Chapter 26: The Plant Kingdom:
Seedless Plants
Charophytes
•
•
•
•
Green algae
Closest ancestor to plants
Evidence
Charales and Coleochaetes
Fig. 29-3
5 mm
Chara species, a pond organism
Coleochaete orbicularis, a
disk-shaped charophyte that
also lives in ponds (LM)
40 µm
Features of Charophytes that promoted
evolution of multicellular land plants
• 1) Cellulose synthesizing complexes nearly
identical (during cell wall formation)
• 2) Apical cells – allow filaments to increase in
length
• 3) Plasmodesmata – communication between
neighboring cells
• 4) Both retain and care for zygote
Adaptations to Life on Land
• Cuticle
– Waxy, aerial, prevents desiccation
• Stomata
– Pores on surface of leaves, stems  Gas exchange
• Gametangia
– Multicellular sex organs
– Embryo develops within female gametangium
(protected)
7 Characteristics of Plants
•
•
•
•
•
•
•
Multicellular, eukaryotic
Photosynthetic
Waxy cuticle
Terrestrial
Stomata and guard cells
Complex fertilization
Cell walls of cellulose and lignin
Alternation of Generations
• Switch between haploid and diploid
– Both multicellular
– Dominant generation
• Haploid (n) = gametophyte
– Mitosis – haploid gametes
– Antheridia – sperm
– Archegonia - egg
• Diploid (2n) = sporophyte
– Meiosis – haploid spores
• Zygote (sperm + egg)  multicellular embryo (in
archegonium)
Fig. 29-5b
2 µm
Embryo
Maternal tissue
Wall ingrowths
Placental transfer cell
(outlined in blue)
Embryo (LM) and placental transfer cell (TEM)
of Marchantia (a liverwort)
10 µm
Fig. 29-5a
Gametophyte
(n)
Mitosis
n
n
Spore
MEIOSIS
Gamete from
another plant
Mitosis
n
n
Gamete
FERTILIZATION
2n
Mitosis
Sporophyte
(2n)
Alternation of generations
Zygote
• Fertilization  zygote  embryo mature
sporophyte  sporogenous cells  meiosis
 spores  mature gametophyte 
archegonia or antheridia  egg/sperm
Check your Understanding
• 1. What are the benefits of a lands existence
for plants?
• 2. What traits are shared by both charophytes
and land plants?
• 3. What is the role of each generation in the
alternation of generations life cycle?
4 Major Plant Groups
• Bryophytes
– Small, nonvascular, seedless, use haploid spores
• Ferns
– Seedless, vascular, spores
• Gymnosperms
– Vascular, seeds (unprotected)
• Angiosperms
– Vascular, flowering, seed in a fruit
Fig. 29-7
1 Origin of land plants (about 475 mya)
2 Origin of vascular plants (about 420 mya)
3 Origin of extant seed plants (about 305 mya)
Hornworts
1
Mosses
Pterophytes (ferns,
horsetails, whisk ferns)
3
Angiosperms
450
400
350
300
Millions of years ago (mya)
50
0
Seed plants
Gymnosperms
Vascular plants
2
Seedless
vascular
plants
Lycophytes (club mosses,
spike mosses, quillworts)
500
Land plants
ANCESTRAL
GREEN
ALGA
Nonvascular
plants
(bryophytes)
Liverworts
Mosses and other Bryophytes
•
•
•
•
Nonvascular – so small
Mosses, liverworts, hornworts
Moist environment – growth and reproduction
3 phyla
– Bryophyta
– Hepaticophyta
– Anthocerotophyta
Mosses - Bryophyta
• Dense colonies or beds
• Individual plant
– Rhizoids (absorb)
– Upright, stem like
– Leaf like blades
• No true roots, stems or leaves
• Alternation of generations
• 3 groups: peat moss, granite moss, true moss
Fig. 29-9d
Polytrichum commune,
hairy-cap moss
Capsule
Seta
Sporophyte
(a sturdy
plant that
takes months
to grow)
Gametophyte
Fig. 29-8-3
Raindrop
Sperm
“Bud”
Male
gametophyte
(n)
Key
Haploid (n)
Diploid (2n)
Antheridia
Protonemata
(n)
“Bud”
Egg
Spores
Gametophore
Archegonia
Female
gametophyte (n)
Spore
dispersal
Rhizoid
Peristome
FERTILIZATION
Sporangium
MEIOSIS
Mature
sporophytes
Seta
Capsule
(sporangium)
Foot
(within archegonium)
Zygote
(2n)
Embryo
2 mm
Archegonium
Capsule with
peristome (SEM)
Young
sporophyte
(2n)
Female
gametophytes
Moss Gametophyte
Moss spores
Moss protonema
Fig. 29-9a
Thallus
Gametophore of
female gametophyte
Sporophyte
Foot
Seta
Marchantia sporophyte (LM)
500 µm
Marchantia polymorpha,
a “thalloid” liverwort
Capsule
(sporangium)
Moss importance
• Ecological
– Form soil, prevent erosion
– Rainforest beauty
• Commercial
– Peat moss (sphagnum)
• Absorb and hold water
• Soil conditioner – add to sand
• Fuel source – if dried
Fig. 29-11a
(a) Peat being harvested
Liverworts - Hepaticophyta
• Dominant gametophyte
• Thallus – body – flattened, lobed
– No leaves, stems, roots
– Resemble lobes of liver
– Underside – rhizoids – anchor
– No stomata – some surface pores
• Others
– Leafy liverworts – no lobes
THALLOID Liverwort
Fig. 29-9b
Plagiochila
deltoidea,
a “leafy”
liverwort
Basics of liverwort life cycle
• Sexual - Similar to mosses
• Asexual
– Form gemmae in gemmae cup
Hornworts - Anthocerotophyta
•
•
•
•
Inconspicuous thalloids
Disturbed habitats – fallow fields, roadsides
Cell structure – single chloroplast
Sporophyte projects out of thallus like horn
Fig. 29-9c
An Anthoceros
hornwort species
Sporophyte
Gametophyte
Lycophytes: Vascular Tissue
• Seedless vascular plants
– Stems, roots, leaves
•
•
•
•
•
Conducting cells
Lignin
Cooksonia = rhyniophyte
Microphylls
Club mosses
Club mosses - Lycophyta
• Coal deposits
• True roots, rhizomes, aerial stems
– Short, erect branches
• Evergreen
Fig. 29-15a
Lycophytes (Phylum Lycophyta)
2.5 cm
Isoetes
gunnii,
a quillwort
Strobili
(clusters of
sporophylls)
1 cm
Selaginella apoda,
a spike moss
Diphasiastrum tristachyum, a club moss
Lycophyte
CYU
• 1. Name two features of lycophytes significant
to the evolution of land plants.
Seedless Vascular Plants – Pterophyta
(Pteridophytes)
• Ferns, horsetails, whisk ferns
• Adaptations
– Vascular – xylem and phloem
• Support
• Conduction
• larger
– Most – true roots, stems, leaves
– Megaphylls
Ferns
• Most abundant – warm, tropics
• True roots, stems, leaves
• Fronds
Fig. 29-15f
25 cm
Athyrium
filix-femina,
lady fern
Fig. 29-13-3
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Spore
dispersal
Spore
(n)
Sporangium
Sporangium
Antheridium
Young
gametophyte
Mature
gametophyte
(n)
Archegonium
Egg
Mature
sporophyte
(2n)
New
sporophyte
Zygote
(2n)
Sorus
Gametophyte
Fiddlehead
FERTILIZATION
Sperm
Fern Sorus
Fern – Older sporangium
Fern germinating
Fern Gametophyte
CYU
• How is the life cycle of a fern different from
the life cycle of a moss?
Whisk ferns - Psilotophyta
• Simplest vascular
– Stems –
• horizontal underground
• Vertical aerial - photosynthesize
• Lack true roots, leaves
• Dichotomous branching – stem divides into 2
equal halves
Fig. 29-15h
2.5 cm
Psilotum
nudum,
a whisk
fern
Horsetails - Sphenophyta
• Ancient – coal deposits
• Wet, marshy
• True roots (rhizome), stems (aerial), small
leaves
– Hollow, jointed stems – silica – gritty
– Scouring rushes – pots/pans
Fig. 29-15g
Equisetum
arvense,
field
horsetail
Vegetative stem
1.5 cm
Strobilus on
fertile stem
Horsetail
• Homospory – meiosis produces 1 type of spore
• Heterospory – meiosis produces 2 different spore
types: microspores and megaspores
• Microsporangia – produce microsporocytes 
meiosis  haploid microspores  male
gametophyte  sperm cells in antheridia
• Megasporangia – make megasporocytes 
meiosis  haploid megaspores  female
gametophyte  eggs in archegonia
Fig. 29-UN3
Homosporous spore production
Sporangium
on sporophyll
Single
type of spore
Typically a
bisexual
gametophyte
Eggs
Sperm
Heterosporous spore production
Megasporangium
on megasporophyll
Megaspore
Female
gametophyte
Eggs
Microsporangium
on microsporophyll
Microspore
Male
gametophyte
Sperm
You should now be able to:
1. Describe four characteristics of plants
2. Distinguish between the phylum Bryophyta and
bryophytes
3. Diagram and label the life cycle of a bryophyte
4. Explain why most bryophytes grow close to the
ground and are restricted to periodically moist
environments
5. Explain how vascular plants differ from bryophytes
6. Distinguish between homosporous and
heterosporous
7. Diagram and label the life cycle of a seedless
vascular plant