Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures for Biology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris Romero(5)(5) Chapter 38Chapter 38Angiosperm Reproduction and Biotechnology被子植物生殖與生物技術Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsTo Be or Not to Be (?)Overview: To Seed or Not to SeedThe parasitic plant Rafflesia arnoldiiProduces enormous flowers that can produce up to 4 million seedsFigure 38.1Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsKey ConceptsConcept 38.1: Pollination enables gametes to come together within a flower (受粉作用使得花中的配子聚在一起)Concept 38.2: After fertilization, ovules develop into seeds and ovaries into fruitsConcept 38.3: Many flowering plants clone (複製) themselves by asexual reproductionConcept 38.4: Plant biotechnology is transforming agricultureCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 38.1: Pollination enables gametes to come together within a flower (受粉作用使得花中的配子聚在一起)In angiosperms, the dominant sporophyte (孢子體)Produces spores that develop within flowers into male gametophytes (pollen grains) (雄配子體、花粉粒)Produces female gametophytes (embryo sacs) (雌配子體、胚囊)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFlower StructureFlowersAre the reproductive shoots of the angiosperm sporophyte (被子植物配子體)Are composed of four floral organs: Sepals (萼片)Petals (花瓣)Stamens (雄蕊)Carpels (雌蕊)FilamentAnther雄雄蕊蕊Stamen花瓣花瓣PetalReceptacleSepal萼片萼片Style花柱花柱OvaryCarpel雌雌蕊蕊Stigma花藥花藥花絲花絲卵房卵房柱頭柱頭花托花托Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings被子植物花的多樣性Many variations in floral structure have evolved during the 140 million years of angiosperm historyBilateral symmetry(orchid)SepalRadial symmetry(daffodil)Fused petalsSemi-inferior ovaryInferior ovarySuperior ovaryLupine inflorescenceSunflower inflorescenceMaize, a monoecious speciesDioecious Sagittaria latifolia (commonarrowhead) SYMMETRY OVARY LOCATION FLORAL DISTRIBUTION Figure 38.3 REPRODUCTIVE VARIATIONS Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsGametophyte Development and PollinationIn angiosperms (被子植物)Pollination (受粉作用) is the transfer of pollen from an anther (花藥) to a stigma (柱頭)If pollination is successful, a pollen grain (花粉粒) produces a structure called a pollen tube (花粉管), which grows down into the ovary (卵房) and discharges sperm near the embryo sac (胚囊)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsAn overview of angiosperm reproductionFigure 38.2a, bAnther attip of stamenPollen tubeGerminated pollen grain(n) (male gametophyte)on stigma of carpelOvary (base of carpel)Ovule (卵胞卵胞)Embryo sac (n)(female gametophyte)FERTILIZATIONEgg (n)Sperm (n)KeyHaploid (n)Diploid (2n)(b) Simplified angiosperm life cycle.See Figure 30.10 for a more detailedversion of the life cycle, including meiosis.Mature sporophyteplant (2n) withflowersSeed(developsfrom ovule)Zygote(2n)Embryo (2n)(sporophyte)Simple fruit(develops from ovary)GerminatingseedSeedFilamentAntherStamenPetalReceptacleSepalStyleOvary(a) An idealized flower.CarpelStigmaCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings(3) A pollen grain becomes a mature male gametophyte when its generative nucleus divides and forms two sperm. This usually occurs after a pollen grain lands on the stigma of a carpel and the pollen tube begins to grow. (See Figure 38.2b.) Development of a male gametophyte (pollen grain)雄配子體(花粉粒)的發育(a)(2) Each microsporocyte divides by meiosis to produce four haploid microspores (n), each of which develops into a pollen grain.Pollen sac(microsporangium)Micro-SporocyteMicro-spores (4)Each of 4microsporesGenerativecell (willform 2sperm)Nucleus of tube cell(1) Each one of the microsporangia contains diploid microsporocytes (2n) (microspore mother cells).75 m20 mRagweedpollen grainFigure 38.4aMEIOSIS減數分裂減數分裂MITOSIS有絲分裂有絲分裂KEY to labelsHaploid (2n)Diploid (2n)Pollen (花粉)-Develops from microspores (雄孢子) within the sporangia (孢子囊) of anthersMaleGametophyte(pollen grain)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsKey to labels有絲分裂有絲分裂MITOSIS減數分裂減數分裂MEIOSISOvuleOvuleIntegumentsEmbryo sacMega-sporangiumMega-sporocyteIntegumentsMicropyleSurvivingmegasporeAntipodelCells (3)PolarNuclei (2)Egg (1)Synergids (2) Development of a female gametophyte (embryo sac)雌配子體(胚囊)的發育(b)(1) Within the ovules megasporangium is a large diploid cell called the megasporocyte (megaspore mother cell).(3) Three mitotic divisions of the megaspore form the embryo sac, a multicellular female gametophyte. The ovule now consists of the embryo sac along with the surrounding integuments (protective tissue).Female gametophyte(embryo sac)Diploid (2n)Haploid (2n)Figure 38.4b100 m(2) The megasporocyte divides by meiosis and gives rise to fourhaploid cells, but in most species only one of these survives as the megaspore.Embryo sacs-Develop from megaspores within ovulesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsMechanisms That Prevent Self-Fertilization (自我受精)Many angiosperms (被子植物)Have mechanisms that make it difficult or impossible for a flower to fertilize itself (自我受精) Figure 38.5Stigma柱頭柱頭Anther withPollen 有花有花粉的花藥粉的花藥Stigma柱頭柱頭Pin flowerThrum flowerCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe most common anti-selfing mechanism in flowering plantsIs known as self-incompatibility (自我排斥、自我不相容), the ability of a plant to reject its own pollenResearchers are unraveling the molecular mechanisms that are involved in self-incompatibilitySome plantsReject pollen that has an S-gene matching an allele in the stigma cellsRecognition of self pollen (自家花粉)Triggers a signal transduction pathway leading to a block (阻礙) in growth of a pollen tubeCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 38.2: After fertilization, ovules develop into seeds and ovaries into fruitsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsDouble Fertilization (雙重受精)After landing on a receptive stigma (花柱)A pollen grain (花粉粒) germinates and produces a pollen tube (花粉管) that extends down between the cells of the style () toward the ovary ()The pollen tube (花粉管)Then discharges two sperm into the embryo sacIn double fertilization (雙重受精)One sperm fertilizes the eggThe other sperm combines with the polar nuclei (極核), giving rise to the food-storing endosperm (胚乳)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsStigma (柱頭)(極核)Polar nucleiEgg(花粉粒)Pollen grainPollen tube (花粉管)2 spermStyleOvaryOvule (containing female gametophyte, or embryo sac)MicropyleOvulePolar nucleiEggTwo sperm about to be dischargedEndosperm nucleus (3n) (2 polar nuclei plus sperm)Zygote (2n) (egg plus sperm)Figure 38.6Growth of the pollen tube and double fertilization(1) If a pollen graingerminates, a pollen tubegrows down the styletoward the ovary.(2) The pollen tubedischarges two sperm intothe female gametophyte(embryo sac) within an ovule.(3) One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei of the embryosacs large central cell, forminga triploid cell that develops intothe nutritive tissue calledendosperm.Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsDevelopment of Ovule and EndospermFrom Ovule to Seed, after double fertilizationEach ovule develops into a seedThe ovary develops into a fruit enclosing the seed(s)Endosperm Development, usually precedes embryo developmentIn most monocots and some eudicots, the endosperm stores nutrients that can be used by the seedling after germinationIn other eudicots, the food reserves of the endosperm are completely exported to the cotyledonsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsEmbryo DevelopmentThe first mitotic division of the zygote is transverseSplitting the fertilized egg into a basal cell and a terminal cellFigure 38.7OvuleTerminal cellEndosperm nucleusBasal cellZygoteIntegumentsZygoteProembryoCotyledonsShoot apexRoot apexSeed coatBasal cellSuspensorEndospermSuspensorCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsStructure of the Mature SeedThe embryo and its food supplyAre enclosed by a hard, protective seed coatIn a common garden bean, a eudicotThe embryo consists of the hypocotyl, radicle, and thick cotyledonsFigure 38.8a(a) Common garden bean, a eudicot with thick cotyledons. The fleshy cotyledons store food absorbed from the endosperm before the seed germinates.Seed coatRadicleEpicotylHypocotylCotyledons胚根種皮子葉上胚軸下胚軸Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe seeds of other eudicots, such as castor beansHave similar structures, but thin cotyledonsSeed coatEndospermCotyledonsEpicotylHypocotylRadicleFigure 38.8bSeed coatEndospermCotyledonsEpicotylHypocotylRadicle(b) Castor bean, a eudicot with thin cotyledons. The narrow, membranous cotyledons (shown in edge and flat views) absorb food from the endosperm when the seed germinates.種皮胚根下胚軸子葉上胚軸胚乳Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe embryo of a monocot (單子葉) has a single cotyledon, a coleoptile, and a coleorhizaFigure 38.8c(c) Maize, a monocot. Like all monocots, maize has only one cotyledon. Maize and other grasses have a large cotyledon called a scutellum. The rudimentary shoot is sheathed in a structure called the coleoptile, and the coleorhiza covers the young root.Scutellum(cotyledon)ColeoptileColeorhizaPericarp fusedwith seed coatEndospermEpicotylHypocotylRadicle(種皮)(胚根)(下胚軸)(上胚軸)(胚乳)(子葉)(芽鞘)(根鞘)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFrom Ovary to FruitA fruitDevelops from the ovaryProtects the enclosed seedsAids in the dispersal of seeds by wind or animalsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFruits are classified into several typesDepending on their developmental originFigure 38.9ac (a) Simple fruit. A simple fruit develops from a single carpel (or several fused carpels) of one flower (examples: pea, lemon, peanut). (b) Aggregate fruit. An aggregate fruit develops from many separate carpels of one flower (examples: raspberry, blackberry, strawberry).(c) Multiple fruit. A multiple fruit develops from many carpels of many flowers (examples: pineapple, fig).Pineapple fruitRaspberry fruitPea fruitStamenCarpel(fruitlet)StigmaOvaryRaspberry flowerEachsegmentdevelopsfrom thecarpel ofone flowerPineapple inflorescenceStamenCarpelsFlowerOvaryStigmaStamenOvulePea flowerSeedCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsSeed Germination (種子萌芽)As a seed maturesIt dehydrates (脫水) and enters a phase referred to as dormancy (休眠)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsSeed Dormancy: Adaptation for Tough TimesSeed dormancyIncreases the chances that germination will occur at a time and place most advantageous to the seedlingThe breaking of seed dormancy Often requires environmental cues, such as temperature or lighting cuesFrom Seed to Seedling (從種子到幼苗) Germination of seeds depends on the physical process called imbibition (浸潤)The uptake of water due to low water potential of the dry seedCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 38.10aCotyledonHypocotylRadicle(胚根)Epicotyl (上胚軸)Seed coat(種皮)CotyledonHypocotylCotyledon (子葉)Hypocotyl (上胚軸)(a)Common garden bean. In common garden beans, straightening of a hook in the hypocotyl pulls the cotyledons from the soil.The radicle (胚軸胚軸) is the first organ to emerge from the germinating seedIn many eudicots, a hook forms in the hypocotyl (下胚軸), and growth pushes the hook above groundFoliage leaves (初生葉)(上胚軸)(上胚軸)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFoliage leavesColeoptileColeoptileRadicle(b) Maize. In maize and other grasses, the shoot grows straight up through the tube of the coleoptile.Monocots (單子葉植物)Use a different method for breaking ground when they germinateThe coleoptile (芽鞘)Pushes upward through the soil and into the airFigure 38.10bCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 38.3: Many flowering plants clone (複製) themselves by asexual reproductionMany angiosperm species reproduce both asexually and sexually (無性及有性)Sexual reproductionGenerates the genetic variation that makes evolutionary adaptation possibleAsexual reproduction in plantsIs called vegetative reproduction (營養繁殖)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsMechanisms of Asexual Reproduction (無性生殖的機制)Fragmentation (裂片)Is the separation of a parent plant into parts that develop into whole plantsIs one of the most common modes of asexual reproduction In some species, the root system of a single parent gives rise to many adventitious shoots that become separate shoot systemsFigure 38.11Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsVegetative Propagation (營養繁殖) and AgricultureHumans have devised various methods for asexual propagation of angiospermsClones from cuttings (切枝、切條)Many kinds of plants are asexually reproduced from plant fragments called cuttingsGrafting (架接、接枝)In a modification of vegetative reproduction from cuttingsA twig or bud from one plant can be grafted onto a plant of a closely related species or a different variety of the same speciesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsTest-Tube Cloning (試管複製) and Related TechniquesPlant biologists have adopted in vitro methods to create and clone novel plant varieties.Figure 38.12a, b(a) Just a few parenchyma cells from a carrot gave rise to this callus, a mass of undifferentiated cells.(b) The callus differentiates into an entire plant, with leaves, stems, and roots.Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsIn a process called protoplast fusion (原生質體融合)Researchers fuse protoplasts, plant cells with their cell walls removed, to create hybrid plantsFigure 38.1350 mVacuoleChloroplastCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 38.4: Plant biotechnology is transforming agriculturePlant biotechnology has two meanings:It refers to innovations in the use of plants to make products of use to humansIt refers to the use of genetically modified organisms (GMO, 基因改造生物) in agriculture and industryCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsArtificial Selection (人工選擇; 人擇)Humans have intervenedIn the reproduction and genetic makeup of plants for thousands of yearsMaize (玉米) Is a product of artificial selection by humansIs a staple (xxxxx) in many developing countries, but is a poor source of proteinInterspecific hybridization of plants (植物的種間雜交)Is common in nature and has been used by breeders, ancient and modern, to introduce new genesFigure 38.14Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsReducing World Hunger and Malnutrition (營養不良)Genetically modified (GM) plantsHave the potential of increasing the quality and quantity of food worldwideFigure 38.15Ordinary riceGenetically modified riceFigure 38.16GM papayaCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Debate over Plant Biotechnology (植物生物技術的爭議)There are some biologists, particularly ecologistsWho are concerned about the unknown risks associated with the release of GM organisms (GMOs) into the environmentIssues of Human HealthOne concern is that genetic engineering may transfer allergens from a gene source to a plant used for foodPossible Effects on Nontarget OrganismsMany ecologists are concerned that the growing of GM crops might have unforeseen effects on nontarget organismsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsAddressing the Problem of Transgene Escape Perhaps the most serious concern that some scientists raise about GM crops is the possibility of the introduced genes escaping from a transgenic crop into related weeds through crop-to-weed hybridization (作物雜草雜交)Despite all the issues associated with GM cropsThe benefits should be consideredThe Debate over Plant Biotechnology (植物生物技術的爭議)Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings報告完畢敬請指教！？！？！？！？！？！？！？！？！？！？！？！？