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{{Taxobox
| color = lightgreen
| name = Mosquito fern
| image = Azolla caroliniana0.jpg
| image_width = 200px
| image_caption = ''Azolla caroliniana''
| regnum = [[Plant]]ae
| divisio = [[fern|Pteridophyta]]
| classis = [[Pteridopsida]]
| ordo = [[Salviniales]]
| familia = '''Azollaceae'''
| familia_authority = [[Richard Wettstein|Wettst.]]
| genus = '''''Azolla'''''
| genus_authority = [[Jean-Baptiste Lamarck|Lam.]]
| subdivision_ranks = Species
| subdivision =
''[[Azolla caroliniana]]'' <small>Willd.</small><br/>
''[[Azolla filiculoides]]'' <small>Lam.</small><br/>
''[[Azolla japonica]]'' <small>Franch. & Sav.</small><br/>
''[[Azolla mexicana]]'' <small>Presl</small><br/>
''[[Azolla microphylla]]'' <small>Kaulf.</small><br/>
''[[Azolla nilotica]]'' <small>Decne. ex Mett.</small><br/>
''[[Azolla pinnata]]'' <small>R.Br.</small>
}}
'''''Azolla''''' ('''mosquito fern''', '''duckweed fern''', '''fairy moss''', '''water fern''') is a [[genus]] of seven species of [[aquatic plant|aquatic]] [[fern]]s, the only genus in the family '''Azollaceae'''. They are extremely reduced in form and specialized, looking nothing like conventional ferns but more resembling [[duckweed]] or some [[moss]]es.
They float on the surface of water by means of numerous, small, closely-overlapping scale-like leaves, with their roots hanging in the [[water]]. They form a [[symbiosis|symbiotic]] relationship with the [[cyanobacterium]] ''[[Anabaena|Anabaena azollae]]'', which allows the plants to [[nitrogen fixation|fix nitrogen]] from the [[air]].
[[Image:Azolla01.jpg|thumb|left|SEM image of Azolla surface]]
Because of their nitrogen-fixing capability, they have enabled an increase in agricultural productivity in parts of southeast [[Asia]]. When [[rice]] paddies are flooded in the spring, they can be inoculated with ''Azolla'', which then quickly multiplies to cover the water, suppressing weeds. As the plants die, they contribute [[nitrogen]] to the rice plants, and as the rice paddy dries out, the ''Azolla'' all eventually die, making an exceptional [[green manure]], providing up to nine tonnes of protein per hectare per year [http://www.fao.org/ag/AGA/AGAP/FRG/afris/DATA/558.htm FAO figures]. As such, ''Azolla'' may be used in place of agrochemicals.
''Azolla'' are also serious [[weed]]s in many parts of the world, covering bodies of water so thickly that no water is exposed. This is where they derive the name 'mosquito fern', from the belief that no [[mosquito]] can penetrate the coating of fern to lay its [[Egg (biology)|egg]]s in the water{{Fact|date=February 2007}}. ''Azolla'' is reputed to be able to grow so quickly that it can double its mass in three days under good conditions.
Most of the species can produce large amounts of [[anthocyanin]]s in bright sunlight, creating an intense red color and causing the water surface to appear to be covered with a red carpet.
Mosquito ferns are safe to grow in cool temperate areas with prolonged freezing in winter, as they cannot overwinter in these conditions. They are often grown as an [[ornamental plant]] by [[water garden|water-garden]] hobbyists.
==Reproduction==
[[Image:Canning rv azolla 02 gnangarra.jpg|thumb|Azolla on the [[Canning River, Western Australia]]]]
Azolla can reproduce [[asexual reproduction|asexual]]y by breaking off. Each branch that breaks off forms a new plant.
Azolla can also reproduce sexually. Like all ferns, Azolla produce [[spores]]. Unlike most [[fern]]s, Azolla produces two kinds of spores. During the summer months, numerous spherical structures called [[Sporocarp (ferns)|sporocarps]] form on the undersides of the branches. The male sporocarp is greenish or reddish and looks like the egg mass of an insect or spider. It is two millimeters in diameter, and inside are numerous male [[sporangia]]. Male spores (microspores) are extremely small and are produced inside each [[microsporangium]]. One very curious thing about microspores is that they tend to stick together in little clumps or masses called [[massulae]].
Female sporocarps are much smaller, and only contain
one sporangium and one functional spore. Since an individual female spore is considerably larger than a male spore, it is termed a [[megaspore]].
Azolla has microscopic male and female gametophytes that develop inside the male and female [[spores]]. The female [[gametophyte]] protrudes from the megaspore and bears one to several [[archegonia]], each containing a single egg. The microspore forms a male gametophyte with a single antheridium which produces eight swimming sperm (Scagel ''et al''. 1966). The barbed [[glochidia]] on the male spore clusters presumably cause them to cling to the female megaspores, thus facilitating fertilization.
==Climatic paleontology==
[[Image:Canning rv azolla 10 gnangarra.jpg|thumb|Azolla covering the Canning River]]
A study of [[arctic]] climatology reported that azolla may have had a significant role in reversing a [[greenhouse effect]] that occurred 55 million years ago that caused the region around the north pole to turn into a hot tropical environment. This research conducted by the Institute of Environmental Biology at [[Utrecht University]] claims that large dense patches of azolla growing around freshwater lakes formed by the climate change eventually consumed enough [[carbon dioxide]] for the greenhouse effect to reverse.
==References==
*[http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?1209 Germplasm Resources Information Network: ''Azolla'']
*[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=103297 Flora of North America: ''Azolla'']
*[http://www.efloras.org/florataxon.aspx?flora_id=3&taxon_id=103297 Flora of China: ''Azolla'' species list]
*[http://aquaplant.tamu.edu/database/floating_plants/mosquito_fern_mgmt.htm aquaplant.tamu.edu]
*[http://plants.usda.gov/java/profile?symbol=AZPI plants.usda.gov]
*[http://www.royalbcmuseum.bc.ca/end_species/species/mfern.html royalbcmuseum.bc.ca]
*[http://waynesword.palomar.edu/plnov98.htm Marriage Between A Fern & Cyanobacterium]
*Scagel, R. F., Bandoni, R. J., Rouse, G. E., Schofield, W. B., Stein, J. R., & Taylor, T. M. C. (1966). ''An Evolutionary Survey of the Plant Kingdom''. Wadsworth.
[[Category:Pteridophyta]]
[[Category:Aquatic plants]]
| color = lightgreen
| name = Mosquito fern
| image = Azolla caroliniana0.jpg
| image_width = 200px
| image_caption = ''Azolla caroliniana''
| regnum = [[Plant]]ae
| divisio = [[fern|Pteridophyta]]
| classis = [[Pteridopsida]]
| ordo = [[Salviniales]]
| familia = '''Azollaceae'''
| familia_authority = [[Richard Wettstein|Wettst.]]
| genus = '''''Azolla'''''
| genus_authority = [[Jean-Baptiste Lamarck|Lam.]]
| subdivision_ranks = Species
| subdivision =
''[[Azolla caroliniana]]'' <small>Willd.</small><br/>
''[[Azolla filiculoides]]'' <small>Lam.</small><br/>
''[[Azolla japonica]]'' <small>Franch. & Sav.</small><br/>
''[[Azolla mexicana]]'' <small>Presl</small><br/>
''[[Azolla microphylla]]'' <small>Kaulf.</small><br/>
''[[Azolla nilotica]]'' <small>Decne. ex Mett.</small><br/>
''[[Azolla pinnata]]'' <small>R.Br.</small>
}}
'''''Azolla''''' ('''mosquito fern''', '''duckweed fern''', '''fairy moss''', '''water fern''') is a [[genus]] of seven species of [[aquatic plant|aquatic]] [[fern]]s, the only genus in the family '''Azollaceae'''. They are extremely reduced in form and specialized, looking nothing like conventional ferns but more resembling [[duckweed]] or some [[moss]]es.
They float on the surface of water by means of numerous, small, closely-overlapping scale-like leaves, with their roots hanging in the [[water]]. They form a [[symbiosis|symbiotic]] relationship with the [[cyanobacterium]] ''[[Anabaena|Anabaena azollae]]'', which allows the plants to [[nitrogen fixation|fix nitrogen]] from the [[air]].
[[Image:Azolla01.jpg|thumb|left|SEM image of Azolla surface]]
Because of their nitrogen-fixing capability, they have enabled an increase in agricultural productivity in parts of southeast [[Asia]]. When [[rice]] paddies are flooded in the spring, they can be inoculated with ''Azolla'', which then quickly multiplies to cover the water, suppressing weeds. As the plants die, they contribute [[nitrogen]] to the rice plants, and as the rice paddy dries out, the ''Azolla'' all eventually die, making an exceptional [[green manure]], providing up to nine tonnes of protein per hectare per year [http://www.fao.org/ag/AGA/AGAP/FRG/afris/DATA/558.htm FAO figures]. As such, ''Azolla'' may be used in place of agrochemicals.
''Azolla'' are also serious [[weed]]s in many parts of the world, covering bodies of water so thickly that no water is exposed. This is where they derive the name 'mosquito fern', from the belief that no [[mosquito]] can penetrate the coating of fern to lay its [[Egg (biology)|egg]]s in the water{{Fact|date=February 2007}}. ''Azolla'' is reputed to be able to grow so quickly that it can double its mass in three days under good conditions.
Most of the species can produce large amounts of [[anthocyanin]]s in bright sunlight, creating an intense red color and causing the water surface to appear to be covered with a red carpet.
Mosquito ferns are safe to grow in cool temperate areas with prolonged freezing in winter, as they cannot overwinter in these conditions. They are often grown as an [[ornamental plant]] by [[water garden|water-garden]] hobbyists.
==Reproduction==
[[Image:Canning rv azolla 02 gnangarra.jpg|thumb|Azolla on the [[Canning River, Western Australia]]]]
Azolla can reproduce [[asexual reproduction|asexual]]y by breaking off. Each branch that breaks off forms a new plant.
Azolla can also reproduce sexually. Like all ferns, Azolla produce [[spores]]. Unlike most [[fern]]s, Azolla produces two kinds of spores. During the summer months, numerous spherical structures called [[Sporocarp (ferns)|sporocarps]] form on the undersides of the branches. The male sporocarp is greenish or reddish and looks like the egg mass of an insect or spider. It is two millimeters in diameter, and inside are numerous male [[sporangia]]. Male spores (microspores) are extremely small and are produced inside each [[microsporangium]]. One very curious thing about microspores is that they tend to stick together in little clumps or masses called [[massulae]].
Female sporocarps are much smaller, and only contain
one sporangium and one functional spore. Since an individual female spore is considerably larger than a male spore, it is termed a [[megaspore]].
Azolla has microscopic male and female gametophytes that develop inside the male and female [[spores]]. The female [[gametophyte]] protrudes from the megaspore and bears one to several [[archegonia]], each containing a single egg. The microspore forms a male gametophyte with a single antheridium which produces eight swimming sperm (Scagel ''et al''. 1966). The barbed [[glochidia]] on the male spore clusters presumably cause them to cling to the female megaspores, thus facilitating fertilization.
==Climatic paleontology==
[[Image:Canning rv azolla 10 gnangarra.jpg|thumb|Azolla covering the Canning River]]
A study of [[arctic]] climatology reported that azolla may have had a significant role in reversing a [[greenhouse effect]] that occurred 55 million years ago that caused the region around the north pole to turn into a hot tropical environment. This research conducted by the Institute of Environmental Biology at [[Utrecht University]] claims that large dense patches of azolla growing around freshwater lakes formed by the climate change eventually consumed enough [[carbon dioxide]] for the greenhouse effect to reverse.
==References==
*[http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?1209 Germplasm Resources Information Network: ''Azolla'']
*[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=103297 Flora of North America: ''Azolla'']
*[http://www.efloras.org/florataxon.aspx?flora_id=3&taxon_id=103297 Flora of China: ''Azolla'' species list]
*[http://aquaplant.tamu.edu/database/floating_plants/mosquito_fern_mgmt.htm aquaplant.tamu.edu]
*[http://plants.usda.gov/java/profile?symbol=AZPI plants.usda.gov]
*[http://www.royalbcmuseum.bc.ca/end_species/species/mfern.html royalbcmuseum.bc.ca]
*[http://waynesword.palomar.edu/plnov98.htm Marriage Between A Fern & Cyanobacterium]
*Scagel, R. F., Bandoni, R. J., Rouse, G. E., Schofield, W. B., Stein, J. R., & Taylor, T. M. C. (1966). ''An Evolutionary Survey of the Plant Kingdom''. Wadsworth.
[[Category:Pteridophyta]]
[[Category:Aquatic plants]]