Study On Seed Biology,seedling Stress Resistance And Chemical Control Technology Of Ipomoea Purpurea

Ipomoea purpurea was an annual climbing herb which became noxious weed after it introduced as a horticultural crop.Ipomoea purpurea occurred in maize,cotton and orange field,the harm was serious in some regions.In order to determine the regularity and the harm character of Ipomoea purpurea and formulate the scientific and effective control strategies,the seed biology of Ipomoea purpurea was studied,including the influence of environment factor（temperature,light,p H,water potential,salt and burial depth）on germination,seed dormancy characteristics and the method of breaking seed dormancy.We also studied the influence of salt stress and drought stress on the seedling growth and the activity of antioxidase.By whole plant dose-response test we evaluated the herbicidal activity of nine soil-applied herbicides and nine foliar-applied herbicides.We also evaluated their safety to crop.The main result were as follow:（1）The effect of temperature,light,p H,water potential,salt concentration and burial depth on seed germination were studied by petri dish germination trial and pot trial.The results showed that temperature could influence the germination of Ipomoea purpurea seeds.Seeds could germinate between 10～30℃,but could not germinate at 5℃.The germination rate was highest at25℃,which could reach 95.33%.Light was not necessary for the germination.There was not significant difference in germination under the all-light,all-dark and half-light.The Ipomoea purpurea seeds could germinate between p H 4～10,the germination rate was highest at p H 7.The Ipomoea purpurea seeds showed tolerance under the salt stress,germination rate was 50%at the salt concentration of 160.24 mmol/L.The seeds could not germinate at the salt concentration of320 mmol/L.The Ipomoea purpurea seeds were sensitive to the change of water potential,germination was 50%when water potential was-0.182 MPa.Seeds could not germinate when water potential was-0.8 MPa.The emergence rate decreased by the increase of burial depth.The emergence rate was highest when the burial depth was 2 cm.（2）The dormancy characteristics of seeds were studied by petri dish germination trial,we also studied the effect of different treatment on seed dormancy.The results showed that freshly harvested Ipomoea purpurea seed would dormancy,the germination rate was lower than seeds harvested last year.Different method had different effect on seed dormancy.In physical method,rubbing seed coat had the best effect on the breaking dormancy of seeds,the germination rate was36%higher than control after treatment,and the water absorption rate of seeds was also significantly improved after treatment.The germination rate was 22%higher than control after soaking in 70℃water.The germination rate of seeds stored at 4℃was 6.67%higher than control,but the effect was not significant.In chemical method,10 g/L KNO₃had the best effect on the breaking dormancy and the germination rate was 28%higher than control after treatment.The next was soaking seeds in sulfuric acid for 30 min,and the germination rate was 9.34%higher than control after treatment.The germination rate was increased by 5.34%after Na OH treatment.By using plant growth regulators,the germination rate was 20%higher than control after soaking in1000 mg/L GA₃for 12 h.IAA had limited effect on breaking dormancy of seeds,and the germination rate was 8.67%higher than control after control.When ultrasound power was 600 W and ultrasound time was 25 min,the germination rate was increased by 37.34%,and the dormancy was broken obviously.These results indicated that the dormancy of Ipomoea purpurea seeds was mainly caused by seed coat inhibition.（3）The effect of plant height,root length,aerial part fresh weight,root fresh weight and activity of protective enzyme under different stress was studied by pot trial.The results showed that plant height,root length,aerial part fresh weight and root fresh weight of Ipomoea purpurea seedlings decreased in different levels under the different levels of salt stress.The deeper salt stress,the stronger the inhibition effect.With the increase of stress time,the activity of POD and CAT in the seedlings increased slowly under low salt stress,and the activity of SOD,POD and CAT in other treatments increased first and then decreased.At the same stress time,the activity of the three protective enzymes increased first and then decreased as the salt stress increased.Under different levels of drought stress,the change of plant height,root length and biomass of Ipomoea purpurea seedlings were basically same as those under salt stress,but drought stress had greater inhibition on physiological indexes.By the increase of stress time,the activity of CAT in the seedlings increased slowly under low drought stress,and the change of the SOD,POD and CAT activity in other treatments were basically the same as those under salt stress,but the increase of enzyme activities was significantly higher than that under salt stress.（4）The herbicidal activity and the safety to crop were studied by whole plant dose-response experiments.In nine soil-applied herbicides,isoxaflutole 20%SC,thiencabazone-methyl·isoxaflutole 26%SC,saflufenacil 70%WG and sulfentrazone 50%SC had the best control effect on Ipomoea purpurea,GR₉₀were much lower than their recommend dose.Metribuzin 480g/L SC and acetochlor 900 g/L EC had a poor control effect on Ipomoea purpurea,GR₉₀were higher than recommend dose.The GR₉₀of all nine foliar-applied herbicides were lower than recommend dose.Fluroxypyr 200 g/L and fomesafen 250 g/L AS had the best control effect on Ipomoea purpurea,GR₉₀were much lower than recommend dose.The selective index of all herbicides for test was higher than 2.All herbicides for test were safety to their crop.The safety of thiencabazone-methyl·isoxaflutole 26%SC and atrazine 38%SC were the best for maize,the safety of saflufenacil 70%WG and fomesafen 250 g/L AS were the best for soybean.