TECHNICALREPORTS:HEAVYMETALSINTHEENVIRONMENTWhiteCloverNodulationIndexinHeavyMetalContaminatedSoils–APotentialBioindicatorNicolasManier*andAnnabelleDeramUniversitéDroitetSantédeLilleKrisBroosFlemishInstituteforTechnologicalResearchFranck-OlivierDenayerandChantalVanHaluwynUniversitéDroitetSantédeLilleThemorphologicaleffectsofheavymetalstressonthe–+lantsacquireNbyassimilationofNO3andNH4fromnodulationabilityofRhizobiumspp.andgrowthofwhitethesoilsolution,orfromatmosphericNfixationthroughP2clover(TrifoliumrepensL.)werestudiedinthelaboratoryasymbioticassociationwithN–fixingbacteria.Thissymbioticundercontrolledconditions.Fourteentopsoilswerecollected2fromanareawithelevatedmetalconcentrations(Cd,Zn,andprocessofN2fixationistypicalforleguminousplantsthatarePb).Whitecloverwascultivatedusingaspecialized“rhizotron”abletotakeupsignificantamountsofNbyformingnodulesmethodtoobservethedevelopmentofrootandnoduleontheirrootsinsymbiosiswithaparticularbacteriaspeciescharacteristics.ResultsshoweffectsofincreasingheavymetalcalledRhizobium.Therearenumerousfactorsthatcanaffectthisconcentrationsonnodulationdevelopment,especiallytherelationship(DeMingandMartin,1986;McGrathetal.,1988;nodulationindex(i.e.,thenumberofnodulespergramofthetotalfreshbiomass).AsignificantdecreaseinnodulationindexFordeandLorenzo,2001;Peralta-Videaetal.,2001;Wolfandwasobservedatabout2.64mgCdkg–1,300mgZnkg–1,andRohrs,2001;TsvetkovaandGeorgiev,2003;Broosetal.,2005a)130mgPbkg–1inthesesoils.Thesensitivityofthenodulationoftenresultinginstressesonthenodulationprocess,theN2–indexinrelationtoothermorphologicalcharacteristicsisfixingability,oranalterationinthestructureoftherootnodules.discussedfurther.ItisproposedthatthenodulationindexofSoilinorganicNcontent,acidicpH,andelevatedheavymetalwhitecloverisasuitablebioindicatorofincreasedheavymetalconcentrationsinsoil.concentrationsinsoilseemtobethemostimportantfactorsthatcaninfluencelegumenodulation(Yeetal.,2001).Thetoxicityofheavymetalsonthenodulationprocessofleg