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Nonvascular Plants: Mosses, Liverworts, and Hornworts (Characteristics of…
Nonvascular Plants: Mosses, Liverworts, and Hornworts
Characteristics of Nonvascular Plants
Technically, nonvascular plants are embryophytes that do not have vascular tissue.
They have multicellular paranoia and gametangia.
Reproductive cells are always surrounded by one or several layers of sterile cells.
Their bodies are not composed of filaments as in many algae, but rather of true parenchyma.
All mosses and many liverworts have leafy stems that look remarkably like small versions of flowering plants.
Almost exclusively terrestrial and have a cuticle over much of their bodies, and many have stomata.
Have a life cycle with an alteration of heteromorphic generations.
The sporophyte and gametophyte differ from each other structurally.
Classification of Nonvascular Plants
Liverworts
Division Hepatophyta
Hornworts
Division Anthocerotophyta
Mosses
Division Bryophyta
Previously all grouped together in Bryophyta
Liverworts
Hepaticae
Mosses
Musci
Hornworts
Anthocertae
Division Bryophyta: Mosses
The Gametophyte Generation
Mosses are ambiguous occurring in all parts of the world and in almost every environment.
Morphology
The leafy stems, gametophores, of many moss plants grow close together, forming dense mounds.
In other species, particularly those of cool wet areas, the plants are more open and loose.
Scouleria gametophores grow as ribbons up to 15 cm long.
All moss stems have leaves, but they are not homologous.
Water Transport
The innermost cortex of the family Polytrichaceae cells are called hydroids
They conduct water and dissolved minerals.
They are elongated cells that lose their cytoplasm when mature.
Species that have hydroids typically have leptoids cells
Cells that resemble sieve cells
At the base of the stem are rhizoids
Small, unicellulartrichome-like structures that penetrate the surface of the substrate.
Development
Growth of the gametophore begins when a spore germinates and sends out a long, slender chlorophyllous cell.
This cell undergoes mitosis and produces a branched system of similar cells, the entire network is called a protonema.
Reproduction
The gametophore at some point produces gametangia.
The Sporophyte Generation
The upper cell grows by cell division and expansion into a simple apical sporangium called the capsule.
Metabolism and Ecology
Division Hepatophyta: Liverworts
The Gametophyte Generation
The Sporophyte Generation
Division Anthocerotophyta: Hornworts
The Gametophyte Generation
The Sporophyte Generation