Biol 108 - Topic 14

Bryophytes

Bryophytes are early land plants forming a _____group of small, nonvascular species.

paraphyletic

Three phyla of small herbaceous (nonwoody) plants

• Hepatophyta (liverworts; ~9,000 species),

• Bryophyta (mosses; ~12,000 species) - most diverse + distributed bryophytes

• Anthocerophyta (hornworts; ~225 species)

Key characteristics

• No vascular tissue or lignin → small size (limited b/c of no vascular transport+no struc support tissues)

  • Most tissues are one/few cells thick

• water absorbed across surfaces. (have to live where H2O is abundant)

• No true roots, stems, or leaves; anchored by rhizoids.

• Gametophyte (1n) is dominant, larger, and longer-lived; sporophyte (2n) is small, small period of time, and dependent on gametophyte.

• Sporophytes are unbranched, lack roots and leaves.

• Moss and hornwort sporophytes have stomata for gas exchange; liverworts do not.

  • No living gametophytes have stomata

• Require moist environments for reproduction.

Lifecycle

1. Spores (1n) germinate into a threadlike protonema (n), which develops into a gametophore via mitosis.

2. Antheridia (male) produce flagellated sperm; archegonia (female) produce eggs (Both via mitosis within gametangia).

   1. Female gametangia (archegonia) is site of fertilization (egg retained in archegonia)

3. Fertilization requires water: flagellated sperm swim to fertilize eggs.

4. Zygote (2n) → sporophyte embryo (2n) (foot, seta (long talk that emerges from archegonium), capsule (sporangium)) attached to gametophyte.

   1. Attached by foot, sporophyte is nutritionally dep on gametophyte

   2. Bryophyte sporophytes (2n) grow out of archegonia and are the smallest and simplest sporophytes of all plant groups

5. Meiosis in a capsule produces spores that disperse by air.

6. Water is needed for fertilization, not dispersal.

Bryophytes are common in _____.

moist forests and wetlands

Sphagnum (peat moss) forms___, which regulate water flow and store large amounts of carbon (slow decay due to low pH, oxygen, and temperature).

peat bogs

• Mosses can lose most cellular water, and then rehydrate and reactivate cells when moisture becomes available

• carbon reservoirs

Bryophates are the _____ lineages to diverge from the CA of plants

earliest

Diff btn Bryophyte sporophytes + vascular plant sporophytes

Sporophytes of vascular plants are branched and have leaves + roots

Mosses often have _____ male and female gametophytes

separate

Many bryophytes spread thru ______, eg. brood bodies are small gametophyte plantlets that detach from the parent plant and grow into new, genetically identical copies

asexual reproduction

Diploid (2n) zygote, embryo, and sporophyte are____ and nourished by the gametophyte

retained

Spores disperse in the ___ : dispersal is ___ of water

air; independent

Fertilization requires ____: flagellated sperm swim through a film of water to fertilize eggs

water

Peat

extensive deposits of undecayed organic material

• formed from Sphagnum bogs