31 plant structure and functn revised 2
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© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey
Chapter 31 Plant Structure, Growth,and Reproduction
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Introduction: Extreme Tree Climbing
• Some plants, such ascoast redwoods, are
among the largest andoldest organisms on earth
• Coast redwoods aregymnosperms, a kind of
plant that bears seeds oncones
• Angiosperms, or floweringplants, bear seeds in fruits
• Most plants areangiosperms, which willbe the focus of this uniton plant structure
Coast redwood
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Figure 31.0_2
Chapter 31: Big Ideas
Plant GrowthPlant Structure
and Function
Reproduction of
Flowering Plants
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PLANT STRUCTURE AND FUNCTION
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The two main groups of angiosperms are the monocots and the eudicots
• Monocots and eudicots differ in – Number of cotyledons (seed leaves)
– Pattern of leaf venation
– Arrangement of stem vascular tissue
– Number of flower parts
– Root structure
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• Monocots – One cotyledon
– Parallel leaf venation
– Scattered vascular bundles
– Flower parts in 3s or multiples of 3
– Fibrous roots
The two main groups of angiosperms are themonocots and the eudicots
MONOCOTS
EUDICOTS
Seed leaves Leaf veins Stems Flowers Roots
One cotyledon Veins usually parallel Vascular bundles in complex arrangement Floral parts usually in multiples of three Fibrous root system
Taproot usually present
Floral parts usually in multiples of four or five
Vascular bundles arranged in ring Veins usually branched
Two cotyledons
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• Plant Shoot System• Stems, leaves, and
reproductive structures
• Stems provide support
• Leaves carry outphotosynthesis
• Plant Root System• Anchor plant
• Absorb water andnutrients
• Store food
A typical plant body contains three basic organs:roots, stems, and leaves
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Many plants have modified roots, stems, and leaves
• Modifications of plant parts are adaptations forvarious functions
– Food or water storage
– Asexual reproduction – Protection
– Climbing
– Photosynthesis
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•Root modifications – Food storage
– Large taproots store starches
– Examples include carrots, turnips, sugar beets, sweet
potatoes
Many plants have modified roots, stems, and leaves
Modified root of a sugar beet plant
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• Stem modifications
– Stolon —asexualreproduction
– Rhizomes —storage, asexualreproduction
– Tubers —storage, asexualreproduction
– Cactus stem —water storageandphotosynthesis
Many plants have modified roots, stems, and leaves
Strawberryplant
Potato plant
Tuber
Taproot
Rhizome
Stolon (runner)Ginger plant
Rhizome
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•Leafmodifications
• Climbing
• Pea plant tendril
• Protection
• Cactus spine
Many plants have modified roots, stems, and leaves
Tendrilsof
pea plant
Cactusspines
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Three tissue systemsmake up theplant body
• Dermal tissue
– Outer protectivecovering
• Vascular tissue
– Support andlong-distance
transport
• Ground tissue
– Bulk of the plantbody
– Food production,
storage, support
Eudicot leaf
XylemPhloem
Vein
Guard
cellsStoma
Sheath
Eudicot stem Vascular
bundle
Pith
Cortex
Epidermis
Eudicot root
Endodermis
Cortex
Epidermis
PhloemXylem Vascular
cylinder
Mesophyll
Cuticle
Upper epidermis
Lower epidermis
Monocot stem
Vascular
bundle
Epidermis
Key
Ground tissue systemDermal tissue system
Vascular tissue system
The Three Tissue Systems
Th i k h l b d
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Three tissue systems make up the plant body• Dermal tissue
– Layer of tightly packed cells called the epidermis
– First line of defense against damage and infection
– Waxy layer called cuticle reduces water loss
• Vascular tissue
– Composed of xylem and phloem
– Arranged in bundles
• Ground tissue
– Lies between dermal and vascular tissue
– Eudicot stem ground tissue is divided into pith and cortex
– Leaf ground tissue is called mesophyll
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Plant cells and tissues are diverse in structure andfunction
• Plants cells have three structures that distinguishthem from animals cells
– Chloroplasts used in photosynthesis
– A large, fluid-filled vacuole
– A cell wall composed of cellulose
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Plant cells and tissues are diverse in structure andfunction
• Plant cell wall – Some plant cell walls have two layers
– Primary cell wall —outermost layer
– Secondary cell wall —tough layer inside primary wall
– A sticky layer called the middle lamella lies betweenadjacent plant cells
– Openings in cell walls called plasmodesmata allow cellsto communicate and exchange materials easily
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Pit
Plasmodesmata
Plasma
membrane
Cell walls ofadjoining cells
Secondarycell wall
Middlelamella
Cell walls
Primary cell wall
Centralvacuole
ChloroplastNucleus
Endoplasmic
reticulum
Mitochondrion
Golgiapparatus
Ribosomes
Microtubules
Plasma membrane
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• Plant cell structure is related to function• There are five major types of plant cells
– Parenchyma cells
– Collenchyma cells
– Sclerenchyma cells
– Water-conducting cells
– Food-conducting cells
Plant cells and tissues are diverse in structure andfunction
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Plant cells and tissues are diverse in structure andfunction
• Parenchyma cells
• Most abundant cell type
• Thin primary cell wall
• Lack secondary cell wall
• Alive at maturity
• Function inphotosynthesis, food andwater storage
Starch-storing vesicles
Primarycell wall(thin)
Pit
Parenchyma cell
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• Collenchyma cells
• Unevenly thickened primary cell wall * Alive at maturity
• Lack secondary cell wall * Provide flexible support
Plant cells and tissues are diverse in structure andfunction
Primarycell wall(thick)
Collenchyma cell
Pl t ll d ti di i t t d f ti
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• Sclerenchyma cells
– Thick secondary cell wall containing lignin
– Lignin is a main component of wood
– Dead at maturity
– Rigid support
– Two types of sclerenchyma cells are fibers and sclereids
– Fibers —long and thin, arranged in bundles
– Sclereids —shorter than fibers, present in nut shells and pear tissue
Plant cells and tissues are diverse in structure and function.
Primarycell wall
Sclereid
Pits
Secondarycell wall
Sclereidcells
Secondarycell wall
Pits
Primarycell wall
Fiber
Fibercells
Pl t ll d ti di i t t d
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• Water conducting
cells—tracheids andvessel elements
– Both have thicksecondary cell walls
– Both are dead atmaturity
– Chains of tracheidsand vesselelements formtubes that make upthe vascular tissuecalled xylem
Plant cells and tissues are diverse in structure andfunction
Pits
Vessel element
Tracheids
Pits
Openingsin end wall
Water-conducting cells
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• Food-conducting cells—
sieve tube members
– No secondary cell wall
– Alive at maturity but
lack most organelles
– Companion cells
– Contain organelles
– Control operations
of sieve tube
members
– Chains of sieve tube
members, separated by
porous sieve plates,
form the vascular tissue
called phloem
Plant cells and tissues are diverse in structure andfunction
Food-conducting cell (sieve-tube member)
Cytoplasm
Sieve plate
Companioncell
Primarycell wall
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PLANT GROWTH
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Primary growth lengthens roots and shoots
• Plant growth is indeterminate – Growth occurs throughout a plant’s life
– Plants are categorized based on how long they live
– Annuals complete their life cycle in one year
– Biennials complete their life cycle in two years
– Perennials live for many years
• Animal growth is determinate
– Growth stops after a certain size is reached
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Primary growth lengthens roots and shoots
• Plant growth occurs in specialized tissues called
meristems
• Meristems are regions of active cell division
• Apical meristems are found at the tips of roots andshoots
• Primary growth occurs at apical meristems
• Primary growth allows roots to push downward through thesoil and shoots to grow upward toward the sun
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Axillary buds
Terminal bud
Arrows =directionof growth
Root
tips
Primary growth lengthens roots and
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Primary growth lengthens roots andshoots
• The apical meristems of
root tips are covered by
a root cap
• Root growth occursbehind the root cap in 3
zones
– Zone of celldivision—the apicalmeristem
– Zone of cellelongation—cellslengthen by asmuch as 10 times
– Zone of maturation —cells differentiateinto dermal,vascular, andground tissues
Cellulosefibers
Key
Ground tissue system
Dermal tissue system
Vascular tissue system
Apicalmeristemregion
Zone ofelongation
Zone of
maturation
Zone of
cell division
Rootcap
Epidermis
Cortex Vascular cylinder
Root hair
Primary growth lengthens roots and Lea esl
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Primary growth lengthens roots andshoots
• The apical meristems of shoottips occur as buds at the stem
tip and at the base of leaves
• Cells produced in the shootapical meristem differentiate intodermal, vascular, and groundtissues
• Vascular tissue producedfrom the apical meristem is
called primary vasculartissue
– Primary xylem
– Primary phloem
Leaves Apicalmeristem
Axillary budmeristems
1 2
Primary growth of a shoot
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Secondary growth increases the girth of woody plants
• Secondary growth occurs at lateral meristems
• Lateral meristems are areas of active cell division thatexist in two cylinders that extend along the length of rootsand shoots
• Vascular cambium is a lateral meristem that liesbetween primary xylem and phloem
• Cork cambium is a lateral meristem that lies at the
outer edge of the stem cortex
Secondary growth increases the girth of woody plants
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Secondary growth increases the girth of woody plants
• Vascular cambium produces cells in two directions
– Secondary xylem produces wood toward the interior of the stem
– Secondary phloem produces the inner bark toward the exterior of the stem
• Cork cambium produces cells in one direction
– Cork cambium produces the outer bark , which is composed of cork cells
Secondary xylem(2 years’ growth)
G r o w t h
Shedepidermis
Year 1Late Summer
Key
Ground tissue system
Dermal tissue system
Vascular tissue system
G r o w t h
G r o w t h
Year 2Late Summer
Year 1Early Spring
Bark
Secondaryxylem (wood)
Secondaryphloem
Corkcambium
Cork
Primaryphloem
Primaryxylem
Vascularcambium
Epidermis
Cortex
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Secondary growth increases the girth of woody plants
•Wood annual rings show layers of secondary xylem
– In temperate regions, periods of dormancy stop growthof secondary xylem
– Rings occur in areas when new growth starts each year
• The bark (secondary phloem and cork) is sloughedoff over time
Secondary growth increases the girth of woody plants
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Secondary growth increases the girth of woody plants• Wood rays are parenchyma tissue that radiate from the stem’s center
– Wood rays function in lateral transport and storage
• Most transport occurs near the vascular cambium
– Sapwood near the vascular cambium transports water
– Heartwood stores resins and wastes
– Transport of sugars occurs in the secondary phloem near the vascular cambium
Sapwood
Heartwood
Bark
Rings
Woodrays
Heartwood
Sapwood
Vascular cambium
Secondary phloemCork cambiumCork
Anatomy of a locust log
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Th fl i th f l d ti i i
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The flower is the organ of sexual reproduction in angiosperms
•Flowers typically contain four types of highlymodified leaves called floral organs
– Sepals —enclose and protect flower bud
– Petals —showy; attract pollinators
– Stamens —male reproductive structures
– Carpels —female reproductive structures
The flower is the organ of sexual reproduction in
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• A stamen has two parts
– Anther —producespollen, which house
cells which develop
into sperm
– Filament —elevates
anther
• A carpel has three parts
– Stigma —site of
pollination
– Style —“neck” thatleads to ovary
– Ovary —houses
ovules, which contain
developing egg
The flower is the organ of sexual reproduction inangiosperms
Petal
Ovule
Filament
Sepal
Anther
Ovary
Style
Stigma
Th fl i th f l d ti i
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• Angiosperm life cycle overview
– Fertilization occurs in the ovule; the fertilized eggdevelops into an embryo encased in a seed
– The ovary develops into a fruit, which protects the seed
and aids in dispersal
– The seed germinates under suitable conditions toproduce a seedling, which grows into a mature plant
The flower is the organ of sexual reproduction inangiosperms
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Ovary, containingovule
Mature plant withflowers, wherefertilization occurs
Life cycle of a generalized angiosperm
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Ovary, containingovule
Mature plant withflowers, wherefertilization occurs
Fruit (mature ovary),containing seed
Embryo
Seed
Life cycle of a generalized angiosperm
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Ovary, containingovule
Mature plant withflowers, wherefertilization occurs
Fruit (mature ovary),containing seed
Embryo
Seed
Germinatingseed
Life cycle of a generalized angiosperm
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Ovary, containingovule
Mature plant withflowers, wherefertilization occurs
Fruit (mature ovary),containing seed
Embryo
Seed
Germinatingseed
Seedling
Life cycle of a generalized angiosperm
The development of pollen and ovules culminates in
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The development of pollen and ovules culminates infertilization
•Plant life cycles involve alternating diploid (2n) andhaploid (n) generations
– The diploid generation 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 haploidgeneration
– The haploid generation is called the gametophyte
– Gametophytes produce gametes via mitosis
The development of pollen and ovules culminates in
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•The male gametophyte is a pollen grain
– A cell in the anther undergoes meiosis to produce fourhaploid spores
– Each spore divides via mitosis to produce two cells
called the tube cell and generative cell
– A tough wall forms around the cells to produce a pollengrain
– Pollen grains are released from the anther
The development of pollen and ovules culminates infertilization
The development of pollen and ovules culminates in
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•The female gametophyte is an embryo sac
– A cell in the ovule undergoes meiosis to produce fourhaploid spores
– Three of the spores degenerate
– The surviving spore undergoes a series of mitoticdivisions to produce the embryo sac
– One cell within the embryo sac is an egg ready for
fertilization – One central cell within the embryo sac has two nuclei
and will produce endosperm
The development of pollen and ovules culminates infertilization
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Development of Male Gametophyte(Pollen grain)
Development of Female Gametophyte(Embryo sac)
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Double fertilization#
One sperm nucleus fertilizes the egg, generating a (2N) diploid zygote. Another sperm nucleus fertilizes a polar cell, generating a (3N) triploid endosperm,
which provides nutrients to the developing embryo
The development of pollen and ovules culminates in fertilization
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• Pollination
– Transfer of pollen from anther to stigma
– Pollen is carried by wind, water, and animals
• Pollen grain germination
– Tube nucleus produces pollen tube, which grows down throughthe style to the ovary
– Generative nucleus divides to produce two sperm
CoInc.Double fertilization
– One sperm fertilizes the egg to produce a zygote
– One sperm fuses with the central cell nuclei to produce 3n endosperm
– Endosperm nourishes the developing embryo
Development of male
gametophyte
( ll i )
Development of female
gametophyte
( b )
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(pollen grain) (embryo sac)
Survivingcell (haploid
spore)
Ovule
Ovary
Meiosis
Mitosis
Anther
Cell within
anther
Meiosis
Pollengerminates
Four haploidspores
Singlespore
Wallforms Pollination
Mitosis(of each spore)
Two cellsEmbryosac
Eggcell
Pollen grain
released from
anther
Two sperm
in pollen
tube
Two sperm
discharged
Pollentubeentersembryo sac
Triploid (3n)endosperm
nucleus
Diploid (2n)zygote
(egg plus sperm)
Double
fertilization
occurs
Gametophyte development & fertilization in an angiosperm
Development of male
hDevelopment of female
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gametophyte
(pollen grain)
gametophyte(embryo sac)
Survivingcell (haploidspore)
Ovule
Ovary
Meiosis
Mitosis
Anther
Cell withinanther
Meiosis
Four haploidspores
Singlespore
Wallforms
Mitosis(of each spore)
Two cells
Embryosac
Egg cell
Pollen grainreleased fromanther
Polleni t
Wall
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germinatesforms Pollination
Two cells
Embryosac
Eggcell
Pollen grainreleased fromanther
Two spermin pollentube
Two spermdischarged
Pollentubeentersembryo sac
Triploid (3n)endospermnucleus
Diploid (2n)zygote(egg plus sperm)
Doublefertilization
occurs
The ovule develops into a seed
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p• The zygote divides many
times via mitosis to producethe embryo
• The embryo consists of tinyroot and shoot apicalmeristems and one or twocotyledons
• A tough seed coat develops
• Seed dormancy
– Embryo growth anddevelopment aresuspended
– Allows delay ofgermination untilconditions are favorable
A Development of a eudicot plant embryo
Zygote
Two cells
Embryo
Seed
Ovule
Root
Shoot
Endosperm
Cotyledons
Seedcoat
The ovule develops into a seed
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The ovule develops into a seed
•Eudicot seeds (Exalbuminous)
– Two cotyledons
– Apical meristems lack protective sheaths
– Endosperm absorbed by cotyledons• Monocot seeds ( Albuminous)
– Single cotyledon
– Apical meristems have a protective sheaths – Endosperm is present
Embryonic
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Cotyledon
Cotyledons
EmbryonicShoot(plumule)
Embryonicshoot(plumule)
Embryonicroot(radicle)
EndospermEmbryonic
leaf
Fruit tissue
Seed coat
Sheath
Corn (monocot)
Common bean (eudicot)
Seed coat(Testa)
EmbryonicRoot
(radicle)
Embryonicleaves
• Albuminous
• Exalbuminous
The ovary develops into a fruit
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The ovary develops into a fruit
•Hormonal changes induced by fertilization trigger theovary to develop into a fruit
• Fruits protect the seed and aid in dispersal
• Mature fruits may be fleshy or dry – Fleshy fruits—oranges, tomatoes, grapes
– Dry fruits—beans, nuts, grains
ASSIGNMENT: (To be submitted 1st mtg. after APEC)I l d it ti ti /it
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Include proper citations per question/item.
1. Describe two main kinds of flowering plants and how they differ in number ofseed leaves and in structures such as stems, roots, leaves, and flowers
2. Name the three tissue systems that make up the plant body and the functions ofeach
3. Describe the structure and function of five types of cells found in the plant body
4. Give the name and location of the specialized areas where most plant growthoccurs
5. Explain the difference between primary and secondary growth6. Describe the source and pattern of secondary plant growth
7. Describe the structure of an angiosperm flower and the function of each part
8. Explain the difference between the angiosperm sporophyte and gametophyte
9. Describe the series of events that occur in the angiosperm life cycle from sporeproduction to seed germination
10. Describe some modes of plant asexual reproduction and conditions that favorasexual reproduction
11. Identify evolutionary adaptations that allow plants to live very long lives