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CHAPTER 28
The Life of a Flowering Plant
PowerPoint® Lectures for
Essential Biology, Third Edition
– Neil Campbell, Jane Reece, and Eric Simon
Essential Biology with Physiology, Second Edition
– Neil Campbell, Jane Reece, and Eric Simon
Lectures by Chris C. Romero
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Biology and Society:
Plant Cloning—Feast and Famine
• For the past ten thousand years, humankind has
cultivated plants to ensure an adequate food supply.
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• Potatoes, introduced to Europe in the sixteenth
century, provide a good example.
– They can be cloned very easily, allowing
extensive cultivation.
• Cloned potatoes
– Fed enormous numbers of people in Ireland in the
1800s.
– Are more susceptible to environmental changes
due to their lack of genetic diversity.
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• In the 1840s, a funguslike organism began to infect
Irish potatoes, resulting in a major famine.
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Figure 28.1
• In addition to their importance to humans,
– Plants are vital to the well-being of the Earth’s
biosphere.
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The Structure and Function of a Flowering Plant
• Angiosperms
– Have dominated the land for over 100 million
years.
– Account for nearly 90% of the plant kingdom.
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Monocots and Dicots
• Botanists have traditionally classified most
angiosperms into two groups, monocots and dicots,
on the basis of several structural features.
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Figure 28.2
• The names of the groups refer to cotyledons, or
seed leaves found in the embryo.
• Most angiosperms are dicots.
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Plant Organs: Roots, Stems, and Leaves
• A plant body consists of a root system and a shoot
system, each depending on the other.
How Plants Obtain Minerals from Soil
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Figure 28.3
Roots
• A plant’s root system
– Anchors it in the soil.
– Absorbs and transports minerals and water.
– Stores food.
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• Root hairs
– Are tiny projections near the root tips.
– Increase the surface area of the root.
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• Large taproots, such as those found in carrots,
turnips, sugar beets, and sweet potatoes,
– Store food in the form of carbohydrates such as
starch.
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Figure 28.4
Stems
• The shoot system of a plant is made up of stems,
leaves, and, in angiosperms, flowers.
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• When a plant stem is growing in length, the
terminal bud at the apex of the stem has developing
leaves.
• In many plants, the terminal bud produces
hormones that cause a phenomenon called apical
dominance.
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• In many types of plants, removing the terminal bud
stimulates growth of the axillary buds.
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Figure 28.5
• Stems take many forms.
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Figure 28.6
Leaves
• The leaves
– Are the primary sites of photosynthesis in most
plants.
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• Plant leaves are highly varied in their
arrangements.
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Figure 28.7
• Plant leaves also vary in their shapes.
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Figure 28.8
Plant Cells
• Plant cells are unique in many ways.
• Plant cells contain
– Chloroplasts containing chlorophyll.
– A large central vacuole.
– Cell walls.
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Figure 28.9
• Parenchyma cells
– Are the most abundant type of cell in most plants.
– Perform a variety of functions, such as food
storage and photosynthesis.
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Figure 28.10a
• Collenchyma cells
– Provide support for parts of the plant that are still
growing.
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Figure 28.10b
• Sclerenchyma cells
– Have thick secondary cell walls that provide
support to the plant.
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Figure 28.10c
• Water-conducting cells
– Convey water from the roots to the stems and
leaves.
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Figure 28.10d
• Food-conducting cells
– Convey food throughout a plant.
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Figure 28.10e
Plant Tissues and Tissue Systems
• The cells of plants
– Are grouped into tissues with characteristic
functions.
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• Vascular tissue called xylem
– Contains water-conducting cells.
• Vascular tissue called phloem
– Contains food-conducting cells.
• Plant tissues
– Are organized into tissue systems.
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• Roots, stems, and leaves are made up of three
tissue systems:
– The dermal tissue system, the vascular tissue
system, and the ground tissue system
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Figure 28.11
• The dermal tissue system
– Covers and protects the leaves, stems, and roots.
• The vascular tissue system
– Is made up of xylem and phloem.
• The ground tissue system
– Makes up the bulk of a young plant.
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• A cross section of a root shows what the three
tissue systems look like under a microscope.
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Figure 28.12
• The three tissue systems in leaves
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Figure 28.13
• Stomata, tiny pores that allow gas exchange,
– Occur in the epidermis of leaves.
• The mesophyll
– Is the ground tissue system in a leaf.
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Plant Growth
• Most plants display indeterminate growth,
continuing to grow as long as they live.
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• Species called annuals
– Complete their life cycle in a single year or
growing season.
• Species called biennials
– Complete their life cycle in two years.
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Figure 28.14a, b
• Plants known as perennials
– Live and reproduce for many years.
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Figure 28.14c
Primary Growth: Lengthening
• Growth in all plants
– Is made possible by tissues called meristems.
• A meristem
– Consists of unspecialized cells that divide and
generate new cells and tissues.
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• Apical meristems
– Are found at the tips of roots and in the terminal
and axillary buds of shoots.
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Figure 28.15
• Primary growth
– Consists of cell division in the apical meristems
of roots and shoots.
– Produces the new cells that enable a plant to grow
in length.
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• A growing root
– Is pushed through the soil by primary growth.
– Contains a root cap that protects the actively
dividing cells.
Root Growth in a Radish Seed (time lapse)
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Figure 28.16
Secondary Growth: Thickening
• Secondary growth
– Results in the thickening of stems and roots.
– Involves division in two meristems, the vascular
cambium and the cork cambium.
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• The vascular cambium
– Gives rise to wood near its inner surface.
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Figure 28.17 part 1
Figure 28.17 part 2
Figure 28.17 part 3
• Over the years, a woody stem adds more layers,
resulting in annual growth rings.
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Figure 28.18
• The cork cambium
– Is outside the vascular cambium and produces
cork, one component of bark.
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The Life Cycle of a Flowering Plant
• Many flowering plants can reproduce both sexually
and asexually.
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• Through asexual reproduction, a single plant can
produce many offspring quickly and efficiently.
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Figure 28.19
The Flower
• Sexual reproduction in plants produces genetically
distinct offspring.
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• In angiosperms,
– The structure specific to sexual reproduction is
the flower.
Flower Blooming (time lapse)
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Figure 28.20
• The flower’s reproductive organs are the stamen
and the carpel.
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• The stamen
– Consists of the filament and the anther.
• In the anther
– Meiosis occurs, producing pollen grains that
house the cells that develop into sperm.
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• The carpel
– Consists of the stigma, style, and ovary.
• The stigma receives pollen grains.
• The style leads to the ovary, which houses ovules
that contain developing eggs, at the base of the
stigma.
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Pollination and Fertilization
• The plant life cycle
– Alternates between haploid and diploid
generations.
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• The sexual life cycle of an angiosperm
Time Lapse of Flowering Plant Life Cycle
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Figure 28.21
• The diploid plant body
– Is called the sporophyte.
• The haploid plant body
– Is called the gametophyte.
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• Fertilization
– Occurs when the female and male gametes unite,
producing a diploid zygote.
• The life cycle is completed
– When the zygote divides by mitosis and develops
into a new sporophyte.
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• The formation of the male and female
gametophytes
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Figure 28.22 part 1
Figure 28.22 part 2
• The first step leading to fertilization is pollination,
the delivery of pollen to the stigma of a carpel.
Plant Fertilization
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Figure 28.23
• Many angiosperms are dependent on animals to
transfer their pollen.
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• After pollination,
– The pollen grain germinates on the stigma
forming two sperm.
• Each sperm fertilizes a cell in the ovule in a
process called double fertilization:
– One fertilizes the egg, and the other fertilizes a
second cell in the ovule.
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Seed Formation
• After fertilization,
– The ovule begins developing into a seed.
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• The zygote
– Divides via mitosis into a ball of cells that
becomes the embryo.
• The endosperm also forms from the other fertilized
cell and provides nourishment for the embryo.
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• The result of embryonic development is a mature
seed with a tough protective seed coat.
Fruit Development
Seed Development
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Figure 28.24
Fruit Formation
• A fruit
– Is a mature ovary that houses and protects seeds
and aids in their dispersal.
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• Pea pods
– Are a type of fruit.
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Figure 28.25
• Fruits are highly varied.
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Figure 28.26
Seed Germination
• Germination
– Usually begins when the seed takes up water.
• The hydrated seed expands and bursts its seed coat.
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• Germination in a garden pea
– Involves the formation of the root and then the
shoot.
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Figure 28.27
Evolution Connection:
The Interdependence of Angiosperms and Animals
• Most angiosperms
– Depend on various animals for pollination and
seed dispersal.
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• The flowers of many angiosperms
– Attract pollinators that rely entirely on the
flowers’ nectar and pollen for food.
Bat Pollinating Agave Plant
Bee Pollinating
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Figure 28.28
• Many animals
– Have very defined relationships with various
flower species.
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