Research On The Tolerance Of Submerged Macrophytes To Two Herbicides And The Removal Of Pendimethalin

In order to explore the causes of the degradation of submerged macrophytes in lakes and rivers and the purification of water polluted by herbicide by submerged macrophytes.In this paper,Elodea nuttallii,Ceratophyllum demersum,Hydrilla verticillata and Myriophyllum verticillatum as experimental materials,adopt laboratory hydroponic test,Physiological and biochemical reactions of submerged macrophytes under the conditions of different concentrations(0,0.1,0.2,0.5,1,2,4 mg·L^-1)of pendimethalin or bentazon were explored,removal rate of submerged macrophytes under the different concentrations(0,0.1,0.2,0.5mg·L^-1)conditions of pendimethalin were explored.The main conclusions are as follows:（1）Under the condition of the pendimethalin concentration was 0.1mg·L^-1,The physiological activities of Elodea nuttallii,Ceratophyllum demersum,Hydrilla verticillata were little affected;At pendimethalin concentrations ranging from 0.2 to 4 mg·L^-1,The contents of Chl,Chl.a and SP decreased,while the contents of Chl.b and Pro increased,it indicated that the normal physiological activities of the three plants had been affected;Under the concentration of 0.2mg·L^-1,the second day,The MDA contents of Ceratophyllum demersum increased significantly,while the MDA contents of Elodea nuttallii and Hydrilla verticillata unchanged,it indicated that Ceratop-hyllum demersum were better sensitive to pendimethalin than Elodea nuttallii and Hydrilla verticillata.（2）The damage degree to Elodea nuttallii,Ceratophyllum demersum and Hydrilla verticillata of pendimethalin was related to the time: respectively at low concentrations(≤1mg·L^-1)and lower concentration(≤0.5mg·L^-1)conditions,the MDA contents of Elodea nuttallii and Ceratophyllum demersum gradually increased with the time passed.At the concentration of 0.1mg·L^-1,the MDA contents of Hydrilla verticillata showed the trend of increased firstly and then decreased,on the tenth days,the content of MDA was slightly lower than that of the control group.On the second days,the SOD activities of the three plants was lower than that of CK,on the tenth days,the SOD activities of Elodea nuttallii and Ceratophyllum demersum were still lower than that of CK,while the SOD activities of Hydrilla verticillata were significantly higher than that of CK at the concentrations of more than or equal to 1mg·L^-1.The changes of the POD activities of the three plants increased firstly and then decreased.The results showed that the relationship among tolerance of the three plants to pendimethalin was as follows: Hydrilla verticillata>Elodea nuttallii>Ceratophyllum demersum.（3）On the second day,when the bentazon concentrations were less than or equal to 0.5mg·L^-1,the SOD,POD activities of Hydrilla verticillata and Myriophyllum verticillatum changed significantly,while Ceratophyllum demersum little changed,it indicated that Ceratophyllum demersum appear to be better tolerated than Myriophyllum verticillatum and Hydrilla verticillata.On the sixth day,with the increased of bentazon stress concentration,the greater inhibition of the Chl and Chl.a contents of Myriophyllum verticillatum,Ceratophyllum demersum and Hydrilla verticillata,it indicated that bentazon stress affected the photosynthesis of the plants.On the tenth day,with the increased of bentazon stress concentration,the SP contents of Myriophyllum verticillatum,Ceratophyllum demersum and Hydrilla verticillata were generally increasing inhibited,the Pro contents were generally increasing promoted,it indicated that bentazon affected the normal physiological activities of the three plants,the plants could resist bentazon stress by changing the osmotic potential.（4）The damage degree to Elodea nuttallii,Ceratophyllum demersum and Hydrilla verticillata of bentazon was related to the time: Hydrilla verticillata and Ceratophyllum demersum respectively at lower concentrations(≤0.5mg·L^-1)and low concentrations(≤2mg·L^-1)conditions,Ceratophyllum demersum at 0.1 and 0.5 mg·L^-1 concentration conditions,the MDA content of the three plants increased gradually;Hydrilla verticillata and Ceratophyllum demersum at higher concentrations(≥1mg·L^-1)and Myriophyllum verticillatum at 4mg·L^-1 concentration,The MDA contents of the three plants increased firstly and then decreased,It was speculated that high concentrations of bentazon stress might cause irreversible damage to the cytoplasmic membrane of plants.The SOD activities of the three plants were induced in varying degrees,the SOD activities of Hydrilla verticillata,Ceratophyllum demersum and Myriophyllum verticillatum respectively reach the maximum on the sixth,fourth and eighth days,it indicated that the relationship among sensitivity of the three plants to bentazon as follows: Ceratophyllum demersum>Hydrilla verticillata>Myriophyllum verticillatum.（5）The pH and pendimethalin removal rate in the plant treatment group were higher than those of the control group,the three plants had adsorption effect on pendimethalin.When the initial pendimethalin concentration was 0.1mg·L^-1,it had little effect on the physiological activities of the three plants,so the removal rate is the highest,the relationship was as follows: Hydrilla verticillata（89.53 ﹪）> Elodea nuttallii（84.28﹪）>Ceratophyllum demersum（83.96﹪）,1.47,1.39 and 1.38 times as much as that of the blank control group,in keeping with the relationship among the adsorption rate of three plants.It indicated that plants play an important role in the removal of pendimethalin.We can priority select Hydrilla verticillata as repair plants in the lower concentrations of pendimethalin pollution,followed by Elodea nuttallii and Ceratophyllum demersum.