Transcript Ch. 27 - Flowering Plants: Reproduction

Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 27
Flowering Plants:
Reproduction
Lecture Outline
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Outline
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27.1 Sexual Reproductive Strategies
27.2 Seed Development
27.3 Fruit Types and Dispersal
27.4 Asexual Reproductive Strategies
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27.1 Sexual Reproductive
Strategies
• Plants have a two-stage, alternating life
cycle
– Sporophyte produces haploid spores by
meiosis
– Spores divide mitotically to become haploid
gametophytes
– Gametophytes produce gametes
– Gametes fuse to produce a diploid zygote
– Zygote divides mitotically to become the
diploid sporophyte
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Sexual Reproduction
in Flowering Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
anther
2
ovule
ovary
microspore
megaspore
4
Sexual Reproduction
in Flowering Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
anther
7
seed
2
zygote
ovule
ovary
6
MEIOSIS
FERTILIZATION
3
egg
sperm
5
microspore
megaspore
4
Male gametophyte
(pollen graIn)
Female gametophyte
(embryo sac)
5
Sexual Reproduction
in Flowering Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
8
anther
1
7
sporophyte
seed
2
zygote
diploid(2n)
6
ovule
ovary
MEIOSIS
FERTILIZATION
haploid(n)
3
egg
sperm
5
microspore
megaspore
4
Male gametophyte
(pollen graIn)
Female gametophyte
(embryo sac)
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Sexual Reproductive Strategies
• A flower produces two types of spores
– Microspore - Male gametophyte
• Undergoes mitosis
• Becomes pollen grain
– Megaspore - Female gametophyte
• Undergoes mitosis
• Becomes the female gametophyte, an embryo
sac within an ovule within an ovary
• Ovule becomes a seed
• Ovary becomes a fruit
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Sexual Reproductive Strategies
• Flowers
– Flowering occurs in response to
environmental signals such as day length
• In monocots, flower parts occur in threes and
multiples of three
• In eudicots, flower parts occur in fours or fives and
multiples of four or five
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Sexual Reproductive Strategies
• A typical flower has four whorls of modified leaves
attached to a receptacle at the end of a flower stalk
called a peduncle
– Sepals protect the bud
– Petals attract pollinators
– Stamens are male portion of flower
• Anther - Saclike container
• Filament - Slender stalk
– Carpel is the female portion of flower
• Stigma - Enlarged sticky knob
• Style - Slender stalk
• Ovary - Enlarged base enclosing ovules
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Anatomy of a Flower
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
stamen
anther
filament
petal
sepal
carpel
stigma
style
ovary
ovule
receptacle
peduncle
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Monocot vs. Eudicot Flowers
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
p3
p2
carpel
stamen
p4
petal
p1
p5
b. Festive azalea, Rhododendron sp.
b: © Pat Pendarvis
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Life Cycle of Flowering Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
anther
ovule
ovary
Sporophyte
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Life Cycle of Flowering Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
anther
Development of the male
gametophyte:
Development of the female
gametophyte:
In pollen sacs of the anther, a
microspore mother cell undergoes
meiosis to produce 4 microspores
each.
In an ovule within an ovary, a
megaspore mother cell
undergoes meiosis to
produce 4 megaspores.
anther
ovule
ovary
Sporophyte
Pollen sac
ovary
microspore
mother cell
Ovule
megaspore
mother cell
MEIOSIS
MEIOSIS
ovule
wall
Microspores
Megaspores
megaspore
3 megaspores
disintegrate
integument
micropyle
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Life Cycle of Flowering Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
anther
Development of the male
gametophyte:
Development of the female
gametophyte:
In pollen sacs of the anther, a
microspore mother cell undergoes
meiosis to produce 4 microspores
each
In an ovule within an ovary, a
megaspore mother cell
undergoes meiosis to
produce 4 megaspores
anther
ovule
ovary
Pollen sac
ovary
microspore
mother cell
Sporophyte
Ovule
megaspore
mother cell
MEIOSIS
MEIOSIS
ovule
wall
tube cell
Microspores
Megaspores
generative cell
ovule
wall
Pollen grain
(male gametophyte)
antipodals
polar nuclei
egg cell
synergids
Microspores
develop into male
gametophytes
(pollen grains).
One megaspore
becomes the
embryo sac
(female
gametophyte).
Embryo sac
(mature female gametophyte)
(Top): Courtesy Graham Kent; (Bottom): © Ed Reschke
megaspore
3 megaspores
disintegrate
integument
micropyle
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Life Cycle of Flowering Plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
anther
Mature Seed
Development of the male
gametophyte:
In pollen sacs of the anther , a
microspore mother cell undergoes
meiosis to produce 4 microspores
each
seed coat
The ovule
develops into a
seed containing
the embryonic
sporophyte and
endosperm.
Development of the female
gametophyte:
In an ovule within an ovary, a
megaspore mother cell
undergoes meiosis to
Produce 4 megaspores.
anther
mitosis
ovule
ovary
Pollen sac
ovary
Ovule
embryo
microspore
mother cell
endosperm (3n)
Sporophyte
Seed
megaspore
mother cell
diploid (2n)
MEIOSIS
DOUBLE FERTILIZATION
MEIOSIS
haploid (n)
ovule
wall
tube cell
Pollination
Microspores
During double
fertilization, one
sperm from the
Male gametophyte
Will fertilize the
egg; another
Sperm will join with
polar nuclei to
produce the 3n
endosperm.
Development of
the sporophyte:
pollen
tube
Pollination
occurs;
a pollen grain
germinates and
produces a pollen
sperm
Mature male
gametophyte
polar nuclei
egg
sperm
tube
cell
nucleus
generative cell
Megaspores
ovule
wall
Pollen grain
(male gametophyte)
antipodals
polar nuclei
egg cell
Microspores
develop into male
gametophytes
(pollen grains).
One megaspore
becomes the
embryo sac
(female
gametophyte).
megaspore
3 megaspores
disintegrate
integument
micropyle
synergids
Embryo sac
(mature female gametophyte)
(Top): Courtesy Graham Kent; (Bottom): © Ed Reschke
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Sexual Reproductive Strategies
• Male Gametophytes
– Microspores are produced in anthers
– Each anther has four pollen sacs, each with
many microspore mother cells
• Microspore mother cells undergo meiosis to
produce microspores
• Microspores undergo mitosis to produce pollen
grains
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Sexual Reproductive Strategies
• The ovary contains one or more ovules
– An ovule has a central mass of parenchyma cells
covered by integuments
– One parenchyma cell enlarges to become a
megaspore mother cell
• The megaspore mother cell undergoes meiosis to produce
four haploid megaspores, three of which are nonfunctional
• The functional megaspore divides mitotically until there are
eight nuclei in the female gametophyte
– The female gametophyte (embryo sac) contains
• One egg cell associated with two synergid cells
• One central cell with two polar nuclei
• Three antipodal cells
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Sexual Reproductive Strategies
• Pollination
– The transfer of pollen from an anther to the
stigma of a carpel
• Self-pollination occurs if the pollen is from
the same plant
• Cross-pollination occurs if the pollen is from
a different plant
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Sexual Reproductive Strategies
• Fertilization
• When a pollen grain lands on the stigma, it
germinates, forming a pollen tube
• The pollen tube passes between the stigma and style
to reach the micropyle of the ovule
• Double fertilization occurs
– One sperm nucleus unites with the egg nucleus, producing a
2n zygote
– The other sperm nucleus unites with the polar nuclei, forming
a 3n endosperm nucleus, which develops into the
endosperm
• A mature seed contains the embryo, stored food, and
the seed coat
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Plants and Their Pollinators
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
b.
Ba: © Anthony Mercieca/Photo Researchers, Inc.; Bb: © Merlin D. Tuttle/Bat Conservation International;
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27.2 Seed Development
• Development:
– Programmed series of stages from a simple to
a more complex form
– Development of a eudicot embryo
• After double fertilization, the zygote divides
repeatedly to form a proembryo and a suspensor
– During the globular stage, the proembryo is a
ball of cells
• The outermost cells will become dermal tissue
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Seed Development
• Heart and Torpedo Stages
• The embryo is heart shaped when
cotyledons appear
• The embryo enlarges, elongates, and takes
on a torpedo shape
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Seed Development
• Mature Embryo
– The epicotyl is the portion between cotyledons
contributing to shoot development
– The hypocotyl is the portion below that contributes
to stem development
– The radicle is the embryonic root
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Development of an Eudicot
Embryo
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Arabidopsis thaliana
endosperm
endosperm nucleus
embryo
suspensor
zygote
1
zygote
Zygote stage: Double
fertilization results in zygote
(true green) and endosperm.
basal cell
2
Proembryo stage: Embryo
(green) is multicellular and
the suspensor (purple) is
functional.
(Proembryo): Courtesy Dr. Chun-Ming Liu; (Torpedo): © Biology Media/Photo Researchers, Inc.; (Mature embryo): © Jack Bostrack/Visuals Unlimited
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Development of an Eudicot
Embryo (continued)
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A. thaliana
A. thaliana
endosperm
cotyledons appearing
Capsella
shoot apical
meristem
Capsella
bending
cotyledons
hypocotyl
(root axis)
epicotyl (shoot
apical meristem)
seed
coat
endosperm
root
apical
meristem
3 Globular stage:
Embryo is globe
shaped.
4
Heart stage: Embryo is
heart shaped.
5
Torpedo stage: Embryo is
torpedo shaped; the
cotyledons are obvious.
radicle
(root apical
meristem)
cotyledons
6 Mature embryo stage: The
epicotyl will be the shoot
system; the hypocotyl will
be the root system.
(Proembryo): Courtesy Dr. Chun-Ming Liu; (Torpedo): © Biology Media/Photo Researchers, Inc.; (Mature embryo): © Jack Bostrack/Visuals Unlimited
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Monocot vs. Eudicot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
seed coat
plumule
pericarp
hypocotyl
endosperm
coleoptile
radicle
cotyledon
embryo
embryo
plumule
cotyledon
radicle
coleorhiza
a.
b.
a: © Dwight Kuhn; b: Courtesy Ray F. Evert/University of Wisconsin Madison
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27.3 Fruit Types and Seed
Dispersal
• A fruit is a mature ovary
• Simple Fruits
– Simple fruits are derived from single ovary with one or
several chambers
• Compound fruits develop from several groups of
ovaries
– Aggregate Fruits
• Ovaries are from a single flower one receptacle
• Blackberry
– Multiple Fruits
• Ovaries are from separate flowers clustered together
• Pineapple
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Fruit Types and Seed Dispersal
• Fruit Development
– The ovary wall thickens to become the
pericarp, which can have three layers
• The exocarp forms the outermost skin
• The mesocarp is the fleshy tissue between the
exocarp and the endocarp
• The endocarp is the boundary around the seeds
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Fruit Types and Seed Dispersal
• Fruit Types
– In dry fruits, the pericarp is paper, leathery, or
woody when the fruit is mature
• Dehiscent - the fruit splits open when ripe
– Legumes
• Indehiscent - the fruit does not split open when ripe
– Grains
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Fruit Types and Seed Dispersal
• Dispersal of Fruits
– Many dry fruits are dispersed by wind
• Woolly hairs, plumes, wings
– Many fruits attract animals and provide them
with food
• Peaches, cherries, tomatoes
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Fruit Dispersal by Animals
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a.
b.
a: © Marie Read/Animals Animals/Earth Scenes; b: © Scott Camazine/Photo Researchers, Inc.
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Fruit Types and Seed Dispersal
• Seed Germination
– When seed germination occurs, the embryo
resumes growth and metabolic activity
– Length of time seeds retain their viability is
quite variable
– Some seeds do not germinate until they have
been through a dormant period
• Temperate zones - Cold Weather
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Fruit Types and Seed Dispersal
• Environmental requirements for seed
germination
– Availability of oxygen for metabolic needs
– Adequate temperature for enzyme activity
– Adequate moisture for hydration of cells
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Eudicot and Monocot Seed
Structure and Germination
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
pericarp
cotyledons
plumule (two)
endosperm
cotyledon
(one)
coleoptile
hypocotyl
radicle
plumule
seed coat
radicle
cotyledon
coleorhiza
Corn kernel
Seed structure
true leaf
first true leaves
(primary leaves)
seed
coat
epicotyl
withered
cotyledons
cotyledons
(two)
first leaf
hypocotyl
coleoptile
coleoptile
prop root
radicle
hypocotyl
primary
root
Bean germination and growth
a.
secondary
root
primary
root
adventitious
root
primary root
coleorhiza
Corn germination and growth
b.
a: © Ed Reschke; b: © James Mauseth
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