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Inhibition

By Kathryn Thompson,2014-02-18 10:38
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Inhibition

    Inhibition

    transcribed,splicedandtranslatedasinmaize.TheenzymeactivityofleafPEPCintransgenicwheathasbeendetected.The

    activitiesofleafPEPCincreasedover3-5timesinsometransgenicplants.Thedataofphotosynthesisrateandtranspiration

    rateoftransgenicwheatflagleavesshowedthattheC??4??pepcgenecanincreasethephotosynthesisrateandtranspiration

    rateoftransgenicwheat.

    Keywords:C4photosynthesispathway;pepcgene;transgenicwheat

    CHINESESCIENCEBULLETIN2004,49(20):21372143

    Effectsofnitrogendeficiencyongasexchangelchlorophyllfluorescencel andantioxidantenzymesinleavesofriceplants

    Huang,ZAJiang,DAYang,YSun,JWJin,SH

    ZhejiangUniv,CoilLifeSci,StateKeyLabPlantPhysiol&Biochem,Hangzhou310029,PeoplesRChina.

    Abstract:Gasexchange,chlorophyll(Ch1)fluorescence,andcontentsofphotosyntheticpigments,solubleproteins(ribulose

    1,5

    bisphosphatecarboxylase/oxygenase,RuBPCO),andantioxidantenzymeswerecharacterizedinthefullyexpanded6

    (tl1)leavesinriceseedlingsgrownoneithercomplete(CK)oronnitrogen

    deficientnutrient(N-deficiency)solutionsduring

    a20

    chaseperiod.Comparedwiththecontrolplants,thelowerphotosyntheticcapacityatsaturationirradiance(P-max)was

    accompaniedbyanincreaseinintercellularCO2concentration(Ci),indicatingthatinN

    deficientplantsthedeclineinPmax

    wasnotduetostomatallimitationbutduetothereducedcarboxylationefficiency.ThefluorescenceparametersPhi(PS2),

    FV'/Fm',electrontransportrate(ETR),andq(p)showedthesametendencyasP

    maxinN-deficientplants.Correspondingly,

    ahigherq(N)paralleledtheriseoftheratioofcarotenoid(Car)toChlcontents.However,F

    v/Fmwasstilldiminished,

    suggestingthatphotoinhibitiondidoccurinthephotosystem2(PS2)reactioncentres.Inaddition,theactivitiesofantioxi

    dantenzymesonafleshmassbasisweregraduallylowered,leadingtotheaggravationofmembranelipidperoxidationwith

    theproceedingN

    deficiency.TheaccumulationofmalonyldialdehyderesultedinthelesseningofChlandsolubleprotein

    content.AnalysesofregressionshowedPS2excitationpressure(1

    qP)waslinearlycorrelatedwiththecontentofChland

    inverselywithsolubleprotein(particularlyRuBPCO)content.TherewasalagphaseintheincreaseofPS2excitation

    pressurecomparedtothedecreaseofRuBPCOcontent.Therefore,theincreasedexcitationpressureunderNdeficiencyis

    probablytheresultofsaturationoftheelectrontransportchainduetothelimitationoftheuseofreductantsbytheCalvin

    cycle.RiceplantsrespondedtoNdeficiencyandhighirradiancebydecreasinglight

    harvestingcapacityandbyincreasing

    thermaldissipationofabsorbedenergy.

    Keywords:catalase;leafsenescence;malonyldialdehyde;Oryzasativa;peroxidase;photosynthesis;photosystem2:ribu

    lose1,5

    bisphosphate;carboxylase/oxygenase;stomatalconductance;transpirationrate PHOTOSYNTHETICA2004,42(3):357364

    Inhibitionofphotosynthesisbyshiftinthebalanceofexcitation,energy

    distributionbetweenphotosystemsindithiothreitoltreatedsoybeanleaves Jiang,CDGao,HYZou,QJiang,GM

    

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ShandongAgrUniv,DeptPlantSci,TaiAn27l0I8,PeoplesRChina.

    ChineseAcadSci,InstBot,LabQuantitatVegetatEcol,Beijing100093,PeoplesRChina Abstract:Chlorophyllfluorescencekineticswasusedtoinvestigatetheeffectofl,4dithiothreitol(DTT)onthedistribution

    ofexcitationenergybetweenphotosystem1(PS1)andphotosystem2(PS2)insoybeanleavesunderhighirradiance(111).

    ThemaximumPS2quantumyield(Fv/F

    m)washardlyaffectedbythepresenceofDTT,however,photon.saturated

    photosynthesiswasdepresseddistinctly.PhotochemicalefficiencyofopenPS2reactioncentresduringirradiationfF.v'/F.

    m')wasenhancedbyabout30

    40%byDTTtreatment,whereasphotochemicalquenching(q(p))wasdepressedbyabout 40%underHI.DTTtreatmentcauseda30%decreaseinallocationofexcitationenergytoPSIunderHIanda20%increase

    toPS2.AnobviousshiftinthebalanceofexcitationenergydistributionbetweenphotosystemswasobservedinDTT-

    treatedleaves.Thoughhighexcitationpressure(1q(p))resultedfromDTrtreatment,non

    photochemicalquenching(q

    (N))waslower.DTTcompletelyinhibitedtheformationofzeaxanthinandalsodistinctlydepressedthestatetransition(q

    (T)).TheshiftinthebalanceofexcitationdistributionbetweenthetwophotosystemsinducedbyDTrwasmainlydueto

    theenhancementofexcitationenergycapturebyPS2antennaandtheinhibitionofstatetransition.Itmightbetheshiftin

    thebalancebetweenthetwophotosystemsthatmainlyinducedthedepressionofphotosynthesis.Thus,tokeephigh

    utilizationefficiencyofabsorbedphotonenergy,itisnecessarytomaintainthebalanceofexcitationdistributionbetween

    PS2andPS1.

    Kcywords:chlorophyllfluorescence;excitationenergydistribution;netphotosyntheticrate;photosystems;quenching;

    statetransition;xanthophyllcycle.

    PHOTOSYNTHETICA2004,42(3):409-415

    Acomparativeanalysisoffour

    in

    modelsofphotosynthesisfor11plantspecies

    theLoessPlateau

    Gao,QZhang,XSHuang,YMXu,HM

    BeijingNormalUniv,lnstResourcesSci,Beijing100875,PeoplesRChina. Abstract:Wecomparedperformanceandbehavioroftwosuitesofmodelsofphotosynthesisbasedonfielddataof11plant

    speciesinthesemiaridI~essPlateauinnorthemChina.DiurnalnetphotosynthesisratesandstomatalconductanceOftwo

    C.3treesofRobiniapseudoacaciaL.andMaluspumilaMil1..twoC

    3shrubsofCaraganakorshinskiiKom.andHippophae

    rhamnoidesL.,aC.3subshrubofLespedezadavurica(Laxm.)Schind1.,twoC.3forbsofArtemisiagmeliniiWeb.ExStechm.

    andA.giraldiiPamp.,twoC-4grassesofPanicumvirgatumandBothriochloaischaemum(L.)Keng,andtwoC4cropsofZea

    maysL.andSetariaitalica(L_),wereobservedinfieldinthreemonthsofMay,JulyandSeptemberin2002.Netphotosyn

    thesisratesofthe11specieswerethenfittedwithFarquhar'sbiochemicalmodelofphotosynthesisforC3species,Berry

andFarquhar'sintercellulartransportmodelforC

    4species.andmodifiedThornleyandJohson'sleafphotosynthesis

    modelsforC.3andC.4species.andtheobservedstomatalconductancewasfittedwithastomatalconductancemodel,by

    meansofnonlinearleastsquareregression.Thefourphotosynthesismodelswerethencoupledwiththestomatalconduc

    tancemodeltopredictnetassimilationratesoftheseplantsunderextrapolatedmicro-environmentalconditions.Theresults

    ofnonlinearleast.squareregressionshowedthatthebiochemicalmodelsexplainedonaverage66%and82%ofvariations

    inobservednetphotosynthesisratesfortheC3andC

    4plants.respectively,incomparisonwiththeexplanationsOf72%

    and76%bvtheleafphotosynthesismodels.Themoremechanistic,detailedtreatmentofbiochemicalprocessesinthe

    

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