全 文 ：热带亚热带植物学报　2011, 19(2):120 ～ 126
JournalofTropicalandSubtropicalBotany
Received:2010-08-17　　　Accepted:2010-12-08
Foundationitems:SupportedbytheScienceandTechnologyCommissionofShanghaiMunicipality(08390513800);LeadingAcademicDiscipline
ProjectofShanghaiMunicipalEducationCommission(J50401)
＊ Correspondingauthor, email:gsg@shnu.edu.cn
多蒴灰藓对强紫外线照射的生理响应
沈蕾 1 , 杨武2 , 郭水良1＊, 曹同1
(1.上海师范大学生命与环境科学学院 ,上海 200234;2.浙江师范大学化学与生命科学学院 ,浙江金华 321004)
摘要:将多蒴灰藓(Hypnumfertile)置于紫外辐射下照光 3周 , 研究了紫外辐射对多蒴灰藓的损害及其生理响应。
结果表明:与对照(自然环境)相比 ,多蒴灰藓的叶绿素和类胡萝卜素含量均随紫外辐射时间的延长而减少 , MDA
含量却明显增加 , SOD、POD和 CAT活性也相应增加;增加紫外辐射量会引起多蒴灰藓的氧化胁迫 ,其能通过增加
抗氧化酶的活性来减轻这种胁迫。
关键词:多蒴灰藓;叶绿素;类胡萝卜素;抗氧化酶;紫外辐射
中图分类号:Q948.112.1　　　　　文献标识码:A　　　　　文章编号:1005-3395(2011)02-0120-07
doi:10.3969/j.issn.1005-3395.2011.02.004
PhysiologicalResponsestoEnhancedUV-BRadiationofHypnumfertile
SHENLei1 , YANGWu2 , GUOShui-liang1＊, CAOTong1
(1.ColegeofLifeandEnvironmentalSciences, ShanghaiNormalUniversity, Shanghai200234, China;
2.ColegeofChemistryandLifeScience, ZhejiangNormalUniversity, Jinhua321004, China)
Abstract:ThedamagesofHypnumfertile(Bryopsida:Musci)anditsphysiologicalresponseswerestudiedunder
enhancedUV-Bradiationfor3 weeks.ThedosesofbiologicalyefectiveUV-Biradiationwere6.93 kJm-2d-1
(ambientUV-Bradiation)and9.01 kJm-2d-1(enhancedUV-Bradiation, about30% higherthanambientUV-B
radiation), respectively.TheresultsshowedthatthecontentsofchlorophylandcarotenoidofH.fertileboth
decreasedwithtimeunderenhancedUV-Bradiation, whereasMDAcontentsignificantlyincreased, andthe
activitiesofSOD, PODandCATalincreased.ItissuggestedthatenhancedUV-Bradiationcausedoxidative
stresstoH.fertileandtheoxidativestressmightbealeviatedbyincreasingtheenzymesactivities.
Keywords:Hypnumfertile;Chlorophyl;Carotenoid;Antioxidantenzymes;UV-Bradiation
Inspiteofthecurentefortstorestrictthe
productionofozone-depletingsubstances, thinningof
the stratospheric ozone layer and increasing
penetrationofultraviolet-Bradiation(280-320 nm)
totheEarthssurfacewilcontinuefordecades.
Atmosphericozoneremainsdepletedandtheannual
averageozonelossisapproximately3% globaly[ 1-2] ,
causingnotonlythedramaticAntarcticozoneholebut
alsothegeneraldeclineattemperate and high
latitudesinbothhemispheres[ 3] .
AnincreaseinUV-BradiationatEarthssurface
wilhavepotentialyadverseefectsonterrestrial
ecosystems include agricultural lands, agro-
ecosystems, andlesintensivelymanagedlandssuch
as forests, grasslands, savannahs, deserts,
tundra, etc[ 4-5] .
Becauseplantspecies, evendiferentgenotypesof
thesamespecies, varyconsiderablyintheirsensitivityto
thisradiation, intensificationofsolarUViradiancemay
altercompetitivebalanceofplants[ 6-7] .Manystudies
haveshownadeleteriousUV-Befectonplantcelssuch
asreduced photosynthesisandbiomas, decreased
第 2期 沈蕾等:多蒴灰藓对强紫外线照射的生理响应 121　
proteinsynthesis, impairedchloroplastfunction, damage
toDNA, etc[ 8-9] .
Mosses, thoughmorphologicalandanatomical
simple, are important members of terrestrial
ecosystem.Inrecentyears, therearemuchworks
refertotheefectofUV-Bonmosses[ 10] .Themain
variablesusedtoassesstheefectsofUV-Bradiation
involvedshootgrowth, bothinlengthanddrymass,
and photosynthesisrates, photosynthetic pigment
composition(chlorophyls, carotenoids), chlorophyl
fluorescence variables, UV-absorbing compounds,
carbohydrates, aswel asthemorphologicaland
ultrastructuralfeatures[ 11] . However, thepresent
resultsweresomewhatcontradictory.Noconsistent
conclusionconcerningthesusceptibilityofmossto
UV-Bradiationwasformedsofar[ 10-12] .
Themoss, Hypnumfertile, whichhasawiderange
ofgeographicaldistribution, isofmedialsizeandcrawl
growthtype, andmaysuferfrommoreUV-Bradiation
thanothermosses.Therefore, Hypnumfertileisanideal
experimentalmaterial in conducting research on
bryophytephysiologicalresponsestoenhancedUV-B
radiation.Thegoalsofourworkweretoascertainthe
efectsofenhancedUV-BradiationonHypnumfertile
anditsphysiologicalresponsestoUV-Bstressbythe
variablesofchlorophylandantioxidantenzymes, thusto
understandwelaboutthephysiologicalresponsesof
mosestoenhancedUV-Bradiation.
1 Materialandmethods
1.1Plantmaterial
ThesamplesofH.fertilewerecolectedfromthe
sameplace, thesummitofBeiMountain(alt.1200
m), 29°06′N, 119°39′EinJinhua, Zhejiang
Province, China, on15 April, 2007.Atthisplace,
theygrowninanopenhabitatandnoshrubsand
arborsshelterfromlight.Thecolectedmaterialwere
storedonwetfilterpapersfor2 daysthenusedtobe
treated.Inthecourseoftreatment, thematerialswere
retainedhydratedbykeepingthepaperswetlestthe
influencebydrought.After7 , 14, 21 daysofUV-B
radiation, respectively, thematerialswerecolectedat
9:00, andapical3 cmgametophyteswerewashedin
distiledwaterforthreetimesthenusedtodetermine
thephysiologicalindices.
1.2 UV-Biradiationandcultivationenvironment
Theexperimentwasconductedatabout10 m
abovesealevelandthesupplementalUV-BBE dosein
simulatedambientUV-Biradiationwas6.93kJm-2d-1
ascontrol.Themossmaterialusedintheexperiment
colectedfromrelativelyopenhabitatsatahighsea
level(ca.1200 m).Theintensityofultraviolet
radiationincreasesby1.3% whenthealtituderises
100 m.ConsideringthattheUVintensityofthehabitat
wherethemossmaterialcolectedwas15% stronger
thanthatoftheexperimentalcondition, moreover, the
annualrateofozonedestructionis3%, therefore, we
appliedatreatmentintensity30% higherthanthatof
theground, thatistosay, theUVintensityofthe
experimentaltreatmentwas actualy about 15%
strongerthanthatofthecolectinghabitat.
Visible radiation (photosynthetic active
radiation, PAR from 400 nm to 700 nm) and
supplementaryUV-Bradiationwerebothsuppliedfor
twotreatments.Visibleradiationwassuppliedby
FSL-T8 lamps(FoshanElectricalandLightingCo.
Ltd.China).Polyesterfilm(LuckyFilmsCo.Ltd.,
Baoding, China), 0.125mmthick, wasusedtofilter
bothUV-CandUV-Birradiation.Theintensityof
PAR was60μmolm-2 s-1.SupplementaryUV-B
radiationwassuppliedbyUV-Bfluorescentlamps
(BeijingInstituteofOpto-Electronic, Technology,
Beijing, China).Thelampswerewrappedwith0.125
mmthickcelulosediacetatefilm(LuckyFilmsCo.
Ltd., Baoding, China)filteringUV-C(<280 nm)
irradiationtosupplyUV-Birradiation.Althelamps
weremountedinmetalframes.Thedistancefromthe
lampstoplantwas70 cm.Thespectraliradiancewas
weightedaccordingtothegeneralizedplantaction
spectrum[ 13] andnormalizedat300 nm toobtain
efectiveradiation(UV-BBE).ThesupplementalUV-
BBE doseinsimulatedambientUV-Biradiationwas
6.93 kJ.m-2 d-1 usingascontrolandenhancedUV-B
radiation was 9.01 kJm-2d-1 UV-BBE (with 30%
diference).Thepolyesterandcelulosediacetate
122　 　热带亚热带植物学报 第 19卷
filmswerepre-solarizedfor8 handchangedevery7
daystoensuretheuniformityofiradiation.ThePAR
lampsiradiatedfor12hoursfrom7:00to19:00per
day, andUV-Bfor8hoursfrom9:00to17:00.The
treatmentswereachievedunderairtemperatureof(25
±1)℃.
1.3Photosyntheticpigments
Gametophyteswerehomogenizedinpre-chiled
95% ethanol, the contents ofchlorophyl and
carotenoidweredeterminedspectrophotometricalyby
readingabsorbanceat470 nm, 649 nmand665 nm
asdescribedbyBaoandLi[ 14] .
1.4Antioxidantenzymeassays
Enzymeswereextractedbygrinding0.5 gof
uppergametophytesinapre-chiledmortarandpestle
byliquidnitrogenwith6 mlof100mmol/Lpotassium
phosphatebufer, pH 7.8 containing1% polyvinyl
polypryrolidone(PVP).Thehomogenatewasfiltered
throughfourlayersofcheeseclothandcentrifugedat
12000×gat4℃ for20 minutesandsupernatantwas
usedforenzymeassays.
SODactivitywasmeasuredaccordingtoBeyer
andFridovich[ 15] withsomemodifications, 3 mL
reactionmediumcontained50 mmol/LK-phosphate
bufer, pH7.8, 14 mmol/Lmethionine, 75 μmol/L
NBT(nitrobluetetrazolium), 0.1 μmol/LEDTA,
2 μmol/Lriboflavin.0.1 mLofenzymeextractwas
addedtostartthereactionandincubateat25℃under
30 μmolm-2s-1iradiancefor10minutes.Thereaction
mixturewithoutenzymeextractdevelopedmaximum
colorduetomaximumrateofreductionofNBT.A
non-iradiatedreactionmixturedidnotdevelopcolor
andwasusedasthecontrol.Theformationofblue
formazanwasmonitoredbytakingtheabsorbanceat
560nm.OneunitofSODactivitywasdefinedasthe
amountofenzymerequiredtocause50% inhibitionof
therateofNBTphotoreduction.
ForthedeterminationofPODactivity, analiquot
ofthesupernatantwasdiluted1:24withbuferbefore
assay.Thereactionmediumwasformedby50 mLK-
phosphatebuferwithadditionof28 μLguaiacoland
19 μLH2O2.Thereactionwasstartedbyadding100
μLdilutedenzymeextractto3 mLreactionmedium.
Increaseintheabsorbanceduetoguaiacoloxidation
wasmeasuredat470nm.Enzymeactivitywasdefined
astheincreaseinabsorbancerecordedatoneOD
valueofA470perminuteunderassaycondition[ 16] .
CATactivitywasassayedaccordingtothemethod
ofZhangetal.[ 17] .TwoErlenmeyerflasksnumbered
wereaddedwith200 μLenzymeextractand9.8 mL
K-phosphatebufer, respectively, thenaddedwith5
mL1.8 mol/LH2SO4 toNo.2 flasktodenaturethe
enzyme.Twoflaskswereincubatedat22℃ for20
minutes, thenrespectivelyadded5 mL0.02 mol/L
H2O2 toreactfor5 minaccurately, lateradded5 mL
1.8 mol/LH2SO4 toNo.1 flask.Thenadded1 mL
20% KI, 3 dropsof10% ammoniummolybdate, 5
dropsof1% amylumtothetwoflasks, thetitration
waswith0.02 mol/LNa2S2O3.TheactivityofCAT
canbecalculatedbythedecompositionofH2O2.
1.5 Assayoflipidperoxidation
Oxidativedamagestolipidswereestimatedasthe
contentoftotal2-thiobarbituricacid(TBA)reactive
substancesandexpressedasequivalentsofMDA
according to the method of Zou[ 18] . Upper
gametophyteswere(0.8 g)homogenizedin6 mLof
10% (w/v) trichloroaceticacid (TCA), then
centrifugedat10000×gfor10minutes.Analiquotof
2mLofsupernatantwasmixedwith2mLof0.6% 2-
thiobarbituricacidin10% TCA.Themixturewas
heatedat95℃ for15 minutesandquicklycooledin
anice-waterbath, aftercentrifugationagain.The
concentration ofMDA wascalculated from the
absorbanceat532 nm (correctionwasdoneby
subtractingtheabsorbanceat600 nmforunspecific
turbidity) by using extinction coeficient of
155mmol-1cm-1.　
1.6 Statisticalanalysis
Valuespresentedin thetextindicatemean
values±S.E.ofthreeindependentexperiments.The
significanceofdiferencesbetweencontrolandUV-B
exposedmaterialwasanalyzedusingtheStudentst-
testforcomparison ofmeansatthe levelof
第 2期 沈蕾等:多蒴灰藓对强紫外线照射的生理响应 123　
significanceofP<0.05 orP<0.01.
2 Results
2.1EffectofUV-Bonphotosyntheticpigments
EnhancedUV-B radiation markedlyreduced
Chla, Chlb, andChl(a+b)contentsofHypnum
fertile(Table1)comparedtocontrol, andthe
contentsdecreasedwithtime.AfterHypnumfertile
wereexposedfor7 days, 14 daysand21 days,
respectively, thecontentofChlareducedby6.0%,
13.4%, 15.0%;Chlbreducedby6.2%, 7.0%,
14.6% andtotalchlorophyl reducedby6.1%,
11.3%, 14.9%, andcarotenoidreducedby14.
3%, 21.0%and20.9%, respectively.
Table1EfectsofUV-BradiationonchlorophylcontentofH.fertile
Radiationdays Treatment Chlorophylcontent(mgg
-1FW)
Chla Chlb Chl(a+b) Chla/b
Carotenoidcontent
(mgg-1FW)
7 Control 0.842±0.012 0.418±0.008 1.261±0.020 2.014±0.012 0.237±0.009
Treatment 0.794±0.012＊ 0.408±0.011 1.201±0.011 1.949±0.072 0.203±0.014
14 Control 0.818±0.018 0.400±0.011 1.218±0.014 2.050±0.089 0.219±0.009
Treatment 0.705±0.024＊ 0.382±0.013 1.08±0.018＊＊ 1.852±0.112 0.173±0.011＊
21 Control 0.742±0.018 0.379±0.011 1.121±0.029 1.958±0.015 0.206±0.010
Treatment 0.63±0.016＊ 0.324±0.016 1.001±0.022＊ 1.724±0.088 0.163±0.007＊
　　n=3.＊, ＊＊ indicatesignificantdiferencesat0.05and0.01levelsbyStudentsttest, respectively.
2.2EffectofUV-Bonlipidperoxidation
Fig.1 showedthatenhancedUV-Biradiation
resultedinsignificantincreaseofMDAcontentofH.
fertile compared to control. Itsuggested that
membrane was damaged by enhanced UV-B
irradiation.Theinjuryaggravatedwithexposuretime.
Afterexposedfor7, 14, and21 days, MDAcontent
increasedby29.4%, 36.9%, 45.2%, respectively.
Fig.1 EfectofUV-BonMDAcontentofHypnumfertile
n=3;＊, ＊＊ indicatesignificantdiferencesat0.05and0.
01levelsbyStudentsttest, respectively.
2.3EffectofUV-BontheactivitiesofSOD, POD
andCAT
TheactivitiesofSOD, POD, andCAT al
increasedunderenhancedUV-Bradiationafter7, 14,
21daysoftreatmentascomparedwithcontrol(Fig.2
to4), butthetimefortheiractivitiestoreach
significantdiference(P<0.05)werediferent.For
SODactivity, enhancedUV-Biradiationfor7 days
hasnodiferencefrom control, aftertreatedfor
14daysand 21 days, the diferenceexhibited
significant.ForPODactivity, after21 daystreatment
Fig.2EfectofUV-BonSODactivityofHypnumfertile
n=3.＊, ＊＊ indicatesignificantdiferencesat0.05and0.01
levelsbyStudentsttest, respectively.
ofenhancedUV-Bradiation, thediferenceexhibited
significant(P<0.05).CATactivityaftertreatedby
UV-Bfor7 daysincreasesignificantlycomparedwith
control.Aftertreatedfor7, 14, and21 days, SOD
activityincreasedby9.0%, 19.9%, and17.2%,
124　 　热带亚热带植物学报 第 19卷
Fig.3EfectofUV-BonPODactivityofHypnumfertile
n=3.＊, ＊＊ indicatesignificantdiferencesat0.05and0.01
levelsbyStudentsttest, respectively.
PODactivityincreasedby1.1%, 15.2% and26.
8%, and POD activity increased by 11.5%,
15.3%, 34.2%, respectively.
3 Discussionandconclusions
TheefectsofUV-B onchlorophylcontents
variedamongdiferentmosses.Inthemajorityofthe
bryophytesinvestigated, chlorophyl concentrations
arenotinfluencedbyUV-Bexposure.However, after
exposuretosupplementalUV-Bradiation, Sphagnum
fuscum exhibited decreasing of chlorophyl a
concentration, whilechlorophyllevelsinSphagnum
balticumincreased[ 12] .Inthisstudy, Chla, Chlb,
totalChl, andCarcontentsalgradualyreduced
under enhanced UV-B radiation compared to
simulatedambientUV-Bradiation.Similarresults
werealsoreportedinpreviousstudiesofotherhigher
plants[ 1, 8, 19] .SuchreductioninthelevelofChlunder
UV-Benhancedradiationmaybeduetoinhibitionin
theirbiosynthesisorbreakdownofpigmentsortheir
precursors[ 19] .Moreover, Chlorophylsexistina
highlyorganizedstatebyformingcomplexeswith
proteinsandlipids;therefore, theUV-Binduced
degradationofproteinandlipidscomplexesassociated
withpigmentsinthethylakoidmembraneresultedin
thedecreaseofChla[ 20] .Thedecreasesofchlorophyl
mayprotecttherestofthecel[ 8] .Severalstudies
showedthatChlacontentreducedmorequicklythan
ChlbandCarcontents, andresultedinthedecrease
Fig.4EffectofUV-BonCATactivitiyofHypnumfertile
n=3.＊, ＊＊ indicatesignificantdiferencesat0.05and0.
01levelsbyStudentsttest, respectively.
ofChla/b[ 3, 21] , which isnotobserved in our
experiments.Sincecarotenoidsprotectchlorophyl
from photooxidative destruction, therefore, any
reduction in carotenoids could have serious
consequencesonchlorophyl[ 3, 20] .However, wecan
explainthephenomenoninotherway, thequick
reduction of carotenoide content because the
absorbanceofUV-Bradiationbyitsconjugateddouble
bonds, thusprotectingitschlorophylsfromtheUV-B
radiation.
StudiesshowedthatUV-B radiationproduces
oxidativestress, itisgeneralyacceptedthatthe
mechanism ofUV-B toxicity involves oxidative
damage[ 22] .Aneficientantioxidantdefensesystemis
presentinplantstocounteractoxidativestress.Itis
composed by enzymatic and non-enzymatic
mechanisms. The former includes superoxide
dismutase(SOD), catalase(CAT), peroxidase
(POD), etc.Thenon-enzymaticmechanismsconsist
ofantioxidants such as ascorbate, glutathione,
tocopherolandcarotenoids[ 23] .Superoxidedismutase
acceleratestheconversionofsuperoxidetohydrogen
peroxide, catalaseandperoxidasecatalyseH2 O2
breakdown[ 22] .Inregardtotheactivitiesofdefense
enzymesinhigherplantstoenhancedUV-Bradiation,
therestilexistcontradictoryresults[ 8, 22, 24] .Thisstudy
showedhattheactivitiesofSOD, POD, andCATal
increasedinthemosofH.fertileunderenhanced
第 2期 沈蕾等:多蒴灰藓对强紫外线照射的生理响应 125　
UV-Bradiationcomparedwiththecontrol.Ourresults
suggestedthatenhancedUV-Bradiationinducedthe
enzymaticantioxidantdefensesystem, whichhelpthe
mossinacclimationtothestress.
MDA isanindicatoroflipidperoxidationof
membrane, and can be used to evaluate the
impairmentoflmembrane.MDAcontentinH.fertile
increasedwithstresstimeunderenhancedUV-B
radiation, thisindicatedthemembranewasdamaged
byactiveoxygen.TheincreaseofMDAcontentmay
beduetothecontentofactiveoxygenexceededthe
scavengecapabilityofantioxidantdefensesystemin
despiteoftheactivitiesofSOD, POD, CATal
increased.
Concerningthesusceptibilityofmosstolight
radiation, onemayassumedthatthemajorityof
mossesaresusceptibletoUV-Bradiation.Becauseof
theirsimplestructure, onlyonecellayerofaleave,
lackingprotectionbyacuticle, anundiferentiated
leafanatomy, leafwatercontentdependsonair
humidityandtheyarerootlessandthuslackbufering
againstaboveground stress[ 25] . The nutrition of
Hypnumfertileismainlyfromatmosphericdeposition
andrain.Thefactorefectedthegrowthofbryophyte
ismainlyhumidity.Culturingmosswithwetfilter
paper, notonlyformthesamebackgroundfordiferent
treatments, butalsoprovidehumiditytomaintainthe
vitalityofmoss.
Whereasthe hitherto studies indicated the
bryophytesarenotmoresusceptiblethanvascular
plants.HavingstudiedtheefectsofenhancedUV-B
radiationonHylocomiumsplendensandPolytrichum
commune, Gehrkelsuggestedthatmorphologicaland
functionalcomplexityofaspeciesmaynotenhancethe
abilityofindividualstocopewithdisturbancesinitialy
oron ashort-term scale[ 25] . Photosyntheticand
photoprotectivepigmentsareoftenusedtoassessthe
efectsofUV-Bradiationonplants, butchangesof
thesepigmentsinmossesunderUV-Bradiationare
also existcontradictory results[ 11] . Our results
suggested thatenhanced UV-B radiation caused
oxidativestress, the mossofH. fertile could
aleviatedstressbyincreasingthecelprotective
enzymesactivities.ThoughtheactivitiesofSOD,
POD, andCATalincreasedunderenhancedUV-B
radiation, butthetimefortheiractivitiestoreach
significantdiferencevariedmuch, whichmayresult
fromthediferenceoftheirsensitivitytooxidative
stressfromenhancedUV-Bradiation.
Thisexperimentwasmanipulatedinlaboratorywith
certainPARandUV-Bradiationandthematerialwas
keepingwetalalone.Innaturalconditions, moses
oftensuferfrom drought, thePAR/UV-B ratiois
diferent, therearemanyotherfactorscouldinfluence
theresults.Furthermore, thematerialswereirradiated
foronlythreeweeks, hence, diferentresponsesare
likelytobeappearunderlong-termUV-Biradiation.
Furtherstudiesshouldconsiderthesefactors.
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