Topic 13: Nonvascular Plants (Bryophytes)

Comprehensive vocabulary flashcards covering the characteristics, classification, life cycle, reproductive structures, and ecological significance of nonvascular plants (bryophytes).

Bryophytes

The earliest lineages of plants to diverge from the common ancestor of plants before the evolution of vascular tissues; a paraphyletic group of small, herbaceous (non-woody), nonvascular plants.

Phylum Hepatophyta (Liverworts)

A diverse and widespread group of nonvascular plants consisting of approximately $9{,}000$ species whose sporophytes lack stomata, comprising both thalloid and leafy forms.

Marchantia polymorpha

A species of "thalloid" liverwort whose flattened gametophyte thallus bears gametophores and small sporophytes composed of a foot, seta, and capsule.

Phylum Bryophyta (Mosses)

The most diverse and widely distributed bryophyte phylum, containing approximately $12{,}000$ species; sporophytes in this group possess stomata for gas exchange.

Phylum Anthocerophyta (Hornworts)

The least diverse bryophyte phylum, containing only approximately $225$ species, characterized by elongated, horn-like sporophytes that possess stomata.

Rhizoids

Cellular filaments that anchor bryophytes to the substrate; unlike true roots, they do not conduct vascular transport, and bryophytes absorb water directly through their surfaces.

Gametophyte

The free-living, haploid ($1n$) generation that represents the larger, longer-living, and dominant phase of the bryophyte life cycle.

Sporophyte

The diploid ($2n$) life cycle phase in bryophytes that is unbranched, lacks roots and leaves, is present only part of the time, and remains attached to and nutritionally dependent on the gametophyte.

Gametangia

Multicellular organs on the gametophyte where gametes are produced by mitosis, consisting of female archegonia and male antheridia.

Antheridia

Multicellular male gametangia in bryophytes that produce and release flagellated sperm that must swim through a film of moisture to reach an egg.

Archegonia

Multicellular female gametangia in bryophytes that produce an egg, retain it, and serve as the site of fertilization and embryonic development.

Protonema

A threadlike mass of haploid ($1n$) cells produced by a germinating spore that divides by mitosis and forms buds that grow into gametophores.

Gametophore

The mature, gamete-producing leafy or upright shoot of a bryophyte gametophyte that develops from buds on the protonema.

Foot

The basal region of a bryophyte sporophyte embedded within the gametophyte that absorbs nutrients to support the sporophyte.

Seta

The elongated stalk of a bryophyte sporophyte that emerges from the archegonium and elevates the capsule for spore dispersal.

Capsule (Sporangium)

The terminal structure of the bryophyte sporophyte where meiosis takes place to produce thousands of haploid ($1n$) spores.

Peristome

A specialized ring of interlocking tooth-like structures at the top of a moss capsule that opens and closes to control the gradual release and dispersal of spores into the air.

Sporopollenin

A durable polymer embedded in the cell walls of bryophyte spores that protects them against desiccation during aerial dispersal.

Brood Body

A small gametophyte plantlet used in asexual reproduction that detaches from the parent plant and grows into a genetically identical copy.

Sphagnum

A genus of moss ("peat moss") capable of surviving extreme water loss that plays a vital role in regulating water flow and forming extensive peat deposits in wetlands.

Peat

Extensive deposits of partially decayed organic material formed in wetlands where low temperatures, low pH, and low oxygen levels inhibit the decay of Sphagnum and other organisms.

Muskegs

Peat-forming wetland ecosystems prevalent in Arctic and boreal regions that serve as large carbon reservoirs, stabilizing atmospheric $CO_2$ levels.