Biology 1010
Chapter 20
Bryophytes
Bryophytes
► What
are they??
► Where
► What
are they found??
is their evolutionary & ecological
importance??
Points to Ponder
► Differentiate
the bryophyte phyla from each
other and other phyla
► Describe the bryophyte adaptations to
terrestrial environments
► Describe reproduction in bryophyte phyla
► Describe the ecological role of bryophytes
Kingdom Plantae
► Bryophytes:
simplest plants
 Include liverworts, hornworts, mosses
 Fossils from 400 mya
►Molecular
evidence suggests 700 mya
► Economically
important species
 Sphagnum moss from peatlands
►Cool
northern areas: Canada, n. US, Ireland
►Modifies soil to retain H2O, adds organic material
►Fuel source
►Acid pH or antibiotic compounds: aid wound healing
Bryophyte Overview
► Life
on land possible when
 Oxygen level > 2 %
►Present
oxygen level??
 Water can be retained
► Bryophytes
found in moist environments
 Term refers to nonvascular plants
►Formerly
► Now:
one phylum
three phyla
 Each evolved independently
 From the same green algal ancestors
Phylum Hepatophyta
► Liverworts
 6000 spp
► 1st
land plant fossil 450
mya
 Probably liverwort
► Advantages
of land:
 Intense sunlight
 Rocks rich in minerals
Phylum Anthocerophta
►
100 spp
 Hornworts
► Possible
path of
evolution:
 Stranding of green
algae with prior
adaptations
Adaptations include:
vertical stems
underground stems for
H2O & nutrient uptake
Phylum Bryophyta
► 9,600
spp
 Mosses
► Bryophytes
limited to
moist environments
 Sperm requires water
► Just
as amphibians do
 Some can live in dry
sites
► Do
not fossilize well
► Molecular evidence
 700 mya
Bryophyte characteristics
► Nonvascular:
no xylem & phloem
 Restricts size, limits distribution on land
► Gametophytes
have structures
 Resemble stems & leaves
► Without
internal ‘veins’
 Hydroids: conduct H2O
 Leptoids: conduct food
 Thallus: body of a bryophyte
 Rhizoid: anchors bryophyte to substrate
► Absorption
occurs through contact
Bryophytes similar to Charophyceae
& vascular plants
► Classification
of algae &
plants unsettled
 Should reveal phylogeny
► Similarities
between
charophyceae & plants
 Cellulose in cell walls
 Mitotic spindles remain
during cytokinesis
 Pigments:
► Phytochrome,
carotenoids,
Chla, b,
 Thylakoids stacked in
grana
Bryophytes similarity to plants
► Characteristics
land
that enhance survival on
 Protect gametes and spores
►Sterile
cells protect structures producing male and
female gametes
►multicellular embryo protected within female
parent
►Multicellular, diploid sporophyte meiosis → spores
►Sterile cells protect multicellular sporangia
► Natural
selection guided bryophyte
evolution from green algae differently than
plants
Bryophyte
Alternation of Generations
►
Gametophyte dominant
 Haploid
 Gametangia: mitosis →
gametes
► Antheridia: male
► Archegonia: female,
egg
►
►
Sporophyte attached to
gametophyte
one
 Depends on gametophyte for its
nutrition
 Diploid
 Meiosis → haploid spores in
sporangium
Spore germinates → protonema
Bryophyte Asexual Reproduction
► All
3 phyla can
reproduce by
fragmentation
► Reproduce through
specialized brood
bodies
 Gemmae
 bulbils
Ecological roles of Bryophytes
► Plant
succession
 Mosses colonize rock surfaces, crevices
►→ soil
 Rhizoids secrete acid to dissolve rock
 Bodies add organic matter, collect dust
►Seeds
► Epiphytic
germinate in these pockets
mosses:
 Grow in tropical and temperate rain forest
trees
► Important
in tundra
 NOT “reindeer moss” = lichen
Bryophytes tolerate drought
► Liverworts
into tube
may roll
 Protects upper surface
► Tortula
spp
 Moss can dehydrate
 Produce mRNA
► Codes
for protein to
repair damage
 Rehydration →
resumption of
photosynthesis
P. Hepatophyta
= liverworts
► Earliest
land plants?
 Closely related to green
algae
 Lack DNA characteristic of
other bryophytes, plants
► Horizontal,
mosses
flatter than
 Leaves usually thin, flat
► Categories:
 Thalloid or leafy
Liverwort life cycle
► Gametophyte
dominant
 Marchantia
 Lobed gametophyte large
► Rhizoids
penetrate soil
► Antheridia & archegonia
elevated
► Antheridiophore
flattened, bears
antheridia, catch rain
drops
► Archegoniophore
suspends archegonia
beneath tops
 Sporophyte inconspicuous
► Zygote
in archegonium
► Forms spores
P. Anthocerophyta
= hornworts
► Conspicuous
hornshaped sporophytes
 Stomata with guard
cells: new feature
► Gametophytes
to liverworts
similar
 Rumpled, green sheet
 N-fixing bacteria
symbionts
Hornwort life cycle
► Gametophyte
form antheridia
 Become visible when sterile cells dry & break
► Archegonia
form from surface cells
 Thallus cells surround egg
 Fertilization → zygote with ‘horn’
►Sporophyte foot anchors it to gametophyte
 Gametophyte provides water, minerals, some food
►Sporophyte grows from its base not its apex
 photosynthetic as in liverworts, NOT mosses
►Produces
spores from apex of sporangium to base
P. Bryophyta
= mosses
► bryophytes
refers to ALL nonvascular plants
► P. Bryophyta = scientific classification





Mosses usually with a leafy thallus
Vertical gametophyte
Usually in moist, forested sites, wetlands
Sometimes in deserts, dry rock outcrops
Some aquatic
Class Spagnopsida
aka Sphagnidae
► 150
spp, peat mosses
► Sheet like protonema
 Dead cells with thick walls
hold water
 spherical sporangia attach
to stalks of gametophytes
Class Andreaeopsida
= granite or rock mosses
► 100
spp
► Live at high altitudes
► Cold, temperate sites
► Live on rock, snow, ice
► Sporangia with four
slits allow dispersal of
spores
Class Bryopsida
aka Bryidae
► 9,000
spp
► Common mosses
► Growth patterns vary





May grow in clumps
As pendulous epiphytes
May remain filamentous
May be seasonal
May grow on polluted soil
Life cycle of Polytrichum
► Typical
moss life cycle
 Dominant gametophyte
► Survives
drought
► Originates from spore
 Spore → protonema
► Bud
→ gametophyte leaf
 → Antheridia &/or
archegonia
► Water
→ fertilization
 Zygote develops in
archegonium
 → sporophyte with setae
►
foot absorbs food
Questions
► Thought
and Discussion
►2
►4
► Evolution
Connection