29 Lecture Plant Diversity i

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LECTURE PRESENTATIONS

For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

© 2011 Pearson Education, Inc.

Lectures by

Erin Barley

Kathleen Fitzpatrick

Plant Diversity I: How Plants

Colonized Land

Chapter 29



Overview: The Greening of Earth

• For more than the first 3 billion years of Earth’shistory, the terrestrial surface was lifeless

• Cyanobacteria likely existed on land 1.2 billion

years ago• Around 500 million years ago, small plants,

fungi, and animals emerged on land




• Since colonizing land, plants have diversified intoroughly 290,000 living species

• Land plants are defined as having terrestrial

ancestors, even though some are now aquatic

• Land plants do not include photosynthetic

protists (algae)

• Plants supply oxygen and are the ultimate

source of most food eaten by land animals




1 m

Figure 29.1



Concept 29.1: Land plants evolved from

green algae

• Green algae called charophytes are the closest

relatives of land plants




Morphological and Molecular Evidence

• Many characteristics of land plants also appear ina variety of algal clades, mainly algae

• However, land plants share four key traits withonly charophytes

– Rings of cellulose-synthesizing complexes

– Peroxisome enzymes

– Structure of flagellated sperm

– Formation of a phragmoplast




1 m

Figure 29.2

30 nm



• Comparisons of both nuclear and chloroplastgenes point to charophytes as the closest living

relatives of land plants

• Note that land plants are not descended from

modern charophytes, but share a common

ancestor with modern charophytes




1 m

Figure 29.3

Chara species, a pond organism

Coleochaete orb icu laris, adisk-shaped charophytethat also lives in ponds (LM)

40 m

5 mm



1 m

Figure 29.3a

Chara species, a pond organism

5 mm



1 m

Figure 29.3b

Coleochaete orb icular is, adisk-shaped charophyte thatlives in ponds (LM)

40 m



Adaptations Enabling the Move to Land

• In charophytes a layer of a durable polymer calledsporopollenin prevents exposed zygotes from

drying out

• Sporopollenin is also found in plant spore walls

• The movement onto land by charophyte ancestors

provided unfiltered sun, more plentiful CO2,

nutrient-rich soil, and few herbivores or pathogens

• Land presented challenges: a scarcity of waterand lack of structural support




• The accumulation of traits that facilitated survivalon land may have opened the way to its

colonization by plants

• Systematists are currently debating the

boundaries of the plant kingdom

• Some biologists think the plant kingdom should be

expanded to include some or all green algae

• Until this debate is resolved, we define plants asembryophytes, plants with embryos




1 m

Figure 29.4

Red algae

Chlorophytes

Charophytes

Embryophytes

ANCESTRALALGA

V i r i d i

pl an t a e S

t r e p t o ph y t a

P l an t a e



Derived Traits of Plants

• Four key traits appear in nearly all land plants butare absent in the charophytes

– Alternation of generations and multicellular,

dependent embryos

– Walled spores produced in sporangia

– Multicellular gametangia

– Apical meristems




Alternation of Generations and Multicellular,Dependent Embryos

• Plants alternate between two multicellular stages,

a reproductive cycle called alternation ofgenerations

• The gametophyte is haploid and produceshaploid gametes by mitosis

• Fusion of the gametes gives rise to the diploidsporophyte, which produces haploid spores bymeiosis




Fi 29 5



1 m

Figure 29.5a

Gamete from

another plant

Key

Haploid (n )Diploid (2n )

Gametophyte(n )

Mitosis Mitosis

Spore Gamete

MEIOSIS FERTILIZATION

Zygote

MitosisSporophyte(2n )

Alternation of generations

2n

n

n n

n

Fi 29 5b



1 m

Figure 29.5b

Embryo

Maternal tissue

Embryo (LM) andplacental transfer cell (TEM)

of Marchant ia (a liverwort)

Wall ingrowths

Placental transfercell (outlined inblue)

10 m

2 m

Fi 29 5b



1 m

Figure 29.5ba

Embryo

Maternal tissue

10 m

Figure 29 5bb



1 m

Figure 29.5bb

Wall ingrowths

Placental transfer

cell (outlined inblue)

2 m



Walled Spores Produced in Sporangia• The sporophyte produces spores in organs called

sporangia

•

Diploid cells called sporocytes undergo meiosisto generate haploid spores

• Spore walls contain sporopollenin, which makes

them resistant to harsh environments


Figure 29 5c



1 m

Figure 29.5c

Spores

Sporangium

Longitudinal section ofSphagnum sporangium (LM)

Sporophyte

Gametophyte

Sporophytes and sporangia of Sphagnum (a moss)

Figure 29 5ca



1 m

Figure 29.5ca

Sporangium

Sporophyte

Gametophyte

Sporophytes and sporangia of Sphagnum (a moss)

Figure 29 5cb



1 m

Figure 29.5cb

Spores

Sporangium

Longitudinal section of

Sphagnum sporangium (LM)



Multicellular Gametangia• Gametes are produced within organs called

gametangia

•

Female gametangia, called archegonia, produceeggs and are the site of fertilization

• Male gametangia, called antheridia, produce and

release sperm


Figure 29 5d



1 m

Figure 29.5d

Female

gametophyte

Male

gametophyte

Archegonia,each with anegg (yellow)

Antheridia

(brown),containingsperm

Archegonia and antheridia of Marchant ia (a liverwort)

Figure 29 5da



1 m

Figure 29.5da

Female

gametophyte

Malegametophyte



Apical Meristems• Plants sustain continual growth in their apical

meristems

•

Cells from the apical meristems differentiate intovarious tissues


Figure 29.5e



1 m

gu e 9 5e

Apical meristemof shoot

Developingleaves

Shoot100 m100 m

Root

Apicalmeristemof root

Apical meristems of plantroots and shoots

Figure 29.5ea



1 m

g

100 mRoot

Apicalmeristemof root

Figure 29.5eb



1 m

g


Developingleaves

Shoot100 m



• Additional derived traits include Cuticle, a waxy covering of the epidermis

Mycorrhizae, symbiotic associations between

fungi and land plants that may have helped plants

without true roots to obtain nutrients

Secondary compounds that deter herbivores and

parasites




The Origin and Diversification of Plants

• Fossil evidence indicates that plants were on landat least 475 million years ago

• Fossilized spores and tissues have been extracted

from 475-million-year-old rocks


Figure 29.6



1 m

(a) Fossilizedspores

Fossilizedsporophytetissue

(b)

Figure 29.6a



(a) Fossilizedspores

Figure 29.6b



Fossilizedsporophytetissue

(b)



•Those ancestral species gave rise to a vastdiversity of modern plants


Figure 29.7



1 m

Origin of land plants (about 475 mya)

Origin of vascular plants (about 425 mya)

Origin of extant seed plants (about 305 mya)

2

1

3

2

1ANCESTRALGREENALGA

500 450 400 350 300 50 0

Millions of years ago (mya)

Liverworts

Mosses

Hornworts

Lycophytes (clubmosses, spikemosses, quillworts)

Pterophytes (ferns,horsetails, whisk ferns)

Gymnosperms

Angiosperms

L an d

pl an t s

V a s c ul ar pl an t s

N onv a s c ul ar

pl an t s

( b r y o ph y t e s )

S e e d l e s s

v a s c ul ar

pl an t s

S e e d

pl an t s

3

Figure 29.7a



1 m

Origin of land plants (about 475 mya)

Origin of vascular plants (about 425 mya)

Origin of extant seed plants (about 305 mya)

3

ANCESTRALGREENALGA

500 450 400 350 300 50 0

Millions of years ago (mya)

Liverworts

Mosses

Hornworts



Gymnosperms

Angiosperms

2

1

1

2

3

Figure 29.7b



1 m

Liverworts

Mosses

Hornworts



Gymnosperms

Angiosperms

L an d

pl an t s

V a s c ul ar pl an t

s

N onv a s

c ul ar

pl an t s

( b r y o ph

y t e s )

S e e d l e s s

v a s c ul ar

pl an t s

S e e d

pl an t s



•Land plants can be informally grouped based onthe presence or absence of vascular tissue

• Most plants have vascular tissue; these constitute

the vascular plants

• Nonvascular plants are commonly called

bryophytes

• Bryophytes are not a monophyletic group; their

relationships to each other and to vascular plantsis unresolved




•Seedless vascular plants can be divided intoclades

– Lycophytes (club mosses and their relatives)

– Pterophytes (ferns and their relatives)

• Seedless vascular plants are paraphyletic, and are

of the same level of biological organization, or

grade




• A seed is an embryo and nutrients surrounded bya protective coat

• Seed plants form a clade and can be divided into

further clades

– Gymnosperms, the “naked seed” plants,

including the conifers

– Angiosperms, the flowering plants


Table 29. 1



1 m



Concept 29.2: Mosses and other nonvascular

plants have life cycles dominated by

gametophytes

• Bryophytes are represented today by three phylaof small herbaceous (nonwoody) plants

– Liverworts, phylum Hepatophyta

– Hornworts, phylum Anthocerophyta

– Mosses, phylum Bryophyta

•

Bryophyte refers to all nonvascular plants,whereas Bryophyta refers only to the phylum ofmosses


Figure 29.UN01



1 m

Nonvascular plants (bryophytes)

Seedless vascular plantsGymnosperms

Angiosperms



Bryophyte Gametophytes

•In all three bryophyte phyla, gametophytes arelarger and longer-living than sporophytes

• Sporophytes are typically present only part of the

time


Figure 29.8-1



Protonemata(n )

Key

Haploid (n )

Diploid (2n )

“Bud”

“Bud”

Male

gametophyte(n )

GametophoreSporesSporedispersal

Peristome

Female

gametophyte(n ) Rhizoid

Sporangium Seta

Capsule(sporangium)

Foot

MEIOSIS

Mature sporophytes

2 m m

Capsule withperistome (LM)

Female

gametophytes

1 m

Figure 29.8-2



Protonemata(n )

Key

Haploid (n )

Diploid (2n )

“Bud”

“Bud”

Male

gametophyte(n )

AntheridiaSperm

Egg

ArchegoniaGametophoreSpores

Sporedispersal

Peristome

Female


FERTILIZATION

(within archegonium)Sporangium Seta

Capsule(sporangium)

Foot

MEIOSIS

Mature sporophytes

2 m m


Femalegametophytes

1 m

Figure 29.8-3



Protonemata(n )

Key

Haploid (n )

Diploid (2n )

“Bud”

“Bud”

Male

gametophyte(n )

AntheridiaSperm

Egg

ArchegoniaGametophoreSpores

Sporedispersal

Peristome

Sporangium

Female


FERTILIZATION

(within archegonium)Zygote(2n )

Archegonium

Embryo

Seta

Capsule(sporangium)

Foot

Youngsporophyte(2n )

MEIOSIS

Mature sporophytes

2 m m


Femalegametophytes

1 m

Figure 29.8a



1 m

2 m

m

Capsule with peristome (LM)



•

A spore germinates into a gametophyte composedof a protonema and gamete-producinggametophore

• The height of gametophytes is constrained by lack

of vascular tissues • Rhizoids anchor gametophytes to substrate

• Mature gametophytes produce flagellated sperm

in antheridia and an egg in each archegonium• Sperm swim through a film of water to reach and

fertilize the egg





Animation: Moss Life Cycle

http://localhost/var/www/apps/conversion/tmp/scratch_10/29_08MossLifeCycle_A.html



Bryophyte Sporophytes

•

Bryophyte sporophytes grow out of archegonia,and are the smallest and simplest sporophytes of

all extant plant groups

• A sporophyte consists of a foot, a seta (stalk),

and a sporangium, also called a capsule, whichdischarges spores through a peristome

• Hornwort and moss sporophytes have stomata for

gas exchange; liverworts do not


Figure 29.9a



1 m

Sporophyte

Thallus

Gametophore of

female gametophyte

Marchant ia polym orph a, a “thalloid” liverwort

Marchantiasporophyte (LM)

Foot

Seta

Capsule(sporangium)

5 0 0 m

Plagioch i la deltoid ea, a“leafy” liverwort

Figure 29.9aa

Gametophore of



1 m

Thallus female gametophyte

Marchant ia polym orpha, a “thalloid” liverwort

Figure 29.9ab



1 m

Marchantiasporophyte (LM)

Foot

Seta

Capsule(sporangium)

5

0 0 m

Figure 29.9ac



1 m

Plagiochi la

deltoidea, a “leafy” liverwort

Figure 29.9b



1 m

An Anthoceros hornwort species

Sporophyte

Gametophyte

Figure 29.9c



1 m

Poly t r ichum commune, hairy-cap moss

Capsule

Seta

Sporophyte(a sturdyplant thattakes monthsto grow)

Gametophyte



The Ecological and Economic Importance

of Mosses

• Mosses are capable of inhabiting diverse and

sometimes extreme environments, but are

especially common in moist forests and wetlands

• Some mosses might help retain nitrogen in the

soil


Figure 29.10



1 mWith moss Without moss

RESULTS

A n n u a l n i t r o g e n l o s s

( k g / h a )

6

5

4

3

2

1

0



•

Sphagnum, or“peat moss,

” forms extensivedeposits of partially decayed organic material

known as peat

• Peat can be used as a source of fuel

• Sphagnum is an important global reservoir oforganic carbon

• Overharvesting of Sphagnum and/or a drop inwater level in peatlands could release stored CO2

to the atmosphere






Figure 29.11b



1 m

“Tollund Man,” a bog mummy dating from405 –100 B.C.E.

(b)



Figure 29.UN03



1 m

Nonvascular plants (bryophytes)

Seedless vascular plants

Gymnosperms

Angiosperms



Origins and Traits of Vascular Plants

•

Fossils of the forerunners of vascular plants dateback about 425 million years

• These early tiny plants had independent,

branching sporophytes

• Living vascular plants are characterized by

Life cycles with dominant sporophytes

Vascular tissues called xylem and phloem

Well-developed roots and leaves


Figure 29.12

Sporangia



1 m



L ife Cycles with Dominant Sporophytes •

In contrast with bryophytes, sporophytes ofseedless vascular plants are the larger generation,

as in familiar ferns

• The gametophytes are tiny plants that grow on or

below the soil surface


Animation: Fern Life Cycle

Figure 29.13-1

http://localhost/var/www/apps/conversion/tmp/scratch_10/29_13FernLifeCycle_A.html



1 m

Key

Haploid (n )

Diploid (2n )

MEIOSISSporedispersal

Maturesporophyte(2n )

Fiddlehead (young leaf)

Sporangium

Sorus

Sporangium

Figure 29.13-2



1 m

Key

Haploid (n )

Diploid (2n )


Spore(n )

Younggametophyte

Rhizoid

Undersideof maturegametophyte(n )

Antheridium

Sperm

Archegonium

Egg

FERTILIZATION



Sporangium

Sorus

Sporangium

Figure 29.13-3



1 m

Key

Haploid (n )

Diploid (2n )


Spore(n )

Younggametophyte

Rhizoid

Undersideof maturegametophyte(n )

Antheridium

Sperm

Archegonium

Egg

FERTILIZATIONZygote(2n )

Gametophyte

Newsporophyte



Sporangium

Sorus

Sporangium

T t i X l d Phl



Transport in Xylem and Phloem

•

Vascular plants have two types of vascular tissue:xylem and phloem

• Xylem conducts most of the water and mineralsand includes dead cells called tracheids

• Water-conducting cells are strengthened by lignin and provide structural support

• Phloem consists of living cells and distributessugars, amino acids, and other organic products

• Vascular tissue allowed for increased height,which provided an evolutionary advantage


E l ti f R t



Evolution of Roots •

Roots are organs that anchor vascular plants• They enable vascular plants to absorb water and

nutrients from the soil

• Roots may have evolved from subterranean stems


E l ti f L



Evolution of Leaves •

Leaves are organs that increase the surface areaof vascular plants, thereby capturing more solar

energy that is used for photosynthesis

• Leaves are categorized by two types

Microphylls, leaves with a single vein

Megaphylls, leaves with a highly branched

vascular system




•

According to one model of evolution, microphyllsevolved as outgrowths of stems

• Megaphylls may have evolved as webbing

between flattened branches


Figure 29.14



1 m

Vascular tissue Sporangia Microphyll

(a) Microphylls (b) Megaphylls

Overtoppinggrowth

Megaphyll

Otherstemsbecomereducedandflattened.

Webbingdevelops.



Figure 29.14b



1 m(b) Megaphylls

Overtoppinggrowth

Megaphyll

Otherstemsbecome

reducedandflattened.

Webbingdevelops.

S h ll d S V i ti



Sporophyl ls and Spore Variations •

Sporophylls are modified leaves with sporangia• Sori are clusters of sporangia on the undersides

of sporophylls

• Strobili are cone-like structures formed from

groups of sporophylls




•

Most seedless vascular plants are homosporous,producing one type of spore that develops into abisexual gametophyte

• All seed plants and some seedless vascular plants

are heterosporous • Heterosporous species produce megaspores,

which give rise to female gametophytes, andmicrospores, which give rise to male

gametophytes






Figure 29.15aa

Selaginella

moel lendorff i i ,



1 m

moellendorff i i ,

a spike moss

1 c m

Figure 29.15ab



1 m

Isoetes

gunni i ,a quillwort

Figure 29.15ac

2.5 cm



1 mDiphasiastrum tr is tachyum,

a club moss

Strobili(clusters ofsporophylls)

Figure 29.15b

Athyr ium Equisetum arvense,

fi ld h il



1 m

f i l ix-femina,

lady fern

field horsetail

Vegetative stem

Strobilus on

fertile stem

Psi lotum

nudum,

a whisk

fern

4 c m

2 5 c m

1 . 5 c m

Figure 29.15ba

Athyr ium



1 m

Athyr ium

fi l ix-femina,

lady fern

2 5 c m

Figure 29.15bb



1 m

Equisetum arvense,field horsetail

Vegetative stem

Strobilus on

fertile stem

1

. 5 c m

Figure 29.15bc



1 m

Psi lo tumnudum,

a whisk

fern

4

c m

Phylum Lycophyta: Club Mosses Spike



Phylum Lycophyta: Club Mosses, Spike

Mosses, and Quil lworts • Giant lycophytes trees thrived for millions of years

in moist swamps

• Surviving species are small herbaceous plants

• Club mosses and spike mosses have vascular

tissues and are not true mosses


Phylum Pterophyta: Ferns Horsetai ls and



Phylum Pterophyta: Ferns, Horsetai ls, and

Whisk Ferns and Relatives • Ferns are the most diverse seedless vascular

plants, with more than 12,000 species

• They are most diverse in the tropics but also thrive

in temperate forests

• Horsetails were diverse during the Carboniferous

period, but are now restricted to the genus

Equisetum• Whisk ferns resemble ancestral vascular plants

but are closely related to modern ferns


The Significance of Seedless Vascular Plants



The Significance of Seedless Vascular Plants

•

The ancestors of modern lycophytes, horsetails,and ferns grew to great heights during the

Devonian and Carboniferous, forming the first

forests

• Increased growth and photosynthesis removedCO2 from the atmosphere and may have

contributed to global cooling at the end of the

Carboniferous period

• The decaying plants of these Carboniferous

forests eventually became coal


Fern Lycophyte trees Horsetail

Tree trunk

covered with

ll l

Lycophyte tree

reproductive

t t

Figure 29.16



small leaves structures

1 m

Figure 29.UN02



1 m

Figure 29.UN04



1 m

Homosporous spore production

Heterosporous spore production

Sporangium

on sporophyllSingle

type of spore

Typically a

bisexual

gametophyte

Eggs

Sperm

Megasporangium

on megasporophyllMegaspore Female

gametophyte

Male

gametophyte

Eggs

SpermMicrosporeMicrosporangiumon microsporophyll

Gametophyte

Mitosis Mitosis


Developingleaves

Figure 29.UN05



Mitosis Mitosis

SporeGamete


Zygote

Mitosis

Sporophyte

Haploid

Diploid

Alternation of generations

4

21

3

Apical meristems

Archegonium

with egg

Antheridium

with sperm

Sporangium Spores

Multicellular gametangia Walled spores in sporangia

n

n n

n

2n

1 m

Figure 29.UN05a



1 m

Gametophyte

Mitosis Mitosis

SporeGamete


Zygote

Mitosis

Sporophyte

Haploid

Diploid

Alternation of generations1

n

n n

n

2n

Figure 29.UN05b



1 m

Apical meristem

of shoot

Developing

leaves

Apical meristems2

Figure 29.UN05c



1 m

Archegoniumwith egg

Antheridiumwith sperm

Multicellular gametangia3

Figure 29.UN05d



1 m

Sporangium Spores

Walled spores in sporangia4

Figure 29.UN06



1 m

Figure 29.UN07



1 m



Figure 29.UN09



1 m

Figure 29.UN10



1 m

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29 Lecture Plant Diversity i