§    Bryophytes (nonvascular plants) are mosses and their relatives

§    They do not have vascular tissues which allow plants to conduct water and nutrients.

§    Their life cycle depends on water for reproduction.

§    The sperm must swim through water to reach the eggs.

Groups of Bryophytes

§    Bryophytes are low-growing plants found in moist shady areas.

§    They can be found from polar regions to tropical areas as long as there is water.

§    Bryophytes include:

v    mosses

v    liverworts

v    hornworts

Mosses

§    mosses are members of the phylum Bryophyte

§    grow in areas of moisture - swamps and bogs, near streams and rain forests

§    They tolerate low temperatures so they can grow in harsh environments where other plants cannot.

§    It is the most abundant plant in the polar regions.

§    vary in appearance from miniature evergreen trees to small, filamentous plants that resemble a carpet of green

§    when mosses reproduce, they produce thin stalks, each containing a capsule (sporophyte stage)

§    each moss plant has a thin upright shoot that looks like a stem with tiny leaves (gametophyte stage)

§    these are NOT true stems or leaves because they DO NOT contain vascular tissue

§    "Leaves" are only one cell thick and lose water quickly i f the air is dry

§    DO NOT have "true roots" instead they have rhizoids which anchor them and absorb water and nutrients

Liverworts

§    Liverworts are members of the phylum Hepaticophyta

§    Some species resemble the shape of a liver

§    The gametophyte stage produces gametes in structures that look like little green umbrellas

§    Reproduce asexually by means of gemmae

§    Gemmae are small circular spheres that contain many haploid cells

§    In some species, gemmae are produced in cuplike structures called gemma cups

Hornworts

§    Hornworts are members of the phylum Anthocerophyta

§    Found only in soil that is damp year-round

§    Hornworts have sporophytes that looklike tiny green horns

Life Cycle of Bryophytes

§    Reproduce with alternation of generations

§    The gametophyte is the dominant, recognizable stage and the stage that carries out the most photosynthesis

§    The sporophyte is dependent on the gametophyte for supplying water and nutrients

Dependence on Water

§    For fertilization to occur, the sperm must swim to an egg

§    Sometimes raindrops splash sperm from one plant to another

§    Bryophytes must live in habitats where water is available

Life Cycle of a Moss

1. A moss spore lands in a moist place, germinates and grows into a mass of tangled green filaments called a protonema.

2. The protonema grows and forms rhizoids that grow into the ground and shoots that grow into the air.

3. Shoots grow into the familiar green moss plants which are the gametophyte stage.

4. Gametes are formed in reproductive structures at the tips of the gametophytes.

5. Sperm in the antheridia and eggs cells in archegonia.

6. Sperm are released, reach egg cells and fertilization produces a diploid zygote.

7. The zygote is the beginning of the sporophyte stage.

8. It grows directly out of the body of the gametophyte and depends on it for water and nutrients.

9. The mature sporophyte is a long stalk ending in a capsule.

10. Inside the capsule, haploid spores are produced and when the capsule ripens, it opens releasing the spores to start the cycle again.

Human Use of Mosses

§    Sphagnum mosses thrive in acidic water of bogs. They absorb many times their own weight in water and act as a "natural sponge".

§    Dead remains of sphagnum accumulate to form thick deposits of peat. Peat can be cut from the ground and burned as a fuel.

§    Peat moss is also used in gardening.

§    It is added to soil to improve the soil's ability to retain water.

§    Peat moss also has a low pH so it increases the soiI's acidity. Some plants, such as azaleas, grow well in acidic soil.