1. Introduction to the Plant Kingdom: Bryophytes
Chapter 20

2. Outline Introduction Introduction to the Bryophytes
Phylum Hepaticophyta – Liverworts
Phylum Anthocerophyta – Hornworts
Phylum Bryophyta – Mosses
Human and Ecological Relevance of Bryophytes

3. Introduction Plants and green algae share:
Chlorophylls a and b, carotenoids
Starch as food reserve
Cellulose in cell walls
Phragmoplast and cell plate during cell division
Shared features suggest common ancestor
Land plants first appeared 400 mya
Ancestor progressed from aquatic to land habitat even earlier

4. Introduction Features preventing dessication:
Plant surfaces developed fatty cuticle to retard H2O loss
Gametangia (gamete-producing structures) and sporangia (spore-producing structures) became multicellular and surrounded by jacket of sterile cells
Zygotes developed into multicellular embryos within parental tissues originally surrounding egg

5. Introduction to the Bryophytes
Ca. 23,000 species of bryophytes
Include mosses, liverworts, and hornworts
Occupy wide range of habitats:
Damp banks, trees, logs
Bare rocks in scorching sun
Frozen alpine slopes
In elevations from sea level up to 5,500 m or more

6. Introduction to the Bryophytes
Bryophytes often have mycorrhizal fungi associated with rhizoids
Peat mosses ecologically important in bogs
Luminous mosses found in caves and other dark, damp places
None have true xylem or phloem
Many have hydroids for H2O conduction
Most H2O absorbed directly through surface
Few have leptoids for food-conduction
Need H2O to reproduce sexually

7. Introduction to the Bryophytes
Exhibit alteration of generations
In mosses, leafy plant = gametophyte generation
Sporophyte generation grows from gametophyte
3 distinct bryophyte phyla
None appear closely related to other living plants
Bryophyte lines may have arisen independently from ancestral green algae

8. Phylum Hepaticophyta – Liverworts
Structure and form:
Most common and widespread liverworts have flattened, lobed thalli (singular: thallus)
Thalloid liverworts constitute ca. 20% of spp.
Other 80% leafy
Thalli or leafy gametophytes develops from spores
When spores germinate they may produce protonema - immature gametophyte consisting of short filaments
Thalloid liverworts growth prostrate and one-celled rhizoids on lower surface anchor plant

9. Phylum Hepaticophyta – Liverworts
Thalloid liverworts
Best known species in genus Marchantia
Thallus forks dichotomously as it grows
Each branch apical notch and central groove
Meristematic cells in notch continue to divide
Bottom layer of thallus - epidermis from which rhizoids and scales arise

10. Phylum Hepaticophyta – Liverworts
Marchantia
Upper surface divided into diamond-shaped segments marking limits of chambers below
Each segment has small bordered pore opening into chamber
Short, erect rows of cells with chloroplasts sit on floor of chambers

11. Phylum Hepaticophyta – Liverworts
Thalloid liverworts
Marchantia - asexual reproduction:
Gemmae (singular: gemma) - tiny, lens-shaped pieces of tissue become detached from thallus
Produced in gemmae cups scattered over upper surface of thallus

12. Phylum Hepaticophyta – Liverworts
Thalloid liverworts
Marchantia - sexual reproduction:
Gametangia formed on gametophores
Male gametophore = antheridiophore
Antheridia containing flagellated sperm found on upper surface

13. Phylum Hepaticophyta – Liverworts
Marchantia - sexual reproduction cont’d.:
Female gametophore = archegoniophore
Archegonia with eggs in rows and hang down beneath spokes of archegoniophore

14. Phylum Hepaticophyta – Liverworts
Marchantia - sexual reproduction cont’d.:
Embryo dependent on gametophyte for sustenance
Foot of sporophyte anchors to archegoniophore
Seta - short stalk
Capsule - meiosis produces 1n spores inside
Also contains 2n elaters with spiral thickenings
Immature sporophyte protected by calyptra = caplike tissue that grows out from gametophyte

15. Phylum Hepaticophyta – Liverworts
Marchantia - sexual reproduction cont’d.:

16. Phylum Hepaticophyta – Liverworts
Leafy liverworts
2 rows of partially overlapping leaves
No midrib
Often have folds or lobes
Cells contain oil bodies
3rd row of underleaves often present
Archegonia and antheridia produced in cuplike structures composed of modified leaves, in axils of leaves or on separate branches
Sporophyte pushes out from among leaves

17. Phylum Anthocerophyta – Hornworts
Structure and form:
Mature sporophytes look like miniature greenish-blackish rods
Gametophytes thalloid
Cells with only 1 large chloroplast
Thalli have pores and cavities filled with mucilage often containing N2-fixing bacteria
Ca. 100 spp. worldwide
Asexual reproduction by fragmentation of thallus

18. Phylum Anthocerophyta – Hornworts
Sexual reproduction:
Archegonia and antheridia produced in rows just beneath upper surfaces of gametophytes
Sporophyte:
Numerous stomata
Meristem above foot continually increases length of sporophyte from base
Meiosis produces 1n spores
2n elaters also produced

19. Phylum Bryophyta – Mosses
Structure, form and classes:
Ca. 15,000 spp. of mosses
Divided into 3 classes:
Peat mosses
True mosses
Rock mosses
A true moss

20. Phylum Bryophyta – Mosses
Structure, form and classes cont’d.:
Leaves of moss gametophytes have blades nearly always one-cell thick, except at midrib, and never lobed or divided
Cells usually contain numerous chloroplasts
Peat moss leaves have large transparent cells without chloroplasts that absorb H2O; and small, green, photosynthetic cells sandwiched between
Axis stemlike, without xylem or phloem
Often with hydroids
Cells of peat moss leaves

21. Phylum Bryophyta – Mosses
Sexual reproduction:
Gametangia at apices of leafy shoots
Archegonium cylindrical with egg in swollen base, and neck above containing narrow canal
Multicellular filaments = paraphyses scattered among archegonia

22. Phylum Bryophyta – Mosses
Sexual reproduction cont’d.:
Antheridia on short stalks, surrounded by walls 1 cell thick
Sperm cells, each with pair of flagella, formed inside
Sperm forced out top of antheridium
Paraphyses scattered among antheridia

23. Phylum Bryophyta – Mosses
Sexual reproduction cont’d.:
Archegonia release substances attracting sperm
Sperm swim down neck of archegonium
Zygote grows into spindle-shaped embryo
Top of archegonium splits off and forms cap on top of sporophyte = calyptra
Mature sporophyte consists of capsule, seta and foot

24. Phylum Bryophyta – Mosses
Sexual reproduction cont’d.:
Meiosis produces spores inside capsule
Peristome, composed of 1 or 2 rows of teeth, under operculum at tip of capsule
Peristome opens or closes in response to humidity
Spores develop into filamentous protonema that produces buds developing into leafy gametophytes

25. Phylum Bryophyta – Mosses
Sexual reproduction cont’d.:

26. Human and Ecological Relevance of Bryophytes
Pioneer species on bare rock after volcanic eruptions or other geological upheavals = succession
Accumulate mineral and organic matter utilized by other organisms
Retain moisture, and reduce flooding and erosion
Indicators of surface H2O

27. Human and Ecological Relevance of Bryophytes
Peat mosses most important bryophyte to humans
Soil conditioner due to high absorptive capacity
Poultice material due to antiseptic properties and absorbency
Fuel

28. Review Introduction Introduction to the Bryophytes
Phylum Hepaticophyta – Liverworts
Phylum Anthocerophyta – Hornworts
Phylum Bryophyta – Mosses
Human and Ecological Relevance of Bryophytes