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1、(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 c
2、ome 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: Pollinatio
3、n 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 repro
4、ductive 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 dur
5、ing 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),SYMME
6、TRY OVARY LOCATION FLORAL DISTRIBUTION,Figure 38.3,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
7、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
8、 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
9、(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 occur
10、s 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 (
11、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
12、)-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),Syn
13、ergids (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 integume
14、nts (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,Mech
15、anisms 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 pla
16、nts 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 3
