Toxicity Of Commonly Used Herbicide Bensulfuron-methyl To Anabaena Azotica

Anabaena azotica is a beneficial cyanobacteria without toxins,it can improve soil fertility by fixing nitrogen from atmosphere and was widely used in the weed control and clean energy.Bensulfuron-methyl(3-(4,6-dimethoxy pyrimidine-2-base)-1-(2-methoxy methyl benzyl)sulfonylurea))is a sulfonylurea herbicide,which is widely used in agriculture for nearly 30 years.Sulfonylurea herbicides destruct the synthesis of valine,leucine and isoleucine by inhibiting the acetolactate synthase in plants,thereby inhibiting protein synthesis,hinder cell division,and eventually lead to the death of plants.Long-term usage of sulfonylurea herbicide has caused serious effect on non-target organisms has been drawn increasingly attention in recent years,but there are few reports about the growth,cell morphology and DNA damage et al.So we adopt a great deal of technology in Toxicology,Cytology,Physiological and Biochemical and Molecular biology on A.azotica studies.Our experiments contain: the effect of different concentrations of bensulfuron-methyl on growth,photosynthetic pigments of A.azotica;the study on cell morphology,antioxidant enzyme system and enrichment and degradation effect of A.azotica;the effect on DNA damage and field application and so on.The results are as follows:1.The growth effect of bensulfuron-methyl on A.azotica:Low concnentrations(0.00001-0.1mg/L)of bensulfuron-methyl stimulate growth of A.azotica and cell numbers,growth rate,dry weight and photosynthetic pigment contents increasing steadily,but high concentrations(1mg/L and 10 mg/L)significantly inhibited.2.Effect of bensulfuron-methyl on cell morphology of A.azotica:Cyanobacteria cells can grow well under low concentrations(0.0001-0.1mg/L)of bensulfuron-methyl,and heterocyst numbers keep more than control,high concentrations(1mg/L and 10 mg/L)had caused the yellowing,damage and even disintegration of cells and the cell life cycle shortened significantly.3.The enrichment and degradation ability of A.azotica on bensulfuron-methylA.azotica had a high enrichnment and degradation ability on bensulfuron-methyl.The highest enrichment quantity can reach 22% at 96 h and the maximum degradation rate at 168 h was as high as 10.7%.The biological enrichment coefficient of A.azotica was higher,which further confirmed that A.azotica has the enrichment and degradation ability of bensulfuron-methyl.4.Effect of bensulfuron-methyl on antioxidant system of A.azoticaBensulfuron-methyl significantly inhibited the growth of A.azotica,and keep the enzyme activity at a higher level.The CAT and POD activity increased at the first 96 h and SOD at 72 h then continued to decline at low concentrations.MDA content of A.azotica sustained increasing and significantly higher than control and reached the peak value at 168 h,the MDA content of higher groups were much higher than lowers.5.Effect of bensulfuron-methyl on DNA damage of A.azoticaUsing comet assay method to study the DNA damage effect of different concentrations of bensulfuron-methyl on A.zotica,analysis,calculated and determined the comet tail length and tail moment and so on using the comet images,then deduced that A.azotica had less DNA damage under low concentrations but high concentrations opposite.6.The paddy application effect of bensulfuron-methyl on A.azoticaBased on the field experiment,we explored the optimal combination mode between bensulfuron-methyl and A.azotica.While rice planting,sprayed bensulfuron-methyl at the same time and discuss the optimal time to put in A.azotica during 0-45 d.Finally assured that put in A.azotica after rice planting 30 d can obtain better ecological and economical benefits.This study reveals the toxic effect of bensulfuron-methyl to A.azotica,enrich the cyanobacterial testing methods and has an important academic value.It also provide a scientific basis for rational usage of herbicides for agriculture and has an essential application value.