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Chapter 38 - Chapter38 10:00:00 o 4kseedsinRafflesia...

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Chapter 38 13/02/2007 10:00:00 Angiosperm Reproduction and Biotechnology Sexual vs Asexual plant reproduction o 4k seeds in Rafflesia parasitic seeds Genetic manipulation of plants is the basis of agriculture o Few hundred o Speed Alternation of generations life cycle o Meiosis Haploid organism (gametophyte) Plant which will produce gamete o Mitosis Diploid organism (sporophyte) Dominant in angiosperms Parts of the flower o Receptacle o Sepals o Petals o Stamen Filament
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Anther o Carpel Ovary Style Stigma Pollination Fertilization o Zygote o Endosperm has polar nuclei Starts generating nutrients 3n Floral Variation o Complete and incomplete flowers No petals/sepals o Bisexual and unisexual flowers o Monoecious and dioecious plant species Reproductive cycle cont’d o Spores and gametes o Gametophyte Anther Microsporocyte > microspores
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o Pollination Pollen tube extends down style o Fertilization Pollen tube penetrates micropyle Sperm enters ovule Egg fertilized first Basal cell Keeps developing zygote in contact with suspensor After Ovary Becomes fruit Ovule Becomes seed Nutrients From endosperm o Double fertilization Fertilization of polar nuclei and egg by second sperm Zygote created first Advantage Food storage and provision through the endosperm (3n) Self-Pollination
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o Structural barriers o Selfing Plant reproduces with self In rhizotomous plant o Self incompatibility genes, S-genes Gametophytic self-incmpatibility: Style destroys tube with RNA  hydrolyzing enzymes Sporophytic self incompatibility: at stigma no cues are given to  pollen grain Seed structure o Monocot Radicle, seed coat, epicotyl, hypocotyl, cotyledon, endosperm o Dicot Scutellum (cotyledon), coleoptile, coleorhiza, pericarp fused with  seed coat, endosperm, epicotyl, hypocotyl, radicle Fruit Development Seed Germination o Seed dormancy advantage o Conditions for dormancy Asexual Reproduction o Natural mechanisms of vegetative reproduction o Fragmentation (creosote bushes): plant parts New plant from fragment o Apomixes (dandelions): clone seed
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No fertilization Advantages Assured reproduction in the absence of pollinators, such  as in extreme environments Maternal energy not wasted in unfit offspring (cost of  meiosis) Some apomictic plants (but not all) avoid the male energy  cost of producing pollen Disadvantages Can’t control accumulation of deleterious genetic  mutations Usually restricted to narrow ecological niches
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