| Talk in general about bryophyte reproduction | Bryophytes display two adaptations that first made the move onto land possible. They are covered by a waxy cuticle that helps the body retain water, and their gametes develop within gametangia. Bryophytes include mosses, liverworts and hornworts. |
| Talk about asexual reproduction of bryophytes. | Asexual reproduction in Bryophyta (mosses, liverworts and hornworts) may occur by fragmentation or by gemmae.
- Fragmentation: Pieces of a gametophyte can break off and form new bryophyte plants.
- Gemmae (e.g. Marchantia: class Hepaticopsida) are tiny, multicellular propagules, cup-shaped structures on the gametophytes. Raindrops separate gemmae from the parent plant so they can spread and form new gametophytes. |
| Talk in general about bryophyte sexual reproduction | Bryophytes are characterized by a haplodiplontic life cycle. The gametophyte generation (conspicuous vegetative plant) is dominant and the sporophyte is dependent on the gametophyte. |
| Talk about steps of bryophytes sexual reproduction | Gametophytes can form multiple gametangia, each of which produces gametes. Male gametophytes develop reproductive structures called antheridia (flagellated, motile) that produce sperm cells by mitosis. Female gametophytes develop archegonia (sing. archegonium) that produce eggs by mitosis. Each archegonium produces one egg, whereas each antheridium produces many flagellated sperm. Some bryophytes bear antheridia and archegonia within the same gametophyte.
Fertilization occurs in the presence of water. The type of reproduction is oogamy. |
| Talk about bryopsida (Mnium) sexual reproduction | Mosses have an alternation of generations (haplodiplontic cycle), the sporophyte grows on the female gametophyte and remains attached and nutritionally dependent on the gametophyte throughout its existence |
| Talk about steps of bryopsida sexual reproduction | Flagellated sperm cells travel to a neighboring plant via a water droplet and are chemically attracted to the entrance of the archegonium. Fertilization occurs when one of the sperm cells fuses with the egg (oogamy). The diploid zygote formed as a result of fertilization grows into a multicellular embryo by mitosis, and matures into a moss sporophyte. The embryonic sporophyte develops within the archegonium, and the mature sporophyte stays attached to the female gametophyte throughout its existence. The sporophyte is not photosynthetic. Thus both the embryo and the mature sporophyte are nourished by the photosynthetic gametophyte.
Meiosis of the sporocytes (spore mother cells), within the capsule of the sporophyte, forms haploid spores. When the spores are mature, the capsule opens and the spores are dispersed by wind or rain. If a moss spore lands on a suitable spot, it germinates and grows into a filamentous thread of cells called protonema. The protonema forms buds, each of which grows into a leafy gametophyte plant, and the life cycle continues. |
