Study On The Discipline Of Fluorescence Response To Herbicides

The residue and migration of herbicides in soil and water have caused environmental pollution.The effect of single herbicides and mixed agent on microalgae photosynthetic characteristics in aquatic ecosystem,the synergism of ammonium sulfate additive on herbicide,and the biological toxicity of herbicides to microalgae was studied in this paper.This experiment used atrazine,diuron,propanil,bentazone as representative herbicide,Chlorella pyrenoidosa,Microcystis aeruginosa and Scenedesmus obliquus as the research object,Through the research and analysis of 3 microalgae log phase,the best response time of microalgae on herbicide in the optimal detection conditions,chlorophyll fluorescence parameters and the change of chlorophyll content,to explore the response mechanism of 4 kinds of herbicide toxicity to microalgae.The results showed that:1)The adjustment period?lag phase?of Chlorella pyrenoidosa was 1⁵ days,and the logarithmic phase started from the sixth days.The adjustment period of Microcystis aeruginosa was 1⁷ days,and the logarithmic phase started from the eighth days.The adjustment period of Scenedesmus obliquus was 1⁶ days,and the logarithmic phase started from the seventh days.2)The best response time of Chlorella pyrenoidosa to atrazine,diuron,propanil and bentazone were 10 min,10 min,40 min,50 min.Microcystis aeruginosa corresponded to:40 min,10 min,20 min,20 min.Scenedesmus obliquus corresponds to:40 min,60 min,60min,10 min.3)The sensitivity of 3 microalgae to herbicides toxicity was different,and the changes of chlorophyll fluorescence parameters and chlorophyll content were compared.It was found that Chlorella pyrenoidosa was more sensitive to herbicide response than Microcystis aeruginosa and Scenedesmus obliquus,and could be used as monitoring algae for herbicides.4)The additive concentration of ammonium sulfate,temperature,pH value will affect the response of the algae chlorophyll fluorescence parameters and chlorophyll content to herbicides?atrazine and bentazone?.In the conditions of optimal concentration of ammonium sulfate(atrazine:1?g·L^-1,bentazone:5?g·L^-1),temperature?40??and,pH value?pH=5?the parameters changed significantly.At the same time the additives of ammonium sulfate on herbicides?atrazine and bentazone?have synergistic effect,additives of atrazine group on Scenedesmus obliquus maximum photosynthetic efficiency?Fv/Fm?decline rate was 2.8 times than non additive group,the decrease of chlorophyll content was 2.4 times than the non additive group decreased.5)The atrazine and diuron mixture on Chlorella pyrenoidosa and Scenedesmus obliquus chlorophyll fluorescence parameters Fv/Fm,the actual photosynthetic efficiency Y?II?,the photochemical quenching coefficient?qP?and the absolute electron transport rate?ETR?have antagonistic effect.While atrazine and propanil,atrazine and bentazone on Chlorella pyrenoidosa,Microcystis aeruginosa and Scenedesmus obliquus Y?II?,qP and ETR have synergistic effect,and atrazine propanil mixture had synergistic effect on Scenedesmus obliquus Fv/Fm.