Download Ch 31: Plant Structure and Reproduction

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 31
Plant Structure, Reproduction,
and Development
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
A Gentle Giant
• This giant sequoia,
the General Sherman,
is the largest plant on
Earth
– It is 84 m (275 ft) tall
– Its trunk is 10m in
diameter
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• The General Sherman
has been growing for
about 2,500 years
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• Growth rings mark each year in a tree's life
– Rings vary in thickness depending on weather
conditions during the growing season
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• Humans depend on plant products
– Lumber
– Fabric
– Paper
– Food
– Industrial chemicals
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• Plants are vital to Earth's well-being
– They provide food for land animals
– They offer shelter and breeding areas for
animals, fungi, and microorganisms
– Their roots prevent soil erosion
– Photosynthesis in plant leaves helps reduce
carbon dioxide and adds oxygen to the air
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31.1 Talking About Science: Plant scientist
Katherine Esau was a preeminent student of
plant structure and function
• Katherine Esau was one of the twentieth
century's most prolific plant scientists
• Her early research
on sugar beets led
to important
discoveries about
– phloem
– viral infections
of plant tissue
Figure 31.1A
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• Dr. Esau later used an
electron microscope to
continue studying the
relationship between
plant structure and
function
• She discovered that
plant viruses are
transmitted through
plant tissues via
plasmodesmata
Figure 31.1B
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PLANT STRUCTURE AND FUNCTION
31.2 The two main groups of angiosperms are the
monocots and the dicots
• Angiosperms, or flowering plants, are the most
familiar and diverse plants
• There are two main types of angiosperms
– Monocots include orchids, bamboos, palms,
lilies, grains, and other grasses
– Dicots include shrubs, ornamental plants, most
trees, and many food crops
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• Monocots and dicots differ in seed leaf number
and in the structure of roots, stems, leaves, and
flowers
SEED LEAVES
LEAF VEINS
STEMS
FLOWERS
ROOTS
MONOCOTS
One
cotyledon
Main veins
usually parallel
Vascular bundles in
complex arrangement
Floral parts usually
in multiples of three
Fibrous
root system
DICOTS
Two
cotyledons
Main veins
usually branched
Vascular bundles
arranged in ring
Floral parts usually in
Taproot
multiples of four or five usually present
Figure 31.2
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31.3 The plant body consists of roots and shoots
• Root system
– Provides anchorage
– Absorbs and transports minerals and water
– Stores food
• Root hairs increase the surface area for
absorption
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• Shoot system
– Consists of stems, leaves, and flowers in
angiosperms
– Stems are located above the ground and support
the leaves and flowers
– Leaves are the main sites of photosynthesis in
most plants
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Terminal bud
Blade
Leaf
Flower
Petiole
Axillary bud
Stem
SHOOT
SYSTEM
Node
Internode
Taproot
ROOT
SYSTEM
Root
hairs
Figure 31.3
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• The terminal bud is located at the tip of a stem
– It is the growth point of the stem
• Axillary buds can give rise to branches
• In apical dominance, the terminal bud produces
hormones that inhibit the growth of axillary
buds
– This results in a taller plant that has greater
exposure to light
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31.4 Many plants have modified roots and shoots
• Roots and stems are adapted for a variety of
functions
– Storing food
– Asexual reproduction
– Protection
• Plant breeders have improved
the yields of root crops by
selecting varieties, such as
the sugar beet plant, with
very large taproots
Figure 31.4A
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• Modified stems
include
STRAWBERRY
PLANT
– runners, for
asexual
reproduction
Runner
POTATO
PLANT
– rhizomes, for
plant growth and
food storage
– tubers, for food
storage in the
form of starch
Rhizome
IRIS
PLANT
Rhizome
Tuber
Taproot
Root
Figure 31.4B
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• Modified leaves include tendrils and spines
– Tendrils help plants to climb
– Spines may protect the plant from plant-eating
animals
Figure 31.4C
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31.5 Plant cells and tissues are diverse in structure
and function
Figure 31.5A
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• There are five major types of plant cells
– Parenchyma
– Collenchyma
– Sclerenchyma
– Water-conducting cells
– Food-conducting cells
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• Parenchyma cells function in food storage,
photosynthesis, and aerobic respiration
Primary
wall
(thin)
Pit
Figure 31.5B
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• Collenchyma cells provide support in parts of
the plant that are still growing
Primary
wall
(thick)
Figure 31.5C
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• Sclerenchyma cells provide a rigid scaffold that
supports the plant
– Fiber cells
Pits
Secondary
wall
Fiber
cells
Primary
wall
FIBER
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Figure 31.5D
– Sclereids (stone cells)
Secondary
wall
Primary
wall
Sclereid
cells
Pits
SCLEREID
Figure 31.5D continued
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• Water-conducting cells convey water from the
roots to the stems and leaves
– Chains of
tracheids or
vessel
elements form
a system of
tubes for water
transport
Pits
Tracheids
Vessel element
Pits
Openings
in end wall
Figure 31.5E
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• Food-conducting cells function in the transport
of sugars, other compounds, and some mineral
ions
– Sieve-tube members are arranged end-to-end,
forming tubes
– Their end walls are perforated with
plasmodesmata, forming sieve plates
– At least one companion cell flanks each sievetube member
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Sieve plate
Companion
cell
Cytoplasm
Primary
wall
Figure 31.5F
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• Complex tissues are composed of more than
one type of plant cell
• Vascular tissues are complex tissues that
conduct water and food
– Xylem contains water-conducting cells that
convey water and dissolved minerals
– Phloem contains sieve-tube members that
transport sugars
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31.6 Three tissue systems make up the plant body
• Roots, stems, and
leaves are made
of three tissue
systems
Leaf
Stem
– The epidermis
– The vascular
tissue system
– The ground
tissue system
Root
Epidermis
Ground
tissue system Vascular
tissue system
Figure 31.6A
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• The epidermis covers and protects the plant
– The cuticle is a waxy coating secreted by
epidermal cells that helps the plant retain water
• The vascular tissue contains xylem and phloem
– It provides support and transports water and
nutrients
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• The ground tissue system functions mainly in
storage and photosynthesis
– It consists of parenchyma cells and supportive
collenchyma and sclerenchyma cells
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• The ground tissue system of the root forms the
cortex
– The cortex consists mostly of parenchyma tissue
• The selective barrier forming the innermost
layer of the cortex is the endodermis
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VASCULAR
TISSUE
SYSTEM
Xylem
Phloem
Epidermis
GROUND
TISSUE
SYSTEM
Cortex
Endodermis
Figure 31.6B
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• These microscopic cross sections of a dicot and
a monocot indicate several differences in their
tissue systems
Figure 31.6C
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• The three tissue systems in dicot leaves
– The epidermis consist of pores called stomata
(singular, stoma) flanked by regulatory guard
cells
Figure 31.6D
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– The ground tissue system of a leaf is called
mesophyll and is the site of photosynthesis
Figure 31.6D
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– The vascular tissue consists of a network of
veins composed of xylem and phloem
Figure 31.6D
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PLANT GROWTH
31.7 Primary growth lengthens roots and shoots
• Most plants exhibit indeterminate growth
– They continue to grow as long as they live
• In contrast, animals are characterized by
determinate growth
– They cease growing after reaching a certain size
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• Annuals complete their life cycle in a single year
or growing season
– Examples: wheat, corn, rice, and most
wildflowers
• Biennials complete their life cycle in two
years, with flowering occurring in the second
year
– Examples: beets and carrots
• Perennials live and reproduce for many years
– Examples: trees, shrubs, and some grasses
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• Growth in all plants originates in tissues called
meristems
– Meristems are areas of unspecialized, dividing
cells
• Apical meristems are located at the tips of
roots and in the terminal buds and axillary
buds of shoots
– They initiate primary growth, lengthwise
growth by the production of new cells
– Roots and stems lengthen further as cells
elongate and differentiate
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Terminal bud
Axillary buds
Arrows =
direction
of growth
Root
tips
Figure 31.7A
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Cortex
Epidermis
DIFFERENTIATION
Vascular
cylinder
CELL
DIVISION
ELONGATION
Root hair
Cellulose
fibers
Apical meristem
region
Root
cap
Figure 31.7B
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Leaves
Apical
meristem
Axillary bud
meristems
1
2
Figure 31.7C
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31.8 Secondary growth increases the girth of
woody plants
• An increase in a plant's girth results from
secondary growth
• Secondary growth involves cell division in two
cylindrical meristems
– Vascular cambium
– Cork cambium
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• Vascular cambium thickens a stem by adding
layers of secondary xylem, or wood, next to its
inner surface
– It also produces the secondary phloem, which
is a tissue of the bark
• Cork cambium produces protective cork cells
located in the bark
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Figure 31.8A
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• Everything external to the vascular cambium is
considered bark
– Secondary phloem
– Cork cambium
– Protective cork cells
• Heartwood in the center of the trunk consists
of older, clogged layers of secondary xylem
• Sapwood consists of younger, secondary xylem
that still conducts water
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• A woody log is the result of several years of
secondary growth
Sapwood
Rings
Wood
rays
Heartwood
Sapwood
Vascular cambium
Secondary phloem
Bark
Cork cambium
Cork
Heartwood
Figure 31.8B
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PLANT REPRODUCTION
31.9 Overview: The sexual life cycle of a flowering
plant
• The angiosperm
flower is a
reproductive shoot
consisting of
Anther
Carpel
Stigma
Ovary
– sepals
– petals
Stamen
– stamen
Ovule
– carpels
Sepal
Petal
Figure 31.9A
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• Sepals are usually green and resemble leaves in
appearance
– Sepals enclose and protect the flower bud
before the flower opens
• Petals are often bright and colorful
– They attract insects (pollinators)
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• Stamens are the male reproductive organs of
plants
– Pollen grains develop in anthers, at the tips of
stamens
• Carpels are the female reproductive organs of
plants
– The ovary at the base of the carpel houses the
ovule
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• The life cycle of an angiosperm involves several
stages
Ovary, containing
ovule
Embryo
Fruit,
containing seed
Seed
Mature plant with
flowers, where
fertilization occurs
Seedling
Germinating seed
Figure 31.9B
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31.10 The development of pollen and ovules
culminates in fertilization
• The plant life cycle alternates between diploid
(2n) and haploid (n) generations
• Double fertilization is unique to plants
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Figure 31.10
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31.11 The ovule develops into a seed
• After fertilization, the ovule becomes a seed
– The fertilized egg within the seed divides to
become an embryo
– The other fertilized cell develops into the
endosperm, which stores food for the embryo
• A resistant seed coat protects the embryo and
endosperm
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Triploid cell
OVULE
Zygote
Two cells
Cotyledons
Endosperm
Seed coat
Shoot
Embryo
Root
SEED
Figure 31.11A
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• Seed dormancy is an important evolutionary
adaptation in which growth and development
are suspended temporarily
– It allows time for a plant to disperse its seeds
– It increases the chance that a new generation of
plants will begin growing only when
environmental conditions favor survival
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• Comparison between dicot and monocot seeds
Seed coat
Embryonic
shoot
Embryonic
leaves
Embryonic
root
Cotyledons
COMMON BEAN (DICOT)
Fruit tissue
Cotyledon
Seed coat
Endosperm
Embryonic
leaf
Embryonic
shoot
Sheath
Embryonic
root
CORN (MONOCOT)
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Figure 31.11B
31.12 The ovary develops into a fruit
• The ovary develops into a fruit which helps
protect and disperse the seeds
Figure 31.12A
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• There is a correspondence between flower and
fruit in a pea plant
– The wall of the ovary becomes the pod
– The ovules develop into the seeds
Upper part
of carpel
Ovule
Seed
Ovary
wall
Sepal
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Pod
(opened)
Figure 31.12B
– The small, threadlike structure at the end of the
pod is what remains of the upper part of the
flower's carpel
– The sepals of the flower stay attached to the
base of the green pod
Upper part
of carpel
Ovule
Seed
Ovary
wall
Sepal
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Pod
(opened)
Figure 31.12B
• Simple fruits develop from a flower with a
single carpel and ovary
– Apples, pea pods, cherries
• Aggregate fruits develop from a flower with
many carpels
– Raspberries
• Multiple fruits develop
from a group of flowers
clustered tightly together
– Pineapples
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Figure 31.12C
31.13 Seed germination continues the life cycle
• A seed starts to germinate when it takes up
water, expands, and bursts its seed coat
• Metabolic changes cause the embryo to
resume growth and absorb nutrients from the
endosperm
• An embryonic root emerges, and a shoot
pushes upward and expands its leaves
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• Pea
germination
(a dicot)
Foliage leaves
Embryonic
shoot
Cotyledons
Embryonic
root
• Corn
germination
(a monocot)
Foliage
leaves
Protective sheath
enclosing shoot
Embryonic
root
Cotyledon
Figure 31.13A, B
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31.14 Asexual reproduction produces plant clones
• Many plants can reproduce asexually via bulbs,
sprouts, or runners
• Asexual reproduction often involves
fragmentation
– Fragmentation is
the separation of
parts from the
parent plant and
regeneration of
those parts into
whole plants
Figure 31.14A
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• Sprouts from the roots of a coast redwood tree
may eventually take the place of its parent in
the forest
Figure 31.14B
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• These creosote bushes came from generations
of vegetative reproduction by roots
Figure 31.14C
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• Most grasses can propagate asexually by
sprouting shoots and roots from runners
Figure 31.14D
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31.15 Connection: Vegetative reproduction is a
mainstay of modern agriculture
• Propagating plants from cuttings or bits of
tissue can increase agricultural productivity
– But it can also reduce genetic diversity
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• Test-tube cloning is the growth of a plantlet
from a few meristem cells cultured on a
chemical medium
– A single plant can be
cloned into thousands of
copies that will continue
to grow when planted in
soil
– Orchids and certain pine
trees used in mass
plantings are propagated
this way
Figure 31.15A
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• Protoplast fusion is the fusion of plant cells that
have had their cell walls removed by treatment
with enzymes
– Plant species unable to interbreed in nature can
be fused in the laboratory
– This produces a
hybrid plant
with a desirable
combination
of traits
Figure 31.15B
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• "GM" (genetically modified) plants are created
when foreign genes are incorporated into a
single parenchyma cell
– The cell is then cultured until it develops into a
new plantlet
• The commercial adoption of GM crops has
been rapid
– However, many people are concerned about
the potential environmental risks associated
with their use
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• Monocultures are large areas of land planted
with a single crop
• Gene-cloning techniques and monocultures
have led to crop plants with little genetic
diversity
– This increases the likelihood that a small
number of diseases could devastate large crop
areas
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