Chapter 31

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon

Lectures by Chris Romero

Chapter 31Chapter 31

Plant Structure, Reproduction, and Development


A Gentle Giant• Gymnosperms

– Are one of two groups of seed plants

– Bear seeds in cones


• Angiosperms, or flowering plants

– Are the most familiar and diverse group of plants


TALKING ABOUT SCIENCE

31.1 Plant scientist Natasha Raikhel studies the Arabidopsis plant as a model biological system

• Natasha Raikhel

– Is one of America’s most prominent plant biologists

Figure 31.1A


• Dr. Raikhel works with Arabidopsis

– A popular model organism for studying biological systems

Figure 31.1B


PLANT STRUCTURE AND FUNCTION

31.2 The two main groups of angiosperms are the monocots and the dicots

• Monocots and dicots differ in

– The number of seed leaves and in the structure of roots, stems, leaves, and flowers

Figure 31.2

Fibrousroot system

MONOCOTS

Seed leaves Leaf veins Stems Flowers Roots

Onecotyledon Main veins usually parallel

Vascular bundles in complex arrangement

Floral parts usuallyin multiples of three

Twocotyledons Main veins usually branched

Vascular bundles arranged in ring

Floral parts usually inmultiples of four or five

Taprootusually present

DICOTS


31.3 A typical plant body consists of roots and shoots

• A plant’s root system

– Anchors it in the soil

– Absorbs and transports minerals and water and stores food


• The shoot system of a plant

– Is made up of stems, leaves, and adaptations for reproduction, flowers


Terminal bud

Blade

PetioleAxillary bud

Stem

TaprootRoothairs

Epidermal cell

Root hairInternode

Node

Flower

Shootsystem

Rootsystem

Leaf

• The body of a dicot

Figure 31.3


31.4 Many plants have modified roots, stems, and leaves

• Some plants have unusually large taproots

– That store food in the form of carbohydrates

Figure 31.4A


Strawberry plant

Potato plant

Stolon (runner)

Taproot

Rhizome

Tuber

Ginger plant

Rhizome

Root

• Many plants have modified stems

– That store food or function in asexual reproduction

Figure 31.4B


• Other types of plants have modified leaves

– That function in protection or climbing

Figure 31.4C


Figure 31.5A

31.5 Plant cells and tissues are diverse in structure and function

• Most plant cells have three unique structures

– Chloroplasts, the sites of photosynthesis

– A central vacuole containing fluid

– A cell wall that surrounds the plasma membraneChloroplast Central

vacuoleCell walls

Primary cell wall

Middle lamella

Secondary cell wall

Plasmamembrane

Cell walls of adjoining cells

Plasmodesmata

PitPlasma membrane

MicrotubulesRibosomes

Golgiapparatus

Mitochondrion

Endoplasmicreticulum

Nucleus


• Plants have five major types of cells

– Parenchyma, which perform most of the metabolic functions

– Collenchyma, which provide supportPrimary cell wall (thin)

Pit

Starch-storing vesicles

LM 2

70

Figure 31.5B

Primary cell wall (thick)

LM 2

70

Figure 31.5C


– Sclerenchyma, the main component of wood

Figure 31.5D

Secondary cell wall

Pits

Fiber cells

Primary cell wall

Secondary cell wall

Primary cell wall Pits

Sclereid cells

Fiber Sclereid

LM

26

6

LM

20

0


Pits

Openings in end wall

Vessel element Tracheids

Pits

Colorized SEM 150

• Angiosperms have water-conducting cells

– Tracheids and vessel elements

Figure 31.5E


Figure 31.5F

• Sieve-tube members

– Are food-conducting cellsSieve plate

Companion cell

Primary cell wall

Cytoplasm


• Two kinds of vascular tissue are

– Xylem, which conveys water and minerals

– Phloem, which transports sugars


31.6 Three tissue systems make up the plant body

• Each plant organ is made up of threetissue systems

– The dermal,vascular, and ground tissue systems

Vein

Guard cells

Cuticle

Upper epidermis

Mesophyll

Lower epidermis

Stoma

Xylem

Phloem

Dicot leaf

Dicot stem

Sheath

Vascular bundle

Cortex

Pith

Epidermis

Monocot stemVascular bundle

Epidermis

Epidermis

Vascular cylinder

Xylem

Phloem

Cortex

Endodermis

Dicot root

Key

Dermal tissue system

Ground tissue system

Vascular tissue system

Figure 31.6


• The dermal tissue system

– Covers and protects the plant

• The vascular tissue system

– Contains xylem and phloem and provides long-distance transport and support

• The ground tissue system

– Consists of parenchyma cells and supportive collenchyma and sclerenchyma cells


PLANT GROWTH

31.7 Primary growth lengthens roots and shoots

• Meristems, areas of unspecialized, dividing cells

– Are where plant growth originates


• Apical meristems

– Are located in the tips of roots and in the terminal and axillary buds of shoots

– Initiate primary (lengthwise) growth by producing new cells

Figure 31.7A

Terminal bud

Axillary buds

Root tips

Arrows = direction of growth


• Roots are covered with a root cap

– That protects the cells of the apical meristem

Figure 31.7B

Vascular cylinder

Root hair

Cortex

Epidermis

Zone of maturation

Zone of elongation

Zone of cell division

Root cap

Apical meristem region

Cellulose fibers

KeyDermal tissue system




• Axillary bud meristems

– Are found near the apical meristems

Figure 31.7C

Apical meristem

Leaves

Axillary bud meristems

1 2

LM 1

03


31.8 Secondary growth increases the girth of woody plants

• Secondary growth arises from cell division

– In a cylindrical meristem called the vascular cambium


• The vascular cambium thickens a stem

– By adding layers of secondary xylem, or wood, next to its inner surface

Year 1Early Spring

Year 1Late Summer

Year 2Late Summer

GrowthGrowth

Growth

Primary xylem

Vascular cambium

Primary phloem

Cor tex

EpidermisSecondary

xylem (wood)Cork

Corkcambium

Secondary phloem

Bark

Shed epidermis

Secondary xylem (2 years’ growth)

Key

Dermal tissue system



Figure 31.8A


• The heartwood and sapwood

– Consist of different layers of xylem

• Outside the vascular cambium, the bark consists mainly of

– Secondary phloem, cork cambium, and protective cork cells

Figure 31.8B

Heartwood

Sapwood

Rings

Wood rays

Heartwood

Vascular cambium

Sapwood

Secondary phloem

Cork cambium

Cork

Bark


REPRODUCTION OF FLOWERING PLANTS

31.9 Overview: The sexual life cycle of a flowering plant

• The angiosperm flower consists of

– Sepals, petals, stamens, and carpalsStigma

Style

Ovary

Anther

Filament

Stamen

PetalOvule Sepal

Carpel

Figure 31.9A


• Pollen grains develop in anthers

– At the tip of stamens


Ovary, containing ovule

Fruit, (mature ovary), containing seed

Mature plant with flowers, where fertilization occurs

Seedling

Germinating seed

Seed

Embryo

• The tip of the carpel, the stigma– Receives pollen grains

• The ovary, at the base of the carpel– Houses the egg-producing structure, the ovule

Figure 31.9B


31.10 The development of pollen and ovules culminates in fer tilization

• In the diploid sporophyte of an angiosperm

– Haploid spores are formed within ovules and anthers


• The spores in the anthers

– Give rise to male gametophytes, pollen grains, which produce sperm

• A spore in an ovule

– Produces the embryo sac, the female gametophyte, which contains an egg cell


• Pollination

– Is the arrival of pollen grains onto a stigma

• A pollen tube grows into the ovule

– And sperm pass through it and fer tilize both the egg and a second cell in a process called double fer tilization


• Gametophyte development and fertilization in an angiosperm Development of male

gametophyte (pollen grain)

Development of female gametophyte (embryo sac)

Anther

Cell within anther

Meiosis

Four haploid spores

Single spore

Wall formsMitosis

(of each spore)

Two cells Pollen grainreleased from anther

Ovary

Ovule

Surviving cell (haploid spore)

Pollen germinatesMitosis

Embryo sac

Egg cellTwo sperm in pollen tube

Pollen tube enters embryo sac

Two sperm discharged

Triploid (3n) endosperm nucleus

Double fer tilization occurs

Diploid (2n)zygote (egg plus sperm)

Pollination

Meiosis

Figure 31.10


31.11 The ovule develops into a seed

• After fertilization, the ovule becomes a seed

– And the fertilized egg within it divides and becomes an embryo

Figure 31. 11A

Growth

Secondary

xylem (wood)

CorkCork

cambiumSecond

ary phloem

Shed epidermis

Triploid cell

Ovule

Zygote

Embryo

Endosperm

Shoot

Cotyledons

Seed coat

SeedRoot

Two cells


• The other fertilized cell

– Develops into the endosperm, which stores food for the embryo


• The internal structures of dicot and monocot seeds

– Differ in a variety of ways

Figure 31.11B

Embryonicleaves

Embryonicroot

Seed coat Cotyledons

Embryonicshoot

Common bean (dicot)

Cotyledon

Embryonicleaf

Sheath

Fruit tissue

Seed coat

Endosperm

EmbryonicShoot

Embryonicroot

Corn (monocot)


31.12 The ovary develops into a fruit• Angiosperms form fruits

– Which help protect and disperse the seeds

Upper partof carpel

Ovule

Sepal

Ovar ywall

Seed

Pod(opened)

Figure 31.12B

Figure 31.12A

1 2 3


• Angiosperm fruits

– May differ in size and development

Figure 31.12C


31.13 Seed germination continues the life cycle

• A seed starts to germinate

– When it takes up water and star ts to expand

• The embryo resumes growth

– And absorbs nutrients from the endosperm

• An embryonic root emerges

– And a shoot pushes upward and expands its leaves


• In dicot germination, the root emerges first

– Followed by the shoot, which is covered by a protective hook

Figure 31.13A

Foliage leavesEmbryonicshoot

Embryonicroot

Cotyledons


• In monocot germination

– A protective sheath surrounding the shoot breaks the soil

Figure 31.13B

Foliageleaves

Protective sheathenclosing shoot

Embryonicroot Cotyledon


31.14 Asexual reproduction produces plant clones• Asexual reproduction can be achieved via

– Bulbs, sprouts, or runners

Figure 31.14A Figure 31.14B

Figure 31.14DFigure 31.14C


CONNECTION

1.15 Asexual reproduction is a mainstay of modern agriculture

• Propagating plants asexually from cuttings or bits of tissue

– Can increase productivity but can also reduce genetic diversity

Figure 31.15

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Chapter 31

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