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Chapter 10 Plant Reproduction
Honors Biology Chapter 10 Plant Reproduction John Regan Wendy Vermillion Insert Ch opening photo Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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10.1 Sexual reproduction in flowering plants
Alternation of generations Flowering plants have 2 multicellular stages in their life cycle Diploid sporophyte stage alternates with the haploid gametophyte stage The sporophyte produces haploid spores by meiosis spores develop into gameotphytes The gametophyte produces gametes by mitosis after fertilization the cycle returns to the sporophyte stage
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Alternation of generations in flowering plants
Fig 10.1
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Sexual reproduction in flowering plants cont’d.
Overview of plant life cycle Flower- reproductive structure of angiosperms The diploid sporophyte is the predominant stage The sporophyte bears flowers; flowers produce 2 spore types Megaspore-develops into female gametophyte-embryo sac Microspore-develops into the male gametophyte-pollen grain Pollination-deposition of pollen onto female flower parts Pollen grain contains 2 sperm cells; pollen grain digests a tube that the sperm swim through to reach the embryo sac Embryo sac contains an ovum; fertilization occurs and an embryo develops Embryo sac develops into a seed which can be enclosed in a fruit- aids dispersal When seed germinates a new sporophyte develops
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Sexual reproduction in flowering plants cont’d.
Flowers Typical flower has 4 whorls of modified leaves attached to a receptacle Sepals-green leaflike structures that protect bud Petals-attract pollinators Stamens-male structures consist of anthers and filaments Carpel-female structure consists of a stigma, style, and an ovary
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Anatomy of a flower Fig 10.2
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Sexual reproduction in flowering plants cont’d.
Flowers, cont’d. A complete flower has all parts-petals, sepals, stamens, and carpels flower can have a single carpel or multiple Each carpel contains the ovules Bisexual (perfect) flowers- have both stamens and carpels Unisexual (imperfect) flowers-have either stamens or carpels Dioecious plants- have either staminate or carpellate flowers on one plant Monoecious plants- have both staminate and carpellate flowers on the same plant
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Sexual reproduction in flowering plants cont’d.
Production of the male gametophyte Microspores produced in anthers Microspore mother cell divides by meiosis to produce 4 haploid microspores In each, the haploid nucleus divides mitotically and then an unequal cytokinesis occurs the 2 cells are enclosed in a pollen grain; the larger is the tube cell, the smaller is a sperm cell The sperm cell divides again to form 2 sperm
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Life cycle of a flowering plant
Fig 10.5
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Sexual reproduction in flowering plants cont’d.
Pollination Transfer of pollen from an anther to a receptive stigma of a carpel Pollen grain contains 2 cells- generative cell, tube cell Tube cell grows into pollen tube Generative cell ÷ into 2 sperm cells
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Sexual reproduction in flowering plants cont’d.
Production of the female gametophyte Embryo sac ÷3x into 8 nuclei as the functional nucleus divides 4 times by mitosis One small cell becomes the egg Double fertilization- one sperm fertilizes the egg and it becomes the embryo(2n); the other fertilizes the central cell to form the triploid (3n) endoderm Endosperm becomes the food source for the embryo inside the seed
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Pollination Fig 10.6
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Development of a eudicot embryo
Fig 10.7
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Growth and development cont’d.
Development of the eudicot embryo, cont’d. Embryo changes from a ball of cells to a heart-shape Cotyledons-embryonic leaves appear Embryo next becomes torpedo-shaped, and the root tip and shoot tip become visible Epicotyl-portion of embryo between the cotyledons that contributes to shoot development Hypocotyl-portion below the cotyledons that contributes to stem development Radicle-contributes to root development
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Growth and development cont’d.
Monocots versus eudicots Eudicots have 2 cotyledons, monocots have one In monocots, the cotyledons do not store food cotyledon absorbs food from endosperm and passes it to the embryo In eudicots the cotyledons store the nutrients the embryo uses Endosperm disappears as the cotyledons take up the nutrients
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Growth and development cont’d.
seed dispersal- the function of fruits is to disperse seeds seed dispersal Attach to fur of animals or clothing Ex: burrs Passed in feces of bird or mammals Ex: berries Dispersed when buried or stored by animals Ex: acorns Wind-winged or plumed seeds Ex: maple seeds Float-coconut
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Growth and development cont’d.
Germination of seeds Germinate in response to specific environmental conditions Requires both inhibitor and stimulator substances Mechanical stimuli also may be required in some Uptake of water causes seed coat to burst
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Common garden bean seed structure and germination
Fig 10.9
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Growth and development cont’d.
Eudicot versus monocot germination Eudicots Cotyledons shrivel and degrade Epicotyl produces immature leaves- plumule young shoot is hook-shaped as it emerges through the soil Monocots Cotyledon does not have a storage function Plumule and radicle are protected by sheaths called the coleoptile and the coleorhiza respectively Plumule and radicle burst through the sheaths when germination occurs Young shoot is straight, not hooked
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Corn kernal structure and germination
Fig 10.10
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