Theeffectsofauxinonplantgrowthtoapicalmeristemandvaryingeffectsoflightintensities.

TomLawlis,JackParker,andAmandaGreenDepartmentofPlantBiologyOklahomaStateUniversityStillwater,OK

Introduction• Auxin(Indole3-aceticacid)aplanthormone

primarilyinvolvedinregulatingplantgrowthanddevelopment.

• Previousstudieshavebeenconductedtobetterunderstandtheroleauxinplaysinplantgrowthanddevelopment.

• Ourstudyinvestigatestheinteractionbetweenauxinandlightintensities.

• WehypothesisthatifaplantreceivessupplementalAuxintreatment,itwillneedmorelighttogrow/survive.

MaterialandMethodsPlantGeneration:• WisconsinFastPlants(Brassicarapa)• 403-inchpots• fourgroups,10ineach• Twoofthegroupswereplacedinhighlight

incubation(fivelightbulbs)• Twogroupswereplacedinlowlightincubation

(twolightbulbs)• Twodrops(.10ml)of1%auxinsolution,forone

groupundereachlightintensity• Samegroupsofplantsagainreceivedauxin

treatment(.25ml)SubjectMeasurementsandStatisticalAnalysis:• Height• Numberofleaves• Averagewidthofleaves• Numberofreproductivestructures• Shootbiomass• Two-wayAnalysisofVariance.

ReferencesFerguson,BrettJ.,C.Beveridge.RolesforAuxin,Cytokinin,andStrigolactone inregulatingshootbranching. PlantPhysiology.149.4:1929-1944.Muller,Dorte,T.Waldie,K.Miyawaki,J.P.C.To,C.W.Melnyk,J.J.Kieber,T.Kakimoto,O.Leyser.2015.Cytokinin isrequiredforescapebutnotreleasefromauxinmediatedapicaldominance.ThePlantJournal.82:874-886.

Roumeliotis,E.,etal."Theeffectsofauxin andstrigolactonesontuberinitiationandstolonarchitectureinpotato."JournalofExperimentalBotany,vol. 63,no. 12, 2012,pp. 4539-4547.

Young,Linda M.,andMichael L.Evans."Patternsofauxin andabscisic acidmovementinthetipsofgravistimulated primaryrootsofmaize."PlantGrowthRegulation,vol. 20,no. 3, 1996,pp. 253-258.

DiscussionResults

Figure1- Graphofmeansofplantshootmass(g)inhighandlowlight,andauxinapplied(A)ornoapplication(N).

Figure2- Graphofmeansofplantheight(cm)inhighandlowlight,andauxinapplied(A)ornoapplication(N).

Figure3- Graphofmeansofaverageleafwidth(mm)inhighandlowlight,andauxinapplied(A)ornoapplication(N).

Figure4- Graphofmeansofnumberofreproductivestructuresinhighandlowlight,andauxinapplied(A)ornoapplication(N).

• Lightintensity,independentofauxin,wassignificantacrossallvariables(Fig.1).

• Theaffectofauxin,independentoflightintensity,wassignificantinplantheight(P=0.001582)(Fig.2).

• Theaffectofauxin,independentoflightintensity,wasalsosignificantinthenumberofreproductivestructures(P=0.000853)(Fig.4).

• Theinteractionbetweenauxinandlightintensitywassignificantinthenumberofreproductivestructures(P=0.009239)(Fig.4).

• Wehypothesizedthatthehighlightplantswithauxinappliedwouldexhibitthelargestgrowthacrossallmeasuredvariables.

• Incontrast,measurementsshowedthatvaryinglightintensity,independentofauxinapplication,wasthemostsignificantfactorthataffectedtheplantsgrowth.ThiswasseeninthesignificantdifferenceingrowthacrossShootMass(g),PlantHeight(cm),AverageLeafWidth(mm),andNumberofReproductiveStructures.

• Inaddition,theapplicationofauxintotheplantmeristemsshowedtobeinsignificantacrossallvariables,asseenbylesservaluesforShootMass(g),PlantHeight(cm),AverageLeafWidth(mm),andNumberofReproductiveStructures.

• Theapplicationofauxinseemedtostuntthegrowthoftheplants.Afterthefirstapplication,plantswithauxinappliedgrewataslowerrateandhadahighernumberofplantsdie.

• Inconclusion,wedidnotobtainenoughsignificantevidencetosuggestthatvaryinglightintensitiesincreasesthefunctioningofauxinwhenappliedtotheapicalmeristemofplants.

• FutureReference:• Theauxinwasappliedinaninefficientmanner.Infuturestudies,a

differentmethodshouldbeusedtoensurethebestresults.• Futuresstudiescouldbeconductedtoexamineifthelocationofauxin

applicationisafactor.Inaddition,whentheauxinisappliedduringtheplantslifecyclecouldbestudied.

• Examinetheinteractionbetweenauxinandvariableotherthanlight.Effectsofvaryinglightintensitiesandplantgrowthiswelldocumented.

AcknowledgmentsWewouldliketothankT.A.DylanFranksandProfessorAndrewDoust fortheircollaborationonthisproject.Additionally,wethanktheHowardHughesMedicalInstituteforfundingthisproject.