被子植物生殖与生物技术

(5) Chapter38AngiospermReproductionandBiotechnology被子植物生殖與生物技術ToBeorNottoBe(??????)Overview:ToSeedorNottoSeedTheparasiticplant

RafflesiaarnoldiiProducesenormousflowersthatcanproduceupto4millionseedsFigure38.1KeyConceptsConcept38.1:Pollinationenablesgametestocometogetherwithinaflower(受粉作用使得花中的配子聚在一起)Concept38.2:Afterfertilization,ovulesdevelopintoseedsandovariesintofruitsConcept38.3:Manyfloweringplants

clone(複製)themselvesbyasexualreproductionConcept38.4:PlantbiotechnologyistransformingagricultureConcept38.1:Pollinationenablesgametestocometogetherwithinaflower(受粉作用使得花中的配子聚在一起)Inangiosperms,thedominantsporophyte(孢子體)Producessporesthatdevelopwithinflowersintomalegametophytes(pollengrains)(雄配子體、花粉粒)Producesfemalegametophytes(embryosacs)(雌配子體、胚囊)FlowerStructureFlowersArethereproductiveshootsoftheangiospermsporophyte(被子植物配子體)Arecomposedoffourfloralorgans:Sepals(萼片)Petals(花瓣)Stamens(雄蕊)Carpels(雌蕊)FilamentAnther雄蕊Stamen花瓣PetalReceptacleSepal萼片Style花柱OvaryCarpel雌蕊Stigma花藥花絲卵房柱頭花托AnoverviewofangiospermreproductionFigure38.2a,bAntherattipofstamenPollentubeGerminatedpollengrain(n)(malegametophyte)onstigmaofcarpelOvary(baseofcarpel)Ovule(卵胞)Embryosac(n)(femalegametophyte)FERTILIZATIONEgg(n)Sperm(n)KeyHaploid(n)Diploid(2n)(b)Simplifiedangiospermlifecycle.

SeeFigure30.10foramoredetailed

versionofthelifecycle,includingmeiosis.Maturesporophyteplant(2n)withflowersSeed(developsfromovule)Zygote(2n)Embryo(2n)(sporophyte)Simplefruit(developsfromovary)GerminatingseedSeedFilamentAntherStamenPetalReceptacleSepalStyleOvary(a)Anidealizedflower.CarpelStigma(3)Apollengrainbecomesamaturemalegametophytewhenitsgenerativenucleusdividesandformstwosperm.Thisusuallyoccursafterapollengrainlandsonthestigmaofacarpelandthepollentubebeginstogrow.(SeeFigure38.2b.)Developmentofamalegametophyte(pollengrain)雄配子體(花粉粒)的發育(a)(2)Eachmicrosporocytedividesbymeiosistoproducefourhaploidmicrospores(n),eachofwhichdevelopsintoapollengrain.Pollensac(microsporangium)Micro-SporocyteMicro-spores(4)Eachof4microsporesGenerativecell(willform2sperm)Nucleusoftubecell(1)Eachoneofthemicrosporangiacontainsdiploidmicrosporocytes(2n)(microsporemothercells).75m20mRagweed

pollengrainFigure38.4aMEIOSIS減數分裂MITOSIS有絲分裂KEYtolabelsHaploid(2n)Diploid(2n)Pollen(花粉)---Developsfrommicrospores(雄孢子)withinthesporangia(孢子囊)ofanthersMaleGametophyte(pollengrain)Keytolabels有絲分裂MITOSIS減數分裂MEIOSISOvuleOvuleIntegumentsEmbryosacMega-sporangiumMega-sporocyteIntegumentsMicropyleSurvivingmegasporeAntipodelCells(3)PolarNuclei(2)Egg(1)Synergids(2)Developmentofafemalegametophyte(embryosac)雌配子體(胚囊)的發育(b)(1)Withintheovule’smegasporangiumisalargediploidcellcalledthemegasporocyte(megasporemothercell).(3)Threemitoticdivisionsofthemegasporeformtheembryosac,amulticellularfemalegametophyte.Theovulenowconsistsoftheembryosacalongwiththesurroundinginteguments(protectivetissue).Femalegametophyte(embryosac)Diploid(2n)Haploid(2n)Figure38.4b100m(2)Themegasporocytedividesbymeiosisandgivesrisetofourhaploidcells,butinmostspeciesonlyoneofthesesurvivesasthemegaspore.Embryosacs---DevelopfrommegasporeswithinovulesMechanismsThatPreventSelf-Fertilization(自我受精)Manyangiosperms(被子植物)Havemechanismsthatmakeitdifficultorimpossibleforaflowertofertilizeitself(自我受精)

Figure38.5Stigma柱頭AntherwithPollen有花粉的花藥Stigma柱頭PinflowerThrumflowerThemostcommonanti-selfingmechanisminfloweringplantsIsknownasself-incompatibility(自我排斥、自我不相容),

theabilityofaplanttorejectitsownpollenResearchersareunravelingthemolecularmechanismsthatareinvolvedinself-incompatibilitySomeplantsRejectpollenthathasanS-genematchinganalleleinthestigmacellsRecognitionofselfpollen(自家花粉)Triggersasignaltransductionpathwayleadingtoablock(阻礙)ingrowthofapollentubeConcept38.2:Afterfertilization,ovulesdevelopintoseedsandovariesintofruitsDoubleFertilization(雙重受精)Afterlandingonareceptivestigma(花柱)Apollengrain

(花粉粒)germinatesandproducesapollentube

(花粉管)thatextendsdownbetweenthecellsofthestyle()towardtheovary()Thepollentube

(花粉管)ThendischargestwospermintotheembryosacIndoublefertilization

(雙重受精)OnespermfertilizestheeggTheotherspermcombineswiththepolarnuclei(極核),givingrisetothefood-storingendosperm(胚乳)Stigma(柱頭)(極核)PolarnucleiEgg(花粉粒)PollengrainPollentube(花粉管)2spermStyleOvaryOvule(containingfemalegametophyte,orembryosac)MicropyleOvulePolarnucleiEggTwospermabouttobedischargedEndospermnucleus(3n)(2polarnucleiplussperm)Zygote(2n)(eggplussperm)Figure38.6Growthofthepollentubeanddoublefertilization(1)Ifapollengraingerminates,apollentubegrowsdownthestyletowardtheovary.(2)Thepollentubedischargestwospermintothefemalegametophyte(embryosac)withinanovule.(3)Onespermfertilizestheegg,formingthezygote.Theotherspermcombineswiththetwopolarnucleioftheembryosac’slargecentralcell,formingatriploidcellthatdevelopsintothenutritivetissuecalledendosperm.DevelopmentofOvuleandEndospermFromOvuletoSeed,afterdoublefertilizationEachovuledevelopsintoaseedTheovarydevelopsintoafruitenclosingtheseed(s)EndospermDevelopment,usuallyprecedesembryodevelopmentInmostmonocotsandsomeeudicots,theendospermstoresnutrientsthatcanbeusedbytheseedlingaftergerminationInothereudicots,thefoodreservesoftheendospermarecompletelyexportedtothecotyledonsEmbryoDevelopmentThefirstmitoticdivisionofthezygoteistransverseSplittingthefertilizedeggintoabasalcellandaterminalcellFigure38.7OvuleTerminalcellEndospermnucleusBasalcellZygoteIntegumentsZygoteProembryoCotyledonsShootapexRootapexSeedcoatBasalcellSuspensorEndospermSuspensorStructureoftheMatureSeedTheembryoanditsfoodsupplyAreenclosedbyahard,protectiveseedcoatInacommongardenbean,aeudicotTheembryoconsistsofthehypocotyl,radicle,andthickcotyledonsFigure38.8a(a)Commongardenbean,aeudicotwiththickcotyledons.Thefleshycotyledonsstorefoodabsorbedfromtheendospermbeforetheseedgerminates.SeedcoatRadicleEpicotylHypocotylCotyledons胚根種皮子葉上胚軸下胚軸Theseedsofothereudicots,suchascastorbeansHavesimilarstructures,butthincotyledonsSeedcoatEndospermCotyledonsEpicotylHypocotylRadicleFigure38.8bSeedcoatEndospermCotyledonsEpicotylHypocotylRadicle(b)Castorbean,aeudicotwiththincotyledons.Thenarrow,membranouscotyledons(showninedgeandflatviews)absorbfoodfromtheendospermwhentheseedgerminates.種皮胚根下胚軸子葉上胚軸胚乳Theembryoofamonocot(單子葉)hasasinglecotyledon,acoleoptile,andacoleorhizaFigure38.8c(c)Maize,amonocot.Likeallmonocots,maizehasonlyonecotyledon.Maizeandothergrasseshavealargecotyledoncalleda

scutellum.Therudimentaryshootissheathedinastructurecalledthecoleoptile,andthecoleorhizacoverstheyoungroot.Scutellum(cotyledon)ColeoptileColeorhizaPericarpfusedwithseedcoatEndospermEpicotylHypocotylRadicle(種皮)(胚根)(下胚軸)(上胚軸)(胚乳)(子葉)(芽鞘)(根鞘)FromOvarytoFruitAfruitDevelopsfromtheovaryProtectstheenclosedseedsAidsinthedispersalofseedsbywindoranimalsFruitsareclassifiedintoseveraltypesDependingontheirdevelopmentaloriginFigure38.9a–c(a)Simplefruit.Asimplefruitdevelopsfromasinglecarpel(orseveralfusedcarpels)ofoneflower(examples:pea,lemon,peanut).(b)Aggregatefruit.Anaggregatefruitdevelopsfrommanyseparatecarpelsofoneflower(examples:raspberry,blackberry,strawberry).(c)Multiplefruit.Amultiplefruitdevelopsfrommanycarpelsofmanyflowers(examples:pineapple,fig).PineapplefruitRaspberryfruitPeafruitStamenCarpel(fruitlet)StigmaOvaryRaspberryflowerEachsegmentdevelopsfromthecarpelofoneflowerPineappleinflorescenceStamenCarpelsFlowerOvaryStigmaStamenOvulePeaflowerSeedSeedGermination(種子萌芽)AsaseedmaturesItdehydrates(脫水)andentersaphasereferredtoasdormancy(休眠)SeedDormancy:AdaptationforToughTimesSeeddormancyIncreasesthechancesthatgerminationwilloccuratatimeandplacemostadvantageoustotheseedlingThebreakingofseeddormancy

Oftenrequiresenvironmentalcues,suchastemperatureorlightingcuesFromSeedtoSeedling(從種子到幼苗)Germinationofseedsdependsonthephysicalprocesscalledimbibition(浸潤)TheuptakeofwaterduetolowwaterpotentialofthedryseedFigure38.10aCotyledonHypocotylRadicle(胚根)Epicotyl(上胚軸)Seedcoat(種皮)CotyledonHypocotylCotyledon(子葉)Hypocotyl(上胚軸)(a)Commongardenbean.Incommongardenbeans,straighteningofahookinthehypocotylpullsthecotyledonsfromthesoil.Theradicle(胚軸)isthefirstorgantoemergefromthegerminatingseedInmanyeudicots,ahookformsinthehypocotyl(下胚軸),andgrowthpushesthehookabovegroundFoliageleaves(初生葉)(上胚軸)(上胚軸)FoliageleavesColeoptileColeoptileRadicle(b)Maize.Inmaizeandothergrasses,theshootgrowsstraightupthroughthetubeofthecoleoptile.Monocots(單子葉植物)UseadifferentmethodforbreakinggroundwhentheygerminateThecoleoptile(芽鞘)PushesupwardthroughthesoilandintotheairFigure38.10bConcept38.3:Manyfloweringplantsclone

(複製)themselvesbyasexualreproductionManyangiospermspeciesreproducebothasexuallyandsexually(無性及有性)SexualreproductionGeneratesthegeneticvariationthatmakesevolutionaryadaptationpossibleAsexualreproductioninplantsIscalledvegetativereproduction

(營養繁殖)MechanismsofAsexualReproduction(無性生殖的機制)Fragmentation(裂片)IstheseparationofaparentplantintopartsthatdevelopintowholeplantsIsoneofthemostcommonmodesofasexualreproduction

Insomespecies,therootsystemofasingleparentgivesrisetomanyadventitiousshootsthatbecomeseparateshootsystemsFigure38.11VegetativePropagation(營養繁殖)andAgriculturePlantbiologistshaveadoptedinvitromethodstocreateandclonenovelplantvarieties.Figure38.12a,b(a)Justafewparenchymacellsfromacarrotgaverisetothiscallus,amassofundifferentiatedcells.(b)Thecallusdifferentiatesintoanentireplant,withleaves,stems,androots.Inaprocesscalledprotoplastfusion(原生質體融合)Researchersf