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(5) Chapter 38
Angiosperm Reproduction
and Biotechnology
被子植物生殖與生物技術
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
To Be or Not to Be (??????)
• Overview: To Seed or Not to Seed
• The parasitic plant Rafflesia arnoldii
– Produces enormous flowers that can
produce up to 4 million seeds
Figure 38.1
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Key Concepts
Concept 38.1: Pollination enables gametes to
come together within a flower (受粉作用使得花
中的配子聚在一起)
Concept 38.2: After fertilization, ovules develop
into seeds and ovaries into fruits
Concept 38.3: Many flowering plants clone (複製)
themselves by asexual reproduction
Concept 38.4: Plant biotechnology is
transforming agriculture
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Concept 38.1: Pollination enables gametes
to come together within a flower (受粉作用使
得花中的配子聚在一起)
• In angiosperms, the dominant sporophyte (孢
子體)
– Produces spores that develop within
flowers into male gametophytes (pollen
grains) (雄配子體、花粉粒)
– Produces female gametophytes (embryo
sacs) (雌配子體、胚囊)
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Flower Structure
• Flowers
– Are the reproductive shoots of the angiosperm
sporophyte (被子植物配子體)
– Are composed of four floral organs:
• Sepals (萼片)
雄蕊Stamen
• Petals (花瓣)
花藥
Anther
Filament
花絲
• Stamens (雄蕊)
• Carpels (雌蕊)
Carpel雌蕊
Ovary卵房
Sepal萼片
花瓣Petal
Receptacle
花托
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柱頭
Stigma
Style
花柱
被子植物花的多樣性
• Many variations in floral structure have evolved during
the 140 million years of angiosperm history
SYMMETRY
OVARY LOCATION
Bilateral symmetry
(orchid)
Radial symmetry
(daffodil)
FLORAL DISTRIBUTION
Superior
ovary
Sepal
Lupine inflorescence
Semi-inferior Inferior
ovary
ovary
Fused petals
Sunflower
inflorescence
REPRODUCTIVE VARIATIONS
Maize, a monoecious
species
Figure 38.3
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Dioecious Sagittaria
latifolia (common
arrowhead)
Gametophyte Development and Pollination
• In angiosperms (被子植物)
– Pollination (受粉作用) is the transfer of
pollen from an anther (花藥) to a stigma (柱
頭)
– If pollination is successful, a pollen grain
(花粉粒) produces a structure called a
pollen tube (花粉管), which grows down into
the ovary (卵房) and discharges sperm near
the embryo sac (胚囊)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• An overview of angiosperm reproduction
Stamen
Anther
Carpel
Stigma
Style
Filament
Germinated pollen grain
(n) (male gametophyte)
on stigma of carpel
Anther at
tip of stamen
Ovary
Ovary (base of carpel)
Pollen tube
Ovule (卵胞)
Embryo sac (n)
(female gametophyte)
Sepal
Egg
(n)
Petal
FERTILIZATION
Receptacle
Sperm (n)
(a) An idealized flower.
Key
Mature sporophyte
plant (2n) with
flowers
Seed
Seed
(develops
from ovule)
Zygote
(2n)
Haploid (n)
Diploid (2n)
(b) Simplified angiosperm life cycle.
See Figure 30.10 for a more detailed
version of the life cycle, including meiosis.
Figure 38.2a, b
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Embryo (2n)
(sporophyte)
Germinating
seed
Simple fruit
(develops from ovary)
• Pollen (花粉)---Develops from microspores (雄
孢子) within the sporangia (孢子囊) of anthers
(a) Development of a male gametophyte
(pollen grain)雄配子體(花粉粒)的發育
Pollen sac
(microsporangium)
(1) Each one of the microsporangia
contains diploid microsporocytes
(2n) (microspore mother cells).
(2) Each microsporocyte divides by
meiosis to produce four haploid
microspores (n), each of which
develops into a pollen grain.
(3) A pollen grain becomes a mature
male gametophyte when its
generative nucleus divides and
forms two sperm. This usually
occurs after a pollen grain lands on
the stigma of a carpel and the pollen
tube begins to grow. (See Figure
38.2b.)
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MicroSporocyte
MEIOSIS減數分裂
Microspores (4)
Each of 4
microspores
Generative
cell (will
form 2
sperm)
MITOSIS有絲分裂
Male
Gametophyte
(pollen grain)
Nucleus
of tube cell
20 m
KEY to labels
Haploid (2n)
Diploid (2n)
75 m
Ragweed
pollen grain
Figure 38.4a
• Embryo sacs---Develop from megaspores
within ovules
(b) Development of a female gametophyte
(embryo sac)雌配子體(胚囊)的發育
Ovule
減數分裂MEIOSIS
Megasporangium
Megasporocyte
Integuments
Micropyle
Surviving
megaspore
Female gametophyte
(embryo sac)
有絲分裂MITOSIS Ovule
Antipodel
Cells (3)
Polar
Nuclei (2)
Egg (1)
Integuments Synergids (2)
Haploid (2n)
Diploid (2n)
100 m
Key to labels
Embryo sac
(1) Within the ovule’s
megasporangium is a large diploid
cell called the megasporocyte
(megaspore mother cell).
(2) The megasporocyte divides by
meiosis and gives rise to four
haploid cells, but in most
species only one of these
survives as the megaspore.
(3) Three mitotic divisions of the
megaspore form the embryo sac, a
multicellular female gametophyte. The
ovule now consists of the embryo sac
along with the surrounding integuments
(protective tissue).
Figure 38.4b
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mechanisms That Prevent Self-Fertilization (自我受精)
• Many angiosperms (被子植物)
– Have mechanisms that make it difficult or impossible
for a flower to fertilize itself (自我受精)
Stigma
柱頭
Stigma
柱頭
Anther with
Pollen 有花
粉的花藥
Pin flower
Figure 38.5
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Thrum flower
• The most common anti-selfing mechanism in flowering
plants
– Is known as self-incompatibility (自我排斥、自我不
相容), the ability of a plant to reject its own pollen
• Researchers are unraveling the molecular mechanisms
that are involved in self-incompatibility
• Some plants
– Reject pollen that has an S-gene matching an allele
in the stigma cells
• Recognition of self pollen (自家花粉)
– Triggers a signal transduction pathway leading to a
block (阻礙) in growth of a pollen tube
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• Concept 38.2: After fertilization, ovules
develop into seeds and ovaries into fruits
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Double Fertilization (雙重受精)
• After landing on a receptive stigma (花柱)
– A pollen grain (花粉粒) germinates and produces a
pollen tube (花粉管) that extends down between the
cells of the style () toward the ovary ()
• The pollen tube (花粉管)
– Then discharges two sperm into the embryo sac
• In double fertilization (雙重受精)
– One sperm fertilizes the egg
– The other sperm combines with the polar nuclei (極
核), giving rise to the food-storing endosperm (胚乳)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Growth of the pollen tube and double
fertilization
(花粉粒)Pollen grain
(1) If a pollen grain
germinates, a pollen tube
grows down the style
toward the ovary.
(極核)Polar nuclei
Egg
Stigma (柱頭)
Pollen tube (花粉管)
2 sperm
Style
Ovary
Ovule (containing female
gametophyte, or embryo sac)
Micropyle
(2) The pollen tube
discharges two sperm into
the female gametophyte
(embryo sac) within an ovule.
(3) 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.
Ovule
Polar nuclei
Egg
Two sperm about to be discharged
Endosperm nucleus (3n) (2 polar
nuclei plus sperm)
Zygote (2n) (egg plus sperm)
Figure 38.6
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Development of Ovule and Endosperm
• From Ovule to Seed, after double fertilization
– Each ovule develops into a seed
– The ovary develops into a fruit enclosing the
seed(s)
• Endosperm Development, usually precedes
embryo development
– In most monocots and some eudicots, the
endosperm stores nutrients that can be used
by the seedling after germination
• In other eudicots, the food reserves of the
endosperm are completely exported to the
cotyledons
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Embryo Development
• The first mitotic division of the zygote is transverse
– Splitting the fertilized egg into a basal cell and a
terminal cell
Ovule
Endosperm nucleus
Integuments
Zygote
Terminal cell
Basal cell
Zygote
Proembryo
Suspensor
Basal cell
Cotyledons
Shoot apex
Root apex
Seed coat
Endosperm
Figure 38.7
Suspensor
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Structure of the Mature Seed
• The embryo and its food supply
– Are enclosed by a hard, protective seed coat
• In a common garden bean, a eudicot
– The embryo consists of the hypocotyl, radicle, and
thick cotyledons
種皮
Seed coat
Epicotyl 上胚軸
Hypocotyl 下胚軸
Radicle
胚根
Figure 38.8a
Cotyledons
子葉
(a) Common garden bean, a eudicot with thick cotyledons. The
fleshy cotyledons store food absorbed from the endosperm before
the seed germinates.
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• The seeds of other eudicots, such as castor
beans
– Have similar structures, but thin cotyledons
Seed coat
Seed
coat
Endosperm
Endosperm
Cotyledons
Cotyledons
Epicotyl
Epicotyl
Hypocotyl
Hypocotyl
Radicle
Radicle
種皮
胚乳
子葉
上胚軸
下胚軸
胚根
(b) Castor bean, a eudicot with thin cotyledons. The narrow,
membranous cotyledons (shown in edge and flat views) absorb
food from the endosperm when the seed germinates.
Figure 38.8b
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• The embryo of a monocot (單子葉) has a single
cotyledon, a coleoptile, and a coleorhiza
(子葉)Scutellum
(cotyledon)
(芽鞘) Coleoptile
(根鞘) Coleorhiza
Pericarp fused
with seed coat (種皮)
Endosperm (胚乳)
Epicotyl (上胚軸)
Hypocotyl (下胚軸)
Radicle (胚根)
(c) Maize, a monocot. Like all monocots, maize has only one
cotyledon. Maize and other grasses have a large cotyledon called a
scutellum. The rudimentary shoot is sheathed in a structure called
the coleoptile, and the coleorhiza covers the young root.
Figure 38.8c
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From Ovary to Fruit
• A fruit
– Develops from the ovary
– Protects the enclosed seeds
– Aids in the dispersal of seeds by wind or
animals
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• Fruits are classified into several types
– Depending on their developmental origin
Carpels
Ovary
Stamen
Flower
Stigma
Stamen
Ovule
Pea flower
Raspberry flower
Carpel
(fruitlet)
Seed
Stigma
Ovary
Stamen
Pineapple inflorescence
Each
segment
develops
from the
carpel of
one flower
Pea fruit
Raspberry fruit
(a) Simple fruit. A simple fruit
develops from a single carpel
(or several fused carpels) of
one flower (examples: pea,
lemon, peanut).
(b) Aggregate fruit. An
aggregate fruit develops
from many
separate
carpels
Figure
38.9a–c
of one flower (examples:
raspberry, blackberry,
strawberry).
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Pineapple fruit
(c) Multiple fruit. A multiple fruit
develops from many carpels
of many flowers (examples:
pineapple, fig).
Seed Germination (種子萌芽)
• As a seed matures
– It dehydrates (脫水) and enters a phase
referred to as dormancy (休眠)
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Seed Dormancy: Adaptation for Tough Times
• 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 cues
• From Seed to Seedling (從種子到幼苗)
– Germination of seeds depends on the physical
process called imbibition (浸潤)
– The uptake of water due to low water potential of
the dry seed
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• The radicle (胚軸) is the first organ to emerge from the germinating
seed
• In many eudicots, a hook forms in the hypocotyl (下胚軸), and
growth pushes the hook above ground
Foliage leaves (初生葉)
(上胚軸)
Hypocotyl
(上胚軸) Hypocotyl
Cotyledon
Cotyledon
Epicotyl (上胚軸)
Cotyledon (子葉)
Hypocotyl (上胚軸)
Radicle
(胚根)
Figure 38.10a
Seed coat
(種皮)
(a)Common garden bean. In common garden beans,
straightening of a hook in the hypocotyl pulls the
cotyledons from the soil.
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• Monocots (單子葉植物)
– Use a different method for breaking ground when
they germinate
• The coleoptile (芽鞘)
– Pushes upward through the soil and into the air
Foliage leaves
Coleoptile
Coleoptile
Radicle
Figure 38.10b
(b) Maize. In maize and other grasses, the shoot grows
straight up through the tube of the coleoptile.
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• Concept 38.3: Many flowering plants clone (複
製) themselves by asexual reproduction
• Many angiosperm species reproduce both
asexually and sexually (無性及有性)
• Sexual reproduction
– Generates the genetic variation that makes
evolutionary adaptation possible
• Asexual reproduction in plants
– Is called vegetative reproduction (營養繁殖)
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Mechanisms of Asexual Reproduction (無性生殖的機制)
• Fragmentation (裂片)
– Is the separation of a parent plant into parts that develop into
whole plants
– Is one of the most common modes of asexual reproduction
• In some species, the root system of a single parent gives rise
to many adventitious shoots that become separate shoot
systems
Figure 38.11
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Vegetative Propagation (營養繁殖) and Agriculture
• Humans have devised various methods for
asexual propagation of angiosperms
• Clones from cuttings (切枝、切條)
– Many kinds of plants are asexually
reproduced from plant fragments called
cuttings
• Grafting (架接、接枝)
– In a modification of vegetative reproduction
from cuttings
– A twig or bud from one plant can be grafted
onto a plant of a closely related species or a
different variety of the same species
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Test-Tube Cloning (試管複製) and Related Techniques
• Plant biologists have adopted in vitro methods
to create and clone novel plant varieties.
(a) Just a few parenchyma cells from a
carrot gave rise to this callus, a mass
of undifferentiated cells.
(b) The callus differentiates into an
entire plant, with leaves, stems, and
roots.
Figure 38.12a, b
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In a process called protoplast fusion (原生
質體融合)
– Researchers fuse protoplasts, plant cells
with their cell walls removed, to create
hybrid plants
Vacuole
Chloroplast
Figure 38.13
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50 m
• Concept 38.4: Plant biotechnology is
transforming agriculture
• Plant biotechnology has two meanings:
– It refers to innovations in the use of plants
to make products of use to humans
– It refers to the use of genetically modified
organisms (GMO, 基因改造生物) in
agriculture and industry
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Artificial Selection (人工選擇; 人擇)
• Humans have intervened
– In the reproduction and genetic makeup of plants
for thousands of years
• Maize (玉米)
–
Is a product of artificial selection by humans
– Is a staple (xxxxx) in many developing countries,
but is a poor source of protein
• Interspecific hybridization of plants (植物的種間雜交)
– Is common in nature and has been used by
breeders, ancient and modern, to introduce new
genes
Figure 38.14
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Reducing World Hunger and Malnutrition (營養不良)
• Genetically modified (GM) plants
– Have the potential of increasing the quality and
quantity of food worldwide
Genetically modified rice
GM papaya
Figure 38.15
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Ordinary rice
Figure 38.16
The Debate over Plant Biotechnology (植物生物技術的爭議)
• There are some biologists, particularly ecologists
– Who are concerned about the unknown risks
associated with the release of GM organisms (GMOs)
into the environment
• Issues of Human Health
– One concern is that genetic engineering may transfer
allergens from a gene source to a plant used for food
• Possible Effects on Nontarget Organisms
– Many ecologists are concerned that the growing of
GM crops might have unforeseen effects on
nontarget organisms
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The Debate over Plant Biotechnology (植物生物技術的爭議)
• Addressing the Problem of Transgene Escape
– Perhaps the most serious concern that
some scientists raise about GM crops is
the possibility of the introduced genes
escaping from a transgenic crop into
related weeds through crop-to-weed
hybridization (作物雜草雜交)
• Despite all the issues associated with GM
crops
– The benefits should be considered
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