Rootstock control of scion response to water stress in grapevine.

(1)

ContentslistsavailableatSciVerseScienceDirect

Environmental

and

Experimental

Botany

j o u r n a l ho me p ag e:w w w . e l s e v i e r . c o m / l o c a t e / e n v e x p b o t

Rootstock

control

of

scion

response

to

water

stress

in

grapevine

Sara

Tramontini

a,b,∗

_,

_Marco

_Vitali

b

_,

_Luna

_Centioni

b

_,

_Andrea

_Schubert

b

_,

Claudio

Lovisolo

b,c

a_European_Food_Safety_Authority_(EFSA),_Plant_Health_Unit_(PLH),_via_Carlo_Magno_1/a,_43126,_Parma,_Italy1

b_University_of_Turin,_Department_of_{Agricultural,}_Forest_and_Food_Sciences,_(DISAFA)_via_Leonardo_da_Vinci_44,_10095,_Grugliasco,_Italy c_Plant_Virology_Institute,_National_Research_Council_(IVV-CNR),_Grugliasco_unit,_Via_Leonardo_da_Vinci_44,_10095,_Grugliasco,_TO,_Italy

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received26February2013

Receivedinrevisedform18April2013 Accepted22April2013 Keywords: Hydraulicconductance Mercuricchloride Stomatalconductance Transmembranepathway Vitisgenotypes Waterpotential

a

b

s

t

r

a

c

t

Rootstocksplayamajorroleingrapevinetolerancetowaterstressbycontrollingandadjustingthe watersupplytoshoottranspirationdemand.Thisstudyaimedtocharacterizetheinfluenceofrootstock genotypesintheadaptiveresponseofscionstowaterlimitingconditions.Theeffectofrootstockgenotype (140RuandSO4)wasobservedinthedifferentavailabilityofwaterprovidedtothescions(Cabernet Sauvignon,Grenache,Merlot,Syrah),whilescionsinfluencedstomatalcontrolofwatertranspiration. Implicationonthecell-to-cellcomponentofplantwatertransportinbothrootstockandscionimpacted onembolismsformationinrootsandonhydraulicsofleaves.Themainconclusionofthepresentstudy wasthatrootstockandsciongenotypesareabletoconfertotheplanttraitsofdroughtadaptability influencingrespectivelythecapacityofwaterextractionfromthesoilandthesensitivityofthestomatal control.

1. Introduction

Thedehydrationobservedunder droughtconditionsappears

when an imbalance occurs between water extracted from the

substrateandwaterlostbytranspiration(Arocaetal.,2012). There-fore,inplantsthatareroutinelygrafted,suchasgrapevine(Vitis viniferaL.),rootstockeffectonscionperformancemustbe consid-eredinthestudyofadaptabilitytostressconditions.Rootstocks providetolerancetoexogenouslimitingfactors,biotic(e.g., soil-bornepests) andabiotic(e.g.,salinity, wateror oxygendeficit), whileinfluencingtheecophysiologicalbehaviourofthescionand itsberryquality(BavarescoandLovisolo,2000;Padgett-Johnson etal.,2000;Soaretal.,2006;Tramontinietal.,2012;deSouzaetal., 2009;IbacacheandSierra,2009;Rizk-Allaetal.,2011;Marguerit etal.,2012).Stomataare considereddirectresponsible of opti-mizing thebalancebetweencarbon gain and water loss ofthe plant(Rogiersetal.,2012),andthepatternsoftheirresponse,in termsoftimingandintensity,aregeneticallydetermined(Chaves etal.,2010).Significanteffortshave beendonein theselection of the optimal rootstock/scion combinations to satisfy specific

∗ Correspondingauthorat:EuropeanFoodSafetyAuthority(EFSA),PlantHealth Unit(PLH),viaCarloMagno1/a,43126,Parma,Italy.Tel.:+390521036878; fax:+3905210360878.

E-mailaddress:sara.tramontini@efsa.europa.eu(S.Tramontini).

1 _The_positions_and_opinions_presented_in_this_article_are_those_of_the_author_alone

andarenotintendedtorepresenttheviewsorscientiﬁcworksofEFSA.

grapegrowingneeds(e.g.,Koundourasetal.,2008;Hamdanand Basheer-Salimia,2010; Komaret al.,2010).However,theeffect ofrootstock/scioninteractiononplantadaptationtostressisstill verymuchdebated(Gambettaetal.,2012).Sincedrought condi-tionsaffectwatertransportfromthesoilthroughtheplantintothe atmosphereinasoil–plant–aircontinuumthatisinterconnected byacontinuousfilm ofwater,measuringitsinfluenceonplant watertransportrequiresconsideringbothwaterextractionatthe soil–rootinterfaceandwaterreleaseattheleaf–airinterface(Janott etal.,2011).Althoughthekeyroleplayedbybothrootstockand scionisacknowledgedtheirrelativecontributionanddifferences obtainedbyspecificcombinationofgenotypesrequiresomefurther analysis.

Theaimofthisstudywasthereforetoclarifytherelativeroleof rootstockandscioninthehydraulicresponsetolimitationsinwater availability.Inordertodoso,weevaluatedthedifferencesobserved betweentwograpevinerootstockgenotypes(considered represen-tativeoftwoofthemostwidespreadhybrids:Vitisberlandieri×Vitis rupestris,and V.berlandieri×Vitis riparia)and amongfourscion genotypes(cultivars),separatelyandincombination(i.e.ongrafted plants).Therelationshipbetweenstomatalconductance(gs)and

leafwaterpotential(leaf)wasusedtorankthesciongenotypes

fortheirabilitytowithstandwaterstress(Rogiersetal.,2012).Root hydraulicconductivity,intermsofshortandlongdistance trans-port(overmembranesandxylem,respectively)wasconsideredin ordertocharacterizetheresponsesoftherootstocks.Aquaporins playamajorroleintranscellularwatermovementbyfacilitating thetransportofwaterthroughcellmembranes(Kaldenhoffetal.,

(2)

forces, limited by theresistanceproduced by cavitation events (Arocaetal.,2012).Forthisreason,ameasurementonthelevelof embolismsoftherootsystemwasconducted.Ourresultsshowthat therootstockcontrol(basedonroothydraulicconductance)and thescioncontrol(basedonstomatalconductance)followan addi-tivepatternincooperatingtoadaptationtodrought,conﬁrmingthe grapevineasanoptimalmodelplantformolecularand physiologi-calstudiesonbothplantdroughtavoidanceandtolerance(Lovisolo etal.,2010).

2. Materialsandmethods

2.1. Plantmaterial

For those experiments requiring thedestruction of theroot system,theinvestigationwasconductedon2-year-oldplantsof twodifferentgrapevinerootstocks, onederivedfrom hybridiza-tion of V. berlandieri with the xerophylic species V. rupestris (140Ru),and theotherfromV. berlandieriwiththemesophylic speciesV. riparia (SO4),withthree replicatesfor genotype.The twogenotypeswereselectedascharacterizingtheextremesinthe resultsofLovisoloet al.(2008).Alltheotherexperimentswere conductedduringtwoconsecutiveyears (2011and2012)on 2-year-old(and 3-year-old thenextyear) plants of fourcultivars (CabernetSauvignon,Grenache,Merlot,Syrah)graftedonthetwo above-mentionedrootstocks,withfivereplicatesforeach combi-nationrootstock/cultivar.Thefourcultivarswereselectedtaking intoaccounttheirecophysiologicalcharacterizationobtainedby previous authors: Grenache is near-isohydric (Schultz, 2003; Santestebanetal.,2009),Merlotisanisohydric(WilliamsandBaeza, 2007;ShellieandGlenn,2008),Syrahisanisohydric(Schultz,2003; Rogiersetal.,2009;Santestebanetal.,2009),andCabernet Sauvi-gnon is classified as isohydric(Chalmers, 2007)or anisohydric (WilliamsandBaeza,2007),dependingfromtheauthors.Allplants weregrowninagreenhousewithnosupplementarylightor heat-ing,in 4Lpotsfilledwitha substratecomposedof sandy-loam soil/expandedclay/peatmixture(4:2:1involume),withafinalpH of7.3.AdditionalleavesofCabernetSauvignon,Grenache,Merlot, Syrahneededfortheexperimentondetachedleaveswerecollected fromtheexperimentalvineyardlocatedattheFacultyof Agricul-tureoftheUniversityofTurin(Grugliasco,Italy),fromplantsofthe sameclonalorigin.Tothisaim,matureleaves(10thnodeonwards) werecollectedinthemonthof July.Theseleaveswereusedin ordertostudystomatalbehaviourinabsenceofrootstockandshoot effects.

2.2. Leaf,rootandsoilwaterpotentials

Leaf water potential(_leaf)and root water potential(root)

wereestimatedwithapressurechamber(Scholanderetal.,1965; model used:Soil MoistureEquipment Corp.,SantaBarbara, CA,

Wemeasuredhydraulicconductance,itstransmembranewater movementcomponent,andtheintensityofxylemembolization.

Allmeasurements were based ona destructive method witha

controlledtension–pressureapparatus(Lovisoloetal.,2002)and taken in sequence on thesame plantmaterial as described by

Lovisoloetal.(2008).Therootsystemwasgentlycleanedfrom soilunderwaterandcutattheinterfacebetweenrootandshoot. Aftermeasurementofweightandvolume,itwasimmersedintoa tension–pressurechamberﬁlledwithtapwateranditsstalkwas clampedwitharubbersleeve.Aninitialconductancewasmeasured byapplyinganegativepressureof−80kPafor5minthroughthe sleeve:thistensionsimulatesthesuctionforcesthatcausewater transpirativetransportinthepottedroots.Thesamepressurewas thenimposedfor5minafterhavingtreatedtherootwithasolution of0.05mMHgCl2 for60min(+15minforstabilizingthesystem)

inorder toinhibit mercury-sensitiveaquaporins.Thedifference betweenthisconductanceandthepreviousconductancedefines theportionof conductance sustainedby transmembranewater movement.Thesamepressurewasagainimposedforother5min afteraflushingof+100kPafor5mintothewholeroot,inorderto freethesystemfromembolisms.Thedifferencebetweenthisvalue andthepreviousdefinestheconductanceachievablebythesystem throughtheapoplasticpathwayinabsenceofembolisms. 2.4. Stomatalconductance

Inordertoexcludetherooteffectandtoconcentrateonthe characteristicsinducedbythegraftedcultivar,thismeasurement wasconductedondetachedleaves,treatedasself-contained func-tionalunits,asdescribedbyBrodribb(2009).Stomatalconductance (gs) was measured on fully developed leaves with a portable

GasExchangeFluorescenceSystem(GFS-3000,HeinzWalzGmbH, Effeltrich,Germany).Measurementswereconductedbyclamping theleavesintheleafchamber,wherephotosyntheticactive radia-tion,(PAR:1200␮molm−2s−1)andtemperature(25◦C)werekept constant.Azero-pointforCO2wassetatthebeginningofeachday

ofmeasurements.Inthecaseoftheexperimentonattachedleaves, aftermeasuringgs,thesameleafwasusedformeasuringleaf.The

collectionofdatawasconcentratedwithintwoweeks(between 31Mayand15June2012)inordertominimizeanypotential sea-sonalfluctuation(Alsinaetal.,2011).Inthecaseoftheexperiment ondetachedleaves,sevenleavesperreplicatewereexcisedunder waterandimmediatelyplaced in50mLtubeswiththeirpetiole immersedindeionisedwater.Leaveswerekeptinthelaboratory underconstantartificiallight(400␮molm−2s−1PAR)and temper-ature(24–27◦C)andtranspirationwascontinuouslymonitoredon oneofthem.Whentheleafreacheda steadystatein transpira-tion(usuallyafter20min,withacoefficientofvariation<3%for 3min,Nardini and Salleo,2005),all tubeswere simultaneously emptiedfromwater.Sixmeasurementsof_leafwerethentaken witha4-minintervalontheremainingleaves.Lateron,in analy-sisofthecorrelationbetweengs andleaf,itwasdecidednotto

(3)

Fig.1. Relationshipbetweensoilwaterpotential(soil,MPa)andleafwaterpotential(leaf,MPa)onvineplantsoffourcultivars(CabernetSauvignon,Grenache,Merlot

andSyrah)pottedonthesamesubstrateandgraftedontwodifferentrootstocks:140Ru(ﬁlledsquares)andSO4(emptycircles).Theﬁgurereferstodatacollectedduring twoyears:2011(a)and2012(b)betweenendofMayandbeginningofAugust.Eachtrendlinelabelisborderedwiththesamestyleofthelinetowhichitrefers.

considertheﬁrsttwo measurementsof gs due totheobserved

‘Iwanoffeffect’describedby Düring(1993),whichproduced an increaseingsimmediatelyafterremovaloftheleaffromwater.

Fourreplicatemeasurementsweredoneforeachcultivar. 2.5. Transmembranewaterpathinleaves

Inordertocomparethefourcultivarsfortheirtransmembrane

water movement on foliar tissues, the methodology proposed

byTerashima and Ono (2002)wasfollowed and adapted. Each detachedleafwasdividedintwopartsalongthemedianvein.The halfwithoutpetiolewasusedascontrolandthehalfwith peti-olewasleftabsorbinga solutionof50mMof HgCl2 for 60min

beforethemeasurement.Duringthisperiod,theleafwasexposed tolight(1000␮molm−2s−1)tohelpuptakeofthesolutionthrough thepetiolebytranspiration. Fromeach half-leaf20 foliar disks withadiameterof1.2cmwereobtainedwithacircularcutterand weighted.Thediskswereﬂoatedon40mLofdeionizedwaterina Petridishwiththeadaxialsurfaceupwardsandwereshakengently for15min.Theywerethendriedonabsorbingpaperfor5minand weightedagain.Twelvereplicateleaveswereusedforeach culti-var.Theincreaseinturgidityoftheleafdiscswascalculatedwith thefollowingequation:

Averageweightincrease=

(ﬁnalweight−initialweight) initialweight

×100

Theobtainedvaluewastreatedasameasureofthehydraulic conductivityoftheplasmamembraneoftheleafdisc,suchasa rea-sonableapproximationofthetransmembranecomponentofwater transport,independentfromwatermovementviavasculature. 2.6. Statisticalanalysis

Data wereexpressed bymeans and correspondingstandard

errors.Resultsweresubmittedtoone-wayANOVAusingthe statis-ticalsoftwarepackageSPSS(version20,SPSSInc,Cary;NC,USA). Correlated variables were interpolated in ﬁgures by regression curvesplottedbymeansofMicrosoftExcel©_software.

3. Results

3.1. Rootstock–soilandleafwaterpotentials

Inordertocharacterizerootstockcomponentsofthecontrol ofstresseffects,weanalysedtherelationshipbetween_soil and leaf,duringtwoconsecutiveyears,inplantsgraftedon140Ruor

SO4.Atthesamevaluesofleaf,plantsgraftedon140Rushowed

morenegativesoilthanplantsgraftedonSO4.Thisdifferencewas

increasinglyevidentwithlowerleafandwasnotinﬂuencedbythe

scioncultivar(Fig.1).Plantdevelopment,measuredasleafarea, wasnotdifferentbetweenthetworootstocks(datanotshown).

3.2. Rootstock–roothydraulicconductanceandtransmembrane waterpath

Thediverserelationshipbetweensoilandleaf,observedinthe

tworootstockssuggesteddifferencesinthehydraulicconductance oftherootsystem.Weanalysedthisparameterinexcisedrootsof notgraftedplantsof140RuandSO4,atthesametimeevaluating thecomponentofconductancecontrolledbyxylemembolization. Roothydraulicconductance,measuredat−80kPaontheexcised rootbeforeandafterHgtreatment,wasalwayshigherin140Ru thaninSO4.However,Hgtreatmentreducedtheconductanceby 56% in 140Ruand 16% in SO4,a result not farfromthe range recentlyobtainedonrootstocks byGambetta etal.(2012)after H2O2aquaporininhibition.Pressureﬂushinginducedanincrease

ofconductanceof197%and369%respectively(Fig.2).

Fig.2.Hydraulicconductancemeasuredonexcisedrootof140Ru(filledboxes)and SO4(emptyboxes)duringthreesequentialtreatments:(i)depressurizingatthe api-calcutwithavacuumapplicationof−80kPa,(ii)treatingwithHganddepressurizing at−80kPa,and(iii)imposingapressureflushingof+100kPaontheHg-treatedroots. Means±standarderrors.Differencesweretestedwithineachtreatmentseparately. Valueswithdifferentlettersdiffersignificantly(P≤0.05).

(4)

Fig.3.Relationshipbetweenstomatalconductance(gs,mmolH2Om−2s−1)andleafwaterpotential(leaf,MPa)onvineplantsofCabernetSauvignon(a),Grenache(b),

Merlot(c)andSyrah(d)graftedontwodifferentrootstocks:140Ru(ﬁlledsquares)andSO4(emptycircles).Theﬁguresrefertodatacollectedbetween31Mayand15June 2012.Eachtrendlinelabelisborderedwiththesamestyleofthelinetowhichitrefers.

3.3. Scion–stomatalconductanceonattachedleaves

Whileassessingthepatternofgs/leafindetachedscioncultivar

leaves, weestablished ingrafted plants whetherthe genotype-dependentpatternsofgsadaptationtoleafwaterstatuswouldbe

affectedbytherootstock.Asituationconsistenttoallthefour cul-tivarscanbeobserved:atthesamelevelofleaf,infact,plants

graftedon140Rutendtohavehighergsvaluesthanplantsofthe

samecultivargraftedonSO4(Fig.3).Thiswasobservedatleaf

levelshigherthan−1MPa;onlyGrenache(Fig.3b)expressedthis conditionforleafvaluesmorenegativethan−1.1MPa.Theresult

ofatwowayANOVAconductedongsvaluesforthetwofactors

‘cultivar’and‘rootstock’conﬁrmedthatthedifferenceinthemean valuesamongthedifferentcultivarswasgreaterthanwouldhave beenexpectedbychanceafterallowingforeffectsofdifferences inrootstocks(P=0.031)andthatthedifferenceinthemeanvalues

amongthedifferentrootstockswasgreaterthanwouldhavebeen expectedbychanceafterallowingforeffectsofdifferencesin cul-tivars(P=0.037),butwithoutastatisticallysigniﬁcantinteraction between‘cultivar’and‘rootstock’(P=0.559).Whenthedatawere clusteredperrootstock(Fig.4),itwasmoreevidentthat,onboth rootstocks,gsofMerlotwasthelessinﬂuencedbyleafwhilethe

oppositewasforSyrah,whileCabernetSauvignonandGrenache conﬁrmedtheintermediateconditionalreadyobservedatFig.3, thelatterpresentingstrongvariationsofgswhengraftedon140Ru

andminimalvariationswhenonSO4(Fig.4). 3.4. Scion–stomatalconductanceondetachedleaves

Thenextstepwastofocusonthescioncultivarcontrolofgs,

whichwasmeasuredonprogressivelydryingleaves(Fig.5).For thecultivarsCabernetSauvignonandGrenache,thedynamicsofgs

Fig.4.Relationshipbetweenstomatalconductance(gs,mmolH2Om−2s−1)andleafwaterpotential(leaf,MPa)onvineplantsofCabernetSauvignon(crosses),Grenache

(emptydiamonds),Merlot(ﬁlledsquares)andSyrah(emptycircles)graftedontwodifferentrootstocks:140Ru(a)andSO4(b).Theﬁguresrepresentthesamedatashown inFig.3.Eachtrendlinelabelisborderedwiththesamestyleofthelinetowhichitrefers.

(5)

Fig.5.Dynamicsofstomatalconductance(gs,mmolH2Om−2s−1)measuredon

progressivelydrying,detachedleavesofCabernetSauvignon(crosses),Grenache (emptydiamonds),Merlot(ﬁlledsquares)andSyrah(emptycircles).Theinitial pointsrefertoleaveswiththeirpetioleimmersedinwater(negativeminute num-bers),thefollowingrefertomeasurementstakenatincreasingtimeafterextraction fromwater(emptyarrow).Theblackarrowsindicatethemomentsatwhichtheleaf waterpotential(leaf,MPa)wasmeasured(a).Relationshipbetweengsandleaf

showncalculatedonthesameleaves,basedonmeasurementstakenwhen indi-catedbyblackarrows(b).Eachpointisthemeanof4measures±standarderrors. Inframeb,eachtrendlinelabelisborderedwiththesamestyleofthelinetowhich itrefers.

overtime(40min)almostoverlapped,andshowedthelowestgs

valuesforthewholetimeframeamongallcultivars.Merlotwasthe leastrespondingtotheincreasingwaterstressconditions.Syrah,on thecontrary,initiallyhadthehighestgsvalues,but,afterasteep

decline,reachedthesamelowlevelsofCabernetSauvignonand Grenache(Fig.5a).Fromthegs/leafcurvesobtainedonthesame

leaves,furtherinformationonthecultivarbehaviourwasobtained (Fig.5b).Asconcernsleaf,GrenacheandSyrahrepresentedthe

twoextremes,theformerwiththelessnegative,andthelatterwith themostnegativeleafvalues.Thesteepnessoftheinterpolation

curveswashigherforMerlotandCabernetSauvignon,andinthe lattercasegsvaluesdroppeddownby60%betweenthe8thandthe

20thminwhileleafremainedaboutconstantat−2.0MPa.

3.5. Scioncell-to-cellpath

Thepreviousobservationsconcerningdifferencesamong culti-varsatleaflevelwereintegratedwithinformationontheputative cell-to-cellwaterpathway(Fig.6),asdonefortherootstocksat theroot level. Hg treatment signiﬁcantly decreased leaf water uptake inall cultivars. Cabernet Sauvignonand Grenache were stronglyaffectedbyHgtreatment,losingrespectively30%and67% oftheuptakecapacityoftheirfoliartissues.MerlotandSyrahalso

Fig.6.Averageincreaseofleafdiskweight(%)afterimmersioninwaterorHgCl2

solutionforthefourcultivarsCabernetSauvignon(lightgrey-filledboxes),Grenache (dark grey-filledboxes),Merlot(black-filled boxes)and Syrah(empty boxes). Means±standarderrors.Differencesweretestedwithineachtreatmentseparately. Valueswithdifferentlettersdiffersignificantly(P≤0.05).

presentedareduction,albeitlower,ofwateruptake,of28and20% respectively.

4. Discussion

Rootstocksareknowntoplayamajorroleingrapevine toler-ancetowaterstressbycontrollingandadjustingthewatersupply toshoottranspirationdemand(Carbonneau,1985;Soaretal.,2006; Alsinaet al.,2011;Marguerit et al.,2012).Thisstudy aimedto characterizetheinﬂuenceofrootstocksgenotypesintheadaptive responseofscionstowaterlimitingconditions.

WhatshowninFig.1suggestedthat140Rudepletesthewater soilreservesfasterthanSO4.Thiscouldbeexplainedbyitsveryhigh vigour,incomparisonwiththemoderatevigourofSO4(Gambetta etal.,2012),requiringtheextractionofgreateramountsofwater inordertocompensatethewaterlossesforcanopytranspiration (Jones,2012).140Ruisalsocharacterizedbyahighadaptationto waterdeﬁcit,whileforSO4theclassiﬁcationvariesconsiderably withthestudy:fromhigh(e.g.,Carbonneau,1985;Ciramietal., 1994),tomedium(e.g.,Delas,1992;Whiting,2005),tolow(e.g.,

Southey,1992;Dry,2007)andverylow(Galet,1998).Thehigher droughttoleranceof140Rucouldnotbecompletelyexplainedwith itscapacitytoexplorelargeranddeepersoilvolumesconferred bya moredeveloped rootsurface,asthelimitedsubstrate vol-ume(potconditions)andwateravailabilitywerethesameforboth genotypes.Valuabledetailswereprovidedbythesecond experi-ment,onnon-graftedrootstockplants(Fig.2).Theintrinsichigher stressresistanceof140RuthanSO4wasparalleltohigher conduc-tanceoftheexcisedroots(−80kPa),tohighercell-to-cellwater transportandtohigherresistancetoxylemcavitationprocesses, inagreementwithobservationsmadebyLovisolo etal.(2008). Thehigherputativeaquaporinactivity,orabundance,observedon 140Ru,couldnotonlyproduceamoreefficientrecoveryinxylem conduitre-fillingafterdrought-inducedembolisms(Lovisoloetal., 2008;Vandeleuretal.,2009)butalsoexplainthetoleranceofthis genotypetohighertensions()observedongraftedplantsatany levelofwateravailability(Fig.1).However,thecapacityof140Ru toextractwaterfromthesubstrateandtorecoverfromcavitation eventsmoreeasilythanSO4wasnotsubstantiallyreflectedonthe slightlyhighergsatagivenleaf,observedonthefourgrafted

culti-vars(Fig.3).Thislimiteddifferenceontheexpectedperformances atscionlevelmakesustohypothesizethemediationbychemical signaling,andmainlyABA(Soaretal.,2006;Margueritetal.,2012).

(6)

leaves,wherestomatalclosuredelayedtheleafdropbelowthe

thresholdof−2MPa(Fig.5b),couldnotbeexplainedwithinthe contextoftheabove-mentionedhydraulicforcesandcouldimply theinvolvementofcomplexhormonalsignallinginwholeplants, so that Cabernet Sauvignon assumes isohydric or anisohydric behaviour,dependingontheexperimentalconditions.Grenache,in spiteofitsgs/leafcurvesresemblancetoCabernetSauvignonon

wholeplants,presentedthetighteststomatalcontrolonexcised leaves(Fig.5)andthehighesteffectofHg-treatmentamongthe fourcultivars.Thisresultisconsistentwithwhatwasobservedin CabernetSauvignon,withamorecharacterizedisohydricity, prob-ablysupportedbythepredominanceofahydrauliccontrol.Syrah, asexpected,displayedabehavioroppositetoGrenache,butonly onexcisedleaves,withthehighestvaluesofgs,andthemost

dra-maticleafdrop(Fig.5),andthelowestpercentagelossinwater

uptake onHg-treated leaves. However,onwholeplants, there-foreatlessnegativeleaf,thesamecultivarexpressedabehaviour

closertoGrenache(near-isohydric)thantoMerlot(anisohydric), supportingtheresultsobtainedundermoderatewaterstressby

Pouetal.(2012).Finally,Merlotshowedthelowestvariationsof gsbothinwholeplants,andinexcisedleaves,conﬁrmingthe

gen-eralidentiﬁcationsasanisohydriccultivar.Thescarceeffectofthe Hgtreatment,similarasobservedinSyrah,suggeststhatthelow transmembranewatertransportcapacitynegativelyaffected sto-matalcontrol,limitingtranspirationintheformerandfavoringsoil waterdepletioninthelatter.

Theobservationsdoneonwholeplantsandonexcisedleaves allowedtoobtainamorecompletepictureofthecultivareffect on thehydraulic dynamics involved at plant and at leaf level. Further studies will be needed in order to integrate the cur-rentresultswithadditionaldetailsonthecomponentofvariation duetohydraulicandhormonalsignalingbetweenthescionand rootstock(Margueritet al.,2012).From thecombination ofthe obtainedresults,wecouldinterprettherootstockeffectas ‘quan-titative’: the ability of roots to supply water relative to shoot transpirationdemanddisplacedreciprocallytherootstockcurves tohigher/lowerparallel positions.On theotherhand,thescion effectwas‘qualitative’:thefeedbackloop betweengs andleaf

producedatleaflevelmodiﬁedtheslopeofthecurves.

5. Conclusions

Fromthepresentstudy,itwasconcludedthatrootstockand sciongenotypesareabletoconfertotheplanttraitsofdrought adaptabilityinﬂuencingthecapacityofwaterextractionfromthe soilandsensitivityofthestomatalcontrol.Onbothcomponents (rootsandcanopy)thetranscellularpathwayseemstohavestrong relationshipswithstrategiesrelatedtowatertranslocation.Further researchwillbeneededinordertoidentifythepotentialuseof thisinformationinstudiesofstresstoleranceandadaptabilityof rootstocksandcultivarstospeciﬁcecologicalconditions.

hydraulicconductivity.Vitis39,89–92.

Brodribb,T.J.,2009.Xylemhydraulicphysiology:thefunctionalbackboneof terres-trialplantproductivity.PlantScience177,245–251.

Carbonneau,A.,1985. Theearlyselectionofgrapevinerootstocksforresistanceto droughtconditions.AmericanJournalofEnologyandViticulture36,195–198.

Chalmers, Y.M., 2007. Inﬂuence of sustaineddeﬁcit irrigationonphysiology andphenoliccompoundsinwinegrapesandwine.AdelaideUniversity,PhD thesis. http://digital.library.adelaide.edu.au/dspace/bitstream/2440/50101/1/ 02whole.pdf.

Chaves,M.M.,Zarrouk, O.,Francisco,R.,Costa, J.M., Santos,T., Regalado,A.P., Rodrigues,M.L.,Lopes,C.M.,2010.Grapevineunderdeﬁcitirrigation:hintsfrom physiologicalandmoleculardata.AnnalsofBotany105,661–676.

Cirami,R.,Furkaliev,J.,Radford,R.,1994. Summerdroughtandvinerootstocks. AustralianGrapegrowerandWinemaker–AnnualTechnicalIssue336,145.

Daniels,M.J.,Mirkov,T.E.,Chrispeels,M.J.,1994.Theplasmamembraneof Arabidop-sisthalianacontainsamercury-insensitiveaquaporinthatisahomologofthe tonoplastwaterchannelproteinTIP.PlantPhysiology106,1325–1333.

Delas,J.J.,1992. CriteriausedforrootstockselectioninFrance.In:Wolpert,J., Walker,M.A.,Weber,E.,AmericanSocietyforEnologyViticulture:Davis(Eds.), ProceedingsofRootstockSeminar:AWorldwidePerspective.Reno,NV,USA,pp. 83–89.

deSouza,C.R.,Bassoi,L.H.,LimaFilho,J.M.P.,Silva,F.F.S.da,Viana,L.H.,Dantas,B.F., Pereira,M.S.,Ribeiro,P.R.,de,A.,2009.Waterrelationsofﬁeld-growngrapevines intheSãoFranciscoValley.Brazil,underdifferentrootstocksandirrigation strategies.ScientiaAgricola66,436–446.

Dry,N.,2007. GrapevineRootstocks:SelectionandManagementforSouth Aus-tralianVineyards.LythrumPress(Adelaide),Stepney,Australia,pp.85.

Düring,H.,1993. RapidstomatalandphotosyntheticresponsesofVitisberlandieri leavesafterpetioleexcisioninwater.Vitis32,63–68.

Galet,P.,1998.GrapeVarietiesandRootstockVarieties.Oenoplurimedia,Chaintré, France,pp.315.

Gambetta,G.A.,Manuck,C.M.,Drucker,S.T.,Shaghasi,T.,Fort,K.,Matthews,M.A., Walker,M.A.,McElrone,A.J.,2012.Therelationshipbetweenroothydraulicsand scionvigouracrossVitisrootstocks:whatroledorootaquaporinsplay?Journal ofExperimentalBotany63,6445–6455.

Gaspar,M.,Sissoef,I.,Bousser,A.,Roche,O.,Mahe,A.,Hoarau,J.,2001. Transient variationsofwatertransferinducedbyHgCl2inexcisedrootsofyoungmaize plants:newdataontheinhibitionprocess.AustralianJournalofPlantPhysiology 28,1175–1186.

Hachez,C.,Zelazny,E.,Chaumont,F.,2006.Modulatingtheexpressionofaquaporin genesinplanta:akeytounderstandtheirphysiologicalfunctions?Biochimica etBiophysicaActa(BBA)–Biomembranes1758,1142–1156.

Hamdan,A.,Basheer-Salimia,R.,2010. Preliminarycompatibilitybetweensome table-grapevinescionsandphylloxera-resistantrootstockcultivars.Jordan Jour-nalofAgriculturalSciences6,1–10.

Ibacache,G.A.,Sierra,C.B.,2009. Inﬂuenceofrootstocksonnitrogen,phosphorus andpotassiumcontentinpetiolesoffourtablegrapevarieties.ChileanJournal ofAgriculturalResearch69,503–508.

Janott,M.,Gayler,S.,Gessler,A., Javaux,M., Klier,C.,Priesacket,E.,2011. A one-dimensionalmodelofwaterﬂowinsoil–plantsystemsbasedonplant architecture.PlantandSoil341,233–256.

Javot,H.,Maurel,C.,2002. Theroleofaquaporinsinrootwateruptake.Annalsof Botany(Lond)90,301–313.

Jones,H.G.,2012.Howdorootstockscontrolshootwaterrelations?NewPhytologist 194,301–303.

Kaldenhoff,R.,RibasCarbo,M.,FlexasSans,J.,Lovisolo,C.,Heckwolf,M.,Uehlein, N.,2008. AquaporinsandPlantWaterBalance.Plant.CellandEnvironment31, 658–666.

Knipfer,T.,Besse,M.,Verdeil,J.L.,Fricke,W.,2011. Aquaporin-facilitatedwater uptakeinbarley(HordeumvulgareL.)roots.JournalofExperimentalBotany62, 4115–4126.

Komar,V.,Vigne,E.,Demangeat,G.,Lemaire,O.,Fuchs,M.,2010.Comparative per-formanceofvirus-infectedVitisviniferacv.Savagninrosegraftedontothree rootstocks.AmericanSocietyforEnologyandViticulture61,68–73.

Koundouras,S.,Tsialtas,I.T.,Zioziou,E.,Nikolaou,N.,2008.Rootstockeffectsonthe adaptivestrategiesofgrapevine(VitisviniferaL.cv.Cabernet-Sauvignon)under contrastingwaterstatus:leafphysiologicalandstructuralresponses. Agricul-ture,Ecosystems&Environment128,86–96.

(7)

Lee,S.H.,Chung,G.C.,Steudle,E.,2005. Lowtemperatureandmechanicalstresses differentlygateaquaporinsofrootcorticalcellsofchilling-sensitivecucumber and-resistantﬁgleafgourd.Plant,Cell&Environment28,1191–1202.

Lovisolo,C.,Hartung,W.,Schubert,A.,2002. Whole-planthydraulicconductance androot-to-shootﬂowofabscisicacidareindependentlyaffectedbywater stressingrapevines.FunctionalPlantBiology29,1349–1356.

Lovisolo,C.,Perrone,I.,Carra,A.,Ferrandino,A.,Flexas,J.,Medrano,H.,Schubert,A., 2010.Drought-inducedchangesindevelopmentandfunctionofgrapevine(Vitis spp.)organsandintheirhydraulicandnon-hydraulicinteractionsatthe whole-plantlevel:aphysiologicalandmolecularupdate.FunctionalPlantBiology37, 98–116.

Lovisolo,C.,Tramontini,S.,Flexas,J.,Schubert,A.,2008.Mercurialinhibitionofroot hydraulicconductanceinVitisspp.rootstocksunderwaterstress. Environmen-talandExperimentalBotany63,178–182.

Marguerit,E.,Brendel,O.,Lebon,E.,VanLeeuwen,C.,Ollat,N.,2012. Rootstock controlofsciontranspirationanditsacclimationtowaterdeﬁcitarecontrolled bydifferentgenes.NewPhytologist194,416–429.

Maurel,C.,Verdoucq,L.,Luu,D.-T.,Santoni,V.,2008. Plantaquaporins:membrane channelswithmultipleintegratedfunctions.AnnualReviewofPlantBiology59, 595–624.

Moshelion,M.,Becker,D.,Biela,A.,Uehlein,N.,Hedrich,R.,Otto,B.,Levi,H.,Moran, N.,Kaldenhoff,R.,2002. Plasmamembraneaquaporinsinthemotorcellsof Samaneasaman:diurnalandcircadianregulation.PlantCell3,727–739.

Miyazawa,S.-I.,Yoshimura,S.,Shinazaki,Y.,Maeshima,M.,Miyake,C.,2008.

DeactivationofaquaporinsdecreasesinternalconductancetoCO2diffusion intobaccoleavesgrownunderlongtermdrought.FunctionalPlantBiology35, 553–564.

Nardini,A.,Salleo,S.,2005. Waterstress-inducedmodiﬁcationsofleafhydraulic architectureinsunﬂower:co-ordinationwithgasexchange.Journalof Experi-mentalBotany56,3093–3101.

Padgett-Johnson,M.,Williams,L.E.,Walker,M.A.,2000.TheinﬂuenceofVitisriparia rootstockonwaterrelationsandgasexchangeofVitisviniferacv.Carignanescion undernon-irrigatedconditions.AmericanJournalofEnologyandViticulture51, 137–143.

Postaire,O.,Tournaire-Roux,C.,Grondin,A.,Boursiac,Y.,Morillon,R.,Shäffner,A.R., Maurel,C.,2010.APIP1aquaporincontributestohydrostaticpressure-induced watertransportinboththerootandrosetteofArabidopsis.PlantPhysiology152, 1418–1430.

Pou,A.,Medrano,H.,Tomás,M.,Martorell,S.,Ribas-Carbó,M.,Flexas,J.,2012. Aniso-hydricbehaviouringrapevinesresultsinbetterperformanceundermoderate waterstressandrecoverythanisohydricbehaviour.PlantandSoil359,335–349.

Pou,A.,Medrano,H.,Flexas,J.,Tyerman,S.,2013.AputativeroleforTIPandPIP aqua-porinsindynamicsofleafhydraulicandstomatalconductancesingrapevine underwaterstressandre-watering.Plant,Cell&Environment36,828–843.

Rizk-Alla,M.S.,Sabry,G.H.,AdbEl-Wahab,M.A.,2011.Inﬂuenceofsomerootstocks ontheperformanceofredglobegrapecultivar.TheJournalofAmericanScience 7,71–81.

Rogiers,S.Y.,Greer,D.H.,Hatﬁeld,J.M.,Hutton,R.J.,Clarke,S.J.,Hutchinson,P.A., Somers,A.,2012. Stomatalresponseofananisohydricgrapevinecultivarto evaporativedemand,availablesoilmoistureandabscisicacid.TreePhysiology 32,249–261.

Rogiers,S.Y.,Greer,D.H.,Hutton,R.J.,Landsberg,J.J.,2009. Doesnigh-time transpi-rationcontributetoanisohydricbehaviourinaVitisviniferacultivar?Journalof ExperimentalBotany60,3751–3763.

Santesteban,L.G.,Miranda,C.,Royo,J.B.,2009.Effectofwaterdeﬁcitandrewatering onleafgasexchangeandtranspirationdeclineofexcisedleavesoffourgrapevine (VitisviniferaL.)cultivars.ScientiaHorticulturae121,434–439.

Scholander,P.,Hammel,H.,Edda,D.,Bradstreet,E.,Hemmingsen,E.,1965. Sap pressureinvascularplants.Science148,339–346.

Schultz,H.R.,2003.Differencesinhydraulicarchitectureaccountfornear-isohydric andanisohydricbehaviouroftwoﬁeld-grownVitisviniferaL.cultivarsduring drought.Plant,CellandEnvironment26,1393–1405.

Shellie,K.,Glenn,D.M.,2008. Winegraperesponsetokaolinparticleﬁlmunder deﬁcitandwell-wateredconditions.ActaHorticulturae792,587–591.

Soar,C.J.,Dry,P.R.,Loveys,B.R.,2006. Scionphotosynthesisandleafgasexchange inVitisviniferaL.cv.Shiraz:mediationofrootstockeffectsviaxylemsapABA. AustralianJournalofGrapeandWineResearch12,82–96.

Southey,J.M.,1992. Grapevinerootstockperformanceunderdiverseconditionsin SouthAfrica.In:Wolpert,J.,Walker,M.A.,Weber,E.,AmericanSocietyfor Enol-ogyViticulture:Davis(Eds.),ProceedingsofRootstockSeminar:AWorldwide Perspective.Reno,NV,USA,pp.27–51.

Terashima,I.,Ono,K.,2002. EffectsofHgCl2onCO2dependenceofleaf photosyn-thesis:evidenceindicatinginvolvementofaquaporinsinCO2diffusionacross theplasmamembrane.PlantandCellPhysiology43,70–78.

Tramontini,S.,VanLeeuwen,C.,Domec,J.C.,Destrac-Irvine,A.,Basteau,C.,Vitali,M., Mosbach-Schulz,O.,Lovisolo,C.,2012.Impactofsoiltextureandwater avail-abilityonthehydrauliccontrolofplantandgrape-berrydevelopment.Plantand Soil,http://dx.doi.org/10.1007/s11104-012-1507-x.

VanAs,H.,2007.IntactplantMRIforthestudyofcellwaterrelations,membrane per-meability,cell-to-cellandlongdistancewatertransport.JournalofExperimental Botany58,743–756.

Vandeleur,R.K.,Mayo,G.,Shelden,M.C.,Gilliham,M.,Kaiser,B.N.,Tyerman,S.D., 2009. Theroleofplasmamembraneintrinsicproteinaquaporinsinwater transportthroughroots:diurnalanddroughtstressresponsesreveal differ-entstrategiesbetweenisohydricandanisohydriccultivarsofgrapevine.Plant Physiology149,445.

Whiting,J.R.,2005.Grapevinerootstocks.In:Dry,P.R.,Coombe,B.G.(Eds.), Viticul-ture:vol.1–Resources.WinetitlesPtyLtd.,Ashford,Australia,pp.167–188.

Williams,L.E.,Baeza,P.,2007.Relationshipsamongambienttemperatureandvapor pressuredeﬁcitandleafandstemwaterpotentialsoffullyirrigated,ﬁeld-grown grapevines.AmericanJournalofEnologyandViticulture58,173–181.

Wudick, M.M.,Luu, D.-T., Maurel, C.,2009. A lookinside: localization pat-ternsandfunctionsofintracellularplantaquaporins.NewPhytologist184, 289–302.