Bio 100 Chapter 24
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Transcript of Bio 100 Chapter 24
Chapter 24Reproduction
in PlantsLecture Outline
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Alternation of generations Sporophyte
Dominant in flowering plants Bears flowers – reproductive structure Diploid or 2n Produces haploid microspores and megaspores by meiosis
Gametophyte Haploid or 1n Produces gametes Microspore undergoes mitosis and become a pollen grain, a male
gametophyte Megaspore undergoes mitosis to become embryo sac, a female
gametophyte
Upon fertilization, the cycle returns to the 2n sporophyte
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Plant Reproduction, cont.
Once a sperm fertilizes an egg, the zygote becomes an embryo, still within an ovule
Ovule develops into a seed, which contains the embryo and stored food surrounded by a seed coat
Ovary becomes a fruit, which aids in dispersing the seeds
When a seed germinates, a new sporophyte emerges and, through mitosis and growth, becomes a mature organism
Sexual life cycle of flowering plants is adapted to land
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Figure 24.1A Alternation of generations in flowering plants
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mitosis
mitosis
diploid (2n)
haploid (n)
1
2
5
6
7
8
seed
zygote
sporophyte
ovaryovule
FERTILIZATION
egg
Female gametophyte(embryo sac)
Male gametophyte(pollen grain)
anther
3
4
microspore
MEIOSIS
megaspore
sperm
Flowers are unique to angiosperms Produce spores, protect gametophyte, attract
pollinator, produce fruits
Exs. of pollinators: birds, beetles, flies, butterflies, bats
Typical flower 4 whorls of modified leaves attached to a receptacle
1. Sepals – protect bud
2. Petals – attract pollinators
3. Stamens – Male Portion (anther & filament)
4. Carpel – Female Portion (stigma, style & ovary)
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Figure 24.1B Anatomy of a flower
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carpelstamen
antherfilament
petal
sepal receptacle
stigmastyleovaryovule
Figure 24.1C b. Azaleas are eudicots Eudicots have flower parts in fours or fives (p = petal; s = sepal)
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a: © Farley Bridges; b: © Pat Pendarvis
b.
carpelstamen
petal
p3
p4
p5
p1
p2
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Figure 24.1D A corn plant is monoecious (flowers that are only male or only femalea. The staminate flowers produce pollen that is carried by wind to b. the carpellate flowers, where ears of corn develop.
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Figure 24B Butterflies, birds, and bats are adapted for acquiring nectar from certain flowers. Flowers that attract beetles produce much pollen and those that attract flies have the smell of rotting flesh
Sexual reproduction involves1. Production of pollen grains (male gametophytes) in
the anthers of stamens
2. Production of an embryo sac (female gametophyte) in an ovule located within the ovary of a carpel
Pollination Pollen transferred from anther to stigma so an egg
within female gametophyte is fertilized
Most angiosperms use animals to carry out pollination
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Figure 24.2A Life cycle of flowering plants
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Stamenanther
filament
Carpelstigmastyle
ovary
ovule
SporophyteMitosis
fruit(mature ovary)seed(mature ovule)
seedcoat
embryo
endosperm (3n)
Seed
diploid (2n)MEIOSIS MEIOSIS
microsporemother cell
Ovulepollen sac
Anther
Carpel
stigma
style
ovary
megasporemothe rcell
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Figure 24.2A Life cycle of flowering plants (cont.)
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haploid (n)Pollen grain Microspores
(all survive)
Mitosis
MEIOSIS
Megaspores(one survives)
degeneratingmegaspores
Ovule
Mitosis
Embryosac(mature female gametophyte)
eggDOUBLE FERTILIZATION
(mature malegametophyte)
sperm
pollentube
sperm andpolar nucleifuse
sperm andegg fuse
generative cell
POLLINATION
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Figure 24.2B Wind pollination of a grass, with SEM of pollen grains
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Coevolution As one species changes, the other changes too, so that
in the end, the two species are suited to one another
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nectar guides
As a bee sees itAs we see it(both): © Heather Angel/Natural Visions
Double fertilization is unique in angiosperms Results in not only a zygote but also a food source for
the developing zygote Endosperm – nutritive tissue developing embryonic
sporophyte uses as energy source
Mature seed contains Embryo – will develop into the plant Stored food – endosperm Seed coat – develops from ovule wall for protection
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Figure 24.2D The parts of a bean seed, a eudicot
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Embryo
Seed coat
immatureleaves
hypocotyl
Cotyledon(stored food)
radicle
(right): © Dwight Kuhn
24.4 The ovary becomes a fruit, which assists in sporophyte dispersal
Fruit = a ripened ovary
Protects and helps disperse the plant (“marketing for the seeds”)
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24.4 The ovary becomes a fruit, which assists in sporophyte dispersal
Fleshy Versus Dry Fruits
Dry fruits Exs: peas, maples
Fleshy fruits Exs: apples, strawberries, tomatoes, corn
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Figure 24.4 Fruit diversity
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1
pea flower pea pod
stigma
ovary wall
ovule
pericarp(fruit wall)
Pea pods are a dry, dehiscent (can open to reveal seeds) fruit.
seed
Figure 24.4 Fruit diversity (Cont.)
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2 Maple tree fruits are dry, in dehiscent.
wing
seed covered by pericarp
© James Mauseth
Simple Versus Aggregate & Multiple Fruits Simple fruits are derived from the simple ovary of a
single carpel Exs: grapes, tomatoes Accessory fruits form from other flower parts in
addition to ovary Exs: strawberry, apple Aggregate and multiple fruits are examples of
compound fruits derived from several individual ovaries Strawberry – aggregate fruit, each ovary becomes a one-
seeded fruit called an achene Pineapple – a multiple fruit derived from many individual
flowers, each with its own carpel
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Figure 24.4 Fruit diversity (Cont.)
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3
one fruit
flesh is fromreceptacle
Strawberries are a fleshy aggregate fruit.© Corbis RF
Figure 24.4 Fruit diversity (Cont.)
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4 Raspberries are an aggregate fruit.
fruits fromovaries ofone flower
one fruit
© C Squared Studios/Getty RF
Figure 24.4 Fruit diversity (Cont.)
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5
one fruit
Pineapple is a multiple fruit.
fruits fromovaries ofmany flowers
© BJ Miller/Biological Photo Service
Germination – seeds form into a seedling
Doesn’t usually take place until there is sufficient water, warmth, and oxygen to sustain growth
For seeds, dormancy is the time during which no growth occurs, even though conditions may be favorable for growth
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Figure 24.5A Structure and germination of a common bean seed
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Embryo:epicotyl-plumule
hypocotyl
radicle
Seed coat
Cotyledon(stored food)
Cotyledon(two)
Bean seed(right): © Ed Reschke
Figure 24.5A Structure and germination of a common bean seed (Cont.)
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seedcoat
first true leaves(primary leaves) epicotyl
with red cotyledons
hypocotylcotyledons
(two)
hypocotylsecondary
root
primaryroot
primary root
Figure 24.5B Structure and
germination of a corn kernel
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Seed coat
endosperm
cotyledon(one)coleoptile
Embryo:
radicle
coleorhiza
coleoptile
true leaf
prop root
pericarp
plumule
Corn kernel
first leaf
coleoptile
primary root
adventitiousroot
coleorhiza
radicle
(Top right): © James Mauseth
24.6 Plants have various ways of reproducing asexually
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Also called vegetative reproduction Type of cloning – offspring exactly like parent Plants can grow from axillary buds of above or
below ground stems Rhizome – underground horizontal stem (iris, many
grasses) Tuber – enlarged portion of rhizome (potato) Corm – bulbous underground stems (onion)
Figure 24.6 Asexual reproduction in plants 24-30
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Asexually produced offspring
stolon
© G.I. Bernard/Animals Animals
Figure 24.6 Asexual reproduction in plants (cont.) 24-31
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Rhizome
rhizome
adventitious roots
tuber
axillarybud
Tuber Corm
paperyleaves
rhizome
branch
adventitious roots
corm
axillarybud
24.7 Cloning of plants in tissue culture assists agriculture
Tissue culture Growth of a tissue in an artificial liquid or on agar
3 methods Somatic embryogenesis – technique that uses hormones to
cause plant tissues to generate small masses of cells Meristem tissue culture – many new shoot tips from a single
shoot tip Anther tissue culture – produces haploid plantlets or
chromosomal doubling chemically induced
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Figure 24.7A Somatic embryogenesis
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(both): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17:601-604
b. Cell wall regenerationa. Protoplasts, naked cells
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Figure 24.7A Somatic embryogenesis (Cont.)
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c. Aggregates of cells d. Callus, undifferentiated mass
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(both): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17:601-604
Figure 24.7A Somatic embryogenesis (Cont.)
24-35(both): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17:601-604
e. Somatic embryo f. Plantlet
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Figure 24.7B Producing whole plants from meristem tissue
Connecting the Concepts:Chapter 24
Life, as we know it, would not be possible without vascular plants
Although we now live in an industrialized society, we are still dependent on plants and have put them to many more uses We grow plants for food, shelter, beauty and substances for
industry Half of all pharmaceutical drugs have their origin in plants
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