Introduction to Plants
Figure 29.1
Charophytes
Relationship between algae and land plants
Red algae
Chlorophytes
Figure 29.2
Plantae
Embryophytes
Streptophyta
Charophytes
Viridiplantae
ANCESTRAL
ALGA
Green Algae & Plants: shared traits
• Chlorophyll A & B
• Cell walls of cellulos
• Starch as polysaccharide for storage
Charophytes as closest relatives
Shared traits w/ land plants
• Protien rings on cell membrane to make cellulose 30 nm
• Similar sperm (assymetrical arranged flagella)
• Phragmoplasts (microtubule arrangement during mitosis)
• Nuclear and chloroplast DNA similarities
• Some charophytes protect zygote w/ in gametophyte
Derived Traits of Plants
• Five key traits appear in nearly all land plants
but are absent in the charophytes
– Alternation of (heteromophic) generations
– Multicellular, dependent embryos
– Walled spores produced in sporangia
– Multicellular gametangia
– Apical meristems
– Cuticle
– Stomata (except liverworts)
Figure 29.3a
Alternation of generations
Gametophyte
(n)
Mitosis
n
n
Spore
MEIOSIS
Gamete from
another plant
Mitosis
n
n
Gamete
FERTILIZATION
Zygote
2n
Sporophyte
(2n)
Mitosis
Key
Haploid (n)
Diploid (2n)
Figure 29.3b
Multicellular, dependent embryos
Embryo (LM) and placental transfer cell (TEM)
of Marchantia (a liverwort)
Embryo
Maternal
tissue
2 µm
10 µm
Wall
ingrowths
Placental
transfer cell
(blue outline)
Figure 29.3c
Walled spores produced in sporangia
Spores
Sporangium
Longitudinal section of
Sphagnum sporangium (LM)
Sporophyte
Gametophyte
Sporophytes and sporangia of Sphagnum (a moss)
Figure 29.3d
Multicellular gametangia
Female
gametophyte
Archegonia,
each with an
egg (yellow)
Antheridia
(brown),
containing
sperm
Male
gametophyte
Archegonia and antheridia of Marchantia (a liverwort)
Figure 29.3e
Apical meristems
Apical meristem
of shoot
Developing
leaves
Apical meristem
of root
Root
100 µm
Apical meristems of plant roots and shoots
Shoot
100 µm
Figure 29.5
Plant Diversity:
- non-vascular
- seedless vascular
- seed (but no flowers)
- flowering plants (seed + flowers)
Origin of land plants
Mosses
1
Hornworts
Origin of vascular plants
Monilophytes (ferns,
horsetails, whisk ferns)
Gymnosperms
Origin of extant
3 seed plants
Angiosperms
500
450
400
350
300
Millions of years ago (mya)
50
0
Vascular plants
Seedless
Seed
vascular
plants
plants
2
Lycophytes (club mosses,
spike mosses, quillworts)
Land plants
Liverworts
Nonvascular
plants
(bryophytes)
ANCESTRAL
GREEN
ALGA
Table 29.1
Challenges of dry land
• Dryness/relative lack of water
• Gravity (need for support)
Nonvascular plants (24,000 species)
Liverworts, hornworts, & mosses
Nonvascular plants
1. Gameptophyte dominant
2. Dependent sporophyte
3. Flagellated sperm
– Consequences on reproduction?
4. Environment found?
5. Non vascular tissue
– Size?
– Environment found?
Figure 29.6
“Bud”
Sperm
Protonemata
(n)
Antheridia
Male
gametophyte (n)
Key
Haploid (n)
Diploid (2n)
“Bud”
Egg
Spore
dispersal
Spores
Gametophore
Female
Rhizoid
gametophyte
(n)
Peristome
Sporangium
MEIOSIS
Seta
Capsule
(sporangium)
Foot
Capsule with
peristome (LM)
FERTILIZATION
(within archegonium)
Embryo
Zygote
(2n)
Archegonium
2 mm
Mature
sporophytes
Archegonia
Female
gametophyte
Young
sporophyte
(2n)
Animation: Moss Life Cycle
2 mm
Figure 29.6a
Capsule with peristome (LM)
Figure 29.9
(a) Peat being harvested from a peatland
(b) “Tollund Man,” a bog mummy dating
from 405–100 B.C.E.
Seedless Vascular Plants
• Ferns, club mosses, horsetails, wiskferns, etc..
Monilophytes (Phylum Monilophyta)
Strobilus on
fertile stem
Athyrium filix-femina,
lady fern
Equisetum telmateia,
giant horsetail
4 cm
3 cm
25 cm
Vegetative
stem
Psilotum nudum,
a whisk fern
Figure 29.13a
Seedless Vascular Plants: Lycophytes (Phylum Lycophyta)
1 cm
Selaginella
moellendorffii,
a spike moss
Isoetes
gunnii,
a quillwort
Strobili
(clusters of
sporophylls)
Diphasiastrum tristachyum,
a club moss
2.5 cm
Seedless Vascular Plants
• Sprophyte dominant
– Independent gametophyte
• Flagellated sperm
– Impact on reproduction
• Vascular Tissue
– Transport
– Support
Promotes increase in size
Vascular Tissue
• Xylem
– Transports water and minerals (nutrients from
soil)
– Provides support
• Phloem
– Transports sugars
True roots, stems, & leaves
Roots:
• Length via apical meristem
• Contain vascular tissues
• Anchor and absorb
Leaves
• Specialized for photosynthesis
• Microphylls—single vein (of vascular tissue)
• Megaphylls—multiple veins (of vascular tissue)
• Sporophylls—leaves that create/house sporangia
Figure 29.14
Horsetail
Fern
Seed plants: gymnosperms + angiosperms
Seed plant developments
• Pollen
– Distribution (w/o water) and protection of sperm
– Non-flagellated sperm
• Ovule = megasporangium
– Contains egg
– Retained w/ in parent tissue
– After fertilization develops into seed
Seed
•
•
•
•
•
From ovule
Contains embryo (young sporophyte)
Nutrients for embryo
Protects and disperses embryo
Important food source for animals, supported
evolution of faster, larger, more intelligent
organisms.
Figure 30.3-3
Immature
ovulate cone
Integument (2n)
Megaspore (n)
Female
gametophyte (n)
Spore wall
Egg nucleus
(n)
Megasporangium
(2n)
Micropyle
Pollen
grain (n)
(a) Unfertilized ovule
Seed coat
Spore
wall
Discharged
sperm nucleus
(n)
Male
Pollen tube
gametophyte (n)
(b) Fertilized ovule
Food
supply
(n)
Embryo (2n)
(c) Gymnosperm seed
Five Derived Traits of Seed Plants
Reduced
gametophytes
Heterospory
Microscopic male and
female gametophytes
(n) are nourished and
protected by the
sporophyte (2n)
Male
gametophyte
Female
gametophyte
Microspore (gives rise to
a male gametophyte)
Megaspore (gives rise to
a female gametophyte)
Ovules
Integument (2n)
Ovule
(gymnosperm
)
Megaspore (n)
Megasporangium (2n)
Pollen
Pollen grains make water
unnecessary for fertilization
Seeds
Seeds: survive
better than
unprotected
spores, can be
transported
long distances
Seed coat
Food supply
Embryo
Flowering Plants (angiosperms)
Dog rose (Rosa canina), a wild rose
Angiosperm developments
• Flowers
– Promote effective, targeted reproduction
– Transfer of sperm to egg
– Attract w/ sight and smell
– Reward w/ food (pollen and/or nectar)
• Fruit
– Protects and disperses seed more effectively
▼
Tomato
▼
▼
Ruby grapefruit
Nectarine
▼ Hazelnut
▼
Milkweed
Seeds within berries and other
edible fruits are often dispersed
in animal feces.
The barbs of cockleburs facilitate
seed dispersal by allowing the fruits
to “hitchhike” on animals.
Angiosperm Diversity: monocots v. dicots
Embryos
Leaf venation
One
cotyledon
Veins usually
parallel
Stems
Roots
Pollen
Flowers
Pollen grain
with one
opening
Floral organs
usually in
multiples
of three
Taproot
Pollen grain
(main root)
with three
usually present
openings
Floral organs
usually in
multiples of
four or five
Monocot
Characteristics
Root system
Vascular tissue usually fibrous
scattered
(no main root)
Eudicot
Characteristics
Vascular tissue
Two
Veins usually usually arranged
cotyledons
netlike
in ring
PLANT GROUP
Mosses and other
nonvascular plants
Gametophyte Dominant
Sporophyte
Ferns and
other seedless
vascular plants
Reduced,
Independent
(photosynthetic
and free-living)
Reduced, dependent
on gametophyte for Dominant
nutrition
Seed plants (gymnosperms and angiosperms)
Reduced (usually microscopic), dependent on
surrounding sporophyte tissue for nutrition
Dominant
Gymnosperm
Sporophyte
(2n)
Sporophyte
(2n)
Microscopic female
gametophytes (n)
inside ovulate cone
Gametophyte
(n)
Example
Gametophyte
(n)
Microscopic
male
gametophytes
(n) inside pollen
cone
Sporophyte (2n)
Angiosperm
Microscopic female
gametophytes (n)
inside these parts
of flowers
Microscopic
male
gametophytes
(n) inside
these parts
of flowers
Sporophyte (2n)