Evaluation on paper making potential of nine Eucalyptus species based on wood anatomical features

ContentslistsavailableatScienceDirect

Industrial

Crops

and

Products

j ou rn a l h o m epa g e :w w w . e l s e v i e r . c o m / l o c a t e / i n d c r o p

Evaluation

on

paper

making

potential

of

nine

Eucalyptus

species

based

on

wood

anatomical

features

Marília

Pirralho

_,

_Doahn

_Flores

_,

_Vicelina

_B.

_Sousa

_,

_Teresa

_Quilhó

_,

Sofia

Knapic

_,

_Helena

_Pereira

a_{CentrodeEstudosFlorestais,InstitutoSuperiordeAgronomia,UniversidadedeLisboa,TapadadaAjuda,1347-017Lisboa,Portugal}

b_{CentrodeCiênciasAgrárias,DepartamentodeCiênciasFlorestaisedaMadeira,UniversidadeFederaldoEspíritoSanto,AvenidaGovernadorCarlos}

Lindemberg,316,Centro,29550-000JerônimoMonteiro,EspíritoSanto,Brazil

c_{CentrodasFlorestaseProdutosFlorestais,InstitutodeInvestigac¸ãoCientíficaTropical,TapadadaAjuda,1347-017Lisboa,Portugal}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received11November2013

Receivedinrevisedform20January2014

Accepted25January2014

Availableonline23February2014

Keywords:

Woodanatomy

Papermakingpotential

Eucalyptusspecies

Fibrebiometry

Morphologicalratios

a

b

s

t

r

a

c

t

Eucalyptwoodisknownworldwideasaraw-materialforpulpingbutonlyafewspeciesareusedbythe industry.Oneoftheimportantfeaturesforpulpingisthewoodstructureandanatomy,includingcell biometryandcelltypeproportion.Thisworkmakesaprospectivestudyofnineeucalyptspeciesaiming atapulpingusebyanearlyassessmentofwoodanatomicalfeatures.Young50-month-oldtreesgrown inthesameenvironmentofEucalyptuscamaldulensis,Eucalyptusglobulus,Eucalyptusmaculata, Eucalyp-tusmelliodora,Eucalyptusovata,Eucalyptuspropinqua,Eucalyptussideroxylon,Eucalyptustereticornisand Eucalyptusviminaliswerestudiedinrelationtowoodanatomy,cellbiometryandproportion,and mor-phologicalfibreratios.Theninespeciesarestructurallysimilarwithtypicaleucalyptwoodfeatures,e.g. diffuseporositywithpredominantlysolitaryvesselsandsimpleperforationsplates,andmostanatomical differencesbetweenspeciesrelatedtoraysandaxialparenchyma.Thewoodisingeneraluniformand theradialvariationofcellulardimensionsisofsmallmagnitude.Thespeciesshowedahigherdiversity regardingproportionoffibres(15–50%)andmorphologicalcharacteristicse.g.slendernessratio(39–48) andflexibilitycoefficient(0.37–0.65).Theeucalyptspeciespositionthemselvesdifferentlyasregardsthe combinationofmorphologicalparameters,thereforeallowingspeciestargetingforspecificpaper prop-erties.Byconsideringtheseindicators,andtherelativespeciesgrowth,itseemspromisingtofurther studyE.maculata,E.ovataandE.sideroxylonaspotentialnewpapermakingeucalyptspecies,inparallel totheprizedE.globulusandthealreadyusedE.camaldulensis.

©2014ElsevierB.V.Allrightsreserved.

1. Introduction

MostEucalyptusspecieshadtheirorigininAustraliaand

Tasma-nia(Bolandetal.,1992),butsomespecieswereintroducedinother

regionsandarepresenttodayinlargeplantationintemperate,

sub-tropicalandtropicalareas.ThisisthecaseofEucalyptusglobulusin

PortugalandSpain,EucalyptusnitensinPortugal,Spain,Argentina

andChile,Eucalyptusgrandisinthesub-tropicalandtropicalzones

ofArgentina,China,Brazil,India,SouthAfrica,Uruguayand

Viet-nam(Forresteretal.,2010;Pereiraetal.,2011).Infact,Eucalyptus

isoneofthemostvaluableandwidelyplantedhardwoodsinthe

worldwith18millionhain90countries,intropicalandsubtropical

regionsofAfrica,SouthAmerica,AsiaandAustralia,andin

temper-ateregionsofEurope,SouthAmerica,NorthAmericaandAustralia

(Rockwoodetal.,2008).

∗ Correspondingauthor.Tel.:+351918968723.

E-mailaddresses:[email protected],[email protected](S.Knapic).

Eucalyptwoodisknownworldwideasaraw-materialfor

pulp-ingandmostoftheplantationsaredirectedforthepulp&paper

industry. E. globulus was the forerunner and most successful

pulpwood in temperateregions due togood treegrowth,stem

characteristics,wood anatomy and fibrebiometry, aswellas a

favourablepulping chemicalquality.In tropicaland subtropical

regionsothereucalyptspeciesareused,suchasE.grandisandE.

nitens,aswellasdifferenthybridssuchastheextensivelyused

uro-grandishybrid(E.grandis×Eucalyptusurophylla)inBrazil.InSouth

Africa,E.grandis,Eucalyptusmacarthurii,E.nitensandEucalyptus

smithiiareusedforthepulp&paperindustry(LittleandGardner,

2003)andinThailand,Eucalyptuscamaldulensisisthemainraw

materialforpulping(Terdwongworakuletal.,2005).

Other eucalypt species have been tested for their pulping

aptitude such as Eucalyptus badjensis, Eucalyptus dunnii (Little

andGardner,2003),Eucalyptustereticornis,Eucalyptusmicrotheca,

Eucalyptuspaniculata(Khristovaetal.,1997;Khristova,2000),

Euca-lyptuscitriodora(Khristovaetal.,2006).Howeverthenumberof

speciestestedisverysmallincomparisonwiththeover700species

withintheEucalyptusgenus(Rockwoodetal.,2008).

0926-6690/$–seefrontmatter©2014ElsevierB.V.Allrightsreserved.

Oneoftheimportantfeaturesforpulpingisthewoodstructure

andanatomy,includingcellbiometryandcelltypeproportionthat

havebeenshowntovarybetweenspecies,treeandage(Foelkel,

2009).Ingeneral,ahighproportionoffibresisdesired,in

paral-lelwithalowproportionoffinesizedcellsi.e.parenchyma,while

fibrebiometryinrelationtolength,widthandcellwallfractionis

relatedtospecificpulpandpaperproperties.Forexample,Zobel

andVanbuijtenen(1989)reportedthatwoodwiththickcellwalls

tendstoproducepaperswithapoorprintingsurfaceandpoorburst

strength.Thefibrebiometryisimportantfordeterminationofwood

propertiesthathavebeenrecognizedasrelevantforpulpandpaper

properties,e.g.theRunkelratio,wallproportion,flexibility

coeffi-cient,Luce’sshapefactorandslendernessratiothatweresuggested

asselectionindicesforqualitybreeding(Ohshimaetal.,2005)and

arerecognizedasimportanttraitsforpaperevaluation(Amidon,

1981;Kayama,1968;O’Neiletal.,1996).Forexample,theRunkel

ratioisrelatedtopaperconformabilityandpulpyield,andLuce’s

shapefactorandslendernessratioarerelatedtopapersheet

den-sityandtopulpdigestability,respectively(Ohshimaetal.,2005).

Vesselproportionandsizehavealsoaninfluenceonthe

papermak-ingprocess(Amidon,1981),aswellasraysandparenchymacells

thathaveaneffectonthequalityofbothsolidwoodandpulp

prod-ucts(ZobelandVanbuijtenen,1989).Therayandparenchymacells

arethin-walledandveryshort,andthereforecontributelittleto

thestrengthpropertiesofpaper,althoughtheyprovideasmoother

sheetsurface.Therelationshipsbetweencellandpulpproperties

havealsobeenstudiedfortheirwithin-treevariation(Bhatetal.,

1990;Crawfordetal.,1972;Malan,1991).

Thereforewoodanatomicalfeaturesgiveaninitialevaluation

for the potentialpulpwood quality of a raw-material. There is

anextensiveinformationof woodanatomical datafor E.

globu-lusincludingitsvariationwithsite,ageandgenetics,ascompiled

inPereiraetal.(2011).Forothereucalyptspecies,the

informa-tionislessi.e.E.grandis,E.tereticornis,EucalyptussalignaandE.

camaldulensis(Pereiraetal.,2011)aswellasforseveralhybrids

(Prinsenetal.,2012),andscarceforEucalyptusmelliodora,

Eucalyp-tusovata,Eucalyptussideroxylon,Eucalyptusviminalis,Eucalyptus

cypellocarpa,EucalyptuspolyanthemosandEucalyptusregnans.

Theperspectiveofthisworkistomakeaprospectivestudyof

anumberofdifferenteucalyptspeciesaimingatapossibleusefor

papermakingbyanearlyassessmentofwoodanatomicalfeatures

allowingcomparingthespeciespotential.Young treesgrownin

thesameenvironmentofE.camaldulensis,E.globulus,E.maculata,

E.melliodora,E.ovata,Eucalyptuspropinqua,E.sideroxylon,E.

tereti-cornisandE.viminaliswerestudiedinrelationtowoodanatomy,

cellbiometryandproportion,andfibreratios.

Themainpurposeistoanalyzethecomparativepapermaking

potentialof thesespecies,but theinformation isalsonecessary

forsolidwoodprocessingsincephysicalbehaviourand

mechani-calpropertiesareaffectedbyanatomicalcharacteristicse.g.fibre

proportionandcellwallthickness.

Theoverallobjectiveistoexplorethenaturaldiversitywithin

the genus Eucalyptusand to enrich the potential raw-material

feedstocks for the industry and the species diversity in forest

plantations, in accordance with the continuing interest of the

pulp&paperindustryinfindingnewpulpwoodspecieswithgood

papermakingpotential.

2. Materialsandmethods

2.1. Materials

ThestudywasdoneonnineEucalyptusspecies:E.

camaldulen-sis,E.globulus,E.maculata,E.melliodora,E.ovata,E.propinqua,E.

sideroxylon,E.tereticornis,andE.viminalis.Thetreesweregrownon

anexperimentalsitelocatedinthecampusfieldsoftheSchoolof

Agriculture,UniversityofLisbon(ULisbon),atTapadadaAjuda,

Lis-boa,Portugal(38◦42N;09◦10W).Theregionisundertheinfluence

ofamesothermalhumidclimate,withadryseasoninthesummer

extendingfromJunetoAugust,andregisteringabove10◦Cinthe

coldestmonthandbeloworequalto22◦Cinthehottestmonth.The

soilisaVertisolcharacterizedbyafine,ormediumtofine,texture,

derivedfromtuffsorbasalts,frequentlywithlimestoneonthe

infe-riorhorizons,orfromcalcareousrock(inmuchlessextension).The

treeswereplantedfromseedsoriginatedfromAustraliainFebruary

2007inrowswith3m×3mspacingandwithoutfertilization.The

treeswereharvestedinApril2011,at50monthsofage.

Stemdiscs with10cm thicknesswerecollectedat 1.30mof

treeheight(DBH).Themeanoverbarkandwooddiameterswere

measured.Tworeplicatesperspecieswereanalyzed.

2.2. Anatomicalobservations

Thevesselareawasdeterminedfrompithtobark,after

sam-plesurfacesanding,usingtheLeicasoftwareQwinV3.5.0,after

acquisitionofasequenceofimagesofeachradiusthroughadigital

cameraLeicaDFC320coupledtoLeicaMagnifierMZ6.Theimages

wereconvertedtobinaryformatand vesselswereclearly

iden-tifiedasseparateobjectsafterapplyingthresholdandminimum

sizesettings.Theindividualsizeofallthevesselscontainedalong

thefulllengthoftheradialstripandwithina1-mm-widthfield

wasrecorded.Thenumberofvessels,theindividualvesselareaand

thevessellocationcoordinateswererecordedperimageand

pos-itionedalongtheradialstriptotallength.Thefollowingmeanvessel

variableswerecalculated:averagevesselarea,numberofvessels,

vesseldensity(numberofvesselspermm2_{)andvesselproportion}

(vesselareapercentageinrelationtototalarea).

Formicroscopy,samplesweretakenatthreeradialpositionsat

30%,60%and90%oftheradiusfrompithtocambium.Thewood

sampleswerefirstsoftenedinboilingwaterandthensectioned

withaslidingmicrotome.Transversal,tangentialandradialthin

sectionswith17␮mthicknesswereobtainedusingamicrometre,

washedinalcohol,stainedwithsafraninandmountedinEukitt.

Rayheightandnumberofcellsweremeasuredfrom40uniseriate

rays,onthetangentialsections.

Theradialvariationoffibrelength,widthandwallthicknesswas

measuredondissociatedmaterial(40fibres perdetermination)

usingimageanalysisassistedbyacamerafromLeicamicroscope

coupledtoEC3transmittedlightDialux22EBandLASsoftware

V4.2. Onlycomplete fibresweremeasuredand fibrewidthand

lumenweredeterminedatmid-length.Celldissociationwasmade

withJeffrey’ssolutionduring48hat60◦C,washedinwaterand

storedin70%alcohol.

Theproportion ofaxial parenchyma, fibres,raysand vessels

wasmeasuredonthetransversesectionsusinga48point-gridon

successiveareasalongtheradiusandusingLASsoftwareV4.2.

Thedeterminationwasmadedirectlyonthemicroscopewhere

thedifferenttissuesdifferentiateclearlybysizeandcolour.

2.3. Anatomicalratios

Runkelratio,wallproportion,flexibilitycoefficient,Luce’sshape

factorandslendernessratiowerecalculatedaccordingtothe

fol-lowingformula,wherewisthecellwallthickness,Disthefibre

width,disthefibrelumenwidth,andListhefibrelength:

Runkelratio=2w/d

Wallproportion=(2w/D)×100

Luce’sshapefactor=(D2_−d2_)/(D2_+d2₎

Flexibilitycoefficient=d/D

Table1

Stemwooddiameter,textureandgrowthringdefinitionofnineeucalyptspecies(E.

camaldulensis,E.globulus,E.maculata,E.melliodora,E.ovata,E.propinqua,E.

siderox-ylon,E.tereticornis,andE.viminalis)growninthesameenvironmentat50months

ofage.

Species Diameter(cm) Texture Growthring

E.camaldulensis 9.5 Fine Indistinct

E.globulus 11.8 Fine Indistinct

E.maculate 17.7 Moderatelycoarse Indistinct

E.melliodora 8.6 Fine Indistinct

E.ovata 10.3 Fine Indistinct

E.propinqua 8.6 Moderatelycoarse Fairlydistinct

E.sideroxylon 10.6 Fine Indistinct

E.tereticornis 4.3 Fine Fairlydistinct

E.viminalis 12.2 Moderatelycoarse Indistinct

DescriptiveterminologyfollowstheIAWAListofMicroscopic

FeaturesforHardwoodIdentification(IAWACommittee1989).

StatisticalanalysiswasmadeusingtheSPSSsoftware.Analysis

ofvariance(ANOVA)wasappliedtocomparewoodfibrelengthand

wallthickness.

3. Resultsanddiscussion

3.1. Generaldescription

Themacroscopicobservationsoftexture,growthringdefinition

andwoodporosityweresummarizedinTable1,togetherwiththe

informationonthestemwooddiameter.

It wasnoteworthythat thespecies differed ingrowth, with

stemwooddiameters rangingfrom4.5cm to17.7cm in4 years

ofgrowth.ThespecieswiththehighestdiameterswereE.

mac-ulata,E.viminalisandE.globulusandthesmallesttreeswerefrom

E.tereticornis.

Thegrowthringswereindistinctinmostofthespecies,

follow-ingthegeneraltrendin themajorityof eucalyptspecieswhere

growthringsaregenerallyindistinctornotwelldefined(Dadswell,

1972);ringswerehoweverfairlydistinctinE.tereticornisandE.

propinquaduetoabsenceofvesselsandthickenedfibresatring

boundary.

ThesefeatureshavebeenreportedforE.globulus(Pereiraetal.,

2011)andforseveralothereucalyptspeciesi.e.E.regnans,

Eucalyp-tusdelegatensis,Eucalyptusobliqua,Eucalyptusbaxteri,Eucalyptus

globoidea,Eucalyptusmuelleriana,Eucalyptusmacrorhyncha,

Euca-lyptus consideniana and Eucalyptus sieberi (Ilic, 1997, 2002); E.

citriodora, E. maculata, E. grandis, E. saligna, Eucalyptus deanei,

Eucalyptusrobusta,Eucalyptusresinifera,E.propinqua,E.punctata,

E.tereticornis, E. camaldulensis, Eucalyptusalba, Eucalyptus

dun-nii,Eucalyptuscloeziana,Eucalyptuspilularis,Eucalyptusmicrocorys,

EucalyptussiderophloiaandE.paniculata(Alfonso,1987).

Table1 Stemwood diameter, texture,growthring definition

andwoodporositytypeanddistributionofnineeucalyptspecies

(E.camaldulensis,E.globulus,E.maculata,E.melliodora,E.ovata,E.

propinqua,E.sideroxylon,E.tereticornis,andE.viminalis)grownin

thesameenvironmentat50monthsofage.

3.2. Anatomicalstructure

Thewoodanatomicalstructureofthesenineeucalyptspecies

(Fig.1)wasingeneralsimilarnotwithstandingthedifferencesin

vesseloutline,arrangement,typeofaxialparenchymaand rays,

theirdimensionsandproportion.

Allthespecies showeddiffuseporosity, withpredominantly

solitaryvessels,exceptinE.maculatawherethevesselsaregrouped

(2 or more vessels); the vessels were generally randomly

dis-tributedwithanobliquealignmentandmostlyradialinE.maculata;

vesselsoutlinewascirculartooval,morecircularinE.melliodora,

E. ovata and E. tereticornis, and more oval in E. camaldulensis,

E.globulus,E.maculata, E.propinqua, E.sideroxylon,and E.

vim-inalis. The vessel elementswere short with exclusively simple

perforationplates and theinter-vessel pitswere onlyobserved

invesseltips andthevessel-raypitswereroundtoovalmostly

simple.

The axial parenchyma was scarce to abundant but its

arrangementvariedbeingmostlyparatrachealvasicentricaliform,

somewhatconfluentandfairlyapotrachealdiffuseinE.globulus,

E.ovataandE.maculata;and apotrachealdiffuse,inshortlines,

and paratrachealvasicentricin E.camaldulensis,E.melliodora,E.

propinqua,E.sideroxylon,E.tereticornisandE.viminalis.InE.

macu-lataitwasapotrachealdiffuseandinshortlinesandparatracheal

confluentformingtangentialbands.

RayswerehomogeneousandheterogeneousoftypeIII(i.e.in

E.camaldulensis,E.globulus,E.ovata,E.propinquaandE.

tereticor-nis),withbodyraycellsprocumbentwithuprightand/orsquare

marginal cells. Rays were mostly uniseriate in E. globulus, E.

maculata,E.tereticornisandE.viminalis,mostlybiseriateinE.

camal-dulensis and E. propinqua, equally uniseriate and biseriate in E.

melliodora,E.ovataand E.sideroxylon,and rarelytriseriate inE.

propinqua.Alfonso(1987)alsodescribedhomoandheterogeneous

raysofthetype IIIfor E.camaldulensis, E.globulus,E.propinqua

and E.tereticornis. Cellray withcontents wereevidenti.e.in E.

camaldulensis,E.ovataandEpropinqua.

Inallthespecies,thefibreswereofthelibriformtype,

non-septated, withbordered pits mainlyin radialwalls. Vasicentric

tracheidswerepresentinallthespecies,andmostlyconspicuous

inradialsectionsi.e.E.maculata.

AnatomicaldescriptionswithvariabledetailexistforE.

mac-ulata (Dadswell,1972; Oliveira and Freitas, 1970), E.propinqua

(OliveiraandFreitas,1970),E.tereticornis(Dadswell,1972;Oliveira andFreitas,1970)andE.camaldulensis(Alfonso,1987;Dadswell,

1972),E.ovata(OliveiraandFreitas,1970),E.globulus(Dadswell,

1972;Pereiraetal.,2011),E.melliodoraandE.viminalis(Dadswell,

Table2

Biometryofvessels(tangentialdiameter,length,areaandfrequency),fibres(length,width,wallthickness)andrays(numberofcells,height)ofE.camaldulensis,E.globulus,

E.maculata,E.melliodora,E.ovata,E.propinqua,E.sideroxylon,E.tereticornis,andE.viminalisgrowninthesameenvironmentat50monthsofage.

Species Vessels Rays Fibre

Tangential

diameter(␮m)

Length(␮m) Area(mm2_{) Frequency}

(nr/mm2₎

N◦_{cells Height(␮m) Length(mm) Width(␮m) Wallthickness}

(␮m) E.camalduleis 80±19 218±52 0.004±0.002 11 11 148±56 0.670±75 17±0.8 4±0.1 E.globulus 72±23 273±53 0.005±0.0005 18 9 153±47 0.716±34 16±0.9 5±0.3 E.maculata 79±11 195±69 0.008±0.0002 14 9 141±59 0.794±14 18±1 5±0.7 E.melliodora 79±17 197±49 0.007±0.0009 19 6 129±4 0.777±92 17±2 4±0.2 E.ovata 127±19 173±47 0.009±0.0009 13 8 142±53 0.719±49 16±2 4±0.1 E.propinqua 62±12 212±48 0.006±0.0008 23 8 164±73 0.755±300 17±1 4±0.3 E.sideroxylon 54±9 164±32 0.009±0.002 25 9 116±31 0.742±12 16±3 4±0.2 E.tereticornis 88±13 268±50 0.006±0.0002 27 8 141±42 0.777±11 17±0.4 4±0.1 E.viminalis 81±11 183±42 0.004±0.0002 9 9 155±45 0.806±49 19±1 3±0.5

1972).Theobservationsmadehereareinaccordancewithsuch descriptions.

3.3. Cellbiometryandproportion

Thequantificationofanatomicalfeatureswassummarizedin

Table2forcellbiometryandinTable3forcelltypeproportion.Each

anatomicalfeatureshoweddifferencesbetweenthenineeucalypt

species.

Fig.1.Microscopicstructureofthetransverse(a1–i1),tangential(a2–i2)andradial

(a3–i3)sectionsofE.camaldulensis,E.globulus,E.maculata,E.melliodora,E.ovata,

E.propinqua,E.sideroxylon,E.tereticornisandE.viminalis.Scalebar=50␮m(right

column)and150␮m(centralandleftcolumn).

Fig.1. (Continued.)

Asregardsvessels,theirnumberpermm2 _{rangedbetween9}

(E. viminalis)and 27 (E. tereticornis),with tangential diameters

from 54␮m (E. sideroxylon) to 127␮m (E. ovata), mean vessel

areabetween0.004mm2 _{(E.camaldulensisand E.viminalis)and}

0.009mm2_{(E.ovataandE.sideroxylon),andvesselelementlength}

from164␮m(E.sideroxylon)to273␮m(E.globulus).

Rayshadbetween6(E.melliodora)and11cells(E.camaldulensis)

withaheightfrom129␮m(E.melliodora)to164␮m(E.propinqua).

Themeanfibrelengthrangedbetween0.67mm(E.

camaldu-lensis)and0.81mm(E.viminalis),fibrewidthbetween16␮m(E.

globulus,E.ovataandE.sideroxylon)and19␮m(E.viminalis)and

wallthicknessbetween3␮m(E.viminalis)and5␮m(E.globulus

andE.maculata).

ComparisonofcellbiometrytopublishedvaluesiseasyforE.

glo-bulusforwhichmanyquantitativeanatomicalstudiesweremade,

ascompiledinPereiraetal.(2011),althoughdirectcomparisons

withvaluesreportedinthebibliographyaredifficultdueto

differ-encesinsampling(e.g.treeage)andmethodology.Regardingfibre

biometry,fibrelengthvaluesbetween0.78mmand1.12mmwere

reported(Jorgeetal.,1997;Mirandaetal.,2001;TomazelloFilho,

1987;Toméetal.,1996),cellwallthicknessbetween4␮mand 12_␮m(MirandaandPereira,2002;Mirandaetal.,2003;Tomazello Filho,1985)and21.3␮mforfibrewidth(Mirandaetal.,2003).A

vesselfrequencybetween4and27vesselspermm−2witha

tan-gentialdiameterbetween170␮mand221␮m,andmeanvessel

areabetween0.002mm2_and0.021mm2_{werereportedinthe}

liter-ature(Dadswell,1972;Carvalho,1962;Hudsonetal.,1996;Wilson

etal.,1998).

Someinformationabouttheotherspeciescouldalsobefound

intheliterature.

Table3

Celltypeproportion(%)ofvessels,fibresandraysofE.camaldulensis,E.globulus,

E.maculate,E.melliodora,E.ovata,E.propinqua,E.sideroxylon,E.tereticornis,andE.

viminalisgrowninthesameenvironmentat50monthsofage.

Celltypeproportion(%)

Species Vessels Rays Fibre Parenchyma

E.camaldulesis 31 17 44 8 E.globulus 25 19 33 21 E.maculata 19 29 29 23 E.melliodora 22 22 22 22 E.ovata 25 15 50 10 E.propinqua 21 19 33 25 E.sideroxylon 20 22 35 21 E.tereticornis 21 23 35 16 E.viminalis 23 31 25 21

E. camaldulensis: 89–108␮m tangential vessel diameter,

13–22vesselsmm−2,383–408␮mvessellength,0.809–0.880mm

fibrelength,5␮mfibrewallthickness,and 349␮mrayheight

(Alfonso,1987;Dyer,1992;Veeninetal.,2005).

E. maculata: 97–119␮m tangential vessel diameter,

4–12vesselsmm−2,474␮mvessellength,990␮mfibrelength,

and5␮mfibrewallthickness(Alfonso,1987;OliveiraandFreitas,

1970).

E.ovata:45–163_␮mtangentialvesseldiameter,0.763–1.342mm

fibrelength,and10.6–16.5␮mfibrewidth(OliveiraandFreitas,

1970).

E.propinqua:84␮m tangentialvesseldiameter,439␮m vessel

length,0.990mmfibrelength,5␮mfibrewallthickness(Alfonso,

1987).

E.sideroxylon:6–13vesselsmm−2(Searsonetal.,2004).

E. tereticornis: 96–114␮m tangential vessel diameter,

9–12vesselsmm−2, 435–463␮m vessel length, 0.908–1.08mm

fibrelength,4␮m fibrewallthicknessand 324␮m rayheight

(Alfonso,1987;Carvalho,1962;Dyer,1992;Sharmaetal.,2005).

Ingeneralthevaluesfoundinthisworkwereatthelowerrange

ofthosereportedintheliterature,certainlybecausetheanalysis

wasmadeonyoungertreesthanthosestudiedinthereferenced

publications.

The wood structure as regards cell type proportion in the

stemwoodcross-section(Table3)showedconsiderabledifferences

betweenspecies:vesselscorrespondedfrom19%(E.maculata)to

31% (E. camaldulensis),fibres from 25%(E. viminalis) to50% (E.

ovata),raysfrom15%(E.ovata)to31%(E.viminalis)andparenchyma

from8%(E.camaldulensis)to25%(E.propinqua).

Intheliterature,valueswerereportedforoldertrees:E.

glo-buluswith11–13%vessels,64–67%fibres,6–7%axialparenchyma

and14–16%rays(Bamber,1985;Onaetal.,2001)andforE.

camal-dulensiswith16–18%vessels,49%fibres,14%axialparenchyma,

and20–21%rays(Onaetal.,2001).Forasimilartreeage,arecent

studyonpulpedmaterialofseveraleucalypthybrids(Prinsenetal.,

2012)showedthatweredifferencesinthevesselcontentbetween

hybrids.

3.4. Radialvariation

Theradialvariationofcellbiometrywasindicativeofagetrends

andconstitutes valuableinformation e.g.whenanevaluation is

madeinearlieragesthanthenormalrotation.Thiswasthecase

here,sincethetreeswereevaluatedat4yearsofageandthe

nor-malrotationinPortugalis9–12years(about6yearsinsubtropical

regions). 0.002 0.004 0.006 0.008 0.01 0.012 0 9 0 6 0 3 v es se ls a re a (m m 2) Radial Posion (%)

E.camaldulensis E.globulus E.maculata

E.melliodora E.ovata E.propinqua

E.sideroxylon E.viminalis terecornis

Fig.2.Radialvariationofvesselarea,measuredat30%,60%and90%oftheradius,

ofE.camaldulensis,E.globulus,E.maculata,E.melliodora,E.ovata,E.propinqua,E.

sideroxylon,E.tereticornis,andE.viminalisgrowninthesameenvironmentat50

monthsofage.

TheradialvariationofvesselareawasshowninFig.2.Itis

practi-callyconstantinE.sideroxylon,E.propinqua,E.ovata,E.maculata,E.

tereticornisandE.globulus,andincreasesinE.viminalis,E.melliodora

andE.camaldulensis.Thevarianceanalysisindicatedthatspecies,

radialpositionand theirinteractioninfluencedsignificantly the

vesselsarea(p<0.001).

Thisradialpatternconfirmedearlierreportsonvesselarea

vari-ationforE.globulus(Lealetal.,2007;Pereiraetal.,2011;Ramírez

etal.,2009;Tavaresetal.,2011;Wilsonetal.,1997,1998).The

sameradialpatternwasalsofoundinE.regnans(Dadswell,1958),

E.grandis(Taylor,1973)andE.nitens(MckimmandIlic,1987).

Theradialvariationoffibrelength,widthandwallthicknessis

showninFig.3.Fibrewallthicknesswasconstantalongtheradius

inE.tereticornis;increasedtomid-radiusanddecreasedafterwards

inE.camaldulensis,E.globulusandE.melliodora;decreased inE.

propinquaandinE.sideroxylon;andincreasedinE.maculata.

How-evertherewasanoverallnarrowvariationamongthespecies.

Therewereseveralstudiesonradialpatterns:BrasilandFerreira

(1979)foundaradialincreaseofwallthicknessforE.grandis,as wellasTomazelloFilho(1987)forE.globulus,Eucalyptuspellitaand

Eucalyptusacmenioides,whileSharmaetal.(2005)foundaradial

decreaseforE.tereticornis,E.propinquaandE.sideroxylon.

Thefibrelengthradialvariationshoweddifferentpatterns:it

increasedradiallyinE.camaldulensis,E.globulus,E.maculata,E.

mel-liodora,E.propinquaandE.sideroxylon;increasedtomid-radiusand

decreasedsubsequentlyinE.ovataandE.viminalis;anddecreased

0.5 0.7 0.9 30 60 90 Len g th fibre ( mm )

Radial Posion (%)

E.camaldulensis E.globulus

E.maculata E.melliodora

E.ovata E.propinqua

E.sideroxylon E.terecornis

E.viminalis 12 14 16 18 20 22 30 60 90 W Ii d th fibre (μm ) Radial posion (%)

E.camaldulensis E.globulus

E.maculata E.melliodora

E.ovata E.propinqua

E.sideroxylon E.terecornis

E.viminalis 2 3 4 5 6 0 9 0 6 0 3 ce ll wa ll thi ck n e ss ( μm )

Radial Posion (%)

E.camaldulensis E.globulus

E.maculata E.melliodora

E.ovata E.propinqua

E.sideroxylon E.terecornis

E.viminalis

Fig.3.Radialvariationoffibrelength,widthandwallthickness,measuredat30%,60%and90%oftheradius,ofE.camaldulensis,E.globulus,E.maculata,E.melliodora,E.

Table4

Theanatomicalratios(Runkelratio,wallproportion,flexibilitycoefficient,slendernessratio,Luce’sfactor)ofE.camaldulensis,E.globulus,E.maculata,E.melliodora,E.ovata,

E.propinqua,E.sideroxylon,E.tereticornis,andE.viminalisgrowninthesameenvironmentat50monthsofage.

Species Runkelratio Wallproportion% Flexibilitycoefficient Slendernessratio Luce’sfactor

E.camaldulensis 0.79±0.21 43.5±6.5 0.56±0.06 39.4±7.7 0.51±0.08 E.globulus 1.75±0.58 62.0±7.6 0.37±0.07 47.1±8.8 0.74±0.08 E.maculata 1.6±0.8 57.8±12 0.42±0.12 44.6±9.9 0.69±0.15 E.melliodora 1.0±0.41 48.4±9.9 0.51±0.09 47.2±9.3 0.57±0.12 E.ovata 1.1±0.54 50.0±9.6 0.49±0.09 46.9±10.5 0.6±0.1 E.propinqua 1.17±0.34 52.7±7.3 0.47±0.07 46.7±7.8 0.63±0.09 E.sideroxylon 1.2±0.52 52.4±10 0.47±0.1 48.4±8.8 0.62±0.12 E.tereticornis 0.95±0.34 47.5±8.1 0.52±0.08 47.8±11 0.56±0.1 E.viminalis 0.54±0.22 34.1±8.9 0.65±0.08 43.3±9.9 0.39±0.11

tomid-radiusandincreasedsubsequentlyinE.tereticornisandE.

maculata.Thesefindingsdeviatedfromthegeneralviewthatthe

fibrelengthshowedagradualincreasefrompithtoperipheryin

Eucalyptus(Foelkel,2005);theradialpatternoffibrelength

increas-ingwithcambiumagehasbeenfoundfor severalspeciesi.e.E.

globulus(Pereiraetal.,2011;Tavaresetal.,2004;TomazelloFilho,

1987)inE.camaldulensis(SadeghandKiarei,2011),E.terecticornis

(Sangeeta,2012)orEucalyptusurograndis(Quilhóetal.,2006).

Fibre width also showed different radial variation between

species:adecrease tomid-radiusand a subsequentincrease in

E.camaldulensis,E.maculata,E.melliodoraand E.sideroxylon;an

increasetomid-radiusandthenadecreaseinE.globulus,E.ovata,

E.propinqua,E.tereticornisandE.viminalis.Theradialincreaseof

fibrewidthforE.globuluswasreportedbyTomazelloFilho(1987).

Veeninetal.(2005)reportedforE.camaldulensisaradialdecrease

offibrewidth.

Thebetweenspeciesdifferencesinfibrevariableswere

statis-ticallysignificant(p<0.001)andtheinteractionofspecies/radial

positionalsohadasignificantinfluence.Theradialposition

influ-encedfibrelengthwithstatisticalinfluencebutnotfibrewidthand

wallthickness.

Thereweresignificantdifferencesbetweenspeciesandradial

positionsinrelationtoheightrays(p<0.001).

3.5. Morphologicalratios

Table4summarizesthemeanvaluesforthevariousfibreratios

showing that there is a variation between species. E. globulus

reportedthehighestRunkelratio,wallproportionandLuce’s

fac-tor(1.8,62%and0.5respectively),factorsthatwererelatedtothe

factthatthisspecieshascomparativelythinandthickwalledfibres

(Table2).E.viminalishadthelowestRunkelratio,wallproportion

andLuce’sfactor(0.5,34%and0.4respectively),associatedtoits

thinwalledandwide fibres(Table2).For thesamereasonsbut

withopposite results,E.viminalisshowedthehighestflexibility

coefficient(0.65)andE.globulusthelowestvalue(0.37).

Slendernessalsovariedbetweenspecies.E.sideroxylonshowed

thehighestslendernessratioandE.camaldulensisthelowest(48

and39respectively).Regardingflexibilitycoefficient,thehighest

valuewasreportedforE.viminalisandE.camaldulensisandthe

lowestvaluewasfoundforE.globulusandE.maculata.

Therewerefewreferencesonmorphologicalratiosofeucalypts.

Ohshimaetal.(2005)reportedforLuce’sfactorandslenderness

forE.camaldulensis0.37and57,andforE.globulus0.44and60,

respectively.Onaetal.(2001)foundmeanRunkelratiosof0.42and

0.39,andflexibilitycoefficientsof0.69and0.73forE.camaldulensis

andE.globulusrespectively.Ferreiraetal.(2013),reportedaRunkel

ratioof0.45forcommercialE.globuluspulp,howevertheolderages

ofthetreesinthesestudiesdonotallowdirectcomparisonwith

thoseofthepresentwork.

Table4Themorphologicalratios(Runkelratio,Wallproportion,

Flexibilitycoefficient,Slendernessratio,Luce’sfactor)ofE.

camald-ulensis,E.globulus,E.maculata,E.melliodora,E.ovata,E.propinqua,

E.sideroxylon,E.tereticornis andE.viminalisgrown inthesame

environmentat50monthsofage.

3.6. Anatomy-basedpapermakingpotential

Theoverallstructureofthenine eucalyptspecieswasrather

uniform,withafairdistributionofvesselsacrossthematerial,as

showninFig.1,andwithoutconspicuouslayeredarrangements

withverydifferentstructuree.g.fibrecross-sectionaldimensions.

Theradialvariationofcellbiometrywasalsoofsmallmagnitude

(Figs. 2–3).Thesewerefavourablecharacteristicsfora

homoge-neouspulpingprocessandfibreproperties.

Howevertheproportionofcelltypesareacrucialanatomical

parametertoforecastpulpingyieldsandahighproportionoffibres

isapre-requisiteforgoodyields.Infact,smallsizedcellse.g.radial

andaxialparenchymaarelostduringpulpscreening,andvessels

aredestroyedtoalargeextentduringpulprefining.Inthenine

eucalyptspecies,ananalysisofthecelltypeproportion(Table3)

showsthattheproportionoffibresislessfavourableforE.

mel-liodoraandE.viminalis.

Morphological characteristics are among the first indicators

tobeevaluatedfor screeningofpotentialfibrousraw-materials

forpaperproduction.Itisgenerallyknownthatpaperstructure

andmechanical behaviourdependonthespecificfibrefeatures

(Bronkhorst,2003;Clark,1978;Rydholm,1965).Forinstance,fibre

lengthpositivelyinfluencestensileandburststrength,fibre

diam-eterandwallthicknessincreasetearresistance,andslenderness

increasesfibreflexibilityandthechancesofformingwellbonded

paper.

Themorphologicalratiosthatwerecalculated(Table4)canbe

groupedintothosethataremostlydeterminedbythewall

thick-nessinrelationtothetransversedimensionofthefibres(e.g.Runkel

ratio,wallproportion,Luce’sfactorandflexibility)andthoserelated

withthefibrelengthe.g.theslendernessratio.Theformerrelate

withfibrestiffness:forinstance,thehighertherelativeimportance

ofthecellwall,themorerigidisthefibrewhichmaylowerits

con-formabilityandfibre-fibrecontact(Pattetal.,2006).Inthiscasethe

mostrigidfibreswouldbethoseofE.globulus,E.maculataandthe

lessrigidthoseofE.viminalisandE.camaldulensis.Theslenderness

ratioisrelatedwithfibrelengthandwidthandinfluencespaper

sheetdensity and increases tearingresistance (Agnihotri et al.,

2010).ThespecieswiththelowestslendernesswasE.

camaldu-lensis.Inspiteofthevariationthatwasfoundbetweenthenine

eucalyptspecies,theyareoverallsuitedforpulpandpapersheet

formation.Nevertheless theirspecific anatomicalcharacteristics

maybeusedfortargetedpaperproperties,asFig.3showswhen

plottingflexibilityandslenderness.

Itisclearthatotherthananatomicalfactorswillinfluencepaper

pulpaptitude, namelythechemical composition (Pereira etal.,

2003).Neverthelesscombiningthecelltypeproportions(Table3)

andmorphologicalratios(Table2),andalsotakingintoaccount

thecomparativegrowthonthespeciesinthesameenvironment

E.camldulensis E.globulus E.maculata E.melliodora E.ovata E.propinqua E.sideroxylon E.tereticornis E.viminalis 0.3 0.5 0.7 39 42 45 48 Fl ex ib ility C oeffi ci en t

Slenderness ratio

Fig.4.SlendernessratioandflexibilitycoefficientofE.camaldulensis,E.globulus,E.maculata,E.melliodora,E.ovata,E.propinqua,E.sideroxylon,E.tereticornisandE.viminalis

growninthesameenvironmentat50monthsofage.

performanceofE.maculata,E.ovataandE.sideroxylonaspotential

newpulpwoodeucalyptspecies,inparalleltotheprizedE.globulus

andthealreadyusedE.camaldulensis(Fig.4).

4. Conclusions

Thenine Eucalyptusspecies –E.camaldulensis, E.globulus, E.

maculata, E. melliodora,E. ovata, E.propinqua, E. sideroxylon, E.

tereticornisandE.viminalis–arestructurallysimilarwithtypical

eucalyptwoodfeatures,e.g.diffuseporositywithpredominantly

solitary vessels and simple perforations plates. Most

anatomi-caldifferences betweenthespecies relatetotheraysand axial

parenchyma.

Thespeciesshowedahigherdiversityregardingtheir

prospec-tive pulping potential given by the proportion of fibres and

morphologicalcharacteristics.Theeucalyptspositionthemselves

differentlyasregardsthecombinationofdifferentmorphological

parameters,thereforeallowingspeciestargetingforspecificpaper

properties.Byconsideringtheseindicators,andtakingintoaccount

therelativespeciesgrowth,itseemspromisingtofurtherstudyE.

maculata,E.ovataandE.sideroxylonfortheirpulpingperformance

aspotentialnewpapermakingeucalyptspecies,inparalleltothe

prizedE.globulusandthealreadyusedE.camaldulensis.

Acknowledgments

Thisstudy was funded by projectEucPlus – New processes

andusesforeucalyptwoods(PTDC/AGR-CFL/119752/2010)byFCT

(Fundac¸ãoparaaCiênciaeTecnologia,Portugal).Centrode

Estu-dosFlorestaisisaresearchunitsupportedbythenationalfundingof

FCT–(PEst-OE/AGR/UI0239/2011).FundingfromFCTis

acknowl-edgebyVicelinaSousaasadoctoralstudent,andSofiaKnapicasa

post-doctoralresearcher(SFRH/BPD/76101/2011),andthesecond

author acknowledgessponsorshipfrom theprogramme Ciência

semFronteiras,fromBrazil.WethankDr.PaulaSoaresforproviding

thesamplesandtheinformationaboutthetrialwhichwas

spon-soredbyCELPA–Associac¸ãodaIndústriaPapeleira(Portuguese

PulpandPaperIndustryAssociation).

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