Transcript Lab 5 - Mosses and Ferns

Lab #5
Mosses & Ferns
Non-Vascular & Vascular Seedless
Plants
• major division of plants into: non-vascular & vascular
– non-vascular plants are known collectively as the “bryophytes”
– divided into:
• the mosses (Phylum Bryophyta)
• the liverworts (Phylum Hepatophyta)
• the hornworts (Phylum Anthocerophyta)
• vascular plants can be divided into: seedless and seedbearing
• seedless plants are the “lycophytes” and the “pterophytes”
– Division Lycophyta – club mosses
– Division Pterophyta – ferns, horsetails and whisk fers
• the seed bearing plants are divided into:
– the gymnosperms – non-flowering plants
– the angiosperms – flowering plants
• alternation of generations:
alternating between a
multicellular haploid structure
(gametophyte) and a
multicellular diploid structure
(sporophyte)
• alternating between a
gametophyte stage and a
sporophyte stage
Plant Life
Cycles
** as plants evolve there is an
increasing importance of the
sporophyte over the gametophyte
Mitosis
• main steps:
– 1. haploid spore undergoes mitosis to produce the haploid gametophyte
– 2. gametophyte grows and produces male and female reproductive
structures via mitosis – antheridium & archegonium
• artheridium produces sperm, archegonium produces an egg
• egg fertilized by sperm to produce a diploid zygote
– 3. zygote undergoes mitosis to grow into a diploid sporophyte
– 4. sporophyte undergoes meiosis to produce haploid spores
– 5. back to step #1
Plant reproduction terms
• sporophyte (diploid) = spore producing plant that bears
sporangia (singular = sporangium)
• sporangium = structure that produces haploid spores by
meiosis
• spores (haploid) = released cells that will grow via mitosis to
generate a gametophyte
• gametophyte (haploid) = multicellular structure that bears
male and female gametangia (singular = gametangium)
• gametangium (haploid) = multicellular structure for the
production of male and female gametes via mitosis
• archegonium (haploid) = female gametangium that produces
an egg
• antheridium (haploid) = male gametangium that produces
multiple sperm
Non-vascular plants (bryophytes)
• bryophytes = ancient group of non-vascular plants that
share a common ancestor
– ancestor – 475 million years old
• have not given rise to any other living group of plants
– but they still exist today!!
• lack the vascular tissues – xylem & phloem
• gametophyte is still the dominant form of the life cycle
– what we identify as the “plant”
• Phylum Bryophyta
• Phylum Hepatophyta
• Phylum Anthocerophyta
Mnium hornum
Phylum
Bryophyta
Sphagnum
peat moss
• mosses
• gametophyte stage of the life cycle
– thallus (heart-shaped) body
– bears male and female gametophores
with gametangia
– gametophore – leafy shoots of the
moss gametophyte
– thallus anchored to the substrate via
rhizoids
• root-like structures – NOT true roots
• multiple cells that form up end to end
to produce a filament
• non-photosynthetic
• do NOT absorb nutrients and water
• anchorage only
Phylum
Bryophyta
Non-vascular plants
• non-vascular mosses are not to be confused with the vascular
club mosses = lycophytes
• some mosses are NOT mosses at all – Irish moss (red seaweed),
reindeer moss (lichen)
Bryophyte General Life Cycle: The Gametophyte
• dominant stage in all bryophytes
• release of spores onto favorable habitat
• the spore germinates into a threadlike protonema – covers a large surface area
for absorption or water and minerals
• protonema grows into a haploid gametophyte
• each protonema produces a bud with an apical meristem (stem-cell like tissue for
growth)
– the AM develops into the gamete producing gametophyte
– the leafy shoots of the moss gametophyte are called gametophores
– the tips of the gametophore bear the male or female gametangia
the gametophyte of mosses
is the actual moss!!
Bryophyte General Life Cycle : The Gametophyte
• reproductive structures of the gametophyte = gametangia (singular =
gametangium)
• multiple gametangia develop on each gametophyte
– some bryophytes are bisexual – both antheridium and archegonium on the
same gametophyte plant = monoecious
• e.g. liverwort bryophyte
– most moss bryophytes have separate antheridium and archegonium located
on separate gametophytes on separate plants = dioecious
• “male and female” moss plants
• production of the gametes by mitosis since the gametophyte is haploid already!!!
Bryophyte General Life Cycle : The Sporophyte
• fertilization of the egg is followed by development of the embryo
within the archegonium
• the embryo develops into a sporophyte (diploid) - remains
attached to the gametophyte via a foot – for absorption of
nutrients
moss
• sporophyte stage –
dependent upon the
bryophyte gametophyte
– food and water passed to it
via transfer cells
– transfer cells found in
between the sporophyte and
the gametophyte in a
“placenta-like” tissue
The
Sporophyte
– anatomical features:
• 1. seta – stem-like structure organ
connecting sporangium to the
gametophyte
• 2. foot – base of the seta
• 3. sporangium – site of spore
production
– opening = operculum
• 4. calyptra – surrounds and
protects the sporangium
– may be bald or hairy
Moss
Sporophyte
Polytrichum commune
hairy cap moss
calyptra around the sporangium
stem (seta)
SPOROPHYTE
GAMETOPHYTE (leafy shoot)
GAMETOPHYTE
Bryophyte General Life Cycle : The Sporophyte
• haploid spores develop in the sporangium via meiosis since the sporangium is
diploid
• the spores are dispersed and settle onto a new substrate
• from these spores comes new protonemata (singular = protonema)
• hornwort and moss sporophytes tend to be large and more complicated
• liverwort sporophytes are microscopic
liverwort
hornwort
moss
Phylum Hepatophyta
• liverworts
• share some similarities with mosses but there are some distinct differences –
gametophyte and sporophyte form
• gametophyte can be found as either leafy or thalloid (depending on species)
– thallus has no stems or leaves
• thallus gametophyte – can be 1 to 2 cells thick or multicellular with tissue
differentiation
– rhizoids are unicellular (like mosses) –elongated single cells often covered with scales – role in
anchorage only
– many thalloid forms have gemmae cups for asexual reproduction
Phylum Hepatophyta
• leafy gametophyte – can look a lot like the gametophyte of
mosses
– very small leaves (about 1cm long) - arranged as two rows along the sides of
the stem
– rhizoid is very similar to the moss rhizoid
leafy gametophyte
thallus gametophyte
Marchantia Gametophyte
• Marchantia gametophyte is made up of broad shaped leaves = thallus
• growing out of the gametophyte are stalked structures - called gametophores
– “palm-tree female” & “umbrella male”
• since both of these are found on the same sporophyte plant = monoecious
the gametophyte of
the liverwort
is the actual liverwort!!
Archegonium
with egg
Female gametophore
Female gametophore
antheridium
gametangium with
sperm
Male gametophore
Antheridium
with sperm
Male gametophore
Archegonia and antheridia
of Marchantia (a dieocious
liverwort)
egg
archegonium gametangium
• male gametophore looks like a “patio
umbrella” that grows up from the
gametophyte/liverwort
• male gametangia (antheridia) found
embedded in the top surface of the
gametophore
• several antheridia clustered onto an
antheridial head or receptacle
Male
Gametophyte
female gametophore
male
antheridium
Female
Gametophyte
• female gametophore
looks like a palm tree
growing up from the
gametophyte/liverwort
• female gametangia
(archegonia) found
“dangling” underneath
• archegonium = venter
with an egg + tubular
neck
The Liverwort Sporophyte
• in the liverwort – the fertilized egg in the archegonium becomes the embryo
• the embryo develops into the diploid sporophyte
• sporophyte is attached to the female gametophore by a seta and a foot
– the sporophyte is small and “dangles” off the female gametophore like “coconuts”
• end is the sporangium – contains haploid spores formed by meiosis
Sporophyte
• forms after the egg in the archegonium is fertilized
–
–
–
–
comprised of a foot, seta and a “dangling” sporangium
sporagngium is attached to the female gametophore by the foot and a seta
spores are expelled out all at once (unlike mosses)
presence of elaters with contract and expand with humidity to expel the
spores
– once the spores are dispersed, the liverwort sporophyte withers away
(unlike mosses)
Female Gametophore
with archegonia
500 µm
Foot
Seta
Sporangium
Marchantia polymorpha,
a “thalloid” liverwort
Marchantia sporophyte (LM)
Marchantia Asexual reproduction
• some uprisings are called gemmae cups –
contain asexual gemmae – discs of green
tissue that when dispersed generate new
gametophytes
– develop by mitosis from the gametophyte
gemmae cups & cross
section
Phylum Anthocerophyta: Hornworts
An Anthroceros
hornwort species
Sporophyte
Gametophyte
The Economics of Moss
• mosses have very lightweight spores- easy
distribution & the establishment of mosses
around the globe
• very common and diverse in moist forests
and wetlands
• can help retain nitrogenous compounds in
the soil via their relationships with
cyanobacteria
• many species can survive drought and
rehydrate
• one wetland moss = Sphagnum or “peat
moss”
– peat moss = partially decayed remnants of
Sphagnum
– major component of partially decayed
organic material called peat
– 3% of Earth’s surface are peatlands
• peat contains 30% of world’s soil carbon
• 450 billion tons of carbon is stored as peat
Sphagnum moss
Vascular, Seedless Plants
• divided into two big groups
• 1. ferns, whisk ferns, horsetails – Division Pterophyta
• 2. club mosses, quillworts, spike mosses – Division Lycophyta
– called mosses – but they have vascular tissues!!!!
• limited adaptations have restricted many seedless plants to
limited ranges
• have vascular tissue for the conducting of water and nutrients
and metabolites
– similar to the xylem and phloem of seed bearing trees
• only economically important seedless vascular plant is the
fern
Vascular, Seedless Plants
• life cycle is alternation of generations
– the sporophyte is the dominant plant
– the gametophyte is reduced in size – independent of the sporophyte
and is restricted to moist habitats
• still retain flagellated sperm – needs moisture for
reproduction
• well developed leaves and roots, stomata and structural
support tissue
• most species are homosporous
• produce only one type of spore that gives rise to a
haploid, monoecious gametophyte (via mitosis)
Phylum Lycophyta
• 5 existing genera:
– Lycopodium & Phylloglossum (club mosses)
– Selaginella (spike mosses)
– Isoetes and Stylites (quillworts)
Golden club moss
Selaginella
(spike moss)
Quillwort
Isoetes
Division Lycophyta
•
•
•
•
•
club mosses, spike mosses and quillworts
1200 species today
NOT true mosses since they have vascular tissue
most ancient line of vascular plants
modern lycophytes grow on tropical trees as
epiphytes – BUT they are NOT parasites
Strobili
(clusters of
sporangia)
epiphytic ferns
Diphasiastrum tristachyum, a club moss
• club mosses –sporangia are
clustered on strobili (cones)
– strobili look like “clubs”
– strobilus are made up of clusters
of modified leaves called
sporophylls
– sporophylls bear spore-producing
sporangia
– 200 living species
– most inhabit moist environments
– microphylls (leaves) are spirally
arranged
– most are homosporous
– common example:
• Lycopodium – 95 species
– dried spores are flammable due
to fat content and are used as
flash powder in magic acts
Division
Lycophyta
Strobili
(clusters of
sporophylls)
Diphasiastrum tristachyum,
a club moss
Division
Lycophyta
• spike mosses
– e.g. Selaginella lepidophylla
– resurrection plant
– found in the desert as a
dormant plant until
moisture increases
– heterosporous – two types
of spores
Selaginella lepidophylla
a spike moss
• megaspores produce the
female gametophyte via
mitosis
• microspores produce the
male gametophyte via mitosis
Selaginella canaliculata
a spike moss
Selaginella strobili
Lycopodium strobili
megaspores
microspores
Strobili with
sporangia
Division
Lycophyta
• quillworts
– e.g. Isoetes qunnii
– 60 species within the genus
– wet, muddy areas
– heterosporous
– almost every leaf bears a
sporangia
Isoetes
gunnii,
a quillwort
Division Pterophyta
• ferns, whisk ferns & horsetails
• used to be three separate phyla
– Phylum Sphenophyta – horsetails
– Phylum Psilophyta – whisk ferns
– Phylum Pterophyta - ferns
• molecular biology now places them in one
group = Division Pterophyta
Division Pterophyta
• horsetails = Equisetum
– Phylum Arthrophyta – “jointed plants”
– 15 living species
– rings of small leaves or branches can
emerge from each joint
– stem is the main photosynthetic organ
– strobilus is comprised of multiple
sporophylls bearing specialized sporangia
– each sporangium clustered together on an
umbrella-shaped structure =
sporangiophore
– sporangiophores are arranged in a
compact spiral = strobilus
sporangiophore - Equisetum
strobilus
Division
Pterophyta
• whisk ferns
– dichotomously branching stems
but no roots
– homosporous with spores that
give rise to bisexual
gametophytes that grow
underground
– sporangia are called synangia
• look like three sporangia that
have fused
– considered to be living fossils
due to their resemblance to
fossils of ancient vascular plants
Division Pterophyta
• ferns – 12,000 species
– fern is the sporophyte
– sporophyte is comprised of underground,
horizontal stems called rhizomes
– from these come vertical shoots that give
rise to large leaves called fronds divided
into pinna (or leaflets)
– frond grows as the fiddlehead
– mature frond is called the megaphyll
– megaphyll is a compound leaf with a
center rachis and multiple pinna
– the pinna itself may be may up of small
pinnules
– part of the rachis without pinna = stalk
(connects the frond to the rhizome)
– some fern species – e.g. staghorn fern –
have a simple leaf structure
fronds
rhizome
rhizoids
Division Pterophyta
• fern gametophyte:
• is called the prothallus – very small and
dependent on the sporophyte
– one to two cells thick
– heart or kidney shaped
– photosynthetic
• shrivels and dies after the young
sporophyte develops
• anchored by rhizoids – not for
absorption
– similar to Lycophyta
http://www.youtube.com/watch
?v=MQB7Moc3Dos
http://www.youtube.com/watch
?v=mDlHGrRlNPE
Division Pterophyta
• fern sporophyte:
– diploid
– bears sporangia (singular = sporangium) clustered under the
pinna in structures called sori (singular = sorus)
– so one sorus is made up of multiple sporangia
• a sporangium contains spore mother cells (2n)
– the spore mother cells undergo meiosis to produce spores (n)
 haploid gametophyte
The Annulus and spore dispersal from the
Sporangium
• http://www.youtube.com/watch?v=xF83pHEx6Q
• the individual sporangium is a stalked
structure
• at the end is a spring-like devicee that
disperse the spores = annulus
• annulus = a row of cells that bisects
the sporangium like a sturdy spine.
• annulus walls are permeable to water
• evaporating water is drawn out from
the annulus, causing the cells to shrink
– pries the sporangium open
• the presence of water within the
sporangium propels the spores out like
a catapult