被子植物生殖与生物技术.ppt

(5) Chapter 38,Angiosperm Reproduction and Biotechnology 被子植物生殖與生物技術,To Be or Not to Be (?),Overview: To Seed or Not to Seed The parasitic plant Rafflesia arnoldii Produces enormous flowers that can produce up to 4 million seeds,Figure 38.1,Key Concepts,Concept 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 fruits Concept 38.3: Many flowering plants clone (複製) themselves by asexual reproduction Concept 38.4: Plant biotechnology is transforming agriculture,Concept 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),Flower Structure,Flowers Are 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),Filament,Anther,雄蕊Stamen,花瓣Petal,Receptacle,Sepal萼片,Style 花柱,Ovary,Carpel雌蕊,Stigma,花藥,花絲,卵房,柱頭,花托,被子植物花的多樣性,Many variations in floral structure have evolved during the 140 million years of angiosperm history,Bilateral symmetry (orchid),Sepal,Radial symmetry (daffodil),Fused petals,Semi-inferior ovary,Inferior ovary,Superior ovary,Lupine inflorescence,Sunflower inflorescence,Maize, a monoecious species,Dioecious Sagittaria latifolia (common arrowhead),SYMMETRY OVARY LOCATION FLORAL DISTRIBUTION,REPRODUCTIVE VARIATIONS,Gametophyte Development and Pollination,In 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),An overview of angiosperm reproduction,Figure 38.2a, b,Anther at tip of stamen,Pollen tube,Germinated pollen grain (n) (male gametophyte) on stigma of carpel,Ovary (base of carpel),Ovule (卵胞),Embryo sac (n) (female gametophyte),FERTILIZATION,Egg (n),Sperm (n),Key,Haploid (n),Diploid (2n),(b) Simplified angiosperm life cycle. See Figure 30.10 for a more detailed version of the life cycle, including meiosis.,Mature sporophyte plant (2n) with flowers,Seed (develops from ovule),Zygote (2n),Embryo (2n) (sporophyte),Simple fruit (develops from ovary),Germinating seed,Seed,Filament,Anther,Stamen,Petal,Receptacle,Sepal,Style,Ovary,(a) An idealized flower.,Carpel,Stigma,(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.),(2) Each microsporocyte divides by meiosis to produce four haploid microspores (n), each of which develops into a pollen grain.,Pollen sac (microsporangium),Micro- Sporocyte,Micro- spores (4),Each of 4 microspores,Generative cell (will form 2 sperm),Nucleus of tube cell,(1) Each one of the microsporangia contains diploid microsporocytes (2n) (microspore mother cells).,75 m,20 m,Ragweed pollen grain,Figure 38.4a,MEIOSIS減數分裂,MITOSIS有絲分裂,KEY to labels,Haploid (2n),Diploid (2n),Pollen (花粉)-Develops from microspores (雄孢子) within the sporangia (孢子囊) of anthers,Male Gametophyte (pollen grain),Key to labels,有絲分裂MITOSIS,減數分裂MEIOSIS,Ovule,Ovule,Integuments,Embryo sac,Mega- sporangium,Mega- sporocyte,Integuments,Micropyle,Surviving megaspore,Antipodel Cells (3),Polar Nuclei (2),Egg (1),Synergids (2),(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 38.4b,100 m,(2) The megasporocyte divides by meiosis and gives rise to four haploid cells, but in most species only one of these survives as the megaspore.,Embryo sacs-Develop from megaspores within ovules,Mechanisms 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 38.5,Stigma 柱頭,Anther with Pollen 有花粉的花藥,Stigma 柱頭,Pin flower,Thrum flower,The most common anti-selfing mechanism in flowering plants Is known as self-incompatibility (自我排斥、自我不相容), the ability of a plant to reject its own pollen Researchers are unraveling the molecular mechanisms that are involved in self-incompatibility Some plants Reject pollen that has an S-gene matching an allele in the stigma cells Recognition of self pollen (自家花粉) Triggers a signal transduction pathway leading to a block (阻礙) in growth of a pollen tube,Concept 38.2: After fertilization, ovules develop into seeds and ovaries into fruits,Double 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 sac In double fertilization (雙重受精) One sperm fertilizes the egg The other sperm combines with the polar nuclei (極核), giving rise to the food-storing endosperm (胚乳),Stigma (柱頭),(極核)Polar nuclei,Egg,(花粉粒)Pollen grain,Pollen tube (花粉管),2 sperm,Style,Ovary,Ovule (containing female gametophyte, or embryo sac),Micropyle,Ovule,Polar nuclei,Egg,Two sperm about to be discharged,Endosperm nucleus (3n) (2 polar nuclei plus sperm),Zygote (2n) (egg plus sperm),Figure 38.6,Growth of the pollen tube and double fertilization,(1) If a pollen grain germinates, a pollen tube grows down the style toward the ovary.,(2) The pollen tube discharges two sperm into the 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 embryo sacs large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm.,Development of Ovule and Endosperm,From Ovule to Seed, after double fertilization Each ovule develops into a seed The ovary develops into a fruit enclosing the seed(s) Endosperm Development, usually precedes embryo development In most monocots and some eudicots, the endosperm stores nutrients that can be used by the seedling after germination In other eudicots, the food reserves of the endosperm are completely exported to the cotyledons,Embryo Development,The first mitotic division of the zygote is transverse Splitting the fertilized egg into a basal cell and a terminal cell,Figure 38.7,Ovule,Terminal cell,Endosperm nucleus,Basal cell,Zygote,Integuments,Zygote,Proembryo,Cotyledons,Shoot apex,Root apex,Seed coat,Basal cell,Suspensor,Endosperm,Suspensor,Structure of the Mature Seed,The embryo and its food supply Are enclosed by a hard, protective seed coat,In a common garden bean, a eudicot The embryo consists of the hypocotyl, radicle, and thick cotyledons,Figure 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 coat,Radicle,Epicotyl,Hypocotyl,Cotyledons,胚根,種皮,子葉,上胚軸,下胚軸,The seeds of other eudicots, such as castor beans Have similar structures, but thin cotyledons,Figure 38.8b,Seed coat,Endosperm,Cotyledons,Epicotyl,Hypocotyl,Radicle,(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,The embryo of a monocot (單子葉) has a single cotyledon, a coleoptile, and a coleorhiza,Figure 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),Coleoptile,Coleorhiza,Pericarp fused with seed coat,Endosperm,Epicotyl,Hypocotyl,Radicle,(種皮),(胚根),(下胚軸),(上胚軸),(胚乳),(子葉),(芽鞘),(根鞘),From Ovary to Fruit,A fruit Develops from the ovary Protects the enclosed seeds Aids in the dispersal of seeds by wind or animals,Fruits are classified into several types Depending on their developmental origin,Seed Germination (種子萌芽),As a seed matures It dehydrates (脫水) and enters a phase referred to as dormancy (休眠),Seed Dormancy: Adaptation for Tough Times,Seed dormancy Increases the chances that germination will occur at a time and place most advantageous to the seedling The breaking of seed dormancy Often requires environmental cues, such as temperature or lighting cues From 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 seed,Figure 38.10a,Cotyledon,Hypocotyl,Radicle (胚根),Epicotyl (上胚軸),Seed coat (種皮),Cotyledon,Hypocotyl,Cotyledon (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) is the first organ to emerge from the germinating seed In many eudicots, a hook forms in the hypocotyl (下胚軸), and growth pushes the hook above ground,Foliage leaves (初生葉),(上胚軸),(上胚軸),(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 germinate The coleoptile (芽鞘) Pushes upward through the soil and into the air,Figure 38.10b,Concept 38.3: Many flowering plants clone (複製) themselves by asexual reproduction Many angiosperm species reproduce both asexually and sexually (無性及有性) Sexual reproduction Generates the genetic variation that makes evolutionary adaptation possible Asexual reproduction in plants Is called vegetative reproduction (營養繁殖),Mechanisms 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 plants Is 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 systems,Figure 38.11,Vegetative Propagation (營養繁殖) and Agriculture,Humans have devised various methods for asexual propagation of angiosperms Clones from cuttings (切枝、切條) Many kinds of plants are asexually reproduced from plant fragments called cuttings Grafting (架接、接枝) In a modification of vegetative reproduction from cuttings A twig or bud from one plant can be grafted onto a plant of a closely related species or a different variety of the same species,Test-Tube Cloning (試管複製) and Related Techniques,Plant 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.,In a process called protoplast fusion (原生質體融合) Researchers fuse protoplasts, plant cells with their cell walls removed, to create hybrid plants,Vacuole,Chloroplast,Concept 38.4: Plant biotechnology is transforming agriculture Plant biotechnology has two meanings: It refers to innovations in the use of plants to make products of use to humans It refers to the use of genetically modified organisms (GMO, 基因改造生物) in agriculture and industry,Artificial Selection (人工選擇; 人擇),Humans have intervened In the reproduction and genetic makeup of plants for thousands of years Maize (玉米) Is a product of artificial selection by hu