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Angiosperm Reproduction
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What you need to know: The process of double fertilization, a unique feature of angiosperms. The relationship between seed and fruit. The structure and function of all parts of the flower.
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Angiosperms have 3 unique eatures: Angiosperms have 3 unique Features: 1. F 1. Flowers 2. F 2. Fruits F 3. double Fertilization
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Alternation of Generations 1. Sporophyte (mature plant) produces spores 2. Spores develop into male ( ♂ ) gametophyte (pollen) and female ( ♀ ) gametophyte (embryo sac)
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Flower Structure Reproductive shoots of angiosperm sporophyte Flower organs: 1.Sepal – leaflike, protect flower bud 2.Petal – modified leaves, attract pollinators 3.Stamen – ♂ reproductive organ anther + filament 4.Carpel – ♀ reproductive organ stigma + style + ovary Flower attached to stem at receptacle Pollination by wind, insects, birds
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NameStructureFunction Sepals Little green leaflets attached to receptacle Protect the buds PetalsBrightly colored, 2 nd whorlAttract insects & other pollinators StamenAnther + filament ♂ Reproductive organ FilamentThin stalkSupport anther AntherTerminal end of filament Contains chambers to develop male gametophyte (pollen) CarpelStigma + style + ovary ♀ Reproductive organ StigmaSticky end of style“landing platform” for pollen Style Slender neck supporting stigma, leads to ovary Support stigma and pollen tubes OvariesSwollen lower portion of carpelDevelopment of ovules
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Floral Variations Complete: has petals, sepals, stamen, carpels Incomplete: lacks 1+ of the above Perfect: has both stamen + carpel Imperfect: has stamen or carpel, not both (grass - no petals) Monoecious: plant species w/ both staminate and carpellate flowers on the same individual (corn) Dioecious: plant species w/ staminate flowers and carpellate flowers on different individual plants (date palm, arrowhead)
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Male GametophyteFemale Gametophyte = Pollen Sac= Embryo Sac Produced in antherProduced in ovule (in ovary) Has 2 haploid nuclei: 1.Tube nucleus (forms pollen tube) 2.Generative nucleus (divides to form 2 sperm cells) Has 3 important haploid nuclei: 1.Egg (fuses with sperm) 2.2 polar nuclei (fuses with 2 nd sperm to make 3n endosperm)
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Pollination: transfer pollen from anther to stigma Pollen tube grows down into ovary
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Double Fertilization Union of 2 sperm cells with different cells of embryo sac 1. One sperm + egg zygote (2n) 2. One sperm + 2 polar bodies endosperm (triploid 3n) ◦ Endosperm = nutrition for embryo plant 3. Ovule develops into seed; ovary develops into fruit ◦ Seed = embryo + endosperm
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The development of a plant embryo
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Fruit Protects enclosed seed(s) Aids in dispersal by water, wind, or animals SimpleAggregateMultiple Single ovary of one flower Many ovaries of one flower Many ovaries of many flowers CherryRaspberryPineapple
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Developmental origins of fruit
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Seeds Adaptations: 1. Dormancy = “resting” Low metabolic rate, not growing or developing Increases chances of germination in most advantageous time & place 2. Dispersal: variety of methods 3. Protection: well protected by fruit
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Seed Structure
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Germination Imbibition: uptake of H 2 O ◦ Seed expands and seed coat ruptures ◦ Trigger metabolic changes to begin growth ◦ Enzymes digest storage materials of endosperm (cotyledons) ◦ Nutrients transferred to growth regions of embryo
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Germination 1. Radicle Root 2. Shoot tip emerges above ground Stimulated by light 3. Foliage leaves expand & turn green photosynthesis Very hazardous for plants due to vulnerability ◦ Predators, parasites, wind
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Dicot and Monocot Seed Germination
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SexualAsexual Both ways to reproduce Flower seeds Runners, bulb, root, graft, vegetative (grass), fragmentation Genetic diversityClone More complex & hazardous for plant Simpler & safer for plant Monoculture - cultivate w/ 1 plant Reduces competition Benefits farmers Plant Reproduction
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