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Like all land plants (embryophytes), bryophytes have life cycles with alternation of generations. [11] In each cycle, a haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, alternates with a diploid sporophyte, whose cells contain two sets of paired chromosomes. Gametophytes produce haploid sperm and eggs ...
Bryophytes, an informal group that taxonomists now treat as three separate land-plant divisions, namely: Bryophyta (mosses), Marchantiophyta (liverworts), and Anthocerotophyta (hornworts). In all bryophytes, the primary plants are the haploid gametophytes , with the only diploid portion being the attached sporophyte, consisting of a stalk and ...
By contrast, mosses and other bryophytes have only a single set of chromosomes and so are haploid (i.e. each chromosome exists in a unique copy within the cell). There is a period in the moss life cycle when they do have a double set of paired chromosomes, but this happens only during the sporophyte stage.
Embryophyte cells also generally have an enlarged central vacuole enclosed by a vacuolar membrane or tonoplast, which maintains cell turgor and keeps the plant rigid. In common with all groups of multicellular algae they have a life cycle which involves alternation of generations .
Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be unicellular or multicellular. [1]
In the strictest sense, the name plant refers to those land plants that form the clade Embryophyta, comprising the bryophytes and vascular plants.However, the clade Viridiplantae or green plants includes some other groups of photosynthetic eukaryotes, including green algae.
When this happens, the sperm and egg cell fuse to form a zygote, the cell from which the sporophyte stage of the life cycle will develop. Unlike all other bryophytes, the first cell division of the zygote is longitudinal. Further divisions produce three basic regions of the sporophyte.
Bryophytes in soil crusts include mosses and liverworts. Mosses are usually classified as short annual mosses or tall perennial mosses. Liverworts can be flat and ribbon-like or leafy. They can reproduce by spore formation or by asexual fragmentation, and photosynthesize to fix carbon from the atmosphere.