Mosses

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Mosses

• Kingdom Plantae
• Phylum Bryophyta
• Class Muscopsida

Eukaryotic Cellulose and Pectin Cell walls Open
mitosis, phragmoplast cytokinesis Chloroplasts
with chlorophyll a, b xanthophylls,
carotenoids Starch storage Diplohaplontic
(sporic) life history Homosporous
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The green plant is the moss gametophyte
(haploid). It uses chlorophyll a and b,
xanthophylls, and carotenoids for
photosynthesis. It produces starch for storage of
photosynthate.
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The gametophyte can live in creek beds and dry
forests
http//upload.wikimedia.org/wikipedia/commons/thum
b/4/47/Leucobryum_glaucum_2.jpg/800px-Leucobryum_g
laucum_2.jpg
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While many tell about mosses needing lots of
water, mosses can live on bare rock with
virtually no soil. It is true that they need some
rainfall to complete the life cycle and produce
the sporophytes (tan color) shown
here. Nevertheless they can tolerate long periods
of desiccation.
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Talk about a difficult climate, here are mosses
living on a glacier!
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These haploid green moss gametophytes have
produced gametes some time ago. The sperm found
their way to the egg and syngamy took
place. These tan structures are the sporophytes
that grow from the zygote. The diploid sporophyte
is dependent upon the haploid gametophyte for
photosynthetic products.
http//www2.lubw.baden-wuerttemberg.de/public/abt2
/dokablage/oac_168/typ_02/0201703_1.jpg
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The morphology of gametophyte and sporophyte
assist in moss taxonomy. Meiosis takes place
inside the capsule
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The product of meiosis in the moss capsule is
this haploid spore
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The moss spore is a complete haploid cell with
normal plant cell structure. Cell Wall Cell
Membrane Nucleus Chloroplast Mitochondrion Vacuole
Cytosol The cell wall is waterproofed with
sporopollenin to avoid desiccation
http//www.informaworld.com/ampp/image?path/71364
8917/743910100/sgra_a_155555fig003.gif
What process is just finishing in the extremely
large chloroplast?
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After distribution on wind to a new environment
into good conditions, the spore wall cracks open
for germination into a haploid gametophyte
produced by mitosis only.
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http//www.cbe21.com/subject/biology/photo/0305050
1/1008/Young20protonema.jpg
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The spore cell divides mitotically to produce a
haploid multicellular gametophyte. It is
initially filamentous with bright green
chlorplasts and gives every appearance of a green
alga. The terms onotogeny recapitulates
phylogeny comes to mind! This filamentous plant
body is called the protonema and the
chloronema depending upon how far away in time
from germination one is looking.
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Moss protonemata in prepared slides just dont
look so nice. The cell wall picks up the
blue-green dye, masking the normal phenotype of
these cells. But you can see the true branching.
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When moss chloronemata run into bad conditions,
bulbils can be produced to endure the climate
until better conditions return.
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In good conditions, the moss chloronema can
produce parenchyma that organizes into a shoot
with leaves. You should notice the spiral
phyllotaxy.
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A longitudinal section of a moss stem (axis)
shows cortex cells at the far left-edge. Cells
with red walls and simple pits are called
hydroids. The red-staining material is not
lignin, so these cells cannot be called
xylem. Cells with blue walls and blue cytoplasm
conducting photosynthate through the plant are
called leptoids. Are mosses vascular? Ross YES
THEY ARE!
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Polytrichum stem cross section
Epidermis Cortex Hydroids Leptoids
http//www.botany.ubc.ca/bryophyte/6170.jpg
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Moss gametophyte axes has spirally-arranged
phyllids
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The moss phyllid has a midrib, and expanded
blade, and margins
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http//en.wikipedia.org/wiki/FilePlagiomnium_affi
ne_laminazellen.jpeg
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Moss leaves have differing leaf anatomy
Mnium
Polytrichum
cutinized terminal cells
photosynthetic filaments
cutinized lower epidermis
mesophyll
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http//upload.wikimedia.org/wikipedia/commons/thum
b/1/19/Polytrichum_commune_assimilationslamellen.j
peg/250px-Polytrichum_commune_assimilationslamelle
n.jpeg
http//www-biol.paisley.ac.uk/bioref/Bryophyta/Pol
ytrichum_leaf_TS2.jpg
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Polytrichum male gametophytes have a splash cup
of leaves containing antheridia that produce sperm
The first drop fills the cup. Water causes the
sperm to shed into that first drop. Subsequent
drops cause the sperm-water to splash out.
http//www.lamedon.de/moosbilder/images/polytrichu
m_f02.jpg
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Longitudinal section through splash cup reveals
many antheridia
all tissues here are haploid!
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Bryophyte spermatozoid
http//www.biology.duke.edu/bryology/LiToL/Images/
Liverwort20Life20Cycle/Blasia.sperm.jpg
Sketch by K. Renzaglia
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Polytrichum female gametophytes lack the splash
cup
The terminal phyllid tufts include the archegonia.
http//upload.wikimedia.org/wikipedia/commons/thum
b/3/30/Polytrichum_juniperinum.jpg/800px-Polytrich
um_juniperinum.jpg
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archegonium
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The moss sporophyte develops at expense of the
gametophyte
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haploid calyptra shrouds the diploid capsule
(sporangium) within
Developing sporophytes show at least some green
color.
diploid seta
haploid phyllids shroud the embedded diploid foot
haploid gametophytes
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Exploded view of Polytrichum sporophyte and
gametophyte
calyptra
cutinized epidermis
capsule
cortex
seta
leptoids hydroids
foot
gametophyte
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Polytrichum capsule (sporangium) longisection
All these diploid sporophyte cells initially
surrounded diploid sporocytes. The sporocytes
were diploid cells that underwent meiosis. Each
sporocyte produced four haploid cells that
develop desiccation resistant walls to become
spores
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When the calyptra and cap desiccate and abscise
the operculum is exposed. The peristome teeth are
revealed.
The peristome teeth respond to humidity to shed
spores only in dry air for dispersal
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The peristome teeth can be used to help identify
moss species
Genus Tetraphis
Genus Tortula
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Funaria peristome teeth are attached to a small
diaphragm and twist like Venetian blinds to
release spores
Atrichum peristome teeth are attached to a wide
diaphragm and lift the diaphram in dry air to
release spores.
http//farm2.static.flickr.com/1341/1152673291_6e6
4d9e9db.jpg?v0
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http//stapper.monheim.de/orthotrichum20pulchellu
m.jpg
http//www.stapper.monheim.de/ortpat_BLAM.jpg
Orthrotrichum patens
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The peristome teeth reflex like the petals of a
flower and are colorful. The sterile jacket
shrinks downward revealing the columella. The
spores are brightly colored and sticky (insect
dispersed).
Splachnum is a dung moss
Splachnaceae Moss Apophysis Color Dung Collected
Haplodon wormskjolffi Brown purple Human, lemming
Splachum ampullaceum Light Purple Reindeer, moose, cattle, sheep
Splachnum luteum Yellow Reindeer, moose
Splachnum rubrum Dark red Reindeer, moose
Splachnum ovatum Dark purple Cattle
Splachnum vasculosum Dark purple Sheep, reindeer
Tayloria longicollis Brownish green Human
Tetraplodon ongustatus Light brown Carnivores
Tetraplodon mnioides Purplish black Sheep, reindeer, yak
Data from Bequaert (1921), Crum (1972), Iwatsuki
Steere (1975), Koponen Koponen (1978), Nyholm
(1954), Steere (1973), Watson (1955).
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Splachnum rubrum/luteum growing on moose dung
http//i2.tinypic.com/t8xc1e.jpg
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Tetraplodon mnioides growing on moose dung
http//rbg-web2.rbge.org.uk/bbs/meetings/mtgs03ima
ges/TETRAPLODON4.jpg
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Tayloria mirabilis growing on cattle dung
http//www.mun.ca/biology/pmarino/t_mirabilis_chil
e.jpg
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The phyllid color difference here has to do with
water in empty cells rather than air refracting
light.
Sphagnum moss sporophytes (shown attached to
gametophytes) explode to blast their spores into
the air.
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Longitudinal section of a Sphagnum sporophyte
drying out
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Sphagnum moss gametophytes with attached
sporophytes
unshed
shed
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Physcomitrium capsules open into a cup-like form
The pyriform (pear-shaped) capsule opens. The
peristome flares out to form a funnel-like
opening Air moving across the peristome lifts dry
spores into the air for dispersal. This is a
Bernouilli effect.
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When is a moss not a moss?
These hanging plants are often called Spanish
moss. The plant is not a bryophyte. It produces
small flowers and small fruits. The plant is a
relative of pineapple and bromeliads. Tillandsia
usneoides is the name of this flowering plant.