全 文 ：2008年 第 3卷
第 2期,114-122
生 态 毒 理 学 报
AsianJournalofEcotoxicology
Vol.3,2008
No.2,114-122
LaserRadiation Can Retard LeafSenescence ofIsatisIndigotica
SeedlingsExposedtoElevatedUV-B
CHENYi-ping1,*,HANJing2
1.InstituteofEarthEnvironment,ChineseAcademyofSciences,Xi’an710075,China
2.ShaanxiAcademyofTraditionalChineseMedicineandPharmacy,Xi’an710003,China
Abstract:TheobjectiveofthisstudywastodeterminetheregulationefectsofHe-Nelaseronproteinmetabolism,
photosynthesisofIsatisindigoticaseedlingsexposedtoenhancedultraviolet-B(UV-B)lesions.TheIsatisindigoticaseedlings
weresubjectedtoUV-B radiation(10.08kJ·m-2) for8h·day-1 for8daysunderphotosyntheticalyactiveradiation
(220μmol·m-2·s-1)andthenexposedtolaserradiation(633nm;5.23mW·mm-2;beamdiameter:1.5mm)for5mineach
daywithoutambientlightradiation.Changesinanumberofproteinmetabolism parameters,photosynthesisparametersand
biomassweremeasuredandusedasindicatorsoftheregulationcapacityoflaserradiationonUV-Blesions.Theresults
revealedthatlaserhasup-regulationefectsontheproteinmetabolism,photosynthesisandbiomassofseedlingsexposedto
elevatedUV-Blesionsbyenhancingtheactivitiesofproteinase,alanineaninotransferase(ALT),aspartateaninotransferase
(AST),theconcentrationsofsolubleprotein,dissociativeaminoacid,theCPD concentrationandchlorophyl,thenet
photosynthesis(Pn),thestomatalconductance(Gs) andthebiomassaccumulation.Theseresultssuggestedthatlaser
radiationcouldretardleafsenescenceinducedbyUV-Bandup-regulatetheseedlinggrowthofUV-B-inducedlesions.
Keywords:Isatisindigotica;He-Nelaser;UV-Blesions;leafsenescence
激光辐照对UV-B损伤菘蓝叶片衰老的延缓作用
陈怡平 1,*,韩静 2
1.中国科学院地球环境研究所,西安 710075
2.陕西中医药研究院,西安 710003
摘要:以菘蓝(IsatisindigoticaFort)幼苗为实验材料,比较研究了 He-Ne激光对增强 UV-B(辐射强度:10.08kJ·m-2;
照射时间 8h·d-1;共照射 8d)辐射损伤菘蓝叶片衰老的延缓作用.结果表明:与对照相比,UV-B辐射可导致环丁烷
嘧啶二聚体(CPD)形成,显著降低蛋白酶、转氨酶、游离氨基酸、可溶性蛋白质含量,同时降低了叶绿素含量、气孔导
度、水分利用率和生物量;而菘蓝幼苗经 UV-B辐射处理后再用激光辐照(波长:633nm;功率密度:5.23mW·mm-2;
束径:1.5mm;照射时间:5min·d-1),叶片中 CPD含量显著降低,蛋白酶、转氨酶、游离氨基酸、可溶性蛋白质含量、叶
绿素含量、气孔导度、水分利用率和生物量与单独 UV-B处理组相比显著提高.上述结果表明激光辐照可以显著延
缓 UV-B损伤菘蓝叶片的衰老.
关键词:菘蓝;激光;UV-B;叶片衰老
文章编号:1673-5897(2008)2-114-09 中图分类号:R994.2,X171.5 文献标识码:A
Received30November2007 accepted3January2008
SupportedbyWestLightFoundationofTheChineseAcademyofSciences
BiographyCHENYi-ping(1968—),Ph.D;*Correspondingauthor,E-mail:lifekxyj@hotmail.com
CHENYi-pingetal.:LaserRadiationCanRetardLeafSenescenceofIsatisIndigoticaSeedlingsExposedtoElevatedUV-B第 2期
1 Introduction
Ultraviolet-B radiationlevelsarestilrelatively
highattheEarth’ssurfaceduetothedepletionof
stratosphericozonebythechlorofluorocarbonsreleased
intotheatmospheresincethemid-nineteenthcentury.
CurentUV-Blevelsareexpectedtoincreaseinthe
eventofthe MontrealProtocolnotbeing fuly
implementedbythemembercountries(McKenzieet
al.,2003).Sunlightisarequirementforphotosynthesis,
andisthemostimportantforplantprocesses.Itis
essentialforproductionofbiomass.Sincephotosynthesis
dependsonthelight-harvesting propertiesofthe
chlorophyls,ithasbeenshowntobeatargetof
UV-Bradiation(Teramuraetal.,1990).Therefore,
UV-Bradiationhasdetrimentalefectsonplants.UV-
BreducesstomatalconductanceandPn,photosynthetic
pigments(Teramura and Sulivan,1994),down
regulatesphotosyntheticgenesexpression(Stridet
al., 1994), and results in declined proteins
concentration(Stapleton,1992;Jordan,1996;Santos
etal.,1993;Basiounyetal.,1978).Thesechanges
inphotosynthesis,chlorophylandproteinconcentration
areearlysymptomsofleafsenescence(Groveand
Mohanty,1992),whichmodifiesthe leafinternal
structureandfunction(NoodénandLeopold,1988).
Exposuretosuitabledosesoflaserradiationhas
been shown to enhanceenzymaticactivities,and
accelerateplantgrowthandmetabolism(Chenand
Wang,2003;Caietal.,2000;PalegandAspinal,
1970;Qietal.,2000;Chenetal.,2005).Although
Qietal(2002)hasreportedthatlasertreatments
enhancedrepaircapabilitiesofbroadbeanseedlings
exposedtoUV-Bbyenhancingfreeradicalelimination
systemsnoefortsweremadetostudywhetherlaser
hasup-regulationefectontheleafsenescenceof
IsatisindigoticainducedbyenhancedUV-Bradiation.
Ourhypothesisisthatlaserhasup-regulationefect
ontheleafsenescenceofIsatisindigoticainduced
byenhancedUV-Bradiation.Theobjectivesofthis
study were to characterize leaf photosynthesis
parameters,proteinmetabolism parametersandDNA
repairexposedtoelevatedUV-Btoidentifylaserup-
regulationefectsonleafsenescenceinducedbyUV-B.
2 Materialsandmethods
2.1 Plantmaterials
UniformseedsofIsatisindigoticaweresterilized
for10minbyimmersionin0.05% HgCl2,washed
for30mininrunningwater,andsownseparatelyin
24plasticflowerpots(25cm×30cm).Theflowerpots
wereplacedinanglassgreenhousemaintainedat
25℃,70% relativehumidity,and400μmol·mol-1
CO2,withvisiblelightconditionsof1500μmol·m-2·
s-1for8h·day-1.Whentheseedlingswere10days
old,they were then divided randomly into four
groupsand subjected to diferenttreatments.The
fourgroupsconsistedof:(1)seedlingsexposedto
neitherenhancedUV-B norHe-Nelaserradiation
(thecontrol,CK);(2)seedlingsexposedtoHe-Ne
iradiationundertheconditionofnoambientlight
(L);(3)seedlingsexposedtoUV-Biradiation(B);
(4)seedlingsexposedtoHe-Nelaserradiationafter
beingexposedtoUV-Biradiation,underthecondition
ofnoambientlight(BL).Eachflowerpotcontained
tenpotedseedlings.
2.2 UV-Btreatment
The B and BL groups of seedlings were
approximately10daysoldwhentheyweresubjected
toUV-Bexperiments.EnhancedUV-Bradiationwas
providedbyfilteredQinbrand(BaojiLampFactory,
China)30W fluorescence sunlamps folowing the
procedureoutlinedbyQietal(2002).Thelamps
weresuspendedaboveandperpendiculartothepots
and filtered with either0.13mm thick celulose
diacetate(transmissiondownto290nm)forUV-B
iradianceorwith 0.13mm polyesterplasticfilms
(absorbingalradiationbelow320nm)asthecontrol.
Thecelulosediacetatefilterswerepresolarized.The
desiredlevelofiradiationwasobtainedbychanging
thedistancebetweenthelampsandthepots.The
spectraliradiancefrom thelampswasdetermined
with an Optronics Model 742 spectroradiometer
(OptronicsLabs,Orlando,Fla.) andwasweighted
usingageneralizedplantresponseactionspectrum
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生 态 毒 理 学 报 第 3卷
(Caldwel,1971) and normalized at300nm to
obtainthedesiredlevelofbiologicalyefectiveUV-
Bradiation(UV-BBE).Theseedlingswereexposed
to10.8kJ·m-2UV-Biradiationfor8h·day-1for8
days under photosyntheticaly active radiation
(220μmol·m-2·s-1) andthenmovedtothedark
condition.
2.3 He-Nelasertreatments
ThelaserwasconstructedatNorthwestUniversity
(Modelno.:MSHN5-A-B450MM;wavelength:633nm;
powerintensity:5.23mW·mm -2;beam diameter:
1.5mm).Themethodanddosesoflaseriradiation
wereasreportedearlier(ChenandWang,2003).
Forthe“L”experimentalgroup,apicalbuds of
seedlingsweredirectlyiradiatedbylaserfor5min·
day-1 for8daysinthedarkcondition;individual
seedlingswere treated only once.Forthe“BL”
experimentalgroup,theseedlingswerefirstexposed
toUV-BiradiationandthentoHe-Nelaseriradiation
for5min·day-1for8daysundertheconditionofno
ambientlight.
2.4 Determinationofbiochemicalandphysiological
characters
Intactleafsamples(0.5gfreshweight(FW)from
thestilgrowingfourthleaf)weretakenfrom 18-
day-oldseedlingsatthefour-to-fiveleafstageand
placedinamortar,folowedbytheadditionof3mL
phosphatebufer(pH8.0).Afterthoroughgrinding,
the samples were then transfered to a 5mL
centrifugetubeandclarifiedbycentrifugation4000g
for15minat0℃.A0.5mLsupernatantsamplewas
then removed for activities determination. The
activitiesofALTandASTweremeasuredaccording
totheprotocolsofanALTkit(No.20010818)and
anASTkit(No.20010820)(BeijingBITKTClinical
ReagentCo.,Lt,China).TheactivitiesofALTand
ASTwereexpressedasU·g-1FW.
Concentrationofsolubleproteinwasmeasured
accordingtoBradford(Bradford,1976).Intactleaf
samplesof18dseedlings(0.5gFW),whichwereat
4~5leavesstageofdevelopment,materialswere
homogenizedin2.5mL phosphatebuferof0.1M
Tris-HClofpH 8.0(aratioof0.5M ofadded
sucrose,0.06M ofL-ascorbicacidand0.005M of
β-mercaptoethanolper100mLbufer)at0℃,after
thorough grinding,the sampleswere removed to
5mL centrifugation tubeand then centrifuged for
15minat8000g.A0.15mLsupernatantsamplewas
removed with pipete and 0.85mL ofdistilation
waterand5mLof0.1g·L-1G-250coomassiebriliant
bluewereadded.After15mintheabsorbancewas
determinedat595nm.Standardcurvewereprepared
by adding bovine serum albumin(Sigma,ultra
99%),ranginginconcentrationfrom 0to100μg·
mL-1.Concentrationofsolubleproteinwasexpressed
asmg·g-1FW.
Intactleafsamplesof18dseedlings(0.5gFW),
whichwereat4~5leavesstageofdevelopment,
weretakenandhomogenizedin5mLof10% acetic
acidat0℃ ,afterthoroughgrinding,thesamples
werefixedto100mLwithdistiledwater,andthen
centrifugedfor10min at8000g.Concentration of
dissociativeaminoacidwasdeterminedaccordingto
themethodsofRosen(Rosen,1957).Concentration
ofdissociativeaminoacidwasexpressedasμmol·g-1FW.
Intactleafsamplesof18d seedlings(1gFW),
whichwereat4~5leavesstageofdevelopment,
materialswerehomogenizedin5mLphosphatebufer
ofpH 6.0at0℃ ,afterthoroughgrinding,the
sampleswereremovedto10mLcentrifugationtube
and then centrifuged for 20min at 10,000g.
Proteinaseactivitywasdeterminedaccordingtothe
methodsofChrispeelsandBoulter(Chrispeelsand
Boulter,1975).Proteinaseactivitieswasexpressedas
μmolaminoacid·mg-1protein·h-1.
Theconcentrationofchlorophylwasmeasured
according to Zhang(1985).Intactleafsamples
(0.5gfreshweight) weretakenfrom 18-day-old
seedlingsatthefour-to-fiveleafstage,cutinto
smalpieces,andplacedinamortartogetherwith
0.2gsilica,0.2gCaCO3,and15mL80% acetone.
Afterthoroughgrinding,thesampleswerefiltrated
throughtwolayersoffilterpaperbyairpressure
andfixedto25mLwith80% acetone.Absorbanceat
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CHENYi-pingetal.:LaserRadiationCanRetardLeafSenescenceofIsatisIndigoticaSeedlingsExposedtoElevatedUV-B第 2期
663nm and 645nm was determined. Relative
chlorophylconcentrationwascalculatedandexpressed
asmiligramspergramFW.
Netphotosyntheticrate(μmolCO2·m
-2·s-1),
stomatalconductance(μmolH2O·m-2·s-1),andwater-
useeficiency(μmolCO2·mol
-1
H2O)of19-day-oldintact
seedlingsweremeasuredunder1500μmol·m-2·s-1
photosyntheticalyactiveradiation(PAR)at11:30~12:
00a.m.withtheCI-301SPphotosynthesissystem
(CID lnc.)folowingtheoperatingprocedureofthe
manufacturer.
Biomass(gdryweight(DW))wasdetermined
bydrying20seedlingsinanovenat80℃ untila
constantweightwasreached.
Seedlings of the experimental groups were
placedinthedarkconditionfor4.5hand8hfor
DNAanalysis,thefourthleafof18-day-oldseedlings
(4gFW) wasremovedandtheDNA wasextracted
usingEpicentre’sMasterPureTM PlantLeafDNA
Purificationkit(Epicentre,Madison,Wis.)according
totheusermanual.DNA waselectrophoresedon
1% agarose folowed by staining with 0.05%
ethidium bromide.Birnboim and Jevcak(1981)
reportedthatthefluorescentdyeethidium bromide
binds selectively to dsDNA in the presence of
single-strand DNA when shortduplex regionsin
“single-strand”DNA moleculesaredestabilizedby
alkali.Weusedethidium bromideasadirectprobe
of DNA structure and developed an applicable
methodtotestforplantDNA damagedbyUV-B
radiation.TheconcentrationofdsDNAwasdetermined
byarevisedfluorometricanalysisasfolows.The
extractedDNAsamplesweredilutedtoaconcentration
of0.5μg·mL-1withdistiledwater,and9mLaliquots
werethenmixedwith1mLethidiumbromide(5μg·
mL-1) for1hbeforethefluorescencevaluewas
determinedusingafluorescencespectrometer(model
RF-540;Japan)atthefolowingparameters:excitation
wavelength(EX),483.0nm;emission wavelength
(EM),600.0nm;EX/EM=10.0nm/10.0nm;scanning
speed,1200nm·min-1.ThedsDNAconcentrationwas
calculatedbyastandardcurvethatwasmadefrom
standardλDNA/HindII(HuameiCo.,China).
2.5 Statisticalanalysis
Sampleswerearangedincompletelyrandomized
designswithsixreplications.Alofthevalueswere
the mean from six replications. Results from
diferenttreatmentswerecomparedusingone-way
ANOVA(analysisofvariance).FolowingANOVA,
posthoccomparisonsofmeansweremadeusing
Duncan’smultiplerangetests.Statisticalsignificance
wasdeterminedatp<0.05.
3 Results
The photosynthesis parameters of seedlings
exposedtoHe-Nelaseriradiationalonewerenotably
higher than those of the controlseedlings(net
photosynthesis(Pn)(p<0.05),stomatalconductance
(Gs)(p<0.05),waterutilizationeficiency(p<0.05),
and concentrations of chlorophyl a(p<0.05),
chlorophylb(p<0.05),andtotalchlorophyl(p<
0.05)).Incontrast,seedlingssubjectedtoUV-B
radiationonlyshowedasignificantreductioninthese
photosynthesis parameters,with the exception of
chlorophylbconcentration(Pn(p<0.05),Gs(p<
0.05),waterutilizationeficiency(p<0.05),and
concentrationsofchlorophyla(p<0.05),chlorophyl
b(p>0.05),andtotalchlorophyl(p<0.05)).Inthe
caseofseedlingsexposedtoenhancedUV-Btreatment
folowedbyHe-Nelaserradiation,thephotosynthesis
parameters were higher than those of seedlings
exposedtoenhancedUV-Bradiationonly(Pn)(p<
0.05),Gs(p<0.05),waterutilizationeficiency(p<
0.05),andconcentrationsofchlorophyla(p>0.05),
chlorophylb(p>0.05),andtotalchlorophyl(p<
0.05))(Fig.1).
Comparedwiththecontrol(CKgroup),enhanced
UV-Btreatmentalonecausedasignificantdecrease
intheactivitiesofproteinase,AST,andALTand
theconcentrationsofsolubleproteinanddissociative
aminoacid(p<0.05).Incontrast,lasertreatmentalone
caused aincreaseoftheactivitiesofproteinase,
AST,andALT andtheconcentrationsofsoluble
proteinanddissociativeaminoacid(p<0.05).However,
whenUV-Btreatmentwasfolowedbylaserradiation,
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生 态 毒 理 学 报 第 3卷
Fig.1 InfluenceofHe-NelaseriradiationonthephotosynthesisparametersofIsatisindigoticaseedlingsexposedtoenhanced
UV-Blesion.Theexperimentsconsistedoffourtreatments:thecontrol(withoutHe-NelaserandUV-Bradiation,CK);
UV-Bradiationalone(B),He-Nelaserradiationalone(L),UV-BradiationfolowedHe-Nelaser(BL).Dataarethemeansand
standarderor(erorbars)ofsixcompletelyindependentexperimentreplications.Columns(means)withdiferentletersare
significantlydiferentatthe0.5level(n=6)accordingtoDuncan’smultiplerangetest.
(Aisnetphotosyntheticrate;Bisstomatalconductance;Ciswateruseeficiency;Disconcentrationofchlorophyla;
Eisconcentrationofchlorophylb;Fisconcentrationoftotalchlorophyl)
theactivitiesofproteinase,AST,andALTandthe
concentrations ofsoluble protein and dissociative
aminoacidwassignificantlyhigher(p<0.05)than
UV-Biradiationalone(Fig.2).
ChangesintheconcentrationofdsDNA inthe
seedlingsofalfourgroupswereshowninFig.3.In
seedlingsinjuredbyenhancedUV-Bradiationafter
inthedarkfor4.5h,theconcentrationofdsDNA
declinedsignificantly(p<0.05),whileinthosesubjected
to the laser treatment,the decline in dsDNA
concentrationwasinsignificant(p>0.05)aftera4.5h
darkincubation.ThereductionindsDNAconcentration
wasthegreatest(p<0.05)inseedlingsdamagedby
enhancedUV-Biradiationfolowedbylaserradiation
afterin thedark condition for4.5h.When the
seedlingswerecultured in thedark for8h,the
results were diferent for three treatments: in
comparison to the control group, the dsDNA
concentrationoftheseedlingstreatedbythelaser
treatmentaloneandtheUV-Bradiationaloneincreased
slightly(p>0.05)andthatoftheseedlingstreated
firstbyenhancedUV-Bradiationfolowedbylaser
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CHENYi-pingetal.:LaserRadiationCanRetardLeafSenescenceofIsatisIndigoticaSeedlingsExposedtoElevatedUV-B第 2期
radiationincreasedsharply(p<0.05).
Compared with the controlgroup,seedlings
treatedwithUV-Bradiationonlyshowedasignificant
decrease(p<0.05)inleafbiomass(Fig.2F).In
contrast,thetreatmentoflasercausedasignificant
increase(p<0.05)inleafbiomass.However,inthe
seedlings exposed to elevated UV-B iradiation
folowedbylaserradiation,leafbiomasswasnotably
larger(p<0.05)thanthatofseedlingssubjectedto
UV-Btreatmentalone,anditwaslargerthanthatof
thecontrol(p<0.05).
4 Discussion
Various processes of plants growth and
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生 态 毒 理 学 报 第 3卷
developmentaremodulatedbyinternalcuessuchas
thehormonalbalanceandexternalfactors.Results
presentedintheliteratureindicatethatUV-Bradiation,
asapartofsunlight,mayexertanadverseinfluence
onphysiologicalandbiochemicalprocessofplants
(Krameretal.,1991;VanHasseltetal.,1996).
AreviewofUV-Befectsoncropshadshown
thatenhancedUV-B bleachesleafchlorophyland
reduces photosynthesis(Kakani et al., 2003).
Chlorophyldegradationisthefirstvisiblesymptom
ofsenescence.Thechangeincelstructureduring
senescenceisthebreakdownofthechloroplastthat
containsupto70% oftheleafprotein,whichis
mainreasonofdeclineinthePnandphotosynthetic
capacity(BleeckerandPaterson,1997).Inaddition,
stomatalconductanceisafunctionofleafageand
shows a strong relationship with environmental
conditionsandreducesphotosynthesis(Field,1987).
AlthoughthemechanismsofUV-B-inducedstomatal
closureisnotyetclear,leafstomatalconductance
exposuredtoUV-B,similartoPn,wasreducedhave
beendemonstrated(Noguesetal.,1999;Daietal.,
1992).Inthecurentstudy,UV-Bradiationcaused
leafchlorophylconcentrationdecreaseandreduced
photosynthesiscapabilities(e.g.reduced the Pn,
stomatalandwaterutilization) ofleavescompared
withthecontrol.Notably,theseresultsareaccord
with above mentioned conclusions.This notably
suggestedthatUV-Bshouldresultinleafsenescence
ofIsatisindigoticaseedlingsandleadtodeclinein
photosynthesiscapability.
Netlossofproteinisanotherdominantfeature
ofleafsenescence(FelerandFischer,1994).Santos
etal(1993)andBasiounyetal(1978)reportedthat
UV-Bcausedthedegradationofproteincontent,and
theresultsfrom ourexperimentswasconsistentwith
theSantosetal(1993)andBasiounyetal(1978).
Fengetal(1999)hadreportedthatdegradationin
solubleproteinconcentrationwasduetoenhancement
inproteinaseactivitiesbyenhancedUV-Bradiation,
andleadproteindecomposemetabolism toimprove,
sodissociativeaminoacidwasaccumulation.Butour
resultsshowedUV-B down-regulatedtheproteinase
activity,moreoverdissociativeaminoacidwasnot
accumulationcomparedwiththecontrol.Inaddition,
theactivitiesofASTandALTweredown-regulated
by UV-B.Al these resultssustain ouroriginal
hypotheses that degradation in soluble protein
concentrationwasnotduetoproteindecomposingby
proteinase.ReasonsarethatUV-Binducesanumber
of DNA damage photoproducts of cyclobutane
pyrimidinedimers(CPDs)(Fig.3).Pyrimidinedimers
havebeendemonstratedtoblocktheprogressboth
of DNA and RNA polymerase, inhibit DNA
replication and transcription(Mitchel and Nairn,
1989);finaly,DNA synthesis,DNA transcription
and replication were blocked, and resulted in
degradationofproteintranslation,therefore,metabolism
rate(bothdecomposeandsynthesis)ofproteinwas
restrained.AnotherpossiblereasonisUV-Biradiation
destroystheenzymesstructureandresultsindegradation
inproteinmetabolism becausetheproteinsaremajor
componentofthecelcytoskeletonanditsabsorbance
wavelengthinthescopeofUV-B.
Whetherlaserscanup-regulatedphotosynthesis,
protein metabolism and seedlings of the Isatis
indigoticaseedlingsexposedtoelevatedUV-B?No
studywasmadetoresponsethequestion.Itwasthe
hypothesisthatlaserhasup-regulationefectonUV-
B iradiationinduceddetrimentinseedlinggrowth
becauseexposuretosuitabledosesoflaserradiation
hasbeenshowntoenhanceenzymaticactivities,and
accelerateplantgrowthandmetabolism(Palegand
Aspinal,1970;Qietal.,2000;Chenetal.,2005).
Ourresultswereaccordwithoriginalanticipation.
Lasertreatmentup-regulatedtheproteinmetabolism
andcausedsignificantincreaseintheactivitiesof
proteinase,alanineaninotransferase(ALT),aspartate
aninotransferase(AST),theconcentrationsofsoluble
protein,dissociativeaminoacidandchlorophyl,the
netphotosynthesis(Pn),thestomatalconductance
(Gs).Moreover,UV-B-radiation only caused a
significantdecreaseandthelaseronlycausedan
increase in biomass.Notably,in the group of
seedlingssubjectedtoUV-B radiationfolowedby
laser,thebiomasswasenhancedsignificantly.
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CHENYi-pingetal.:LaserRadiationCanRetardLeafSenescenceofIsatisIndigoticaSeedlingsExposedtoElevatedUV-B第 2期
Inconclusion,enhancedUV-B radiationleads
Isatisindigoticaleavestoproducephotoproductsof
cyclobutanepyrimidinedimers(CPDs) andinhibit
DNA replication and transcription(Mitchel and
Nairn,1989),whichdirectlyresultindegradationof
proteintranslation(orUV-Biradiationdestroysthe
enzymesstructure),andfinalyresultindegradation
intheconcentrationsandtheactivitiesofenzymes,
acceleratedleafsenescenceprocess.Therefore,Pn
andphotosynthesisfunctionsdeclineandpresented
biomass degradation. But laser stimulated the
enzymesactivities,retardedleafsenescenceprocess,
improvementPnandphotosynthesiscapabilitiesand
growthofseedlings.
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REACH系统——改进的优先考虑
在 REACH(以及当前的条令)中,产量决定着检测要求.某一专门物质的产量越高,所需要的检测项目也就越宽泛.
把产量作为优先考虑手段的原则,基于这样的设想:产量越高随之的影响潜力就越多,因而不利后果的风险就越大.这是
一个能够理解的论据,但是总产量与风险之间的联系并不是直接的,也绝非必然的.
用产量决定检测要求,至少存在3个问题.首先,由于缺乏这方面的研究,对于产量影响的预期程度基本是无从知晓.
其次,产量与影响之间的实际关系,并不一定等同于产量与风险之间的实际固定关系.风险取决于影响与毒性的合力.低
毒物质可能占有高产量物质的绝大部分.第三,即使一种低产量物质的总影响确实不大,但个别情况其影响可能很大,例
如在使用它的工作场所.
根据我们的观点,产量作为数据收集优先考虑标准的作用应该逐步降低.取而代之,我们提议 3种其他的优先考虑
机制:
1.物质的化学性质
不同化学特性的物质,将给环境带来不同的结局和影响(例如分隔、持久性、生物累积的能力).它们也将需要不同的
检测方法(例如根据它们的亲脂性),他们对生物试样(反应性)有害反应的倾向性也不同.因此有关反应性、持久性和生物
累积潜力的化学特征,既要用于优先考虑,又要用来加大检测力度.
2.低层次的检测结果
分层检测的办法应该加强,这样低层检测的结果就会自动引向进一步的检测要求.举例来说,对水蚤具有急性毒性
的物质,应该检测其对鱼类和藻类的短期影响;假设这些检测得出了确定的结论,那么对水生物种的长期检测也要进行.
3.对自动监测的激励
激励生产者对于最低要求更广泛的特殊的低产量物质进行检测的机制,应该建立.
摘引自《产业与环境》2005年27卷2~3期
SvenOveHansson&ChristinaRudén
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