Engineering4(2018)610–616Contents lists available at ScienceDirectEngineeringResearch
WatershedEcology—Article
ApplicationofHydrogenPeroxideasanEnvironmentalStressIndicatorforVegetationManagement
TakashiAsaeda?,SenavirathnaMudaligeDonHiranyaJayasanka,Li-PingXia,AbnerBarnuevo
DepartmentofEnvironmentalScienceandTechnology,SaitamaUniversity,Saitama338-8570,Japanarticleinfoabstract
Adaptive vegetation management is time-consuming and requires long-term colony monitoring to obtain reliable results. Although vegetation management has been widely adopted, the only method existing at present for evaluating the habitat conditions under management involves observations over a long period of time. The presence of reactive oxygen species (ROS) has long been used as an indicator of environmen-tal stress in plants, and has recently been intensely studied. Among such ROS, hydrogen peroxide (H2O2) is relatively stable, and can be conveniently and accurately quanti?ed. Thus, the quanti?cation of plant H2O2 could be applied as a stress indicator for riparian and aquatic vegetation management approaches while evaluating the conditions of a plant species within a habitat. This study presents an approach for elucidating the applicability of H2O2 as a quantitative indicator of environmental stresses on plants, particularly for vegetation management. Submerged macrophytes and riparian species were studied under laboratory and ?eld conditions (Lake Shinji, Saba River, Eno River, and Hii River in apan) for H2O2 formation under various stress conditions. The results suggest that H2O2 can be conveniently applied as a stress indicator in environmental management.
ó 2018 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY-NC-ND license
Articlehistory:Received11December2017Revised17May2018Accepted3September2018Availableonline8September2018Keywords:MacrophytesRiparianzoneEnvironmentalgradientStressindicatorReactiveoxygenspeciesHydrogenperoxide1.IntroductionVegetationmanagementisanimportantpracticearoundtheworldfortherestorationofvegetation,theprotectionofendangeredspecies,andweedcontrol.Exceptforinstancesofmechanicalweedcontrol,adaptivemanagement-basedmethodsareused;aftertreatmentsareiterativelyimplemented,suchmeth-odsrequirelong-termmonitoringoftheconditionsofacolony.Althoughthisisthemostfundamentalmethodofidentifyingplantconditions,severalyearsandlargebudgetsarerequiredtoobtainreliableresults.Theprosperityorshrinkageofaplantcommunitydependsontherelationshipbetweenitsenvironmentalstressesanditstolerance.Iftherelativeintensityoftheoverallenviron-mentstresscausesthetoleranceofaplantcommunitytochange,thisindicatesthepreferredhabitatconditionlevel.Thus,evaluat-ingtheenvironmentalstressesimposedonaplantcommunityisessentialinordertounderstandthecurrentconditionoftheplantsandpredicttheirfutureprosperity.?Correspondingauthor.E-mailaddress:asaeda@mail.saitama-u.ac.jp(T.Asaeda).Theeffectofenvironmentalstressonplantshasrecentlybeenintenselystudied,resultinginreportsofseveralplantbodyfeaturesbeingsubjectedtostresses[1,2].Theaccumulationofreactiveoxygenspecies(ROS)providesclearevidencefortheiden-ti?cationofenvironmentalstressesonplants,althoughitisrarelyelucidatedinarealisticenvironment[3–5].TheROShydrogenper-oxide(H2O2)isgeneratedatvarioussiteswithintheplantcells,suchaschloroplasts,mitochondria,peroxisomes,cellmembranes,andsoforth.Moreover,itisrelativelystableandcanbetrans-portedthroughbiologicalmembranes[2].Comparedwithother?à)andthehydroxylradicalROS,suchasthesuperoxideradical(O2?(OH),H2O2canbeconvenientlyquanti?edwithminimumlosses;therefore,ithasbeenwidelyusedtoquantifylevelsofROSdamageorstressinmanyplantstudies.TheobjectiveofthisstudywastoelucidatetheapplicabilityofH2O2asaquantitativeindicatorofenvironmentalstressesinplants,andtodirectlyapplyittounderstandingthelevelofenvi-ronmentalstress.Therefore,thegenerationofH2O2insubmergedmacrophytesandriparianvegetationunderlaboratoryandnaturalconditionswasstudied.ThesubmergedmacrophytesEgeriadensa,Vallisneriaasiatica(V.asiatica),Potamogetoncrispus(P.crispus),andElodeanuttallii(E.nuttallii)werestudiedforturbulenceresponses,T.Asaedaetal./Engineering4(2018)610–616611andMyriophyllumspicatum(M.spicatum)wassubjectedtohydro-gensul?de(H2S)stressunderlaboratoryconditions.P.anguillanusandEgeriadensaweresubjectedtolight-responsetestinginnatu-ralconditionsatLakeShinji,SabaRiver,andEnoRiverinJapan.TheriparianvegetativeconditionsofPhragmitesaustralis,Phragmiteskarka,Miscanthussacchari?orus,Salixpierotii,andJuglansmandshuricavar.sieboldianawereobservedalongtheHiiRiverinJapan.2.Materialsandmethods2.1.PlantstockcultureEgeriadensa,V.asiatica,P.crispus,E.nuttalliiandM.spicatumwerecollectedfromnearbyriversandwashedwithdechlorinatedtapwatertoremoveattacheddebris.Whenalgaewereattached,theplantswerecarefullycleanedwiththeaidofforceps.Theplantswerethenplantedandculturedinglasstanksforseveralmonthsunderlaboratoryconditions((25±2)°Cand12/12lightdurationwithaphotosyntheticphoton?uxdensity(PPFD)of100–120lmolámà2ásà1using?uorescentlamps).Theglasstankswerethoroughlywashed,layeredwithcommercialsand(90%particleslowerthan1mmdiameter)asasubstrate,andprovidedwith5%Hoaglandsolutionasthenutrientsource.Priortotrans-plantation,theplantswereobservedforthepresenceofalgae,andalgae-freecultureswereselectedforexperiments.2.2.TurbulencestressV.asiatica,P.crispus,andE.nuttalliiwereusedinexperiments.Theexperimentswereconductedinglasscontainers(5.7cm?15.7cm,24.5cmheight),witha4cmlayerofthoroughlywashedcommercialsand.Similarlysizedapicaltips(3–5cmlong)werecutfromtheculturetanksandplantedsixperexperimentaltank.Thewaterlevel(nutrientmedium:5%Hoaglandsolution)ofeachtankwasmaintainedat17cmabovethesubstrate.Turbulenceconditionsweregeneratedusingaverticallyoscillatinghorizontalgridwithanoscillatingfrequencyof2Hzandanamplitudeof3cm,accordingtopublishedliterature[6,7].Themicrocosmemployedforgeneratingturbulencewasrelativelysmall;however,workatthisscalewasnecessaryinordertooper-atetheDCmotorsunderspeci?cations.Thehorizontalvelocitypro?leofthemicrocosmwasmeasuredusingatwo-dimensionalelectromagneticcurrentmeter(SF-5712,TokyoKeisokuCo.,Ltd.,Japan)fromsixdifferentpointssymmetricallydistributedoverthearea.Ateachpoint,velocity?uctuationsweremonitoredatthreedepths(5,10,and15cmfromthewatersurface),andthetur-bulencevelocitywascalculatedasdescribedpreviouslyforeachdepthbyaveragingallsixmeasurements.Theplantswereacclimatizedtotheexperimentalconditions((25±2)°C,12/12lightdurationwithaPPFDof100–120lmolámà2ásà1using?uorescentlamps)for1weekbeforeturbulenceconditionswereimplemented.Afteracclimatization,theplantswerecontinuouslyexposedtoturbulencetreatmentsfor21d.Upontreatmentcompletion,bothcontrolandtreatmentsampleswereimmediatelysubjectedtochemicalanalyses.2.3.Hydrogensul?destressTwoM.spicatumapicaltips($6cmlong)wereclipped,pluggedintosiliconespongeclumps,andplacedin500mLglassbeakers.Theculturemediumwas5%Hoaglandsolutionwithoutadditionalsubstrate.Theplantsgrowinginbeakersweresubjectedto0(control),0.1,0.2,0.5,and1.0mmoláLà1H2Sexposureintriplicates.FortheH2Streatment,sodiumhydrogensul?de(NaHS)wasappliedasaH2Sdonor.DissolvedH2SlevelswerecolorimetricallydeterminedbythemethylenebluemethoddescribedinRef.[8]usingadiaminereagent:4mLofmixeddiaminereagentwerereactedwith50mLwatersamples,andtheamountofabsorbancewasmeasuredspectrophotometricallyat670nmafter20min.TheNaHScalibrationstandardwasusedtoobtainH2Sconcentrations,andtheresultswereexpressedinmmoláLà1.Theculturemediumforeachtreatmentwasrenewedat24hintervals,accountingfortheshorthalf-lifeofH2S[9].ThepHofthesolutionwasmaintainedina5.0–5.5rangebyadding1moláLà1NaOHorHClasrequired[10,11].Theinitialand?nalshootlengthsweremeasuredandtheshootgrowthrate(SGR)wascalculatedbydividingthediffer-encebetweenthe?nalshootlengthandtheinitialshootlengthbythedurationoftheexperiment.2.4.Fieldobservations2.4.1.SamplingsitesLakeShinjiisabrackishwaterlakeinwesternJapanthatisfamousforitshighyieldofCorbiculabivalves.Recently,P.anguillanusmacrophyteshavegrownthicklyacrossthelake;thisdisturbstheCorbiculaharvests,whicharetakenbyscratchingthebottomsediment[12].Thus,thecauseofthisintensivemacro-phytegrowthanddistributionmustbedeterminedforvegetativemanagement.Observationswereconductedon22August2017,andmacrophyteswereharvestedalongtwotransectsfromtheshorelinetoadepthof2.5m.Recently,thickstandsofaninvasivemacrophyte,Egeriadensa,havedevelopedyearlyinseveralriversinwesternJapanwherenomacrophytesgrewpreviously[13].Thishashinderedthespawningofayu?sh,oneofthemostfavoredfreshwater?shinJapan,andhassigni?cantlydecreasedcatches.FieldobservationswereconductedatseveralsectionsoftheSabaandEnoRivers.Samplingandobservationswereconductedattheselocationson11–15Juneand16–17September2016.HiiRiversamplingsweretakenon11–13October2016.SamplingsectionswereselectedineachriverwhereeitherEgeriadensacreatedathickandhomoge-neousstand,orthevelocitywasrelativelyhighandtheamountofbiomasswassmall.Ateachofthesamplingsections,samplingandmeasurementswereconductedevery2–5m.Streamvelocitiesweremeasuredandrecordedusinganultrasoniccurrentmeterat20%(abovethecolony)and80%(insidethecolony)ofthetotalwaterdepth.2.4.2.SamplingproceduresforsubmergedmacrophytesInthe?eld,P.anguillanusplantsampleswerecollectedfromtwotransects(Tr1andTr2)atdifferentdepthsandstoredinacoolboxcontainingdryice.Collectedsamplesweretransportedtothelaboratoryintheshortestpossibletimeforchemicalanalyses.Inaddition,biomasswascollectedintriplicateforeachquadrat(0.5m?0.5m).ThelightintensityorPPFDinthewaterwasmea-suredusingaportablequantum?uxmeter(MQ-200,ApogeeInstruments,Inc.,Logan,USA)at10cmdepthincrementsfromthebottomtothetopofthewatercolumn.Furthermore,thepH,turbidity,temperature,anddissolvedoxygen(DO)weremeasuredusingaportablewaterqualitymeter(U-53,Horiba,Ltd.,Japan).AsubstantialamountofROSisgeneratedinthephotosynthesisprocess.ToremovethefractionofH2O2generatedbyphotosynthe-sis,darkness-treatedsampleswerecollected.Inthedarknesstreatment,ablackplasticsheet(2m?2m)wasplacedoverthesubmergedplantcoloniesfor30min.In?owingwater,theblackplasticsheetwas?xedusingironpolesto?oatitatthewatersur-facewithoutdisturbingthemacrophytestandorthewatervelocity?eldaroundthecolony.Plantsampleswerecollectedat80%ofthe612T.Asaedaetal./Engineering4(2018)610–616waterdepthwithoutexposuretolight.Similarly,light-exposedsampleswerecollectedfromuncoveredareasofthesamemacro-phytestand.2.4.3.ProceduresfortheriparianzonesamplingHiiRiversamplingswereperformedinselectedareaswherePhragmitesaustralis,Phragmiteskarka,andMiscanthussacchari-?orusstandswereclearlyseparated.Herbaceousplantsampleswerecollectedatdifferentelevations(upto7m)fromtheusualwaterlevelalongaperpendicularlinetotheriver.TheriparianzoneoftheriverisrichinSalixpierotiiandJuglansmandshurica,whicharecommoninJapaneserivers.Ripariantreespecieshaveindividualpreferredelevationsforcolonization.ThenumbersofSalixpierotiiandJuglansmandshuricaindividualswerethereforecountedalonga2kmdistanceofriparianareaat14kmdown-streamfromLakeShinji,withrespecttotheirelevationfromthetypicalwaterlevel.Solar-radiation-exposedleavesanddarkness-treatedleavesfromtheseplantswerecollectedforchemicalanal-ysis.Allplantsampleswereimmediatelyplacedinacoolboxcon-tainingdryiceandtransportedtothelaboratoryforchemicalanalyses.2.5.ChemicalanalysesTheplanttissuesamplesdescribedinSections2.2–2.4wereanalyzedforbiochemicalstressindicators.Chlorophyll-a(Chl-a)andChlorophyll-b(Chl-b)andcarotenoidcontentsweredeter-minedspectrophotometricallybyextractingthepigmentsoffreshshootsinto5mLofN,N-dimethylformamide;thepigmentcontentwascalculatedusingthemethodsandequationsdescribedinRef.[14].Chl-aandChl-bandcarotenoidcontentswereexpressedinlgágà1freshweight(FW).H2O2assayswereperformedbyextractingenzymesfrom$100mgoffreshplantshootsintoice-coldphosphatebuffers(50mmoláLà1,pH6.0)containingpolyvinylpyrrolidone(PVP).Theseextractionswerecentrifugedat5000g(g=9.8másà2)for15minat4°C.Thesupernatantwascollectedandimmediatelystoredatà80°Cuntilanalysis.TheendogenousH2O2concentra-tionwasassayedspectrophotometricallyusingthemethodmodi-?cationsdescribedinRef.[15].Analiquotof750lLwasmixedwith2.5mLof0.1%titaniumsulfatein20%(v/v)H2SO4,andthemixturewascentrifugedat5000gfor15minat20°C.Theintensityoftheresultingyellowcolorwasmeasuredspectrophotometricallyatawavelengthof410nm.H2O2concentrationswereestimatedusingastandardcurveforH2O2,andtheresultswerepresentedinlmolágà1FW.Theindoleaceticacid(IAA)concentrationwasalsomeasuredspectrophotometricallyusingthemethoddescribedinRef.[16]withmodi?cations.Freshplanttissue($100mg)fromtheapicaltipwasgroundin2.5mLofdistilledwaterandcentrifugedat5000gat20°Cfor15min,andthesupernatantwascollected.Then1.0mLofenzymeextractwasmixedwith2.0mLofmodi?edSalkowskireagent;afteranhour,theformationofpinkcolorwasmeasuredatawavelengthof530nm.TheIAAconcentrationwasobtainedfromastandardcurveandpresentedaslgágà1FW.3.Results3.1.LaboratoryexperimentsFig.1presentstherelationshipbetweentheturbulenceintensityandtheconcentrationofH2O2inplantleavesandstems.Extremelyhighspecies-speci?cpositivecorrelationswereobservedbetweenturbulenceintensityandH2O2concentration.TheV.asiaticahasaleafyform,thusdifferingfromP.crispusandFig.1.ThechangeinH2O2concentrationwiththeturbulenceintensityofV.asiatica,P.crispus,andE.nuttallii.P.crispusandE.nuttalliidataarepresentedforbothleavesandstems,whileV.asiaticadataarepresentedforleaves.E.nuttallii,anddisplaysslightlydifferenttrendswithhigherH2O2concentrationthantheothers.MoresimilartrendswereobservedinP.crispusandE.nuttallii.Theassociatedrelationshipsdemonstratedmore?uctuationwithleavesthanstems,astheH2O2concentrationwashigherintheleaves.TherelationshipsoftheChl-acontent,IAAcontent,andelongationratewiththeH2O2concentrationareshowninFigs.2(a),2(b),and2(c),respectively.Theserelationshipsalwaysregisteredasnegativeandwereextre-melydepressedbyH2O2withregardtotheelongationrate.ThisdepressioninelongationwasevidentwhenevenasmallamountofH2O2waspresentinthetissues.TheresponseofM.spicatumtoincreasingH2SconcentrationsinthegrowthmediumisillustratedinFig.3.ThefoliarH2O12concen-trationdecreasedslightlybyasmuchas0.2mmoláLàH2S,andthenincreasedwithhigherH2Sconcentrations.TheChl-aandcarotenoidconcentrationsofM.spicatumareshowninFig.4(a),whichdemonstratesthenegativecorrelationbetweentheChl-acontentandthefoliarconcentrationofH2O2.Thecarotenoidcon-tentexhibitedarelativelyscatteredresponsetoincreasingH2O2intissues.Thespeci?cgrowthrateofM.spicatumwasnegativelyaffectedbytissueH2O2content,andparticularlybycontentgreaterthan8.0lgágà1FW(Fig.4(b)).3.2.LakeShinjiobservationFig.5presentsthefoliarH2O2concentrationwithrespecttothePPFDoftheP.anguillanustopcanopy,whichwasmeasuredatadepthofapproximately20cmdeep.TheH2O2concentrationwaslowuntil200–300lmolámà2ásà1PPFD,afterwhichitincreasedasthePPFDincreased.Fig.6givesthebiomassdistributionofP.anguillanuswithrespecttowaterdepth.Itsbiomasswasgreatestatadepthof1.2manddecreasedatbothshalloweranddeepersites;itwasparticularlynotedthattherewasnobiomassatdepthsoflessthan0.3m.The?gureincludesthemiddayPPFDatdifferentdepthsandat50cmabovethebottomofthelake.Lightintensitywasestimatedusingalightextinctioncoef?cientof0.025percentimeter,whichwasobtainedinthelake.ThePPFDjustbelowthewatersurfacewasassumedtobe1100lmolámà2ásà1,whichisapproximatelythemaximumvalueduringthegrowthseason.3.3.RiverobservationsIntheEnoandSabaRivers,thewatertemperatureswererecordedas(19±1)°CinJune2016andas(24±0.5)°CinSeptember2016.Thetotalnitrogen(TN)andtotalphosphorus(TP)contentwereapproximately0.3–0.8mgáLà1and0.01–0.10mgáLà1,respec-tively;theturbidityandpHofthewaterwererespectivelylessT.Asaedaetal./Engineering4(2018)610–616613Fig.2.(a)Chl-acontentversusplantH2O2concentrationofV.asiatica,P.crispus,andE.nuttallii;(b)IAAcontentversusH2O2concentrationofleavesandstemsofV.asiatica,P.crispus,andE.nuttallii(fortheV.asiatica,onlythedataforleavesarepresented);(c)plantelongationrate(?nalplantlength/initialplantlength)versusH2O2concentrationofV.asiatica,P.crispus,andE.nuttalliiunderturbulenceandmean?owconditions.Fig.3.FoliarH2O2concentrationofM.spicatumunderthepresenceofdifferentH2Sconcentrationsinthegrowthmedium.Errorbarsrepresentstandarddeviation.than100nephelometricturbidityunit(NTU)and6.5–7.5,exceptduring?oods;andtheDOwasnearlysaturated.TheseparametersindicateasuitableconditionforEgeriadensagrowth[17].TypicalviewsoftheseriversareshowninFig.7.Macrophytestandswerenotformedinshallowsiteslessthan40cmdeep;thebiomassbecamerichatapproximately1mdeep,andthendecreasedagainatsitesdeeperthan1.5m.Fig.8showstherelationshipbetweentheturbulenceintensity(rootmeansquarevelocity)at80TpthandtheH2O2concentra-tionofmacrophytesseparatelyforthetwoobservedconditions:lightexposureand30minofimposeddarkness.TheH2O2concen-trationsindarkness-treatedplantsgraduallyincreasedatnearlythesamerateastheincreasingturbulenceintensity.Comparedwiththedarkness-treatedsamples,themacrophytesinlight-exposedconditionshadanearlyconstantlyhigherconcentra-tionofH2O2atequalturbulencelevels.Althoughthedeviationincreasedwithincreasingturbulence,theincreasingrateofH2O2contentwithrespecttoturbulenceintensitywasnearlyequivalentbetweenthedarkness-treatedandlight-exposedsamples.Thedistributionsofthreemajorherbaceousspecies,Phragmitesaustralis,Miscanthussacchari?orus,andPhragmiteskarka,aredepictedinFig.9.Phragmitesaustraliswasdenselypresentinareasthatwereclosetowateratelevationsbelow1m,whereasagrad-ualshifttoMiscanthussacchari?orusoccurredathigherelevations.ThedistributionofPhragmiteskarkarangedfromclosetothewatertohighelevationsupto4m.TheH2O2concentrationofPhragmitesaustraliswaslowatlowerelevationsunderrelativelyhighmois-tureconditionsandrapidlyincreasedwithincreasingelevation,whichrangedfrom0to1m.Conversely,theH2O2concentrationsofMiscanthussacchari?orusremainedhighuntilanelevationof2m,andthendecreasedatgreaterelevations.TheH2O2concentra-tionsofPhragmiteskarkaremainednearlyconstantregardlessofelevation(Fig.10).TherewasnodifferenceintheH2O2concentra-tionoftissuesbetweenlightanddarksamples.TheriparianzoneoftheHiiRiverisprimarilyoccupiedwithherbaceousspecies.Recently,however,treespecies—particularlySalixpierotiiandJuglansmandshurica—areincreasing.SalixpierotiiusuallypreferstogrowclosetowaterwhileJuglansmandshuricagrowsinslightlyelevatedsites,approximately2mabovethenor-malwaterlevel.ThenumberofindividualsandthefoliarH2O2con-centrationsoftwospeciesfromtheobservedareaareshowninFig.11(a)and(b),respectively.Salixpierotiiexhibitedadecreasingtrendinthenumberofindividualsastheelevationincreasedandappearedatalmostzerorecordedelevationshigherthan3m;however,itsH2O2concentrationexhibitedtheoppositetrend.Juglansmandshuricawasnotfounduntilanelevationof1mfromthewaterlevel;after1melevation,thenumberofplantsincreasedFig.4.(a)Chl-acontentandcarotenoidcontentofM.spicatumversusH2O2concentration;(b)speci?cgrowthrate(SGR)versusH2O2concentrationofM.spicatum.Errorbarsrepresentstandarddeviation.614T.Asaedaetal./Engineering4(2018)610–616Fig.5.H2O2concentrationofP.anguillanustopcanopyversusPPFD.Fig.6.Biomass(dryweight)ofP.anguillanusandverticalpro?leofthePPFDdistributionintheplantbiomassofLakeShinji.Inthelegendforbiomass,PPFD–bottomandPPFD–50cmrepresenttheestimatedPPFDinP.anguillanusbiomassatthebottomofthelakeand50cmabovethelakebottom,respectively.Fig.7.Biomassdistributioninsidetherivers.Macrophytesarepresentatdepthsbetween0.4–1.5m,whereasshallowerordeeperareasarefreeofmacrophytes.toamaximumataround2melevation.TheH2O2concentrationofJuglansmandshuricadecreasedwithelevation,andthusexhibitedanoppositetrendtoSalixpierotii.4.Discussion4.1.HydrogenperoxideasanindicatorofenvironmentalstressesWatermovement,andspeci?callythemean?owandturbu-lence,isaubiquitousfactoraffectingaquaticplants.Mean?owFig.8.H2O2responsesofsubmergedmacrophytestodifferentturbulenceinten-sitiesat80TpthintheEnoandSabaRiversduringthemonthsofJune(Jun)andSeptember(Sep).Theterms‘‘light”and‘‘dark”standforlight-exposedsamplesand30mindarkness-treatedsamples,respectively.ThedashlinetrianglereferstotheH2O2incrementassociatedwithturbulence.Fig.9.DistributionofthreeherbaceousspeciesfoundinHiiRiver,Japan.Fig.10.H2O2responsesofthreeherbaceousspeciestodifferentelevationsfromthenormalwaterlevelofHiiRiver.Thecontinuous,dashed,anddottedtrendlinesrepresentPhragmitesaustralis,Miscanthussacchari?orus,andPhragmiteskarka,respectively.Errorbarsrepresentstandarddeviation.theformerbeingrelativelysteadyandunidirectional,whereasturbulenceisduetodeviationsand?uctuationsinthemagnitudeanddirectionoftheinstantaneouswatervelocityovertime.Theresultofthemechanicalstressexperimentshowedthatathigherturbulence,H2O2concentrationsandantioxidantenzymeactivitiesweresigni?cantlyincreased,comparedwiththoseinplantsthatweresubjectedtomean?oworthatwereinstagnantwater.Whenmacrophyteswereexposedtooscillatingmotion,morphologicalchangesoccurredinthecellsandcellwalls[18].Theplantsalso
过氧化氢作为环境胁迫指标在植被管理中的应用 - 图文
