Transcript BIO509 Lecture #11 File

School of Sciences, Lautoka Campus
BIO509 Botany Lecture 11:
Bryophytes
Bryophytes are considered
the most primitive form of the land plants and
are
often conspicuous in moist, terrestrial habitats
Are they really plants?
Phylum Hepaticophyta –
Liverworts
Phylum Anthocerophyta –
Hornworts
Phylum Bryophyta – Mosses
Learning outcomes
• Know the distinguishing features of Kingdom
Bryophytes.
• Understand how bryophytes are similar and different
to higher plants.
• Learn the distinguishing features between liverworts,
hornworts and mosses.
• Know the reproductive structures and lifecycle of a
moss.
• Understand and appreciate the human and ecological
significance of bryophytes.
Bryophytes
• About 23,000 species of bryophytes.
• Include mosses, liverworts, and hornworts.
• Habitats range in elevation from sea level up
to 5,500 meters or more.
• Small, low-to-the-ground plants, moist
shaded habitats.
• Bryophytes of all phyla often have
mycorrhizal fungi associated with their
rhizoids.
General characteristics of Bryophytes
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Major pigments (chlorophylls a and b)
Starch as reserve food product
Cellulose in cell walls
Waxy cuticle
Stomata
Lack a true vascular system
Lack true roots, have rhizoids.
General reproduction
• Mostly sexual reproduction although
asexual forms occur.
• Gametangia protected from desiccation.
• Sperms are the only flagellated cells.
• Embryos are formed.
• Distinct alternation of generations
•The gametophyte is the conspicuous
and dominant generation.
• The gametophyte is nutritionally
independent.
•The sporophyte remains attached to
the gametophyte, and is nutritionally
dependent on it.
All bryophytes have similar life cycles and
habitat.
They are differentiated based on their
structure and reproduction.
Phylum Hepaticophyta – Liverworts
Herbalists thought bryophytes with flattened liver
shaped lobes were useful for treating diseases.
Liverworts
• About 8000 species.
• Most common is flattened, lobed
(‘leaf-like’) thallus.
• Leafy stage is the gametophyte.
• Liverworts lack conducting
elements, a cuticle and stomata.
•Have distinct upper and lower
surfaces.
•One-celled rhizoids that function
in anchorage on the lower surface.
•When spores germinate they may
produce immature gametophyte
(protonema).
•The gametophyte can be
“thallose” or “leafy”
Leafy liverworts
Thalloid liverworts
(Thalloid liverworts)
• Best known species are in the genus Marchantia.
• Thick thallus that forks dichotomously as it grows.
• Consists of parenchyma cells with few, if any,
chloroplasts.
• Upper surface of the thallus has polygon shaped
segments with small boarded pores.
Section of Marchantia Thallus
Reproduction in Marchantia
Sexual
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Male and female gametophores produce antheridia and
archegonia.
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Flagellated sperm fertilize egg in archegonium.
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Embryo (immature sporophyte) develops.
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Sporophyte consists of foot, seta, and capsule.
• Meiosis takes place in the capsule.
• Capsule decays and spores aided
in their release by spiral shaped
elaters.
Asexual
Production of gemmae cups separate
that from parental
thallus and grow into new liverwort.
Male thallus
Female thallus
Marchantia Sporophyte
Asexual Reproduction of Marchantia
Leafy Liverworts
• Always have two rows of partially overlapping “leaves”
whose cells contain distinctive oil bodies.
• Often have folds and lobes.
• Archegonia and antheridia are produced in cup-like
structure.
• At maturity, sporophyte capsule may be pushed out as
the seta elongates.
• Germinating spore produces a protonema.
Phylum Anthocerophyta - Hornworts
Hornworts
• About 100 known species.
• Mature sporophyte looks
like miniature, green cattle
horn.
• Gametophyte look like
flimsy versions of
liverworts.
• Occur in moist, shaded
areas.
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Have only large chloroplast in each cell.
Have rhizoids.
Each chloroplast has a pyrenoid.
Have extensive internal cavities that are
inhabited by cynobacteria that fix nitrogen.
Sexual reproduction.
• Archegonia and antheridia are produced in
rows just beneath the upper surface of the
gametophyte.
• Following fertilization the
sporophyte grows by
increasing length.
• The rod-like sporophyte has
stomata.
• Meiosis occurs within the
sporophyte and spores
produced are released
through splits in sporophyte.
Phylum Bryophyta
Three different classes
Peat moss
true moss
rock moss
Mosses
• About 15,000 species.
• “Leaves” of moss gametophyte are one cell
thick and lack mesophyll tissue, stomata or
veins.
• Leaves are spirally arranged on axis
resembling stem.
• Axis lacks xylem and phloem but has
hydroids and leptoids for conducting food
and water.
Moss reproduction
Sexual reproduction
Male and female gametangia are produced at tips of leafy
gametophytes.
Sperm are flagellated and reach archegonium by swimming in a
film of water.
Sporophyte develops in base of
archegonium and grows into a foot,
seta, and a capsule.
Calyptra sits on top of capsule.
Meiosis takes place in the capsule
producing spores.
Peristome teeth at rim of capsule aid in
dispersal of spores.
Operculum
Peristome
Spores germinate on moist soil and
develop into an algal-like protonema
Protonema develops tiny "leafy" buds
which will produce the upright
gametophytes
Asexual reproduction
Fragments of leaves, stems, and rhizoids can
develop protonema.
Pieces of a Gametophyte can break off & form
new moss plants (fragmentation)
Human and ecological relevance
• Pioneer Species of primary succession, rapidly
colonize bare or burned soil and accumulating organic
matter.
• Contribute to humus formation.
• Reduce flooding and erosion.
• Few mosses are a problem to water reservoirs
clogging the pipes.
• Used for packing and stuffing.
Peat mosses are important to
humans
Peat mosses belong to class Sphagnidae that
contains only one genus Sphagnum.
The Sphagnum sporophyte is different from
that of all other mosses, forming a red or black
sphere raised up on a pseudopodium.
Has unusual protonema (disk shaped).
Explosive operculum mechanism for spore
dispersal.
Peat mosses have impressive water holding capacity.
A number of species are able to hold 20 or more times their
own weight in water
• Sphagnum-dominated peatlands covers more of
the world's land surface than any other single
plant genus.
• Peatlands store large amounts of organic carbon
that is not readily decayed by microorganisms.
• Peat is formed fro accumulation and compression
of mosses, sedges, grass and other plants
growing among them.
Sphagnum sp.
Forms extensive peat bogs in
northern
latitudes (arctic regions) around
world
• Because of its extraordinary water holding
capacity, it is useful for soil conditioning.
• Used as seafood packaging material. Live
shellfish and other organisms are shipped
in peat moss. It is naturally acidic so
prevents bacterial and fungal growth
• Has antibacterial properties and is used
for wound dressings .
• During the production of Scotch whiskey,
barley is dried over using peat moss smoky flavour for whiskey
http://www.sciencedaily.com/releases/2010/04/100427111453.htm
Questions are
welcome?