INBAR_Technical_Report_No18_05

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Fig.133:Vietnameseladies’hatsmadefromNeohouzeauadulloa128

 
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!7DEVELOPMENTANDAGEINGThepreviouschaptershaveoutlinedthegeneralstructu

2、reofmatureculmsanditsvariations.Fewinvestigationshavedealtwithstructuraldevelopmentuntilmaturation(Grosser1971;Fujii1985;AlvinandMurphy1988).Recentobservationshaveshownthatsomestructuralmodificationsoccuraftermaturationalso(LieseandWeiner1996,1997).Theageingofabambo

3、oculminfluencescertainpropertiesand,consequently,itsprocessingandutilization.Thissectiondescribesthechangesduringculmelongationandmaturation,andcertainmodificationsthatoccurinmatureculms.Theelongationofaculmresultsfromtheexpansionofindividualinternodes,alreadypresen

4、tinthebud.Differentiationstartsattheupperpartofaninternodebyelongationofdifferentcelltypes,andproceedsdowntoitsbase.Thedifferentiationofanindividualinternodeiscompletedinjustafewdays(Hsiungetal.1980).Longitudinally,thereisnomajordifferenceinthecompositionandstructur

5、eofthetissuewithinaninternode,exceptfortheexpansionofthecells,especiallythefibres.Thefibresundergoasignificantelongationfromonlyafewmicronstoabout2mm.Withintheinternode,thefibresnearthenodesarealwaysshorterthaninthemiddleportion(seepage61&Fig.82).Elongation,however,

6、causesonlyafewanatomicalchangesalongculmlength.Thenarrowingoftheculmwallintheupperpartresultsinareductionofitsinnerportionwithlessparenchyma,andthevascularbundlesdecreaseinsizebutincreaseinnumber(seepage27).Theupperculmparthasahigherfibrecontentwithahigherspecificgr

7、avity.Theyoungerstageofaculmismarkedbycertainexternalcharacteristicsthatareusefulindicatorstoavoidprematureharvesting.Theseincludethepresenceofculmsheaths,budbreak,branchingpattern,numberofleafscars,andcolourchangesofthestemrangingfromfreshgreentooftenyellow-grey(Ba

8、nik1993).Ayounghairyculmbecomesglabrousatmaturity.Structuralmodificationsduringthematurationphaseandtheyearsfollowingrelatetofibresandpare