植物学及园艺学英文版-botany-and-horticulture-(86)

ThePlantKingdom:FloweringPlantsChapter25LEARNINGOBJECTIVE1•SummarizethefeaturesthatdistinguishfloweringplantsfromgymnospermsKEYTERMS•ANGIOSPERM•Traditionalnameforfloweringplants•Alarge,diversephylumofplantsthatformflowersforsexualreproductionandproduceseedsenclosedinfruitsFloweringPlants•Likegymnosperms:•Floweringplantshavevasculartissuesandproduceseeds•Unlikegymnosperms:•OvulesoffloweringplantsareenclosedwithinanovaryKEYTERMS•OVULE•Structureintheovarythatcontainsafemalegametophyteanddevelopsintoaseedafterfertilization•OVARY•BaseofacarpelorfusedcarpelsthatcontainsovulesanddevelopsintoafruitafterfertilizationOrangeFruitDevelopmentLEARNINGOBJECTIVE2•DescribetheecologicalandeconomicsignificanceofthefloweringplantsEcologyandEconomy•Oursurvivalasaspeciesdependsonfloweringplants•Majorfoodcrops•Products•Cork,rubber,tobacco,coffee,chocolate,aromaticoilsforperfumes•Valuablelumber•FibersandmedicinesEconomicBotany•Subdisciplineofbotanythatdealswithplantsofeconomicimportance•MostofthesearefloweringplantsLEARNINGOBJECTIVE3•Distinguishbetweenmonocotsandeudicots,thetwolargestclassesoffloweringplants•GivespecificexamplesofeachclassKEYTERMS•COTYLEDON•Theseedleafofaplantembryo,whichmaycontainfoodstoredforgerminationKEYTERMS•MONOCOT•Oneoftwomainclassesoffloweringplants;monocotseedscontainasinglecotyledon•Monocotshavefloralpartsinthrees•Monocotsincludegrasses,orchids,irises,onions,lilies,palmsKEYTERMS•EUDICOT•Oneoftwomainclassesoffloweringplants;eudicotseedscontaintwocotyledons•Eudicotshavefloralpartsinfoursorfives•Eudicotsincludeoaks,roses,mustards,cacti,blueberries,sunflowersMonocotsandEudicots(a)Monocots,suchasthisnoddingtrillium(Trilliumcernuum),havetheirfloralpartsinthrees.Notethethreegreensepals,threewhitepetals,sixstamens,andthreestigmas(thecompoundpistilconsistsofthreefusedcarpels).StigmasofpistilAntherofstamenSepalPetalFig.25-2a,p.488(b)MosteudicotssuchasthisTacitusbellushavefloralpartsinfoursorfives.Notethefivepetals,10stamens,andfiveseparatepistils.Fivesepalsarealsopresentbutbarelyvisibleagainstthebackground.PistilsAntherofstamenPetalFig.25-2b,p.488LEARNINGOBJECTIVE4•Brieflyexplainthelifecycleofafloweringplant•DescribedoublefertilizationLifeCycle•Floweringplantsundergoanalternationofgenerations:•Sporophytegenerationislargerandnutritionallyindependent•GametophytegenerationisreducedtoonlyafewmicroscopiccellsKEYTERMS•DOUBLEFERTILIZATION•Aprocessinthefloweringplantlifecycleinwhichtherearetwofertilizations•Oneresultsinformationofazygote•SecondresultsinformationofendospermKEYTERMS•ENDOSPERM•The3nnutritivetissueformedatsomepointinthedevelopmentofallangiospermseedsLifeCycle:FloweringPlantsFlowerofmaturesporophyteSeedlingFruitSeedcoatSeedEmbryoZygote(2n)Endosperm(3n)AntherMegasporangium(ovule)MegasporemothercellOvaryDIPLOID(2n)SPOROPHYTEGENERATIONHAPLOID(n)GAMETOPHYTEGENERATIONMegasporeEggnucleusDoublefertilizationTwospermcellsPollentubePolarnucleiEmbryosac(maturefemalegametophyte)DevelopingpollentubeofmaturemalegametophytePollinationPollengrain(immaturemalegametophyte)EachmicrosporedevelopsintoapollengrainMicrosporeTetradofmicrosporesMicrosporemothercellswithinmicrosporangiaMeiosis12456387Fig.25-3,p.490PollenGrainsLEARNINGOBJECTIVE5•DiscusssomeoftheevolutionaryadaptationsoffloweringplantsAdaptationsofFloweringPlants1•Reproducesexuallybyformingflowers•FormseedswithinfruitsafterdoublefertilizationAdaptationsofFloweringPlants2•Haveefficientwater-conductingvesselelementsinxylemandcarbohydrate-conductingsieve-tubeelementsinphloem•Havepollengrainstransportedbywind,water,insects,otheranimalsKEYTERMS•APOMIXIS•AtypeofreproductioninwhichfruitsandseedsareformedasexuallyAdaptabilityofFloweringPlantsLEARNINGOBJECTIVE6•TracetheevolutionoffloweringplantsfromgymnospermsEvolutionofFloweringPlants•Probablydescendedfromancientgymnospermswithspecializedfeatures•leaveswithbroad,expandedbladesandclosedcarpels•ProbablyaroseonlyonceDrimyspiperitaCarpel(a)Thecarpelresemblesafoldedleafinwhichtheovulesborneonitsuppersurfaceareenclosed.(b)Acrosssectionofthecarpel,cutalongthedashedlinein(a).StigmaStyleOvaryOvulesStigmaFusedmarginCarpelFig.25-6,p.493FossilAngiosperms(a)Theoldestknownfossilangiosperm.ThisfossiloftheextinctplantArchaefructusshowsacarpel-bearingstem.ItwasdiscoveredinnortheasternChinaandisabout125millionyearsold.(b)ThefossilizedfloweroftheextinctplantArchaeanthuslinnenbergeri,whichlivedabout100mya.Thescarsonthereproductiveaxis(receptacle)mayshowwherestamens,petals,andsepalswereoriginallyattachedbutabscised(felloff).Manyspirallyarrangedpistilswerestillattachedatthetimethisflowerwasfossilized.OvuleCarpelScarsonreproductiveaxisPistilsFig.25-7,p.494EvolutionofFloweringPlantsBasalAngiospermsCoreAngiospermsEvolutionofvesselelementsEvolutionoffloweringplants(a)Onehypothesisofrelationshipsamongthefloweringplants,basedonfossilandmolecularevidence.Amborella,waterlilies,andstaranisearelivingplantswhoseancestorsapparentlybranchedofftheangiospermfamilytreeearly.Theseearlygroupswerefollowedbythemagnoliids,themonocotbranch,andtheeudicots.AmborellaWaterlil