+
Chapter 18
Evolution of Plants and Fungi
+
18-2
Plant Characteristics:

Contain chlorophylls a and b and various accessory pigments

Store excess carbohydrates as starch

Have cellulose in their cell wall

Meristem tissue


Plasmodesmata


Openings that allow for passage
Protection of zygote


Produces new cells / organs
Pass nutrients and keep from drying out
Alternation of generations

Sporophyte vs gametophyte
+
18-3
Plants have an alternation of
generations life cycle

2 multicellular individuals alternate, each producing the other

Sporophyte represents the diploid generation (2n)


Produces spores by meiosis

spore is a haploid reproductive cell that develops into a new
organism without needing to fuse with another reproductive cell

spore undergoes mitosis to become a gametophyte
Gametophyte represents the haploid generation (n)

Produces gametes

In plants, eggs and sperm are produced by mitosis

A sperm and egg fuse, forming a diploid zygote that undergoes
mitosis and becomes the sporophyte
+
18-4
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sporophyte (2n)
sporangium (2n)
zygote (2n)
diploid (2n)
FERTILIZATION
haploid (n)
MEIOSIS
spore (n)
(n)
gametes
(n)
gametophyte (n)
+ size of the gametophyte is progressively reduced as the
18-5
sporophyte becomes more dominant
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spores
G
a
m
e
t
o
p
h
y
t
e
(n)
seed
spores
seed
roots
roots
roots
rhizoids
rhizoids
Moss
Fern
Gymnosperm
Angiosperm
S
p
o
r
o
p
h
y
t
e
(2n)
+
18-6
Sporophyte anatomy

Cuticle

Impermeable

Barrier to water loss


Also to gas exchange
Stomata

Openings to allow for gas exchange
+
18-7
Embryophta – land plants

Nonvascular

Bryophytes

Vascular (tracheophytes)

Seedless

Mosses

Lycophytes

Hornworts

Ferns

Liverworts

Seeds

Gymnosperms

Angiosperms (Flowering
plants )
+
18-8
Bryophytes

Hornworts, liverworts, and mosses

Prefer damp shaded areas

Form a mat on ground

Turn brown when dry but becomes green when watered again

First plants to colonize land

Successfully reproduce on land


protect the embryo and produce wind-blown spores
No true roots, stems, or leaves – no vascular tissue

Non-vascular plants
+
18-9
Bryophytes

Bryophyte reproduction

Gametophyte is the dominant generation

Female gametophyte produces eggs in archegonia

Male gametophyte produces flagellated sperm in antheridia

Following fertilization, the zygote becomes a sporophyte

Sporophyte attached to, and derives its nourishment from, the
photosynthetic gametophyte
+
1810
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developing
sporophyte
3 Developing sporophyte:
The sporophyte embryo
is retained within the
archegonium, where
it develops, becoming a
mature sporophyte.
4
The sporophyte:
The dependent sporophyte has a foot buried in female
gametophyte tissue, a stalk, and an upper capsule (the
sporangium), where meiosis occurs and windblown spores
are produced.
Sporangium
Mitosis
Sporophyte
stalk
zygote
diploid (2n)
FERTILIZATION
MEIOSIS
haploid (n)
2
Fertilization:
Flagellated sperm
produced in
antheridia swim in
external water to
archegonia, each
bearing a single egg.
Spores
egg
sperm
Mitosis
foot (n)
5
Archegonia
archegonium
buds
Spore dispersal:
Spores are released
when they are most
likely to be
dispersed
by air currents.
Antheridia
1 The mature
gametophytes:
In mosses, the
dominant
gametophyte shoots
bear either antheridia
or archegonia, where
gametes are
produced by mitosis.
6
antheridium
Gametophytes
(top): © Peter Lilja/Getty Images; (bottom): © Steven P. Lynch
The immature
gametophyte:
A spore germinates
into the first
stage of the male
and the female
gametophytes.
+
1811
Vascular Plants

Have vascular tissue

Xylem transports water



Contain lignin to strengthen cell walls
Phloem transports nutrients
First vascular plants were like Cooksonia

Rhyniophyte that flourished during Silurian period

No roots or leaves

Example of seedless vascular plant

Like lycophytes and ferns
+
Transport begins in both the
leaves and the roots of plants

Xylem
 Carries water and minerals from the roots to the
leaves
 Contain 2 types of nonliving conductive cells
 Tracheids
 allow water to pass between
 Vessel elements
 perforation plates at each end
 form a completely hollow pipeline from roots to
leaves
2212
+
Transport begins in both the
leaves and the roots of plants

Phloem
 Transports sugar to all parts of the plant
 Composed of several cell types
 Sieve-tube members
 living conducting cells, contain cytoplasm but
have no nucleus
 Companion cells
 provide proteins to sieve-tube members

Water is a large part of xylem sap and phloem sap
2213
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water
sugar
xylem
phloem
stoma
O2 CO2
H2O
Phloem is transporting sugar
from the leaf to the root.
sugar
H2O
A plant΄s transport system
blue = phloem;
pink =sugar;
red = xylem;
light blue = water
+
1815
Lycophytes

Lycophytes or club mosses

True stems, leaves, and roots

Leaves are microphylls

Only 1 strand of vascular tissue

Sporophyte is dominant, as it is in all vascular plants

Today there are 3 groups

Ground pines (Lycopodium)

Spike mosses (Selaginella)

Quillworts (Isoetes)
1816
+
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sporangia
strobili
leaves
(microphylls)
sporophyll
Strobilus
stoma
branches
vascular tissue
Leaf
xylem
aerial stem
rhizome
root
Root
phloem
+
1817
Ferns
seedless
plants
Have
vascular
megaphylls
 Broad
leaves with
several strands of
vascular tissue
 Allow plants to
collect more solar
energy
+
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
branched
vascular tissue
single strand of
vascular tissue
a. Microphyll
Megaphyll
One branch began to
dominate the stem system.
branched
stem system
The side branches flattened
into a single plane.
Tissue filled in the spaces
between the side branches.
megaphyll
leaf
b. Megaphyll evolution process
Microphylls and megaphylls
18-18
+
1819
Ferns
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Whisk ferns

Psilotum and
Tmesipteris

Epiphytes


Plants that live on/in
trees
sporangium
scale
No leaves
aerial stem
root
rhizome
(Left): © CABISCO/Phototake
+
Ferns
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Ferns

11,00 species

Megaphylls called
fronds

Leaves first appear as
fiddleheads

2 generations separate
and independent
spores on
fertile frond
Cinnamon fern, Osmunda cinamomea
frond
(undivided)
frond
(divided)
axis
leaflet
Hart’s tongue fern
Campyloneurum scolopendrium
Maidenhair fern,
Adiantum pedatum
(cinnamon fern): © James Randklev/Getty Images; (hart's tongue): © Walter H. Hodge/Peter
Arnold/Photolibrary; (maidenhair): © Jeff Foott/Getty Images
18-20
+
Fern life cycle
1821
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
The sporophyte:
The sporophyte is
dominant in ferns.
Sori
Sporophyte
frond
6
Young sporophyte:
The sporophyte
embryo develops
inside an
archegonium.
As the distinctive
first leaf appears
above the
gametophyte, and
as the roots
develop below it,
the young sporophyte
becomes visible.
Dryopterus
leaflet
sporangium
Sorus
young sporophyte
on gametophyte
fiddlehead
2
The sporangia:
In this fern, the
sporangia are
located within sori
(sing., sorus) on
the underside of
the leaflets.
3
The spores:
Within a
sporangium,
meiosis occurs
and spores are
produced. When a
sporangium opens,
the spores are
released.
roots
Mitosis
zygote
Sporangium
diploid (2n)
FERTILIZATION
MEIOSIS
haploid (n)
5 Fertilization:
Fertilization takes
place when
moisture is
present, because
the flagellated
sperm must swim
in a film of water
from the antheridia
to eggs within
archegonia.
egg
sperm
Spores
Archegonium
Mitosis
germinating
spore
4
Antheridium
Gametophyte
(Top right): © Matt Meadows/Peter Arnold/Photolibrary
The gametophyte:
A spore germinates into a
heart-shaped gametophyte,
which typically bears archegonia
at the notch and antheridia at the
tip between the rhizoids.
+
1822
Seed Plants

Evolution of the seed was the next significant innovation in the
evolution of plants

Gymnosperms and angiosperms are seed plants

Seed


contains a sporophyte generation, along with stored food, within a
protective seed coat
Ability of seeds to survive harsh conditions until the
environment is again favorable for growth largely accounts for
the dominance of seed plants today
+
1823
Gymnosperms

Seeds are naked

Diversity of Gymnosperms



Four groups of living gymnosperms: cycads, ginkgoes, gnetophytes,
and conifers
All have ovules and develop seeds that are exposed on the surface
of cone scales or analogous structures
Conifers


Consist of about 575 species of trees
 Many are evergreens such as pines, spruces, firs, cedars and
hemlocks
Economic Value of Conifers
 Wood of conifers is used extensively in construction
+
1824
Pine life cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
5
The sporophyte
embryo:After
fertilization, the
ovule matures and
becomes the seed
composed of the
embryo, reserve
food, and a seed
coat. Finally, in the
fall of the second
season, the seed
cone, by
now woody and
hard, opens to
release winged
seeds. When
a seed germinates,
the sporophyte
Sporophyte
seed
Seed cones
Pollen cones
Ovule
Pollen sac
sporophyte
embryo
seed coat
seed cone scale
stored food
pollen cone scale
Seed
zygote
Fertilization:
Once a pollen grain
reaches a seed cone,
it becomes a mature
male gametophyte.
A pollen tube digests
its way slowly
toward a female
gametophyte and
discharges
nonflagellated sperm.
The fertilized
egg is
a zygote.
The seed cones:
The seed cones are
larger than the pollen
cones and are located
near the tips of higher
branches.
wing
Mitosis
4
The pollen cones:
Typically, the pollen
cones are quite small
and develop near the
tips of lower
branches.
microspore
mother cell
megaspore
mother cell
MEIOSIS
MEIOSIS
2
Megaspores:
Megaspore mother cell
in ovule undergoes
meiosis to produce
megaspores.One
megaspore will
become the
egg-producing
diploid (2n)
FERTILIZATION
haploid (n)
Pollen grain
Microspores
Mature female gametophyte
Mitosis
egg
Megaspores
Microspores:
Microspore mother
cells undergo meiosis
to produce
microspores. Each
microspore becomes a
pollen grain.
Pollination
ovule
wall
Ovule
Mitosis
Mature male gametophyte
pollen grain
pollen tube
sperm
200 µm
3
The pollen grain:
The pollen grain has two wings and is carried by the
wind to the seed cone during pollination
(Bottom right): © Phototake
+
1825
Angiosperms

Seeds are covered

Angiosperms are flowering plants


Evolved some 200 MYA

Innovations are flower and fruit

240,000 known species

Ovules always enclosed within sporophyte tissue
Angiosperm Diversity

Monocotyledones (or monocots) – One cotyledon

Eudicotyledones (or eudicots) – Two cotyledons

Cotyledons – seed leaves with nutrients that nourish the embryo
+
2126
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terminal bud
petiole
axillary bud
leaf blade
stem

Shoot system – stem,
branches, leaves, and
flowers (organs of
sexual reproduction)

Root system – main
root and its branches
node
internode
node
Shoot system
Root system
lateral
branch
root
root
hairs
primary
root
root tip
vascular tissues
(xylem and phloem)
+
2127
Flowering plants typically have
roots, stems, and leaves
 Roots

3 main functions
Anchor plant in soil
2. Absorb water and minerals from soil
3. Produce hormones
Some also store food
1.

Root hairs increase surface-to-volume
ratio
 Tap roots vs. fibrous roots

+ Taproot system (left) versus fibrous root system (right)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Taproot
Fibroous root system
(taproot): © Jonathan Buckley/Getty Images;; (fibrous root): © The McGraw-hill companies Inc./Evelyn Jo Johnson, photographer
2128
+
2129
Flowering plants are either
monocots or eudicots


Monocots have one cotyledon

Root vascular tissue rings pith

Vascular bundles scattered in stem

Leaf veins are parallel

Flower parts in multiples of three
Eudicots have two cotyledons

Root phloem between arms of xylem

Vascular bundles in a distinct ring

Leaf veins form a net pattern

Flower parts in multiples of four or five
2130
+Monocots and eudicots differ structurally in several ways
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Seed
endosperm
Stem
Root
phloem
Leaf
Flower
pith
Monocots
axillary bud
One cotyledon in seed
xylem
Root xylem and
phloem in a ring
Vascular bundles
scattered in stem
Leaf veins form
a parallel pattern
Flower parts in threes
and multiples of three
xylem
pith
Eudicots
axillary bud
Two cotyledons in seed
phloem
Root phloem between
arms of xylem
Vascular bundles
in a distinct ring
Leaf veins form
a net pattern
Flower parts in fours or
fives and their multiples
+
Fruits and Seeds

Advantage of fruit

Fruits of flowers aid in dispersal of seeds

Eaten by animals


Then transport seeds
Advantage of seeds

Dry environment

129 years!!

Endosperm of seed provide nourishment

Helps new plant until photosynthesis begins
1831
+
1832
Generalized flower
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
stigma
anther
filament
style
stamens
ovary
ovule
carpel
receptacle
petals (corolla)
sepals (calyx)
pollen
tube
Flowering plant life cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Stamen
anther
filament
6 The sporophyte embryo:
The embryo within a seed
is the immature sporophyte.
When a seed germinates,
growth and differentiation
produce the mature
sporophyte of a flowering
plant.
5 The seed:
The ovule now develops into
the seed, which contains an
embryo and food enclosed
by a protective seed coat.
The wall of the ovary and
sometimes adjacent parts
develop into a fruit that
surrounds the seed(s).
stigma
style
ovary
ovule
The carpel:
The ovary at the base of a
carpel contains one or more
ovules. The contents of an
ovule change during the
flowering plant life cycle.
1 The stamen:
An anther at the top of each
stamen has four pollen sacs.
Mitosis
stigma
receptacle
Sporophyte
fruit
(mature ovary)
seed
(mature ovule)
style
Anther
Carpel
ovule
ovary
seed coat
pollen
sac
sporophyte embryo
endosperm (3n)
microspore
mother cell
Seed
diploid (2n)
FERTILIZATION
haploid (n)
(mature male gametophyte)
4 Double fertilization:
On reaching the ovule, the
pollen tube discharges the
sperm. One of the two sperm
migrates to and fertilizes the
egg, forming a zygote; the
other unites with the two
polar nuclei, producing a 3n
(triploid) endosperm nucleus.
The endosperm nucleus
divides to form endosperm,
food for the developing plant.
Carpel
ovule wall
polar nuclei
sperm
egg
megaspore
mother cell
MEIOSIS
Pollen grain
MEIOSIS
Pollination
Microspores
pollen
tube
sperm
Megaspores
polar nuclei
pollen tube
degenerating
megaspores
egg
Double Fertilization
Ovule
Embryo sac
(mature female gametophyte)
3 The mature male gametophyte:
A p[ollen grain that lands on the carpel of the same type
of plant germinates and produces a pollen tube,
which delivers two nonflagellated sperm to the female
gametophyte. A fully germinated pollen grain is the
mature male gametophyte.
The mature female gametophyte:
The ovule now contains the mature female
gametophyte (embryo sac), which typically consists of
eight haploid nuclei embedded in a mass of cytoplasm.
The cytoplasm differentiates into cells, one of which is
an egg and another of which contains two polar nuclei.
2 Microspores:
Microspore mother cells undergo meiosis to produce
microspores. Each microspore becomes a pollen grain.
Megaspores:
Megaspore mother cell inside ovule undergoes meiosis to
produce megaspores. One megaspore will become the
egg-producing female gametophyte.
18-33
+
2234
Adaptations of plants help them
acquire nutrients


Root Nodules

Some plants, such as legumes, soybeans, and alfalfa, have roots
colonized by Rhizobium bacteria

Rhizobium can reduce atmospheric nitrogen (N2) to NH4+ for
incorporation into organic compounds
Mycorrhizae

Involves fungi and almost any type of plant root

Fungus increases the surface area available for mineral and water
uptake and breaks down organic matter in soil
+
Mycorrhizae result in better growth
2235
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Mycorrhizae present
Mycorrhizae not present
mycorrhizae
(plants, top): © Runk/Schoenberger/Grant Heilman Photography; (mycorrhizae, circle): © Dana Richter/Visuals Unlimited
2236
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
+

dodder
(brown)
© Kevin Schafer/Corbis
Parasitic plants,
such as dodders,
broomrapes, and
pinedrops, send
out rootlike
projections called
haustoria that tap
into the xylem and
phloem of the
host stem
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
+
2237
bulbs release
digestive enzymes

Carnivorous
plants, such as the
Venus flytrap and
the sundew, digest
insects as a
source of nitrogen

By-pass need for
nitrates from soil
which may be
lacking
Sundew leaf
enfolds prey
sticky
hairs
narrow
leafform
(sundew leaf, prey): © Dr. Jeremy Burgess/Photo Researchers, Inc .
+
Fungi
Fungi
+
–
Yeasts and molds
•
–
Mushrooms
•
–
–
Multicellular, macroscopic
Cell nucleus and other cellular
structures
Absorb nutrients from their
environment
–
–
Single-celled, microscopic
Saprobes
Widely distributed in water and soil
+
1840
Fungi
 Thermal
dimorphism

grow as molds at 30°C

Grow as yeasts at 37°C
Fungal Organization - Mold
 Fungal

Cell Structure
Hyphae
 Mycelium
Conidia / spores
 Sexual and asexual
reproduction
 Cell walls contain chitin
 Energy reserve is glycogen
 Nonmotile
 Produce wind-blown spores
 Grow toward food source

Fungal Organization

Yeasts

Soft, uniform texture and
appearance
Unicellular (bicellular)
 False hyphae
 Beta-glycan cell wall
structure

+
1843
Fungi have mutualistic relationships
with algae and plants

In a mutualistic relationship, two different species live together
and help each other out

Mycorrhizal fungi form mutualistic relationships (mycorrhizae) with
the roots of most plants


Helps plants grow more successfully in dry or poor soils
particularly those deficient in inorganic nutrients
Lichen – a mutualistic association between a particular fungus and
a cyanobacteria or green algae

Fungal partner is efficient at acquiring nutrients and moisture

Organic acids given off by fungal partner can be used by
photosynthetic partner
+
1844
Land fungi occur in three main
groups

Zygospores

Ascospores

Basidiospores
1845
+
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4
zygospore
3
FERTILIZATION
2n
n
MEIOSIS
Sexual
reproduction
5

Zygospore Fungi
sporangium

Mainly saprotrophs,
but some are
parasites
1
–
Asexual
reproduction
2
germinating
spores
+
mycelium
(top left): © Runk/Schoenberger/Grant Heilman Photography
Black bread mold,
Rhizopus stolonifer
1846
+
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Sac Fungi

Nearly 75% of all
described fungal
species

Name from ascus

Yeast – unicellular
forms mainly in
Ascomycota

No more
Deuteromycota – use
molecular data
ascocarp
ascocarp
Cup fungi
nuclear
fusion zygote
Morel
ascospores
(2n) meiosis
mature
ascus
dikaryotic
hyphae
+ mating type (n)
spore
– mating type (n)
spore
male organ
female organ
Ascocarp of the cup fungus Sarcoscypha
(cup fungi): © Felix Labhardt/Getty RF; (morel): © Robert Marien/Corbis RF
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
+
1847
nuclei in
basidium
fusion meiosis
spores

gill of
mushroom
basidiocarp
Sexual reproduction
+
Club Fungi

Name comes from the
reproductive structure, the
basidium

The basidia are located
within a basidiocarp

When you eat a mushroom,
you are eating a basidiocarp
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1848
Land Fungi Have Economic
and Medical Importance
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Economic Importance

Help produce medicines and many foods


Mold Penicillium was original source of penicillin

Excellent low-calorie meat substitute containing lots of vitamins

Fungal pathogens are a major concern for farmers
Medical Importance

Certain mushrooms are poisonous

Mycoses are diseases caused by fungi

Candida albicans

Ringworm

Aspergillus