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Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 27
Flowering Plants:
Reproduction
Lecture Outline
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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
– Microspore - Male gametophyte
• Becomes pollen grain
– Megaspore - Female gametophyte
• 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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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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Sexual Reproductive Strategies
– Sepals protect the bud
– Petals attract pollinators
– Stamens: male
• Anther - Saclike container
• Filament - Slender stalk
– Carpel: female
• Stigma - Enlarged sticky knob
• Style - Slender stalk
• Ovary - Enlarged base enclosing ovules
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Sexual Reproductive Strategies
• Complete vs. incomplete flowers:
– Complete flowers have sepals, petals, stamens, and a
carpel
– Incomplete flowers are missing one or more of above
• Perfect vs. imperfect flowers:
– Perfect (bisexual)
– Imperfect (unisexual)
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Life Cycle of Flowering Plants
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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
• Pollination
• Transfer of pollen
• Self-pollination vs. Cross-pollination
• Fertilization
• Pollen lands on stigma, germinates, forming a pollen
tube
• Mature seed contains the embryo, stored food, &
seed coat
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Development of an Eudicot
Embryo
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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)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
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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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Fruits
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Drupe
True Berry
exocarp
chamber of
ovary has
many seeds
pericarp
exocarp (skin)
mesocarp (flesh)
endocarp (pit
contains seed)
a. A drupe is a fleshy fruit with a pit containing a single seed
produced from a simple ovary.
b. A berry is a fleshy fruit having seeds and pulp produced
from a compound ovary.
Legume
Samara
seed covered
by pericarp
wing
pericarp
seed
c. A legume is a dry dehiscent fruit produced from a simple ovary.
d. A samara is a dry indehiscent fruit produced from a simple ovary .
Aggregate Fruit
Multiple Fruit
fruit from many
ovaries of a
single flower
e. An aggregate fruit contains many fleshy fruits produced from
simple ovaries of the same flower.
one fruit
fruits from ovaries
of many flowers
f. A multiple fruit contains many fused fruits produced from simple
ovaries of individual flowers.
a, b: © Kingsley Stern; c: © Dr. James Richardson/Visuals Unlimited; d: © James Mauseth; e: Courtesy Robert A. Schlising; f: © Ingram Publishing/Alamy
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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
– Embryo resumes growth & metabolic activity
– Length of viability is 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
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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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Asexual Reproduction in Plants
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Parent plant
stolon
Asexually produced offspring
© G.I. Bernard/Animals Animals/Earth Scenes
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