Teacher's/Lecturer'sSheet
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Rootwithroot-haircells(ItemNo.:P1442401)
CurricularRelevance
AreaofExpertise:
Biologie
Topic:
BiologiederZelle,
Mikroskopie
EducationLevel:
Klasse7-10
Subtopic:
Pflanzlicheund
tierischeZellen
Experiment:
Wurzelmit
Wurzelhaarzellen
Difficulty
PreparationTime
ExecutionTime
RecommendedGroupSize
Easy
10Minutes
30Minutes
1Student
AdditionalRequirements:
ExperimentVariations:
Twodrinkingglassesforgrowingroots
Onion(Alliumcepa)
Spiderwort(Tradescantiaspec.)
Water
Keywords:
Taskandequipment
Informationforteachers
Information
Therootsofplantshaveaveryimportantfunctiontofulfill.Waterandnutrientsaltshavetobetakenupfromthesoil.Thisis
donebytheroot’strichoblasts(haircells).Theydevelopfromprotrusionsoftherootepidermis(=rhizodermis)whichproducesa
considerableenlargementoftheexchangesurface.Wheredowefindthesetrichoblasts?
Astheplantgrowsitsrootsteadilypenetratesintodeeperlayersofsoil.Howistheroottipstructuredtotoleratetheseforces?
Informationonobtainingmaterials
Ifvegetableonionsareusedasdescribedinthestudents’worksheet,apreliminarytestmustbedonerevealingwhetherthe
onionsgrowrootsornot.Someonionssoldatsupermarketshavebeentreatedwithagentssuppressinggermination.Onionsets
fromagardener’sshoparesurelybetter.Tulips,daffodils,andhyacinthonionsarealsosuitable.
Alternatively,seedlingsofvariousplantscanbecultivatedonmoistabsorbentpaper(gardencress,mustard,gardenbeans)and
theirrootspreparedaccordingly.
Spiderwort(Tradescantiavirginica)isparticularlysuitedforthecuttingexperiment.
However,rootingcanalsobeinducedinImpatiensandsometreespecies(Salix).
Cuttingshavetheadvantageoveronionsofbeingaltogethermoretenderintexture.
Informationonroots
Themeristematictissueoftheroottipisprotectedbytherootcap(calyptra).Here,aconstantformationofnewcellsand
subsequentrejectiontakesplacewhichfacilitatesrootsgrowingintothesoil.
Thisisfollowedbyazonecharacterizedbycellelongationwithoutroothairsandthenbytheroot-hairzone.
Theepidermisoftheroot(rhizodermis)consistsofasinglelayerofcells.Shorttotubularprotrusionsareobservableinalmostall
ofthesecells:trichoblastsinastateofcreation.Thisiswheretheuptakeofnutrientsandwaterfromthesoilhappens.
Inthiscontext,theprincipleofsurfaceenlargementinnatureandtechnologyshouldbediscussed.
Informationonpracticalperformances
ad1:Cultivationofroothairs
Thecuttingsandtheonionsmaybepreparedweeksbeforecommencementofmicroscopy.
Aglassvesseleitherimpenetrabletolightorsubsequentlyshieldedshouldbeusedtopreventalgalgrowthontheroots.
ad2and3:Slidepreparationandmicroscopy
Longitudinalsectionsthrougharootaredifficulttoaccomplishforstudents,sincetherootsareslippery.Besides,theroot-hair
zonewhichisofinteresthereislikelytosustaindamage.Averyeasyandsuccessfuloptionthereforeconsistsintheinsertionof
theentirerootbetweentwoslides.Itonlyneedstobeobservedthatasufficientamountofwaterisadded,topreventthe
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Teacher's/Lecturer'sSheet
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entrapmentofairbetweentheslidesclosetotheroot,whichwouldchangetherefractionoflight.Thiswaythestudentshave
theopportunitytoexaminearatherlongpieceofrootfromtheoutside.Thetrichoblastsaretransparent,whichfacilitates
observation.Variousdevelopmentstagesofthehaircellsandthelooselyattachedcellsofthecalyptrawillbecomeidentifiable
withoutdifficulty.
Possibleadditionalassignments:
Stainingwithcarmineaceticacidcanbedoneinordertovisualizethenucleiintheroot-capzone.
Asawhole-bodymount,therootwillnotbetransparent,onlythehaircells.Iftherootsareplacedinethanol(96%),airwillbe
expelledandtransparencyimproved.
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Tradescantia(40x),root
Tradescantia(100x),root-capepithelium
Allium(100x)
Tradescantia(100x)
Tradescantia(100x)
Tradescantia(400x),trichoblast
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Rootwithroot-haircells(ItemNo.:P1442401)
Taskandequipment
Task
Explorethemorphologyofaroot!
Equipment
PositionNo.
Material
OrderNo.
Quantity
1
EuromexBioBlueBB.4250
microscope
EUR-BB-4250 1
2
Microscopicslides,50pcs
64691-00
3
Coverglasses18x18mm,50pcs.
64685-00
1
4
Beaker,lowform,plastic,100ml
36011-01
1
5
Droppingpipettewithbulb,10pcs
47131-01
1
6
Tweezers,straight,pointed,120mm
64607-00
1
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1
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Set-upandprocedure
Information
Therootsofplantshaveaveryimportantfunctiontofulfill.Waterandnutrientsaltshavetobetakenupfromthesoil.Thisis
donebytheroot’strichoblasts(haircells).Theydevelopfromprotrusionsoftherootepidermis(=rhizodermis)whichproducesa
considerableenlargementoftheexchangesurface.Wheredowefindthesetrichoblasts?
Astheplantgrowsitsrootsteadilypenetratesintodeeperlayersofsoil.Howistheroottipstructuredtotoleratetheseforces?
Methodsandobservations
1.Cultivationofroothairs
Ifweweretopulloutplantsbytheirrootsforthisexperiments,somepartsoftherootwouldinevitablybetornoff.Inorderto
obtainacompleteroot,rootsareallowedtogrowinawaterglass.Youmaytrythisoutusingvariousplantspecies.
VariantA:Onion(e.g.kitchenonionortulip)
Oneonionisplacedontopofadrinkingglass.
·Wait1-4weeks,thenrootswillhavegrown.
VariantB:Seedlings(e.g.Tradescantia)
Someplantsgrowrootswhentheyareplacedinwater.Gatherinformationonwhichrootsdoso.
Placeseveralpiecesoftheplantsinaglasswithwater.
Wait1-4weeks,thenrootswillhavegrown.
2.Slidepreparation
Oneroot(approx.4cm)isplacedlengthwiseonaslide.
Addplentyofwaterusingapipetteuntiltherootiswellcovered.
Mountasecondslideandaddsomemorewater,ifnecessary.
3.Microscopy
Nowyouhaveaverythickspecimenandmayviewitunderthemicroscopewithlowandintermediatepower.
Examinetherootsystematically,startingattheroottip.
Makeadrawingthatshowsanoverviewofthewholerootinthereport.
Observetheroottip!
Drawtrichoblastsundegoingvariousstagesofroot-hairformationinthereport.
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Report:Rootwithroot-haircells
Result-Observations1(10Punkte)
Makeadrawingthatshowsanoverviewofthewholeroot.
Result-Observations2(10Punkte)
Drawtrichoblastsundergoingvariousstagesofroot-hairformation.
Robert-Bosch-Breite10
D-37079Göttingen
Tel:+49551604-0
Fax:+49551604-107
[email protected]
www.phywe.com