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Chapter 31
Plant Structure, Growth, and Reproduction
PowerPoint Lectures
Campbell Biology: Concepts & Connections, Eighth Edition
REECE • TAYLOR • SIMON • DICKEY • HOGAN
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Lecture by Edward J. Zalisko
PLANT STRUCTURE AND FUNCTION
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First, some basics about plants…
• multicellular,
photosynthetic autotrophs.
• nonmotile—they cannot
move from place to place.
• cell walls that contain
cellulose.
• includes cone-bearing
(gymnosperms) and
flowering plants
(angiosperms) as well as
mosses and ferns.
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31.2 The two major groups of angiosperms
are the monocots and the eudicots
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31.3 A typical plant body contains three basic
organs: roots, stems, and leaves
• Plant organs consist of several types of tissues that
together carry out particular functions.
• Plants use a root system to
• anchor the plant in the soil,
• absorb and transport water and minerals, and
• store carbohydrates.
• Root hairs are tiny finger-like projections off of roots that
enormously increase the surface area for absorption.
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31.3 A typical plant body contains three basic
organs: roots, stems, and leaves
• A shoot system consists of stems, leaves, and
structures for reproduction.
• A stem has
• nodes, the points at which leaves are attached,
and internodes, the portions of the stem between
nodes.
• The leaves are the main photosynthetic organs in
most plants, although green stems also perform
photosynthesis.
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31.3 A typical plant body contains three basic
organs: roots, stems, and leaves
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31.4 Many plants have modified roots, stems, and leaves
• Modifications of plant parts are adaptations for various functions,
including
• Roots - food or water storage - Unusually large taproots that
store food in the form of carbohydrates such as starch are
found in carrots, turnips, sugar beets, and sweet potatoes.
• Stems - asexual reproduction and storage - stolons, tubers,
rhizomes
• Leaves - protection, climbing, and photosynthesis – tendrils,
cactus spines
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31.5 Three tissue systems make up the plant body
• The organs of plants contain tissues, which are
a group of cells that together perform a
specialized function.
• Xylem tissue contains water-conducting
cells that convey water and dissolved
minerals upward from roots
• tracheids and vessel elements: xylem
elongated cells dead at maturity
• Phloem tissue contains cells that transport
sugars and other organic nutrients from
leaves or storage tissues to other parts of
the plant
• sieve-tube members: phloem tubes alive
at maturity capped by sieve plates (porous
end plates)
• companion cells: (nonconducting)
connected by to sieve tube by
plasmodesmata
.
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31.5 Three tissue systems make up the plant
body
• Each plant organ (root, stem, or leaf) has three
types of tissues.
1. Dermal tissue provides a protective outer
covering (epidermis and cuticle).
2. Vascular tissue provides support and longdistance transport (xylem and phloem)
3. Ground tissue composes the bulk of the plant
body and is involved in
• Photosynthesis (mesophyll layer of leaves),
• storage, and support (pith and cortex of roots).
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31.5 Three tissue systems make up the plant body
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31.5 Three tissue systems make up the plant body
• In a leaf, the epidermis is interrupted by tiny pores called
stomata, which allow exchange of CO2 and O2 between the
surrounding air and the photosynthetic cells inside the leaf.
• Each stoma is flanked by two guard cells that regulate the
opening and closing of the stoma.
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31.6 Plant cells are diverse in structure and function
• Most plant cells have three structures that distinguish them from
animal cells:
1. chloroplasts, the site of photosynthesis,
2. a central vacuole containing fluid that helps maintain cell
turgor (firmness), and
3. a protective cell wall composed of cellulose.
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31.6 Plant cells are diverse in structure and function
• There are five major types of plant cells with
different functions:
1. parenchyma cells: walls thin and
flexible, no secondary walls, large central
vacuole, main workhorse for
photosynthesis
2.
collenchyma cells: unevenly thick
primary walls, used for plant support
3.
sclerenchyma cells: support element
strengthened by secondary cell walls with
lignin (wood), dead at functional maturity,
xylem cells are mostly sclerenchyma fibers (long, slender tapered - rope) and
sclereids (shorter, irregular – nutshells,
seed coats, pear grittiness)
4.
5.
water-conducting cells: xylem
food-conducting cells: phloem
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PLANT GROWTH
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31.7 Primary growth lengthens roots and
shoots
• Most animals are characterized by determinate
growth, stopping growth after a certain size.
• Most plants have indeterminate growth,
continuing to grow throughout a plant’s life.
• Plants are categorized based on the length of their
life cycle.
• Annuals complete their life cycle in one year.
• Biennials complete their life cycle in two years.
• Perennials live for many years.
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31.7 Primary growth lengthens roots and shoots
• Plant growth occurs in specialized
tissues called meristems,
consisting of undifferentiated cells
that divide when conditions permit.
• Apical meristems are found at the
tips of roots and in the buds of
shoots.
• Primary growth
• occurs at apical meristems,
• allows roots to push downward
through the soil, and
• allows shoots to grow upward,
increasing exposure to light
and CO2.
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31.7 Primary growth lengthens roots and shoots
• The apical meristems of root
tips are covered by a root
cap.
• Root growth occurs behind
the root cap in three zones.
1.
2.
3.
Zone of cell division:
primary (apical)
meristem
Zone of elongation: cells
elongate; pushes root tip
Zone of differentiation:
where cells differentiate
into dermal, vascular,
and ground tissues
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31.8 Secondary growth increases the diameter of woody
plants
• Secondary growth
• is an increase in thickness of stems and roots and
• occurs at lateral meristems.
• Lateral meristems are areas of active cell division that exist in
two cylinders that extend along the length of roots and shoots.
1. Vascular cambium is a lateral meristem that lies
between primary xylem and primary phloem.
• Gives rise to secondary xylem (wood) and secondary
phloem (inner bark - diameter increase, annual growth
rings)
2. Cork cambium is a lateral meristem that lies at
the outer edge of the stem cortex.
• Produces cells in one direction – the outer bark (made of
cork cells)
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31.8 Secondary growth increases the diameter of woody
plants
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31.8 Secondary growth increases the diameter of woody
plants
• Wood annual rings = layers
of secondary xylem.
• The bark is sloughed off over
time.
• Wood rays transport water
and nutrients, store organic
nutrients, and aid in wound
repair.
• Sapwood: conducts
xylem fluid (sap).
• Heartwood: stores
resins and wastes.
• Secondary phloem near
the vascular cambium
transports sugars.
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REPRODUCTION OF FLOWERING PLANTS
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31.9 The flower is the organ of sexual reproduction in
angiosperms
Flowers typically contain four types of
floral organs.
1. Sepals protect a flower bud.
2. Petals are often colorful and
fragrant, attract pollinators.
3. Stamens consist of the
filament tipped by an anther,
which contains pollen.
4. Carpels have a style with a
sticky stigma at its tip.
• The base of the carpel is
the ovary, which contains
one or more ovules, each
containing a developing
egg and supporting cells.
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31.9 The flower is the organ of sexual reproduction in
angiosperms
• In the life cycle of a generalized
angiosperm,
1. Fertilization occurs in an
ovule.
2. The ovary develops into a
fruit.
3. The ovule develops into the
seed containing the embryo.
The fruit protects the seed and
aids in dispersing it.
4. Completing the life cycle, the
seed then germinates (begins
to grow) in a suitable habitat.
5. The embryo develops into a
seedling, and the seedling
grows into a mature plant.
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First some weird words for you…
• Plant life cycles involve alternating diploid (2n) and
haploid (n) generations.
• The diploid plant is called the sporophyte.
• Specialized diploid cells in anthers and ovules
undergo meiosis to produce haploid spores.
• The haploid spores undergo mitosis and produce the
haploid generation.
• The haploid generation is called the gametophyte,
which produces gametes via mitosis.
• At fertilization, gametes from male and female
gametophytes unite to produce a diploid zygote.
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31.10 The development of pollen and ovules
culminates in fertilization
• Pollen grains are the male
gametophytes.
• The cells that develop into
pollen grains are found
within a flower’s anthers.
1.Each cell first undergoes
meiosis, forming four
haploid spores.
2.Each spore then divides
by mitosis, forming two
haploid cells, called the
tube cell and the
generative cell.
3.The resulting pollen grain
is ready for release from
the anther.
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31.10 The development of pollen and ovules
culminates in fertilization
• The female gametophyte is an
embryo sac.
• A cell in the ovule
undergoes meiosis to
produce four haploid
spores.
• Three of the spores
degenerate.
• The surviving spore
undergoes a series of
mitotic divisions to
produce the embryo sac,
the female gametophyte.
• The sac contains a large
central cell with two
haploid nuclei.
• One of its other cells is
the haploid egg, ready to
be fertilized.
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31.10 The development of pollen and ovules culminates in
fertilization
• Pollination: pollen goes from anther to
stigma (wind, water, animals).
• The pollen grain germinates on the
stigma.
• The pollen tube grows toward ovule
and mitosis forms two sperm.
• Pollen tube enters ovary and discharges
its two sperm.
• One sperm fertilizes the egg to form the
2n zygote.
• Other sperm combines with two haploid
nuclei to form 3n endosperm (foodstoring tissue which nourishes the
developing seed)
• This formation of a diploid zygote and a
triploid endosperm is called double
fertilization.
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31.11 The ovule develops into a seed
• After fertilization, the ovule
begins developing into a seed.
• Near the end of its maturation,
the seed loses most of its
water and forms a hard,
resistant seed coat.
• Seed dormancy allows time for
a plant to disperse its seeds
and increases the chance that
plants will begin growing only
when environmental
conditions, such as
temperature and moisture,
favor survival.
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31.11 The ovule develops into a seed
• In eudicots, most endosperm is converted into cotyledons;
stays mostly endosperm in monocots.
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31.12 The ovary develops into a fruit
• While the seeds are developing from ovules, hormonal changes
triggered by fertilization cause the flower’s ovary to grow,
thicken, and mature into a fruit.
• A fruit is a mature ovary that protects seeds and helps disperse
them.
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31.12 The ovary develops into a fruit
• Various adaptations of fruits help disperse seeds.
• Seeds of some flowering plants, such as dandelions and
maples, are contained within fruits that function like kites or
propellers.
• Coconuts are adapted to dispersal by water.
• Many angiosperms rely on animals to carry seeds clinging to
fur or ingested with fruits.
Fleshy
Fruits
Dry
Fruits
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31.13 Seed germination continues the life cycle
• At germination, a seed takes up water and restarts the growth that was
suspended during seed dormancy.
• In eudicots, the embryonic root emerges first and grows downward and
shoots emerge from the soil with the apical meristem “hooked” downward
to protect it.
• In monocots,
• A protective sheath pushes upward and breaks through the soil and
the shoot tip then grows up through the tunnel provided by the sheath.
• The cotyledon remains in the soil and decomposes.
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You should now be able to
1.
Explain how the cultivation of wheat has
changed over the past 10,000 years.
2.
Compare the structure of monocots and
eudicots.
3.
Compare the structures and functions of roots,
stems, and leaves.
4.
Distinguish between a taproot, stolon, rhizome,
tuber, bulb, petiole, and tendril, and indicate
common examples of each from a vegetable
garden.
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You should now be able to
5.
Define a tissue system. Describe the three
main types of tissue systems found in young
eudicot roots, stems, and leaves.
6.
Describe the three unique structures found in
most plant cells.
7.
Describe the structures and functions of the five
major types of plant cells.
8.
Distinguish between (a) indeterminate and
determinate growth and (b) annuals, biennials,
and perennials.
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You should now be able to
9.
Describe and compare primary and secondary
growth.
10. Describe the parts of a flower and their
functions.
11. Describe the processes and events that lead to
double fertilization.
12. Explain how a seed forms. Compare the
structures of eudicot and monocot seeds and
explain the significance of seed dormancy.
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You should now be able to
13. Describe the structure and functions of fruit.
14. Describe and compare germination in bean and
corn plants.
15. Describe examples of cloning in plants.
16. Compare the advantages and disadvantages of
asexual versus sexual reproduction.
17. Describe plant adaptations that permit very long
lives.
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Figure 31.UN01
Terminal bud (grows stem)
Flower (reproductive organ)
Shoot system
(site of
photosynthesis)
Stem (supports leaves and flowers)
Axillary bud (produces a branch)
Node
Internode
Blade
Petiole
Root system
(anchors,
absorbs
nutrients,
and stores
food)
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Leaf (main organ of
photosynthesis)
Root hairs
(microscopic;
increase surface
area for absorption)
Figure 31.UN02
Shoot tip
(shoot apical
meristem and
young leaves)
Vascular
cambium
Axillary bud
meristem
Cork
cambium
Lateral
meristems
Root apical
meristems
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Figure 31.UN03
Pollen (n)
Ovary
Embryo
sac (n)
Fertilization
within ovule
Ovule
Mature
plant (2n)
Fruit (from ovary)
Seed (from ovule)
Embryo (2n)
Germinating
seed (2n)
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Figure 31.UN04
Endosperm
nucleus (3n)
(2n central cell
plus sperm)
Zygote (2n)
(egg plus
sperm nucleus)
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