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Chloroplasts (green discs) and accumulated starch granules in cells of Bryum capillare. Botanically, mosses are non-vascular plants in the land plant division Bryophyta. They are usually small (a few centimeters tall) herbaceous (non-woody) plants that absorb water and nutrients mainly through their leaves and harvest carbon dioxide and sunlight to create food by photosynthesis.
Heterospory evolved due to natural selection that favoured an increase in propagule size compared with the smaller spores of homosporous plants. [ 2 ] Heterosporous plants, similar to anisosporic plants [ clarification needed ] , produce two different sized spores in separate sporangia that develop into separate male and female gametophytes.
Many club-moss gametophytes are mycoheterotrophic and long-lived, residing underground for several years before emerging from the ground and progressing to the sporophyte stage. [ 4 ] Lycopodiaceae and spikemosses ( Selaginella ) are the only vascular plants with biflagellate sperm, an ancestral trait in land plants otherwise only seen in ...
Plants that are homosporous produce spores of the same size and type. Heterosporous plants, such as seed plants , spikemosses , quillworts , and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male".
Some lycophytes are homosporous while others are heterosporous. [5] When broadly circumscribed, the lycophytes represent a line of evolution distinct from that leading to all other vascular plants, the euphyllophytes, such as ferns, gymnosperms and flowering plants.
Most heterosporous plants there are two kinds of sporangia, termed microsporangia and megasporangia. Sporangia (clustered in sori) on a fern leaf Equisetum arvense strobilus cut open to reveal sporangia. Sporangia can be terminal (on the tips) or lateral (placed along the side) of stems or associated with leaves.
In the homosporous families Lycopodiaceae and Huperziaceae, spores germinate into bisexual free-living, subterranean and mycotrophic gametophytes that derive nutrients from symbiosis with fungi. In Isoetes and Selaginella , which are heterosporous, microspores and megaspores are dispersed from sporangia either passively or by active ejection. [ 8 ]
Azolla (mosquito fern, water fern, fairy moss) is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, looking nothing like other typical ferns but more resembling the form of some mosses or even duckweeds .