Transcript Chapter 35 Reproduction in Flowering Plants

Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 35
Reproduction in
Flowering Plants
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• A flower may contain
• Sepals
• Petals
• Stamens
• Carpels (pistils)
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
An Arabidopsis thaliana flower
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• Sepals
• Cover and protect the flower
parts when the flower is a bud
• Petals
• Play an important role in
attracting animal pollinators
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CHAPTER 35 Reproduction in Flowering Plants
• Stamens
• Produce pollen grains
• Each stamen consists of
–A filament attached to an anther
–An anther (a saclike structure)
• Carpel
• Female reproductive unit
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CHAPTER 35 Reproduction in Flowering Plants
• Pistil
• May consist of either
–A single carpel or
–A group of fused carpels
• Each pistil has three sections
–Stigma for pollen grains to land on
–Style for pollen tube to grow through
–Ovary containing one or more ovules
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
Cutaway view of an Arabidopsis flower
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• Pollen
• Forms within pollen sacs in the
anther
• Each pollen grain contains two
cells
–One generates two sperm cells
–The other produces a pollen tube so
sperm cells can reach the ovule
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CHAPTER 35 Reproduction in Flowering Plants
• In the ovule the following are
formed
• An egg
• Two polar nuclei
• Several other nuclei
• Both egg and polar nuclei
participate directly in fertilization
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CHAPTER 35 Reproduction in Flowering Plants
Development
of female and
male
gametophytes
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CHAPTER 35 Reproduction in Flowering Plants
• Insect-pollinated flowers
• Often yellow or blue
• Have a scent
• Bird-pollinated flowers
• Often yellow, orange, or red
• Do not have a strong scent
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CHAPTER 35 Reproduction in Flowering Plants
Ultraviolet markings on insect-pollinated flowers
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CHAPTER 35 Reproduction in Flowering Plants
• Bat-pollinated flowers
• Often have dusky white petals
• Are scented
• Wind-pollinated flowers
• Often have smaller petals or
none at all
• Have neither scent nor nectar
• Make large amounts of pollen
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CHAPTER 35 Reproduction in Flowering Plants
Animal pollinators: Archilochus colubris obtains nectar
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
Animal pollinators:
Leptonycteris curasoae obtains nectar
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
Wind pollination
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CHAPTER 35 Reproduction in Flowering Plants
• Coevolution
• Reciprocal adaptation
• Caused by two species
–Forming interdependent relationship
–Affecting the course of each other’s
evolution
• E.g., certain showy flowers +
bees
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CHAPTER 35 Reproduction in Flowering Plants
• Pollination
• Transfer of pollen grains from
anther to stigma
• Fertilization
• Fusion of gametes
• Occurs after pollination
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
Pollination, pollen
tube growth, and
fertilization
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• Double fertilization
• In the ovule, egg fuses with first
sperm cell
• Zygote is formed
• Zygote develops into a
multicellular embryo in the seed
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CHAPTER 35 Reproduction in Flowering Plants
A longitudinal section through a heart-shaped fruit of Capsella
bursa-pastoris reveals numerous tiny seeds, each containing
a mature embryo. Each seed developed from an ovule.
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CHAPTER 35 Reproduction in Flowering Plants
• Double fertilization, cont.
• Two polar nuclei fuse with second
sperm cell
• Triploid nutritive tissue
(endosperm) is formed
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CHAPTER 35 Reproduction in Flowering Plants
• Stages of embryo development
• Dicot embryo develops in the
seed
–From proembryo
–To globular embryo
–To heart stage
–To the torpedo stage
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CHAPTER 35 Reproduction in Flowering Plants
The proembryo in Capsella
bursa-pastoris (the ovule is
shown apart from the ovary)
As cell division continues, the
embryo becomes a ball of cells,
called the globular stage
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CHAPTER 35 Reproduction in Flowering Plants
As the two cotyledons
The
begin to emerge, the
cotyledons continue to elongate,
embryo is shaped like a
forming the torpedo stage
heart
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CHAPTER 35 Reproduction in Flowering Plants
• Mature flowering plant embryo
consists of
• A radicle
• A hypocotyl
• A plumule
• Cotyledons (one in monocots,
two in dicots)
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CHAPTER 35 Reproduction in Flowering Plants
• For use during germination, a
mature seed contains both
• A young embryo
• Nutritive tissue (stored in
endosperm or cotyledons)
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CHAPTER 35 Reproduction in Flowering Plants
A maturing
embryo within
the seed. The
food originally
stored in the
endosperm has
been almost
completely
depleted during
embryonic
growth and
development;
most of the food
for the
embryonic
plant is stored in
its cotyledons
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CHAPTER 35 Reproduction in Flowering Plants
• Ovules
• Structures with the potential to
develop into seeds
• Ovaries
• Structures with the potential to
develop into fruits
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CHAPTER 35 Reproduction in Flowering Plants
• Seeds
• Enclosed within fruits
• Fruits
• Mature, ripened ovaries
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CHAPTER 35 Reproduction in Flowering Plants
• Simple fruits
• Develop from a single pistil
consisting of
–Either a single carpel
–Several fused carpels
• Some are fleshy at maturity
• Others are dry
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CHAPTER 35 Reproduction in Flowering Plants
• Aggregate fruits
• Develop from a single flower with
many separate ovaries
• Multiple fruits
• Develop from the ovaries of many
flowers growing close together on
a common axis
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CHAPTER 35 Reproduction in Flowering Plants
Cutaway view of a Rubus
flower, showing the many
separate carpels in the center
of the flower
A developing blackberry
fruit is an aggregate of tiny
drupes. The little “hairs” on
the blackberry are remnants
of stigmas and styles
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CHAPTER 35 Reproduction in Flowering Plants
• Accessory fruits
• The major part of the fruit consists of
tissue other than ovary tissue
• Dispersal methods of seeds and
fruits include
•
•
•
•
Animals
Wind
Water
Explosive dehiscence
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CHAPTER 35 Reproduction in Flowering Plants
An accessory fruit
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CHAPTER 35 Reproduction in Flowering Plants
• Stems specialized for asexual
reproduction
• Rhizomes
• Tubers
• Bulbs
• Corms
• Stolons
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CHAPTER 35 Reproduction in Flowering Plants
• Rhizome
• Horizontal underground stem
• Tuber
• Fleshy underground stem
enlarged for food storage
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CHAPTER 35 Reproduction in Flowering Plants
Irises have
horizontal
underground
stems called
rhizomes. New
aerial shoots
arise from buds
that develop on
the rhizome
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CHAPTER 35 Reproduction in Flowering Plants
Potato
plants form
rhizomes,
which
enlarge into
tubers (the
potatoes) at
the ends
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CHAPTER 35 Reproduction in Flowering Plants
• Bulb
• Modified underground bud with
–Fleshy storage leaves attached to
–Short stem
• Corm
• Short erect underground stem
covered by papery scales
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CHAPTER 35 Reproduction in Flowering Plants
A bulb is a
short
underground
stem to which
overlapping,
fleshy leaves
are attached;
most of the
bulb consists
of leaves
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CHAPTER 35 Reproduction in Flowering Plants
A corm is an
underground
stem that is
almost
entirely
tissue
surrounded
by a few
papery
scales
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CHAPTER 35 Reproduction in Flowering Plants
• Stolon
• Horizontal aboveground stem
with long internodes
• Plantlets (detachable)
• Arise from meristematic tissue
along margins of some leaves
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CHAPTER 35 Reproduction in Flowering Plants
Strawberries reproduce
asexually by forming
stolons, or runners; new
plants (shoots and roots)
are produced at every
other node
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CHAPTER 35 Reproduction in Flowering Plants
Plantlets
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CHAPTER 35 Reproduction in Flowering Plants
• Suckers
• Develop from adventitious buds
developed from roots
• Produce additional roots
• May give rise to new plants
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CHAPTER 35 Reproduction in Flowering Plants
• Apomixis
• Production of seeds and fruit
without sexual reproduction
• Sexual reproduction
• Involves union of two gametes
• Offspring produced are
genetically variable
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• Sexual reproduction, cont.
• Parental genotypes are not
preserved in offspring
• Genetic diversity among offspring
–May be selectively advantageous
–May let individuals exploit new
environments
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• Sexual reproduction, cont.
• Costly because both male and
female gametes
–Must be produced
–Must meet
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• Asexual reproduction
• Involves formation of offspring
without fusion of gametes
• Offspring are virtually genetically
identical to single parent
–Genetic similarity may be
selectively advantageous
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Biology, Seventh Edition
CHAPTER 35 Reproduction in Flowering Plants
• Asexual reproduction, cont.
• All individuals can produce
offspring
• Genetic variability is increased by
occasional sexual reproduction
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