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 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

Plant Life Cycles

• 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 Mitosis

** as plants evolve there is anincreasing importance of the

sporophyte over the gametophyte

• 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

Phylum BryophytaMnium hornum

Sphagnum peat moss

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

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 mossesis 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

The Sporophyte• 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

MossSporophyte

– 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

Polytrichum communehairy cap moss

SPOROPHYTE

GAMETOPHYTE

calyptra around the sporangium

stem (seta)

GAMETOPHYTE (leafy shoot)

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

moss

hornwort

liverwort

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

Archegonia and antheridiaof Marchantia (a dieocious liverwort)

Male gametophore Antheridiumwith sperm

Female gametophore

Archegoniumwith egg

the gametophyte ofthe liverwortis the actual liverwort!!

antheridium gametangium with sperm

archegonium gametangium

egg

Male gametophore

Female gametophore

Male Gametophyte

female gametophoremale

antheridium

• 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

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 Gametophorewith archegonia

Marchantia polymorpha,a “thalloid” liverwort

Foot

Seta

Sporangium

500 µm

Marchantia sporophyte (LM)

• 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

Marchantia Asexual reproduction

gemmae cups & crosssection

Phylum Anthocerophyta: HornwortsAn Anthroceroshornwort 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 mossSelaginella(spike moss)

QuillwortIsoetes

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 ofsporangia)

epiphytic ferns

Division Lycophyta

Diphasiastrum tristachyum, a club moss

Strobili(clusters ofsporophylls)

• 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

• 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

Division Lycophyta

Selaginella lepidophyllaa spike moss

Selaginella canaliculataa spike moss

Selaginella strobili

Lycopodium strobili

Strobili withsporangiamegaspores

microspores

• quillworts– e.g. Isoetes qunnii– 60 species within the genus– wet, muddy areas– heterosporous– almost every leaf bears a

sporangia

Division Lycophyta

Isoetesgunnii,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 - Equisetumstrobilus

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

rhizoids

rhizome

fronds

• 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=MQB7Moc3Doshttp://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

Division Pterophyta

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