Download Flowering Plants: Reproduction

Chapter 27: pp. 493 - 509
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10th Edition
Sylvia S. Mader
Flowering Plants:
Reproduction
BIOLOGY
© Royalty-Free/Corbis
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
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1
2
Reproductive Strategies
• All plants have a two-stage, alternating life cycle
(alternation of generations)
• Sporophyte produces haploid spores by meiosis
• Spores divide mitotically to become haploid gametophytes
• Gametophytes produce gametes
• Gametes fuse to produce zygote
• Zygote divides mitotically to become diploid sporophyte
3
Alternation of Generations
in Flowering Plants
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8
anther
1
7
sporophyte
seed
2
diploid (2n)
6
zygote
FERTILIZATION
ovule
ovary
MEIOSIS
haploid (n)
3
egg
sperm
5
Male gametophyte
(pollen grain)
Female gametophyte
(embryo sac)
microspore
megaspore
4
4
Reproductive Strategies
Flowers are the reproductive structure (aka genitalia) of
the plant and produces two types of spores
 Microspore - Male gametophyte
 Pollen
 Megaspore - Female gametophyte
 Embryo within the ovary
LE 38-2A
Anther
Stamen
Filament
Stigma
Carpel
Style
Ovary
Sepal
Petal
Key
Haploid (n)
Diploid (2n)
Receptacle
An idealized flower
LE 38-2B
Germinated pollen grain
(n) (male gametophyte)
Anther
Ovary
Ovule
Embryo sac (n) (female
gametophyte)
Pollen
tube
FERTILIZATION
Egg (n)
Mature
Sperm (n)
sporophyte
plant (2n)
Zygote
(2n)
Seed
Key
Seed
Haploid (n)
Diploid (2n)
Germinating
seed
Simplified angiosperm life cycle
Embryo (2n)
(sporophyte)
Simple fruit
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Flowers
• Sepal- green “petals” that protect bud
• Petal- colorful “leaves”
• Stamens- male part
• Anther - Saclike container
• Filament - Slender stalk
• Carpel- female part
• Stigma - Enlarged sticky knob
• Style - Slender stalk
• Ovary - Enlarged base enclosing ovules
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Pollination
• Pollination is 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
Some plants have
ways to prevent
self pollination.
9
Pollination
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a.
b.
118 mm
c.
8 mm
a: © George Bernard/Animals Animals/Earth Scenes; b: © Simko/Visuals Unlimited; c: © Dwight Kuhn
10
Pollinators
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
b.
Aa: © Steven P. Lynch; Ab: © Robert Maier/Animals/Animals/Earth Scenes
11
Pollinators
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a.
b.
Ba: © Anthony Mercieca/Photo Researchers, Inc.; Bb: © Merlin D. Tuttle/Bat Conservation International;
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Fertilization
• When pollen grain lands on stigma, it germinates forming
a 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
zygote
• Other sperm nucleus unites with the polar nuclei, food storage
endosperm
double fertilization animation
LE 38-6
Pollen
grain
Stigma
Pollen tube
If a pollen grain
germinates, a pollen tube
grows down the style
toward the ovary.
2 sperm
Style
Ovary
Polar
nuclei
Ovule (containing
female
gametophyte, or
embryo sac)
Egg
Micropyle
Ovule
Polar nuclei
The pollen tube
discharges two sperm into
the female gametophyte
(embryo sac) within an
ovule.
One sperm fertilizes
the egg, forming the
zygote. The other sperm
combines with the two
polar nuclei of the
embryo sac’s large
central cell, forming a
triploid cell that develops
into the nutritive tissue
called endosperm.
Egg
Two sperm
about to be
discharged
Endosperm
nucleus (3n)
(2 polar nuclei
plus sperm)
Zygote (2n)
(egg plus sperm)
From Ovule to Seed
•
After double fertilization, each ovule develops into a seed
• The ovary develops into a fruit enclosing the seed(s)
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Monocot vs. Eudicot
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seed coat
plumule
pericarp
hypocotyl
endosperm
coleoptile
radicle
cotyledon
embryo
plumule
cotyledon
radicle
coleorhiza
a.
b.
a: © Dwight Kuhn; b: Courtesy Ray F. Evert/University of Wisconsin Madison
embryo
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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.
Samara
Legume
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
Seed Germination
•
As a seed matures, it dehydrates and enters a phase
called dormancy
• Seed dormancy increases the chances that germination
will occur at a time and place most advantageous to the
seedling
• The breaking of seed dormancy often requires
environmental cues, such as temperature or lighting
changes
From Seed to Seedling
•
Germination depends on imbibition, the uptake of water
due to low water potential of the dry seed
• The radicle (embryonic root) emerges first
• Next, the shoot tip breaks through the soil surface
• In many eudicots, a hook forms in the hypocotyl, and
growth pushes the hook above ground
• Time lapse fast growing corn
LE 38-10A
Foliage leaves
Cotyledon
Epicotyl
Hypocotyl
Cotyledon
Cotyledon
Hypocotyl
Hypocotyl
Radicle
Seed coat
Common garden bean
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Simple Fruits
 Dispersal
 Many seeds are dispersed by wind
 Woolly hairs, plumes, wings
 Fleshy fruits - Attract animals and provide them with food
 Peaches, cherries, tomatoes
 Accessory fruit - Bulk of fruit is not from ovary, but from receptacle
 Apples
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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.