1. Lab #5
Mosses & Ferns

2. 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 seed-bearing
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

3. 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

4. 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

5. 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

6. 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

7. Mnium hornum
Phylum Bryophyta
Sphagnum
peat moss

8. Phylum Bryophyta 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

9. 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)

10. 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!!

11. 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!!!

12. 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

13. 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

14. Moss 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

15. Polytrichum commune
hairy cap moss
SPOROPHYTE
GAMETOPHYTE
calyptra around the sporangium
stem (seta)
GAMETOPHYTE (leafy shoot)

16. 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
hornwort
moss
liverwort

17. 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

18. 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

19. 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
Archegonia and antheridia
of Marchantia (a dieocious
liverwort)
Male gametophore
Antheridium
with sperm
Female gametophore
Archegonium
with egg
the gametophyte of
the liverwort
is the actual liverwort!!
antheridium gametangium with sperm
archegonium gametangium
egg

20. 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
antheridium
female gametophore
male

21. 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

22. 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

23. 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
Marchantia polymorpha,
a “thalloid” liverwort
Foot
Seta
Sporangium
500 µm
Marchantia sporophyte (LM)

24. 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

25. Phylum Anthocerophyta: Hornworts
An Anthroceros
hornwort species
Sporophyte
Gametophyte

26. 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

27. 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

28. 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)

29. Phylum Lycophyta 5 existing genera:
Lycopodium & Phylloglossum (club mosses)
Selaginella (spike mosses)
Isoetes and Stylites (quillworts)
Quillwort
Isoetes
Golden club moss
Selaginella
(spike moss)

30. 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
Diphasiastrum tristachyum, a club moss
Strobili
(clusters of
sporangia)
epiphytic ferns

31. Division Lycophyta
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
Diphasiastrum tristachyum,
a club moss
Strobili
(clusters of
sporophylls)

32. Division Lycophyta spike mosses
Selaginella lepidophylla
a spike moss
spike mosses
e.g. Selaginella lepidophylla – resurrection plant
found in the desert as a dormant plant until moisture increases
heterosporous – two types of spores
megaspores produce the female gametophyte via mitosis
microspores produce the male gametophyte via mitosis
Selaginella canaliculata
a spike moss

33. Selaginella strobili Lycopodium strobili Strobili with sporangia
megaspores
microspores

34. Division Lycophyta quillworts e.g. Isoetes qunnii
gunnii,
a quillwort
quillworts
e.g. Isoetes qunnii
60 species within the genus
wet, muddy areas
heterosporous
almost every leaf bears a sporangia

35. 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

36. 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

37. sporangiophore - Equisetum
strobilus

38. 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

39. 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

40. fronds
rhizome
rhizoids

41. 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

42. 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

43. The Annulus and spore dispersal from the Sporangium
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