a,chlorophyll b and total chlorophyll decreased by 1.8 ?g/g,0.7?g/g and 2.5?g/g respectively.Root activity,SOD,POD and CAT activities first increased and then decreased,finally decreased to 40.3 TTF mg·g/Fwh,18.0 Ug/Fw,6.2 Ug/Fw,33.9 Ug/Fw/min on the 8th d.The content of superoxide anion,soluble protein and MDA gradually increased to 160.0 nmol/ml,7.07 mg/g and 23.0 nmol/gFw.(4)With the treatment of 266.7 g ai/ha 4,8-DHT,the root activity of L.procumbens decreased by 20.2 TTFmg-g/Fwh,the leaf water content decreased by 17.7%,and the amount of chlorophyll a,chlorophyll b and total chlorophyll decreased by 9.0?g/g,14.0 ?g/g and 23.0 ?g/g respectively.Superoxide anion content,SOD,POD and CAT activity first increased and then decreased,finally decreased to 195.5 nmol/ml,5.2 Ug/FW,45.6 Ug/FW and 48.9 Ug/FW on the 8th d.The content of soluble protein and MDA gradually increased,and the content on the 8th day was 0.49 mg/g and 30.82 nmol/gFw respectively.