除草剂毒理学

HerbicideToxicology202023年，生产农药234.2万吨（折100%），同比增长18.8%。其中杀虫剂84.5万吨，占31.9%；杀菌剂19万吨，占7.1%；除草剂108.9万吨，占45%。

1第1页HerbicideToxicologyPartI:Introduction,definition

FactorsaffectingitsactivityAbsorptionandTranslocationHerbicideMetabolismPartII:ModeofAction2第2页PartIIntroductionAherbicideisapesticideusedtokillunwantedplants.Herbicidesarechemicalsthatinhibitorinterruptnormalplantgrowthanddevelopment.Weedicide

3第3页PartIIntroductionHerbicidescanprovidecost-effectiveweedcontrolwhileminimizinglabor.Understandinghowherbicidesworkprovidesinsightintohowtousethechemicalsandhelpsdiagnoseperformanceproblemsandrelatedinjurysymptoms.4第4页PartIIntroductionWeedsareproductofhumansociety.Primitiveman,thegathererandhunter,wasnotconsciousofweedsinthemodernsense.Contemporarymanhascreatedtheconceptofweedasaplantinaplacewhereitisnotwanted.5第5页HerbicideSelectivitySelectivity:Thepotentialforaherbicidetokillcertainplantswithoutinjuringothersiscalledselectivity.SelectiveherbicideNon-selectiveherbicideContactherbicideSystemicherbicide6第6页HerbicideSelectivityHerbicidesthatkillorsuppressthegrowthofmostplantspeciesarerelativelynonselective.Glyphosateandparaquathistoricallyhavebeenconsiderednonselectiveherbicides.7第7页HerbicideSelectivityHowever,glyphosateisahighlyselectiveherbicidewhenusedinconjunctionwithcropsthathavebeengeneticallyengineeredwithresistancetoglyphosate8第8页HerbicideSelectivityMostherbicidesusedincropproductionareselective.Herbicideselectivityisrelativeanddependsonseveralfactors,includingplantbiology,environment,herbicideapplicationrate,applicationtiming,andapplicationtechnique.9第9页HerbicideSelectivityHerbicideselectivitymaybebasedonherbicideplacement,differentialsprayretention,absorption,translocation,metabolism,oraninsensitivesiteofaction.10第10页1.FactorsaffectingherbicideactivityFactorsinfluencingherbicideactivityincludeapplicationrate,applicationtechnique,plantmaturity,andenvironmentalconditions.Inaddition,soilcharacteristicscanaffectsoil-activeherbicides.11第11页1.FactorsaffectingherbicideactivityMoistureandtemperatureareenvironmentalfactorsthatinfluenceactivityofsoil-appliedherbicides.12第12页1.Factorsaffectingherbicideactivity1).SoilmoistureSoilmoistureisimportantbecauseitinfluencesherbicideadsorptiontosoils.Therefore,theherbicideisunavailableforplantuptake.Adsorptionoccurswhenherbicidemoleculesadheretosoilparticlesandorganicmatter.Whileadsorbed,herbicidemoleculesareunavailableforabsorptionbyplants.13第13页1.FactorsaffectingherbicideactivityWatermoleculescompetewithherbicidemoleculesforadsorptionsitesonsoilparticlesandorganicmatter.Therefore,herbicideadsorptionishighestunderdrysoilconditions,andlowestinmoistsoils.Consequently,weedcontrolisgenerallybestwithmoistsoilconditionsbecausemoreherbicideisavailableforplantuptakeinthesoilsolutionorgaseousphase.14第14页1.Factorsaffectingherbicideactivity2).TemperatureTemperatureaffectstheactivityofsoil-appliedherbicidesprimarilybecauseofitsinfluenceontherateofseedgermination,emergence,andgrowth.15第15页1.Factorsaffectingherbicideactivity2).TemperatureSeedlingplantstendtobemoresusceptibleto

soil-appliedherbicidesundercoolconditionsthan

underwarmtemperaturesbecauseplantemergence

isdelayedandmetabolismisslowed.Ontheother

hand,extremelyhightemperaturessometimes

increasecropinjurysimplybyplacingtheplant

undermultiplestresses.16第16页1.Factorsaffectingherbicideactivity3).SoilcharacteristicsSoilcharacteristicsaffectingherbicideactivityaretexture,organicmatter,andpH.17第17页1.Factorsaffectingherbicideactivity3).Soilcharacteristics：Soiltexture:Herbicide

adsorptionisgreaterinfine-texturedsoilshighin

organicmatter

thanincoarse-texturedsoilslowin

organicmatter.Thus,alowerproportionof

herbicide

isavailableinthefine-texturedsoils,soahigher

herbicideapplicationrateisrequiredtoprovidethe

samelevelofweedcontrolasinacoarse-textured

soil.18第18页1.Factorsaffectingherbicideactivity3).Soilcharacteristics：Soiltexture:Atthesametime,thechanceofcropinjuryisgreateroncoarse-texturedsoilslowinorganicmatterbecauseahigherproportionoftheappliedherbicideisavailableforplantuptake.Soil-appliedherbicideratesmayneedtobeadjustedaccordingtosoiltextureandorganicmattercontent.19第19页1.Factorsaffectingherbicideactivity3).Soilcharacteristics：SoilpH:SoilpHinfluencestheavailabilityandpersistenceofcertainherbicidesinthesoil.SoilpHcanaltertheionicnatureoftheherbicidemolecule,whichinfluencesadsorption,solubility,andrateofherbicidebreakdown.20第20页1.Factorsaffectingherbicideactivity3).Soilcharacteristics：SoilpH:Thetriazineherbicides(atrazine莠去津)andsomeofthesulfonylureaherbicides(Amber醚苯磺隆,)aremoreactiveandmorepersistentinhighpHsoils(>7.0)thaninlowpHsoils.21第21页1.Factorsaffectingherbicideactivity4)EnvironmentalconditionsEnvironmentalconditionscanhaveatwo-foldeffectontheperformanceofpostemergenceherbicides.Higherhumidityandfavorabletemperaturesgenerallyresultingreaterherbicideabsorptionandactivityinplants.22第22页1.FactorsaffectingherbicideactivityEnvironmentalsoinfluencesherbicideefficacy

byaffectingplantgrowth.Plantsaregenerally

mostsusceptibletopostemergenceherbicideswhen

activelygrowing.Extremeenvironmentalconditions

thatslowplantgrowthandthickenleafcuticlesoften

increaseplanttolerancetoaherbicide.23第23页1.FactorsaffectingherbicideactivityCropinjuryfromaherbicide,however,canincreaseduringpoorgrowingconditionsbecauseofslowermetabolismanddetoxificationoftheherbicide.24第24页1.FactorsaffectingherbicideactivityThus,ifcroptoleranceisbasedontheabilityofthecroptorapidlymetabolizetheherbicide,thepotentialforcropinjurymayincreaseandweedcontroldecreaseifaherbicideisappliedwhenplantsarenotactivelygrowing.25第25页1.FactorsaffectingherbicideactivityForthisreason,mostherbicidelabelscautionagainstapplicationduringextremeenvironmentalconditions.26第26页1.Factorsaffectingherbicideactivity5)PlantsAnnualplantsareusuallymoresusceptibletoherbicideswhentheyaresmallthanwhentheyaremature.Astheymature,plantsdevelopthickerwaxlayersonleafsurfaces,reducingherbicideabsorption.27第27页1.Factorsaffectingherbicideactivity5)PlantsEstablishedperennialweedstendtobemoresusceptibletoherbicidesifappliedduringtheearlyfloweringstageofgrowthortoactivelygrowingplantsinthefall,probablybecauseapplicationatthesetimesresultsinthegreatesttranslocationoftheherbicidetotheroots.28第28页2.Absorption,TranslocationA)Foliarabsorption:cuticlewax(lipophilic):no-polarCuticlecutin(角质,hydrophilic):polarPectin(胶质):hydrophilic29第29页Foliarabsorption30第30页Foliarabsorption31第31页a).FoliarabsorptionAbsorptionoffoliar-appliedherbicidesviathestomata(气孔)canalsobeanimportantrouteofentry.32第32页a).FoliarabsorptionSprayadjuvantsoradditivesoftenimprovesprayretentionandabsorptionbyplantfoliagebyreducingthesurfacetensionofthespraysolution,allowingthespraydroplettospreadmoreevenlyovertheleafsurface.33第33页a).Foliarabsorption34第34页a).FoliarabsorptionHerbicideabsorptionmaybefurtherenhancedbyinteractingwiththewaxycuticularlayerontheleafsurface.35第35页a).FoliarabsorptionSprayadjuvantscanincreaseweedcontrol,butpotentiallycanreduceselectivitybyincreasingthesprayretentionandherbicideabsorptionbythecropmorethanbytheweed.Thus,sprayadjuvantsshouldbeusedonlyifrecommendedontheherbicidelabel.36第36页b).TranslocationinplantsContactherbicidesarenottranslocated.Contactherbicidesgenerallyareineffectiveforlong-termperennialweedcontrol.Systemicherbicidescanbetranslocatedtootherpartsoftheplanteitherinthexylem(木质部)orthephloem37第37页b).TranslocationinplantsThexylemisnonlivingtissuethroughwhichwaterandnutrientsmovefromtherootstotheshootsandleavesofplants.Translocationinthexylemisonlyupwardandoutwardinplantsfromtherootstotheleavesandleafmargins.Phloemisaliving,conductingsysteminwhichmaterialscanmovebothupwardanddownward.38第38页Translocation39第39页b).TranslocationinplantsHerbicidescanbetranslocatedinthexylem,thephloem,orboth.Herbicidestranslocatedonlyinthexylemaremosteffectiveassoil-appliedorearlypostemergencetreatmentsbecausetranslocationisonlyupward.Atrazine(莠去津)isagoodexampleofaherbicidethatistranslocatedonlyinthexylem.40第40页b).TranslocationinplantsPhloemtranslocatedherbicidesthatmovedownwardandsuppressrootandrhizome(根茎)growth,aswellastopgrowth,providethebestperennialweedcontrol.2,4-Disexampleofsystemicherbicidesthatwilltranslocateinthephloemandprovidegood,long-termcontrolofcertainperennialweeds.41第41页3.HerbicideMetabolismMetabolismisoneofthemostimportantwaysaplantcanescapethetoxiceffectsofaherbicide.Herbicide-tolerantplantsoftenhavetheabilitytometabolizeorbreakdownthechemicaltononactivecompoundsbeforeitcanbuilduptotoxiclevelsatthesiteofaction.42第42页3.HerbicideMetabolismSusceptibleplantsareunabletodetoxifyherbicides.Selectivityofmanyherbicidesisbasedondifferingratesofmetabolism.Metabolismcanbereducedincertainenvironmentalconditionssuchascoldweather.Reducedmetabolismofanherbicidecanbethecauseofcropinjury.43第43页4.AlteredSiteofActionAnalteredsiteofactioncanresultindramaticresistancetoaherbicide.Analteredsiteofactionreferstogeneticallydifferentplantbiotypesthathaveastructurallyalteredsiteofactionthatpreventsherbicidebindingandactivity.44第44页4.AlteredSiteofActionAtrazine(莠去津)isineffectiveonresistantbiotypebecauseaconformationalchangeinthechloroplastpreventsitfrombindingatthesiteofaction.45第45页PartII:HerbicideModeofActionHerbicidescanworkatvarioussitesinplants.Theygenerallyinterferewithaprocessessentialfornormalplantgrowthanddevelopment.Herbicidescanbeclassifiedbysiteofactionbasedonhowtheyworkandtheinjurysymptomstheycause.46第46页PartII:HerbicideModeofActionTobeeffective,herbicidesmust1)adequatelycontactplants;2)beabsorbedbyplants;3)movewithintheplantstothesiteofaction,withoutbeingdeactivated;4)reachtoxiclevelsatthesiteofaction.47第47页PotentialSitofActionPhotosynthesis(food)Respiration(energy)Aminoacids(proteins/growth)Lipids(cellmembranes)Pigments(energy/lightcapture)Mitosis(celldivision)48第48页PartII:HerbicideModeofAction1).PhotosynthesisInhibitors2).PigmentInhibition3).AminoAcidSynthesisInhibition4).LipidSynthesisInhibition5).CellMembraneDisruption6).GrowthRegulators7).SeedlingGrowthInhibitors49第49页50第50页1.PhotosynthesisInhibitorsPhotosyntheticinhibitorherbicidescontrolmanybroadleafandsomegrassweeds.Plantsarenotaffectedbytheherbicideuntilaftertheyemergeandbeginphotosynthesis.51第51页1.PhotosynthesisInhibitorsPhotosynthesisinhibitorsshutdownthephotosynthetic(foodproducing)processinsusceptibleplantsbybindingtospecificsiteswithintheplant'schloroplasts.Inhibitionofphotosynthesiscouldresultinaslowstarvationoftheplant.52第52页1.PhotosynthesisInhibitorsHowever,theplantexperiencesamorerapiddeaththatisbelievedtobeduetotheproductionofsecondarytoxicsubstances.Susceptibleplantstreatedwithaphotosyntheticinhibitordiefromabuildupofhighlyreactivemoleculesthatdestroycellmembranes.53第53页1.PhotosynthesisInhibitorsa、阻断电子由QA到QB旳传递：取代脲类，三氮苯类b、克制光合磷酸化：苯氟磺胺c、截获电子到NADP+旳传递：百草枯。54第54页1.PhotosynthesisInhibitorsPhotosystemII,siteATriazine:atrazine莠去津

simazine西玛津PhotosystemII,siteB:Phenylurea:linuron利谷隆

PhotosystemII,siteCbromoxynil溴苯腈,Bentazon苯达松55第55页1.PhotosynthesisInhibitorsTheselectiveactionoftriazine(三嗪类,如莠去津)herbicidesisprimarilydeterminedbydifferentialmetabolism.Plantspeciessuchascornandsorghumpossesstheglutathione-S-transferase(GST)enzymeandcanselectivelymetabolizetriazineherbicidesintonontoxicsubstances.56第56页1.PhotosynthesisInhibitorsSymptomologyInterveinalorveinal(叶脉)yellowingfollowedbydeathofplanttissuefromleafmarginsinwardPostemergenceapplicationscauserapidburningofplanttissueCropstoleranttopostappliedPI’smayexhibitspottedleafyellowingorbronzing57第57页1.PhotosynthesisInhibitorsSymptomBladex草净津;百得斯

Cotoran58第58页1.Symptom59第59页2.PigmentInhibitionThepigmentinhibitorherbicidesinterferewiththeproductionandprotectionofphotosyntheticpigments.Ultimately,chlorophyllproductionisinhibited,andplantfoliageturnswhite.Carotenoid类胡罗卜素60第60页2.PigmentInhibitionPigmentinhibitorspreventplantsfromformingphotosyntheticpigments.Asaresult,theaffectedplantpartsbecomewhitetotranslucent.ThenewlydevelopedfoliageofmanyplantspeciesissosensitivetoCommand(广灭灵)thatverysmallamountscanwhitennewplantgrowth.61第61页2.PigmentInhibitionTheseherbicidescausethegreenpigments(chlorophyll)inplantstobedestroyed.Withoutchlorophyll,plantscannotphotosynthesizeandwilldie.Theseherbicidesareprimarilyxylemtranslocated,sotheyaremosteffectiveaspreemergencetreatments.62第62页Chlorophylsynthesisinhibition63第63页2.PigmentInhibitionProtoporphyrinogenoxidase(原卟啉原氧化酶PPO)inhibitorAcifluorfen(杂草焚),fomesafen(虎威),Oxadiazon(恶草灵,农思它)Sunlightisnecessaryfortheseherbicidestokillorinhibitweeds.64第64页2.PigmentInhibitionPigmentinhibitorscausewhitefoliage(“albinogrowth”)insusceptibleplantsNewgrowthwillnotcontainthenormalgreenpigmentationnecessaryforphotosynthesisAlbino（白化）growthmaybeobservedwithinveinsandbetweenveins(primarilywithCommand)65第65页2.PigmentInhibitionCommandZorial66第66页3.AminoAcidSynthesisInhibitionTheseherbicidesinhibitaminoacidsynthesiswhichisnecessaryfortheformationofplantproteins.67第67页3.AminoAcidSynthesisInhibitionTheaminoacidsynthesisinhibitorsincludethefollowingherbicidefamilies:sulfonylureas(磺酰脲类),imidazolinones(咪唑啉酮类),sulfonamide(磺胺类),andaminoacidderivatives.Aminoacidsynthesisinhibitorsactonaspecificenzymetopreventtheproductionofspecificaminoacids,keybuildingblocksfornormalplantgrowthanddevelopment.68第68页3.AminoAcidSynthesisInhibition69第69页3.AminoAcidSynthesisInhibition(1)Theacetolactatesynthase(ALS乙酰乳酸合成酶)inhibitingherbicideshaveabroadspectrumofselectivityandareusedatlowratesassoil-appliedorpostemergencetreatmentsinavarietyofcrops.TheseherbicidesinhibittheactivityoftheALSenzyme,whichisinvolvedinthesynthesisofbranchchainaminoacids(leucine亮氨酸,ioleucineandvaline缬氨酸).70第70页3.AminoAcidSynthesisInhibitionAminoacidsareessentialbuildingblocksinproteinsandarerequiredforproductionofnewcells.ALSherbicidesarereadilyabsorbedbybothrootsandfoliageandtranslocatedinboththexylemandphloemtothesiteofactionatthegrowingpoints.Selectivityisbasedondifferentialmetabolismandsiteexclusion.71第71页3.AminoAcidSynthesisInhibition(2)TheEPSP(烯醇丙酮酰-莽草酸-磷酸合成酶)inhibitorherbicidesarereadilyabsorbedthroughplantfoliageandtranslocatedinthephloemtothegrowingpoints.TheseherbicidesinhibittheEPSPenzyme,whichisinvolvedinthesynthesisofthearomaticaminoacids(芳氨酸)(tyrosine酪氨酸,tryptophan色氨酸,andphenylalanine苯丙氨酸)72第72页3.AminoAcidSynthesisInhibitionGlyphosate(草甘膦,EPSP克制剂)isarelativelynonselectivepostemergenceherbicidethatisinactiveinthesoilbecauseofadsorption.GlyphosateresistantcropswithanalternativeEPSPenzymehavebeendevelopedthroughgeneticengineering.73第73页3.AminoAcidSynthesisInhibition(3)Liberty(草铵磷,glufosinate)isabroad-spectrumpostemergenceherbicidethathasnosoilactivity.Libertyinhibitstheactivityoftheglutaminesynthetaseenzymethatisnecessaryfortheplanttoconvertammoniaintoothernitrogencompounds.74第74页3.AminoAcidSynthesisInhibitionConsequently,ammoniaaccumulatesandglutaminelevelsdecrease.Plantdamageprobablyoccursduetothecombinedeffectsofammoniatoxicityanddeficiencyofaminoacidsrequiredforothermetabolicprocesses.Libertyhaslimitedtranslocation,sothoroughspraycoverageofsmallweedsgenerallyprovidesthebestperformance.75第75页3.SymptomologyInjurysymptomsongrassincludestunting,purplecoloration,andinhibitedrootsystemswith“bottle-brush”appearanceBroadleafplantsymptomincludesformationofredorpurpleleafveins,yellowingofnewleaftissueandblackeningofterminalgrowthInitialyellowingfollowedbydeathofaffectedtissue76第76页3.SymptomologyCadre“yellowflash”77第77页3.Symptomology78第78页4.LipidSynthesisInhibitionTheseherbicidesactbydisruptinglipidbiosynthesisingrassplants.Plantcellsandcellularorganellesallcontainlipidmembranes.Therefore,theseherbicidesaffectcellmembraneintegrityinthemeristematic(分生组织旳)areas.79第79页4.LipidSynthesisInhibitionLipidsynthesisinhibitorspreventtheformationoffattyacids,componentsessentialfortheproductionofplantlipids.Lipidsarevitaltotheintegrityofcellmembranesandtonewplantgrowth.Thelipidsynthesisinhibitorherbicidesinhibitasinglekeyenzymeinvolvedinfattyacidbiosynthesis.80第80页4.LipidSynthesisInhibitionThelipidsynthesisinhibitorherbicidesinhibitmeristematicactivitybyinhibitingtheacetyl-CoAcarboxylase(ACCase,乙酰辅酶A羧化酶)enzymethatisinvolvedinthesynthesisoflipidsandfattyacids.Fenoxiapro-p-ethyl骠马Easilytodevelopresistance81第81页4.LipidSynthesisInhibition82第82页4.SymptomologyInitialinjuryinmeristematicregionsoccurswherenewestleavesaredevelopingTheseregionswillturnchlorotic,whichisfollowedbynecrosisTheaffectedareawillbecome“rotted”andwilleasilyseparatefromrestofplantInjurywilldevelopslowly(7to14days)83第83页4.Symptomology“rotted”meristem84第84页5.CellMembraneDisruptionCellmembranedisruptersarepostemergencecontactherbicidesthatareactivatedbyexposuretosunlighttoformoxygencompoundssuchashydrogenperoxide.Theseoxygencompoundsdestroyplanttissuebyrupturingplantcellmembranes.Destructionofcellmembranesresultsinarapidbrowning(necrosis)ofplanttissue.85第85页5.CellMembraneDisruptionThecellmembranedisruptorherbicidesdestroycellmembranes,causingcellcontentstoleakoutanddesiccationofplanttissue.Onabrightandsunnyday,herbicideinjurysymptomscanoccurin1to2hours.86第86页5.CellMembraneDisruptionProtoporphyrinogenoxidase(原卟啉原氧化酶PPO)inhibitoraciflourfen杂草焚,fomesafen虎威,PhotosystemIelectrondiverters:paraquat百草枯87第87页5.CellMembraneDisruptionThecellmembranedisruptersareprimarilynontranslocatedherbicidesthatarelightactivated.Paraquat(百草枯)anddiquat(敌草快)arerelativelynonselectivechemicalsusedtocontrolallexistingvegetationandaspreharvestdesiccants.Theseherbicidesquicklyformhighlyreactivecompoundsintheplantsthatrupturecellmembranes,causingthefluidstoleakout.88第88页5.CellMembraneDisruptionThoroughspraycoverageisessentialforgoodpostemergenceweedcontrol.Becausetheyarenottranslocatedtotheroots,theseherbicidesareineffectiveforlong-termperennialweedcontrol.89第89页5.SymptomologyRapidyellowingfollowedbydesiccationofaffectedplanttissueSymptomsgenerallyappearfirstonleaftips．Driftoroff-targetapplicationmayshowspeckledleafburn90第90页5.SymptomologyBlazerInjuryonPeanutValorInjuryonPeanut91第91页5.Symptomology92第92页6.GrowthregulatorherbicidesTheseherbicidesmimicnaturalgrowthhormones,andthus,upsetthenaturalhormonebalanceinplants.Theyaffectseveralplantprocessessuchascelldivision,cellenlargement,proteinsynthesisandrespiration.93第93页6.GrowthregulatorherbicidesThekillingactionofgrowth-regulatingchemicalsisnotcausedbyanysinglefactor,butratherbythedisruptionofseveralgrowthprocessesinsusceptibleplants.2,4-Disverysensitivetocottonplant94第94页6.GrowthregulatorherbicidesSyntheticAuxins:2,4-D,MCPA(2甲4氯)AuxinTransportInhibitors:Diflufenzopyr(氟吡草腙)95第95页6.SymptomologyBroadleafplantstemtwistingandcurlingLeavesonbroadleafplantsexhibitcupping,crinkling,strapping,ordrawstringeffectSymptomsongrassplantsincludeleafrolling,crinkling,bracerootfusionandmalformation.Also,flowersterilityandmissinggrainincrops.96第96页6.SymptomologyMalformedbracerootsBlastedgrainheads97第97页7.SeedlingGrowthInhibitorsSeedlinggrowthinhibitorsinterferewithnewplantgrowth,therebyreducingtheabilityofseedlingstodevelopnormallyinthesoil.Herbicidesinthesefamiliesmustbesoil-applied.Theseherbicidesareonlyeffectiveonseedlingofannualorperennialweeds.98第98页7.SeedlingGrowthInhibitorsTheseherbicidesincludebothseedlingrootinhibitorsandshootinhibitors.(1)Therootinhibitorsinterruptcelldivision(mitosis)stoppingrootgrowthinseedlingplants.(2)Theshootinhibitorsdisruptproteinsynthesis,celldivision,cellenlargementandweakencellmembranes.(3)Themicrotubuleassemblyinhibitor.99第99页7.SeedlingGrowthInhibitorsTheseedlingshootandrootinhibitors(acetamides,suchasalachlor甲草胺,acetochlor乙草胺,butachlor丁草胺)Acetamide(乙酰胺)herbicidesareusedpreemergenceorwithshallowsoilincorporationtocontrolannualgrassesandsomebroadleafweedsinavarietyofcrops.Theacetamidesdonotcontrolemergedplants.100第100页7.SeedlingGrowthInhibitorsTheprimarysiteofabsorptionandactionoftheseherbicidesonbroadleafspeciesistheroots,whiletheprimarysiteofabsorptionandactionongrassspeciesistheemergingshoot.101第101页7.SeedlingGrowthInhibitorsTheacetamidesarenotreadilytranslocatedintheplant,soherbicideplacementandavailabilityareimportant.Themechanismofactionoftheacetamideshasnotbeenwelldefined,butappeartointerferewithnormalcellulardevelopmentinseedlingplants.(克制发芽种子α-淀粉酶及蛋白酶旳活性)102第102页7.SeedlingGrowthInhibitorsThemicrotubuleassemblyinhibitor:Dinitroaniline(二硝基苯胺):trifluralin(Treflan)氟乐灵Dinitroanilineherbicidesaregenerallyappliedpreplantincorporatedtocontrolannualgrassesandsomebroadleafweedsinmanycrops.Trifluralinneedtobeincorporatedtoavoidphotodecompositionandvolatilitylosses.103第103页7.SeedlingGrowthInhibitorsThedinitroanilineherbicidesareabsorbedbybothrootsandshootsofemergingseedlings,butarenotreadilytranslocated.Theemergingshootistheprimarysiteofabsorptionandactionongrassspecies.104第104页7.SeedlingGrowthInhibitorsTheseherbicides(dinitroaniline)aremitoticpoisonsthatinhibitcelldivision.Thus,themeristematicregions,suchasthegrowingpointsofstemsandroots,aremostaffected.Selectivitymaybebasedonmetabolism,aswellasherbicideplacementandtypeofemergenceofthegrassspecies.105第105页7.SymptomologyofRootInhibitorsRootsonsusceptibleplantswillbestubbyandthick,especiallylateralrootsRootlimitationmaycausestuntingofplantsandphosphorusdeficiencysymptomsBroadleafplantsmayhaveswollenhypocotyls(胚轴)106第106页7.SymptomologyofRootInhibitorsProwlInjuryonCorn107第107页7SymptomologyofshootInhibitorsGrasscropsmayleafoutunderground,leavesmayexhibitimproperleafunfurling,andcrinklingAffectedcropsmayshowerraticstandandheightBroadleafplantsmayexhibitleafpuckeringoradrawstringeffect108第108页7SymptomologyofshootInhibitorsDualInjuryonFieldCorn109第109页PartIII:MajorHerbicideThispartissupplementarymaterials.110第110页PartIII:MajorHerbicide2,4-Disacolorless,odorlesspowderusedasaherbicide.Therearemanyformsorderivativesof