- Key People:
- William Starling Sullivant
bryophyte
-
What is a bryophyte?
Bryophytes, also known as nonvascular plants, include mosses, hornworts, and liverworts. They are second to flowering plants in diversity. Lacking roots, stems, or leaves, bryophytes don't have the vascular tissue found in other plants that conduct water and food internally.
Bryophytes are typically small land plants that grow no more than a few centimeters tall. They are mostly found in damp or wet, shaded environments on rocks, trees, and soil because they depend on their surroundings for moisture. Some mosses can survive long periods of dryness and freezing, and they quickly restart photosynthesis when moisture returns.
Bryophytes reproduce sexually with a nonmotile egg and motile sperm. They have existed for around 500 million years and are believed to have evolved from complex green algae that invaded land.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are the main types of plants that are considered bryophytes?
Bryophytes, also known as nonvascular plants, include three main types of plants: mosses (Bryophyta), liverworts (Marchantiophyta), and hornworts (Anthocerotophyta). They do not have specialized vascular tissue, true roots, stems, or leaves.
- Mosses True mosses are in the division Bryophyta. The moss gametophyte has leaflike structures (phyllids) arranged on a stemlike axis (caulid).
- Liverworts Liverworts are in the division Marchantiophyta. Thallose liverworts are branching and ribbonlike, while leafy liverworts can be found on tree trunks in damp woods.
- Hornworts Hornworts are in the division Anthocerotophyta. They are small nonvascular plants that grow on damp soils or rocks in tropical and warm temperate regions.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How are bryophytes different from other plants like ferns or flowering plants?
Bryophytes, including mosses, liverworts, and hornworts, differ significantly from vascular plants like ferns and flowering plants. Bryophytes are nonvascular plants, meaning they lack the specialized vascular tissue (xylem and phloem) for internal water and food conduction found in ferns and flowering plants.
The life cycle of bryophytes is characterized by a dominant gametophyte generation, which is perennial and photosynthetically independent. In contrast, vascular plants have a dominant sporophyte generation. Bryophytes also lack true roots, stems, and leaves, though they have analogous structures on their gametophores.
Bryophytes depend on their immediate surroundings for moisture because they generally lack conducting cells and a well-developed cuticle to limit dehydration.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Where are bryophytes commonly found in nature?
Bryophytes, including mosses, liverworts, and hornworts, thrive in constantly humid and equable climates, from the tropics to polar regions. They are frequently found in wetlands, near watercourses, and in areas with prolonged snowmelt.
Many bryophytes grow on soil, the remains of other plants, or on living or decaying plant matter. Others colonize bare rock surfaces, and some are aquatic. They can be found on forest floors, rock surfaces, and tree trunks, often forming deep carpets in humid temperate or subtropical climates. Some even grow in unusual habitats such as animal waste, cavern mouths, or copper-rich substrates.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do bryophytes reproduce if they don’t have seeds?
Bryophytes, such as mosses, hornworts, and liverworts, are nonvascular seedless plants that reproduce via alternation of generations.
The life cycle alternates between a sexual phase (gametophyte) and an asexual phase (sporophyte). The gametophyte produces sex organs, sperm, and eggs, while the sporophyte produces spores. Sperm fertilizes an egg within the archegonium, resulting in a diploid zygote that develops into an embryonic sporophyte. The sporophyte remains dependent on the gametophyte for water, minerals, and nutrients. Mature bryophytes have a single sporangium that releases spores, which then germinate to produce a protonema, which precedes the gametophyte.
Additionally, the gametophyte of some bryophyte species can reproduce asexually through specialized cells called gemmae or by fragmentation.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why are bryophytes important to the environment and ecosystems?
Bryophytes play a crucial role in various ecosystems. They can endure dryness and freezing, resuming photosynthesis when moisture returns.
Bryophytes contribute to soil formation on barren terrain, retain soil moisture, and recycle nutrients in forests, which helps to determine the productivity and nutrient levels of different forest types. Certain mosses are pioneer plants that can grow in bare areas. The moss genus Sphagnum is key to forming waterlogged, acidic peatlands, which influences the surrounding landscape's hydrology by absorbing and holding water.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
bryophyte, traditional name for any nonvascular seedless plant—namely, any of the mosses (division Bryophyta), hornworts (division Anthocerotophyta), and liverworts (division Marchantiophyta). Most bryophytes lack complex tissue organization, yet they show considerable diversity in form and ecology. They are widely distributed throughout the world and are relatively small compared with most seed-bearing plants.
The bryophytes show an alternation of generations between the independent gametophyte generation, which produces the sex organs and sperm and eggs, and the dependent sporophyte generation, which produces the spores. In contrast to vascular plants, the bryophyte sporophyte usually lacks a complex vascular system and produces only one spore-containing organ (sporangium) rather than many. Furthermore, the gametophyte generation of the bryophyte is usually perennial and photosynthetically independent of the sporophyte, which forms an intimate interconnection with the gametophytic tissue, especially at the base, or foot, of the sporophyte. In most vascular plants, however, the gametophyte is dependent on the sporophyte. In bryophytes the long-lived and conspicuous generation is the gametophyte, while in vascular plants it is the sporophyte. Structures resembling stems, roots, and leaves are found on the gametophore of bryophytes, while these structures are found on the sporophytes in the vascular plants. The sporophyte releases spores, from which the gametophytes ultimately develop.
The gametophyte of some bryophyte species reproduces asexually, or vegetatively, by specialized masses of cells (gemmae) that are usually budded off and ultimately give rise to gametophytes. Fragmentation of the gametophyte also results in vegetative reproduction: each living fragment has the potential to grow into a complete gametophyte. The mature gametophyte of most mosses is leafy in appearance, but some liverworts and hornworts have a flattened gametophyte, called a thallus. The thallus tends to be ribbonlike in form and is often compressed against the substratum to which it is generally attached by threadlike structures called rhizoids. Rhizoids also influence water and mineral uptake.
" height="20" alt="HEW Logo">
General features
Thallose bryophytes vary in size from a length of 20 cm (8 inches) and a breadth of 5 cm (2 inches; the liverwort Monoclea) to less than 1 mm (0.04 inch) in width and less than 1 mm in length (male plants of the liverwort Sphaerocarpos). The thallus is sometimes one cell layer thick through most of its width (e.g., the liverwort Metzgeria) but may be many cell layers thick and have a complex tissue organization (e.g., the liverwort Marchantia). Branching of the thallus may be forked, regularly frondlike, digitate, or completely irregular. The margin of the thallus is often smooth but is sometimes toothed; it may be ruffled, flat, or curved inward or downward.
Leafy bryophytes grow up to 65 cm (2 feet) in height (the moss Dawsonia) or, if reclining, reach lengths of more than 1 metre (3.3 feet; the moss Fontinalis). They are generally less than 3 to 6 cm (1.2 to 2.4 inches) tall, and reclining forms are usually less than 2 cm (0.8 inch) long. Some, however, are less than 1 mm in size (the moss Ephemerum). Leaflike structures, known as phyllids, are arranged in rows of two or three or more around a shoot or may be irregularly arranged (e.g., the liverwort Takakia). The shoot may or may not appear flattened. The phyllids are usually attached by an expanded base and are mainly one cell thick. Many mosses, however, possess one or more midribs several cells in thickness. The phyllids of bryophytes generally lack vascular tissue and are thus not analogous to the true leaves of vascular plants.
Most gametophytes are green, and all except the gametophyte of the liverwort Cryptothallus have chlorophyll. Many have other pigments, especially in the cellulosic cell walls but sometimes within the cytoplasm of the cells.
Bryophytes form flattened mats, spongy carpets, tufts, turfs, or festooning pendants. These growth forms are usually correlated with the humidity and sunlight available in the habitat.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
