are an informal group consisting of three divisions of non-vascular land plants (embryophytes
), the liverworts
They are characteristically limited in size and prefer moist habitats although they can survive in drier environments.
The bryophytes consist of about 20,000 plant species.
Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they do not produce flowers
. They reproduce via spores
. Bryophytes are usually considered to be a paraphyletic
group and not a monophyletic
group, although some studies have produced contrary results. Regardless of their status, the name is convenient and remains in use as an informal collective term. The term "bryophyte" comes from Greek
"tree-moss, oyster-green" and φυτόν, phyton
The defining features of bryophytes are:
Bryophytes exist in a wide variety of habitats. They can be found growing in a range of temperatures (cold arctics and in hot deserts), elevations (sea-level to alpine), and moisture (dry deserts to wet rainforests).
Bryophytes can grow where vascularized plants cannot because they do not depend on roots for an uptake of nutrients from soil. Bryophytes can survive on rocks and bare soil.
Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations. In each cycle, a haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, alternates with a diploid sporophyte, whose cell contain two sets of paired chromosomes. Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes. Sporophytes produce haploid spores by meiosis, that grow into gametophytes.
Bryophytes are gametophyte dominant, meaning that the more prominent, longer-lived plant is the haploid gametophyte. The diploid sporophytes appear only occasionally and remain attached to and nutritionally dependent on the gametophyte. In bryophytes, the sporophytes are always unbranched and produce a single sporangium (spore producing capsule).
This page was last edited on 21 May 2018, at 16:16.
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