RatesofTranspiration
Lab11
Abstract
Thisexperimentwasconductedtomeasuretheratesoftranspiration
between3variables(Control,Wind,Light,Heat).Eachplantwastobemonitored
andmassedover48hours.After48hoursthemasslostwasdividedbythesurface
areaandthiswasmeasuredthroughaT‐Testtoseeifthereweredifferences.The
heatlampwasabletoproduceadifferenceandshowthatheatwouldcausethe
mostwaterlossandproduceahigherrateoftranspiration.
Introduction
Thislabwasperformedtoseethedifferingratesoftranspirationandthe
openingandclosingofstomataonplantleavesbetweencertainconditions.
Differentvariableswereusedtotesthowthestomatawouldreacttoeachcondition
(Heat,Light,Wind)andbemeasuredthroughwaterloss.Anincreasedamountof
waterlosswouldsignalthatthestomataremainedopenlongerandlostmorewater
thereforesupportinghigherratesoftranspiration.
Hypothesis
IftheColeusPlantisplacedunderaheatlampthenitwilllosemoremass
duetotranspirationthantheotherconditions(Control,Light,Wind)
Materials
4xPlasticBags
4xApprox.1footlongstring
4xColeusPlantCuttings
1xWindFan
1xHeatLamp
1xScale
Procedure
I.
Acquire4ColeusCuttings
II.
Cutoffanyflowers/budsonthecuttings
III.
Placeeachofthecuttingsintheirownplasticbagwiththetopwrapped
tightlyaroundthestem(s)ofthecuttingsandtiedinplacewithastring
IV. Masseachcutting(withtheplasticbag)
V. Placeonecuttinginacontrolledenvironment(nearwindow)
VI. Placeaseparatecuttingunderaheatlamp
VII. Placeaseparatecuttingnexttoaconstantfan
VIII. Placeaseparatecuttingunderincreasedlightsources
IX.
Wait24hours
Plant
Control
Wind
Heat
Light
Group1
0.0446
0.0722
0.1002
0.0596
Group2
0.0509
0.0836
0.1065
0.0522
Group3
0.1001
0.0939
0.1406
0.0222
Group4
0.0617
0.0555
0.1040
0.0661
Group5
0.0404
0.0940
0.0760
0.0638
Average
0.0595
0.0798
0.1055
0.0528
T‐Test
None
0.0810
0.0076
0.3140
X.
Masseachcuttingseparately
XI.
Placeeachcuttingintheirrespectiveplacesagain
XII.
Waitanother24hours(48hoursintotal)
XIII.
Masseachcuttingseparately
XIV. RepeatSteps1‐13formultipletrials
Coleus48‐HourTranspirationwithT‐Test(MassofWaterLost/SurfaceArea)
(g/cm2)
NullHypothesis/T‐Test
‐IfaColeusPlantisplacedbesidesasourceofconstantwindthentherewillbeno
difference(Valueof.0810isNOTlessthan.05)NullHypothesisisnotrejected
‐IfaColeusPlantisplacedunderaheatlampthentherewillbenodifference(Value
of.0076ISlessthan.05)NullHypothesisisrejected
‐IfaColeusPlantisplacedunderadirectlightthentheewillbenodifference(Value
of.3140isNOTlessthan.05)NullHypothesisisnotrejected
Graph
Conclusion/Analysis/Discussion/Questions
RatesofTranspirationweremeasuredontheamountofwaterlostbythe
plantsdividedbythesurfaceareaofleaves.Themorewaterlostwouldimplythat
stomatawereopenlongerandmoretranspirationwasoccurring.AfterrunningaT‐
Testforeachaveragevalueofthevariables,onlyonep‐valuewaslessthan.05.Even
ifthedatatablesshoweddifferencesthanthecontrol,theheatvariablewastheonly
variablethatcausedadifferenceaccordingtotheT‐Tests.Withap‐valueof.0076,
theheatlampwasabletorejectthenullhypothesisandinturnsupportthe
alternatehypothesisstatedatthebeginningoftheexperiment.Evenifthevaluesof
.0798(Wind)and.0528(Light)weredifferentthanthecontrol,thep‐valuesfailed
torejecttheirrespectivenullhypothesisandthereforeshownotangibledifference.
Asaresult,ouroriginalhypothesiswassupportedandheatwasabletoincreasethe
rateoftranspiration.LightandWindfailedtoshowadifferenceintheratesoftheir
respectiveplants.
Theexperimentwasvalidandwasrunwithmultipletrials.Thereweresome
discrepanciesthatcouldhavealteredtheexperiment.Thewindfanwasturnedoff
foradecentamountoftimeandcouldhavechangedthevaluesinthewindvariable
plant.Othersmallitemssuchastheconsistencyofthebagstiedaroundeachplant
couldalsoresultinalterations.Theexperimentcouldberunformoretrialsand
havetheseproblemsfixed.Nevertheless,theexperimentwasabletoyieldreliable
results.
‐Whatothervariablescouldbetestedandhowwouldtheyfare?
CompleteDarkness,AridConditions,IncreasedWater?
‐Whyweretheflowers/budscutoff?
Whatwouldbetheeffect?
‐Howwoulddifferentplantsfareinthisexperiment?
Begonias?
‐Howwouldtheexperimentfareifthetimewerelonger
96Hours,144Hours,196Hours?
Sources
Sadava, David E. Life, the Science of Biology. Sunderland, MA: Sinauer Associates,
2011. Print.