Lab #5

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” • Phylum Lycophyta – club mosses • Phylum Pterophyta – ferns, horsetails and whisk ferms • the seed bearing plants are divided into: • the gymnosperms – non-flowering plants • the angiosperms – flowering plants

3. Evolution of Land Plants • 475 MYA • adaptations to survive the variations in sunlight, temperature, moisture, gravitational forces • land plants evolved complex multicellular bodies – specialization for specific functions • 4 major adaptations of land plants: • 1. alternation of generations and the development of protected embryo – land plants are often called embryophytes • 2. walled sporangia in a dominant sporophyte • 3. development of a multicellular gametophyte – production of male and female reproductive structures • 4. development of apical meristems – for tissue differentiation and plant growth

4. Plant Life Cycles ** as plants evolve there is an increasing importance of the sporophyte over the gametophyte • 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 • 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 Mitosis

5. Plant reproduction terms • sporophyte (diploid) = spore producing structure • sporangium = structure on the sporophyte where meiosis produces haploid spores • spores (haploid) = released cells that will grow via mitosis to generate a new 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. Phylum Bryophyta • mosses • gametophyte stage • thallus(heart-shaped) body • bears male and female gametophores with gametangia • 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 • stems – multicellular structures made up of multiple tissue types • cortical cells – most of the stem (parenchyma tissue) • stereid cells for support • hydroid cells for water transport • leptoid cells for nutrient and metabolite transport • leaves – leaf blade = lamina • most are photosynthetic • great degree of cellular specialization • single layer of cells – stereids, leptoids, hydroids • show distinct differences with liverworts and hornworts

8. Phylum Bryophyta • sporophyte stage – parasitic on the 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 • 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 Foot Seta Sporangium

9. Mniumhornum Phylum Bryophyta

10. Polytrichum commune hairy cap moss calyptra stem SPOROPHYTE GAMETOPHYTE Sphagnum peat moss

11. Phylum Hepatophyta • liverworts • share some similarities with mosses but there are some distinct differences • gametophyte has two forms: leafy and thalloid • 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 • no role in absorption, just anchorage (like mosses) • many thalloid forms have gemmae cups for asexual reproduction • 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 • many types have lobed leaves – with a “thumb” at the base of the leaf • stem does not have specialized tissues for water and nutrient transport (unlike mosses) • rhizoid is very similar to the moss rhizoid • sporophyte – very similar to mosses • major differences – spores are expelled out all at once • presence of elaters with contract and expand with humidity to expel the spores • once the spores are dispersed, the liverwort sporophyte withers away – in mosses the sporophyte can persist for months

12. Phylum: HepatophytaMarchantia • thalloid-type gametophyte • grows on damp rock and soil • actual plant is the haploid gametophyte stage • upper epidermis of the gametophyte overlies a diamond-shaped pattern of air chambers • hair-like rhizoids on the lower surface of the thallus – adaptations for anchorage only • underside of the female gametangium bears multiple sporangia for the production of haploid spores • sporangium is connected to the female via a stalk called a seta Female Gametangium and gametophore 500 µm Foot Seta Sporangium Marchantia polymorpha, a “thalloid” liverwort Marchantia sporophyte (LM)

13. stalked uprisings are the gametophores bearing gametangia • male and female gametangia have distinct appearances • underside of the female gametangia bears the sporangium for the production of haploid spores Marchantia female male antheridium archegonium

14. Marchantia • 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

15. An Anthroceros hornwort species Sporophyte Gametophyte Phylum AnthocerophytaHornworts

16. Vascular, Seedless Plants • ferns, whisk ferns, horsetails – Phylum Pterophyta • club mosses, quill worts, spike mosses – Phylum Lycophyta • called mosses – but they have vascular tissues • limited adaptations have restricted many seedless plants to limited ranges • each representative has vascular tissue for the conducting of water and nutrients and metabolites • 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 – need 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 the haploid (bisexual) gametophyte via mitosis • but some species have developed heterospory – two types of spores • megaspores produces the female gametophyte via mitosis • microspores produces the male gametophyte via mitosis • only economically important seedless vascular plant is the fern

17. Strobili (clusters of sporophylls) Diphasiastrumtristachyum, a club moss Phylum Lycophyta • 5 existing genera: Lycopodium & Phylloglossum (club mosses), Selaginella (spike mosses), Isoetesand Stylites (quillworts) • club mosses – the sporophyll bearing sporangia are clustered on strobili • look like “clubs” • 200 living species • most inhabit moist environments • microphylls (leaves) are spirally arranged • most are homosporous • common examples: • Selaginella- some consider these to be a spike moss • Lycopodium – 950 species • temperature climates • dried spores are flammable due to fat content and are used as flash powder in magic actis

18. Phylum Lycophyta • spike mosses • e.g. Selaginellalepidophylla – resurrection plant • found in the desert as a dormant plant until moisture increases • heterosporous – mega and microspores produced by mega- and microsporangia • possess a small flap of tissue on the upper surface of their leaves called a lingule (also seen in the quillworts) Selaginellalepidophylla a spike moss Selaginellacanaliculata a spike moss

19. Selaginella strobili Lycopodium strobili sporophylls Strobili with sporangia megasporophyll megaspores microspores microsporophyll

20. Phylum Lycophyta • quillworts • e.g. Isoetesqunnii • 60 species within the genus • wet, muddy areas • heterosporous • almost every leaf bears a sporangia Isoetes gunnii, a quillwort

21. Phylum Pterophyta • ferns, whisk ferns & horsetails • used to be three separate phyla • molecular biology now places them in one phylum

22. Phylum Pterophyta • horsetails = Equisetum • named for the brushy appearance of the stems – horsetails or scouring rushes • Division Arthrophytes – “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 strobilus

23. sporangiophore- Equisetum Sporangia With spores sporangiophore

24. Phylum Pterophyta • whisk ferns • dichotomously branching stems but no roots • stems have scale-like outgrowths that lack vascular tissue • stems may have evolved as reduced leaves • 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

25. Phylum Pterophyta • ferns: • 12,000 species • Division Pterophyta– includes whisk ferns and horsetails • largest group in this division is called the leptosporangiate ferns • sporophyte: diploid • some species with undergound stems = rhizomes • some species with above ground stems = stolon • some above ground stems can be semi-woody • leafs are megaphylls called fronds • roots are fibrous and are very similar to seed plants in that they have defined tissues for absorption • gametophyte: haploid • is called the prothallus – very small and dependent on the sporophyte • one to two cells thick • heart or kidney shaped • photosynthetic • anchored by rhizoids – not for absorption • similar to Lycophyta

26. fronds rhizome rhizoids • ferns: • sporophyte megaphyll: • emerge from a rhizome via a stalk called a petiole • end of the petiole is the blade – multiple leaflets called pinnae • pinnae are arranged as two lateral rows off the petiole • petiole + blade = frond • rolled up, young frond = fiddlehead

27. ferns: • sporophyte megaphyll: • underside of some leaflets are clusters of sporangia called sori (singular = sorus) • sori contain multiple haploid spores ready for dispersal • the sorus is homosporus • each sporangium is covered by an annulus for spore dispersal • http://www.youtube.com/watch?v=MQB7Moc3Dos • http://www.youtube.com/watch?v=mDlHGrRlNPE fern sorus annulus sporangium