31 Plant Structure and Functn Revised 2

8/18/2019 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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Copyright © 2009 Pearson Education, Inc.

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



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



•Root modifications – Food storage

– Large taproots store starches

– Examples include carrots, turnips, sugar beets, sweet

potatoes


Modified root of a sugar beet plant



• Stem modifications

– Stolon —asexualreproduction

– Rhizomes —storage, asexualreproduction

– Tubers —storage, asexualreproduction

– Cactus stem —water storageandphotosynthesis


Strawberryplant

Potato plant

Tuber

Taproot

Rhizome

Stolon (runner)Ginger plant

Rhizome



•Leafmodifications

• Climbing

• Pea plant tendril

• Protection

• Cactus spine


Tendrilsof

pea plant

Cactusspines



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



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



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




• 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



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• 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


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


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


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


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



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• 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


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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•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



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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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Fruit (mature ovary),containing seed

Embryo

Seed



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Embryo

Seed

Germinatingseed



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Embryo

Seed

Germinatingseed

Seedling


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



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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




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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



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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



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•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

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31 Plant Structure and Functn Revised 2