1. Biology 1010 Chapter 20
Bryophytes

2. Bryophytes What are they?? Where are they found??
What is their evolutionary & ecological importance??

3. Points to Ponder
Differentiate the bryophyte phyla from each other and other phyla
Describe the bryophyte adaptations to terrestrial environments
Describe reproduction in bryophyte phyla
Describe the ecological role of bryophytes

4. Kingdom Plantae Bryophytes: simplest plants
Include liverworts, hornworts, mosses
Fossils from 400 mya
Molecular evidence suggests 700 mya
Economically important species
Sphagnum moss from peatlands
Cool northern areas: Canada, n. US, Ireland
Modifies soil to retain H2O, adds organic material
Fuel source
Acid pH or antibiotic compounds: aid wound healing

5. Bryophyte Overview Life on land possible when
Oxygen level > 2 %
Present oxygen level??
Water can be retained
Bryophytes found in moist environments
Term refers to nonvascular plants
Formerly one phylum
Now: three phyla
Each evolved independently
From the same green algal ancestors

6. Phylum Hepatophyta Liverworts 1st land plant fossil 450 mya
6000 spp
1st land plant fossil 450 mya
Probably liverwort
Advantages of land:
Intense sunlight
Rocks rich in minerals

7. Phylum Anthocerophta Possible path of evolution: 100 spp
Hornworts
Possible path of evolution:
Stranding of green algae with prior adaptations
Adaptations include:
vertical stems
underground stems for H2O & nutrient uptake

8. Phylum Bryophyta 9,600 spp Bryophytes limited to moist environments
Mosses
Bryophytes limited to moist environments
Sperm requires water
Just as amphibians do
Some can live in dry sites
Do not fossilize well
Molecular evidence
700 mya

9. Bryophyte characteristics
Nonvascular: no xylem & phloem
Restricts size, limits distribution on land
Gametophytes have structures
Resemble stems & leaves
Without internal ‘veins’
Hydroids: conduct H2O
Leptoids: conduct food
Thallus: body of a bryophyte
Rhizoid: anchors bryophyte to substrate
Absorption occurs through contact

10. Bryophytes similar to Charophyceae & vascular plants
Classification of algae & plants unsettled
Should reveal phylogeny
Similarities between charophyceae & plants
Cellulose in cell walls
Mitotic spindles remain during cytokinesis
Pigments:
Phytochrome, Chla, b, carotenoids,
Thylakoids stacked in grana

11. Bryophytes similarity to plants
Characteristics that enhance survival on land
Protect gametes and spores
Sterile cells protect structures producing male and female gametes
multicellular embryo protected within female parent
Multicellular, diploid sporophyte meiosis → spores
Sterile cells protect multicellular sporangia
Natural selection guided bryophyte evolution from green algae differently than plants

12. Bryophyte Alternation of Generations
Gametophyte dominant
Haploid
Gametangia: mitosis → gametes
Antheridia: male
Archegonia: female, one egg
Sporophyte attached to gametophyte
Depends on gametophyte for its nutrition
Diploid
Meiosis → haploid spores in sporangium
Spore germinates → protonema

13. Bryophyte Asexual Reproduction
All 3 phyla can reproduce by fragmentation
Reproduce through specialized brood bodies
Gemmae
bulbils

14. Ecological roles of Bryophytes
Plant succession
Mosses colonize rock surfaces, crevices
→ soil
Rhizoids secrete acid to dissolve rock
Bodies add organic matter, collect dust
Seeds germinate in these pockets
Epiphytic mosses:
Grow in tropical and temperate rain forest trees
Important in tundra
NOT “reindeer moss” = lichen

15. Bryophytes tolerate drought
Liverworts may roll into tube
Protects upper surface
Tortula spp
Moss can dehydrate
Produce mRNA
Codes for protein to repair damage
Rehydration → resumption of photosynthesis

16. P. Hepatophyta = liverworts
Earliest land plants?
Closely related to green algae
Lack DNA characteristic of other bryophytes, plants
Horizontal, flatter than mosses
Leaves usually thin, flat
Categories:
Thalloid or leafy

17. Liverwort life cycle Gametophyte dominant Marchantia
Lobed gametophyte large
Rhizoids penetrate soil
Antheridia & archegonia elevated
Antheridiophore flattened, bears antheridia, catch rain drops
Archegoniophore suspends archegonia beneath tops
Sporophyte inconspicuous
Zygote in archegonium
Forms spores

18. P. Anthocerophyta = hornworts
Conspicuous horn-shaped sporophytes
Stomata with guard cells: new feature
Gametophytes similar to liverworts
Rumpled, green sheet
N-fixing bacteria symbionts

19. Hornwort life cycle Gametophyte form antheridia
Become visible when sterile cells dry & break
Archegonia form from surface cells
Thallus cells surround egg
Fertilization → zygote with ‘horn’
Sporophyte foot anchors it to gametophyte
Gametophyte provides water, minerals, some food
Sporophyte grows from its base not its apex
photosynthetic as in liverworts, NOT mosses
Produces spores from apex of sporangium to base

20. P. Bryophyta = mosses bryophytes refers to ALL nonvascular plants
P. Bryophyta = scientific classification
Mosses usually with a leafy thallus
Vertical gametophyte
Usually in moist, forested sites, wetlands
Sometimes in deserts, dry rock outcrops
Some aquatic

21. Class Spagnopsida aka Sphagnidae
150 spp, peat mosses
Sheet like protonema
Dead cells with thick walls hold water
spherical sporangia attach to stalks of gametophytes

22. Class Andreaeopsida = granite or rock mosses
100 spp
Live at high altitudes
Cold, temperate sites
Live on rock, snow, ice
Sporangia with four slits allow dispersal of spores

23. Class Bryopsida aka Bryidae
9,000 spp
Common mosses
Growth patterns vary
May grow in clumps
As pendulous epiphytes
May remain filamentous
May be seasonal
May grow on polluted soil

24. Life cycle of Polytrichum
Typical moss life cycle
Dominant gametophyte
Survives drought
Originates from spore
Spore → protonema
Bud → gametophyte leaf
→ Antheridia &/or archegonia
Water → fertilization
Zygote develops in archegonium
→ sporophyte with setae
foot absorbs food

25. Questions
Thought and Discussion 2 4
Evolution Connection