Role of Trichomes in Regulation of Optical Properties in Carya glabra and Carya ovataAlexa Korsberg ’17, Jacob Scharfetter ‘17, & Professor Christopher Bickford

Abstract Trichomes–leafhairs–havemanyfunc3onsincludingherbivoreandradia3ondefenseaswellastemperatureandwaterregula3on.Whiletrichomefunc3onandpurposeiswellunderstoodmostresearchhasbeendoneonadaxialtrichomes,whileli>leisknownaboutthefunc3onofabaxialtrichomes.Wehypothesizedthatthepurposeofabaxialtrichomesistore-reflecttransmi>edlightbackintotheleaftoop3mizelightefficiencyandincreasetheamountofphotonsgoingintotheleaf.Weobservedtwolinesofhickorytrees-Caryaglabra(Pignut,glabrous)andCaryaovata(Shagbark,pubescent)–andlookedattheop3calproper3esoftheabaxialsurface,gasexchangevalues,andleafmass.Wefoundthatwhileneitherthepignutnorshagbarklinesdifferedineitherstomatalconductance(p=0.871)orleafmass/area(p=0.302),pignutleaveshadhigherphotosynthe3cratesthanshagbark,9.00micromolCO2m2s-1(SE=+/-0.315)and7.40micromolCO2m2s-1(SE=+/-0.190)respec3vely(p=0.0001).Shagbarkhadhigherreflectanceandtransmi>ancevaluesthanpignutbetweenwavelengths450-700nm(P<<0.05),whilepignuthadgreaterabsorptancethanshagbarkbetweenwavelengths513-604nmand694-700nm(P<0.05).Thereisacleardifferencebetweentheop3calproper3esofpignutandshagbarktrees,howeverfutureexperimentsmustbeconductedwheretheleavesaremanipulatedtoconfirmwhetherornottrichomesarecontribu3ngtothisdifference.

Introduction

Discussion

Acknowledgments IwouldliketothankJacobScharfe>erforbeinganextremelyhelpfulandresourcefullabpartner.IwouldalsoliketothankProfessorChristopherBickfordforhisguidancethroughouttheproject.Finally,IwouldliketothankKenyonCollegeandthebiologydepartmentforitsfunding,resources,andfacili3es.

Results

Trichomesaresmallhair-likestructuresfoundonmanyplantsurfaces.Therearetwokindsoftrichomes–glandular,whichcontaindefensecompounds,andnon-glandular.Bothkindsoftrichomesareimportantforbothherbivoreandpathogendefense.Otherfunc3onsincludeUVprotec3onandwaterregula3onbothintheinteriorandontheexterioroftheleaf(Bickford2016).Wewereinterestedinnon-glandulartrichomestoseeiftheirpresencehadanimpactontheop3calproper3esofplantleaves.

Figure4.Leafmassperarea.Leafpuncheswerecollectedusingleafpuncheswithacircumferenceof1.04cm.2-SampleT-Test,ErrorBars=SEM,p=0.302.

Wefoundfourglabrousandfivepubescenthickorytreesoutsideandcollectedsamples.Wecutmul3plebranchesoffeachtreethenimmediatelytrimmedabout2inchesoffthebo>omofeachbranchtoremoveanyembolismscreatedduringtheini3alcut.Thisallowedthebranchestocon3nueonwithnormalphotosynthe3cratesaswellasstomatalconductanceaeerbeingcut.Op3calproper3esoftheleaves-reflectance,transmi>ance,andabsorptance-weremeasuredusingaJaz-TR-Spectroclip(OceanOp3cs).Photosynthe3candstomatalconductancemeasurementsweretakenusinganLI-6400XTLi-CorBiosciencesbasedontheCO2flux.Leafmasssampleswerecollectedusinga1.04cmcircumferenceleafpunch.Samplesweredriedfor24hoursandweighed.Leafshavingmethodswereexperimentedwithusingscotchtape,maskingtape,genericrazorblades,andop3calknivesofvarioussizesrangingfrom1.2-1.8mm.Weexperimentedwithvariousmethodsonboththeadaxialandabaxialsurfaces.

Methods

Figure1.Reflectanceoflightontheabaxialsurfaceoftheleaves.Thelightorangelinerepresentsglabrousleaveswhilethedarkorangerepresentspubescentleaves.2-SampleT-Test,ErrorBars=SEM,p<<0.05betweenwavelengths450-700.

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Figure2.Transmi>anceoflightmovingthroughtheleaffromtheabaxialsurface.Thelightbluelinerepresentsglabrousleaveswhilethedarkbluerepresentspubescentleaves.2-SampleT-Test,ErrorBars=SEM,p<<0.05betweenwavelengths450-700nm.

Figure3.Absorptanceoflightinthemesophylloftheleaves.Thelightgreenlinerepresentsglabrousleaveswhilethedarkgreenlinerepresentspubescentleaves.2-SampleT-Test,ErrorBars=SEM,p<0.05betweenwavelengths513-604nmand694-700nm.

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Figure5.Photosynthe3cratesweremeasuredwithalicoraeerthestemswerere-cutunderwater.2-SampleT-Test,ErrorBars=SEM,p=0.0001.

Nosugges3onsthatre-reflectedlightintotheleafenhancesphotosynthesisbecauseglabrousleaveshadhigherphotosynthe3cratesthanpubescentleaves.Speciesdifferencespoten3allycontributetothephotosynthe3cdifferencesTheymayhavedifferentamountsofimportantenzymesPubescenceappearstoincreasere-reflectanceoflightintotheleafMoretransmi>anceinpubescentleaveswasunexpectedaswebelievedtrichomeswouldincreasereflectancewhilereducingtransmi>anceAbsorptancewashighintheredandbluespectrumasexpectedbecausethatiswhatisusedforphotosynthesisUnderstandinghowtrichomesworkisimportantwhenunderstandinghowplantshaveevolvedandhowtheyfunc3onindifferentclimatesbecauseoftheirdefensiveandregulatoryquali3esPossibletobio-engineercropsthatincreasethealbedotohelpmi3gateclimatechange

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Shagbarkleaf(above)www.extension.iastate.edu

Pignutleaf(below)h>p://www.florafinder.com