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Chapter 29. Plant Diversity I How Plants Colonized Land. Land plants evolved from Charophytes ( Chara ) green algae . 4 key traits plants share with Charophytes (Morphological and Biochemical Evidence): 1. Rose-shaped complexes for cellulose synthesis 2. Peroxisome enzymes - PowerPoint PPT Presentation
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Plant Diversity I How Plants Colonized Land
Chapter 29
Plants vs. Algae • Land plants evolved from Charophytes (Chara)
green algae
• 4 key traits plants share with Charophytes (Morphological and Biochemical Evidence):
1. Rose-shaped complexes for cellulose synthesis2. Peroxisome enzymes3. Structure of flagellated sperm4. Formation of a phragmoplast
5 key traits in nearly all land plants but are absent in the charophytes:
1. apical meristems 2. multicellular dependent embryos3. alternation of generations 4. walled spores produced in sporangia5. multicellular gametangia
females – archegonia & males – antheridia
Fig. 29-5e
Apicalmeristemof shoot
Developingleaves
Apical meristems
Apical meristemof root Root100 µm 100 µmShoot
Fig. 29-5b
EmbryoMaternal tissue
Wall ingrowthsPlacental transfer cell(outlined in blue)
Embryo (LM) and placental transfer cell (TEM)of Marchantia (a liverwort)
2 µm
10 µm
Fig. 29-5a
Gametophyte(n)
Gamete fromanother plant
n
n
Mitosis
Gamete
FERTILIZATIONMEIOSIS
Mitosis
Sporen
n
2n Zygote
Mitosis
Sporophyte(2n)
Alternation of generations
Fig. 29-5c
SporesSporangium
Sporophyte
Longitudinal section ofSphagnum sporangium (LM)
Gametophyte
Sporophytes and sporangia of Sphagnum (a moss)
Fig. 29-5d
Female gametophyte
Malegametophyte
Antheridiumwith sperm
Archegoniumwith egg
Archegonia and antheridia of Marchantia (a liverwort)
Fig. 29-7
Origin of land plants (about 475 mya)1
2
3
1
2
3
Origin of vascular plants (about 420 mya)
Origin of extant seed plants (about 305 mya)
ANCES-TRALGREENALGA
Liverworts
Hornworts
Mosses
Lycophytes (club mosses,spike mosses, quillworts)
Pterophytes (ferns,horsetails, whisk ferns)
Gymnosperms
Angiosperms
Seed plantsSeedlessvascularplants
Nonvascular
plants(bryophytes)
Land plants
Vascular plants
Millions of years ago (mya)500 450 400 350 300 50 0
Characteristics of all land plants:• eukaryotic, multicellular, autotrophic• cell walls made mostly of cellulose• chlorophylls a & b• Domain Eukarya, Kingdom Plantae
In many plants, additional terrestrial adaptations, such as vascular tissues and secondary compounds, also evolved.
Nonvascular plants
1. Represented by three phyla:a. phylum Hepatophyta – liverwortsb. phylum Anthocerophyta – hornwortsc. phylum Bryophyta - mosses
Liverworts
HornwortsMoss
Fig. 29-9a
ThallusGametophore offemale gametophyte
Marchantia polymorpha,a “thalloid” liverwort
Marchantia sporophyte (LM)
Sporophyte
FootSeta
Capsule(sporangium)
500
µm
• gametophyte - mass of green, branched, one-cell-thick filaments• sporophytes are smaller; only present part of the time• spores germinate in favorable habitats
sporophyte
gametophyte
sporophyte
gametophyte
2. The gametophyte is the dominant generation in the life cycle
Fig. 29-8 The life cycle of a moss.
KeyHaploid (n)Diploid (2n) Protonemata
(n)
“Bud”
“Bud”
Malegametophyte(n)
Femalegametophyte (n)
Gametophore
Rhizoid
Spores
Sporedispersal
Peristome
SporangiumMEIOSIS Seta
Capsule(sporangium)
Foot
Maturesporophytes
Capsule withperistome (SEM)
Femalegametophytes
2 m
m
Raindrop
Sperm
Antheridia
Egg
Archegonia
FERTILIZATION(within archegonium)
Zygote(2n)
Embryo
Archegonium
Youngsporophyte(2n)
3. Bryophyte sporophytes disperse enormous numbers of spores
• sporophytes remain attached to gametophyte throughout the lifetime– depends on the gametophyte for sugars, amino acids, minerals and
water.
• sporangium (site of meiosis and spore production) can generate over 50 million spores.
4. Bryophytes provide many ecological and economic benefits
• distributed worldwide• common and diverse in moist forests and wetlands• Some common in extreme environments (mountaintops,
tundra, and deserts)
• Sphagnum, a wetland moss, is especially abundant and widespread.• forms extensive deposits of undecayed organic material,
called peat• Wet regions dominated by Sphagnum or peat moss are known
as peat bogs
Fig. 29-11
(a) Peat being harvested
(b) “Tollund Man,” a bog mummy
Bog People
THE ORIGIN OF VASCULAR PLANTS1. Two conducting tissues of the vascular system
A. Xylem – Dead tissue, water-conducting
B. Phloem –Living tissue, food-transporting
2. Water-conducting cells are strengthened by lignin and provide structural support
3. Sporophyte generation is dominant in vascular plants.
Seedless vascular plants4. Two modern phyla:
a. phylum Lycophyta – club mossesb. phylum Pterophyta - ferns, whisk ferns, and horsetails
Club moss
Horsetail
Whisk fern
Fern
Fig. 29-15a
Lycophytes (Phylum Lycophyta)
Selaginella apoda,a spike moss
Isoetesgunnii,a quillwort
Strobili(clusters ofsporophylls)
2.5 cm
Diphasiastrum tristachyum, a club moss1 cm
Fig. 29-15e
Pterophytes (Phylum Pterophyta)Athyriumfilix-femina,lady fern
Vegetative stem
Strobilus onfertile stem
1.5
cm
25 c
m
2.5
cm
Psilotumnudum,a whiskfern
Equisetumarvense,fieldhorsetail
5. Most seedless vascular plants are homosporous, producing one type of spore that develops into a bisexual gametophyte• both archegonia (female sex organs) and antheridia (male sex
organs) • Eg., ferns
sporophyteSingle type of spore
Bisexual
gametophyte
eggs
sperm
Fig. 29-13 The life cycle of a fern.
KeyHaploid (n)Diploid (2n)
MEIOSISSporedispersal
Sporangium
SporangiumMaturesporophyte(2n)
Sorus
Fiddlehead
Spore(n)
Younggametophyte
Maturegametophyte(n) Archegonium
Egg
Antheridium
Sperm
FERTILIZATIONNewsporophyte
Gametophyte
Zygote(2n)
6. seedless vascular plants are most common in damp habitats 7. ferns produce clusters of sporangia, called sori, on the back
of leaves
Seedless vascular plants formed vast “coal forests” during the Carboniferous period• These plants left not only living representatives
and fossils, but also fossil fuel in the form of coal.
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