-1-MeasurementandcalculationofleafareaAbstractEthodsofleafareameasurementareusefulforsmallplantpopulations,suchasexperimentswithpottedplants,andallowthemeasurementofthesameplantseveraltimesduringthegrowingperiod.Amethodologywasdevelopedtoestimatetheleafareaindexofcucumberandtomatoplantsthroughtheevaluationoftheleafareadistributionpatternoftheplantsandtherelativeheightoftheleavesintheplants.Plantandleafheight,aswellasthelengthandwidthofallleavesweremeasuredandtheareaofsomeleaveswasdeterminedbyadigitalareameter.Theobtainedregressionequationswereusedtoestimatetheleafareaforallrelativeheightsalongtheplant.TheLADPadjustedtoaquadraticmodelforbothcropsandLAIwereestimatedbymeasuringthelengthandwidthoftheleaveslocatedattherelativeheightsrepresentingthemeanleafareaoftheplants.TheLAIestimationspresentedhighprecisionandaccuracywhentheproposedmethodologywasusedresultingintimeandeffortsavingsandbeingusefulforbothcrops.Keywords:CucumissativusL.,LycopersiconesculentumMill.,greenhouse,leafareaindex.-2-Leafisanimportantplantorgan,andisassociatedwithphotosynthesisandevapotranspiration；therefore,leafareameasurementsarerequiredinmostphysiologicalandagronomicstudiesinvolvingplantgrowth.Manymethodsofleafareameasurementshavebeendeveloped.Directmethodsfordeterminingleafareaarerestrictedtotheuseofanautomaticarea-integratingmeter.Tracing,shadowgraphingortheuseofaplanimetertomeasuretheleafareaofleavesattachedtoshootsistimeconsumingandtedious；also,insomeexperimentstimeisinsufficienttomakesuchmeasurements.Estimationofleafareafrommathematicalmodelsinvolvinglinearmeasurementsofleavesisrelativelyaccurateandnon-destructive.CucumberandtomatoaresomeofthemaincropscultivatedingreenhouseinBrazilandresearcheswiththesecropsareessentialtoestablishthebestmanagementpracticestoincreaseyieldandfruitquality.Researcheswithplantscultivatedinpotsarecommonundergreenhouseconditionsbecauselessspaceisrequiredandthenumberoftreatmentsandreplicationscanbequiteincreased.Underpotcultivation,anon-destructivemethodforLAIevaluationisrequiredwiththeadvantagethatthesameplantcanbemeasuredseveraltimesduringthegrowingperiod,thusleadingtoamorerealcurveofLAIincreasealongthegrowingseason.MATERIALANDMETHODSInthefirstcucumberseason,agreenhouseof1.6mheightoflateralopening,10mwideand20mlongandcoveredwithapolyethylenefilmof0.15mm-3-thicknesswasused.ThelateralcurtainswereclosedatnightandopenedduringthedaygreenhousewaslocatedinaexperimentalareaoftheUniversidadede,Piracicabacity,Brazil.Cucumberseedlings,weretransplantedon13thJanuary,1999,infourbeds,eachonewithtworowsofplants,givingaplantpopulationof2.5plantsm-2.Plantsweretrainedwithasinglestemalongandaroundaverticalplasticstring.Waterwasappliedbyadripirrigationsystem,withonedripperperplant,andfertilizerscontainingN,P,K,Ca,Mgandwereappliedwiththeirrigationwaterinallirrigations,followingtheuptakerateofcucumberingreenhouse.Fortydaysaftertransplanting,fiveplantswereselectedandthewidthandlengthofallleavesweremeasuredwithasimpleruler.Inaddition,plantheightandtheinsertionheightofthepetiolefromeachleafwasalsoobtainedtocalculatetherelativeleafheightbytheequation.whereRLHistherelativeleafheight,LHistheleafheight,thatis,thedistancebetweenthesoilsurfaceandthenodecorrespondingtotheleaf,andPHtheplantheight.Inthesameday,leavesofdifferentsizeswereselectedtorepresentthefullspectrumofmeasurableleafsizesandtheirareasweremeasuredusingaLI-COR3000leafareameter.Lengthwasmeasuredfromlaminatiptothepointofintersectionofthelaminaandpetioleandwidthweremeasuredfromtiptotipbetweenthewidestlaminalobes.Therelativeleafarea(RLA)wascalculatedbydividingtheareaofeachleafbythemeanleafareaoftheplantforeachRLHasfollows:-4-whereRLAistherelativeleafarea,LAistheleafareaofagivenleaf(cm2)andLAMisthemeanleafareaoftheplant(cm2leaf-1)givenbythesumoftheLAofallleavesdividedbythenumberofleavesofeachplant.TheRLHwasplottedagainstRLAinordertodeterminetheleafwhosearearepresentsthemeanleafareaoftheplantToevaluatetheperformanceofthemethodology,theLandWofallleavesoffiveplantsdifferentfromthoseusedinthemodeldevelopment,fromeachcropandseasonweremeasuredand,theareasoftheleaveslocatedattherelativeheightsthatrepresentedtheLAMwereusedtocalculatetheLAIbytheequation:WhereNisthenumberofleavesintheplantandAthearea(cm2)occupiedbyoneplantinthecroppedarea.EstimatedLAIwascorrelatedtothemeasuredLAI,thesumoftheareasofallleavesdividedbyA,andtheresultswereplottedandanalysedbymeansoftheregressionslope,coefficientofdetermination(r2)andcoefficientofWillmott(Willmott,1981).RESULTSANDDISCUSSIONTheequationsrelatingtheleafareawiththeL,WandLxWforallcropsareshown.EquationsthatuseonlyLorWshowedgoodrelationshipswithLA,whichdemandlesseff