mosquito fern

mosquito fern

▪ fern genus
      any of six species in the fern family Salviniaceae of the division Pteridophyta (the lower vascular plants (plant)). This family contains only one other genus, Salvinia (10–12 species). Members of Azolla are distributed nearly worldwide but are most diverse in tropical regions. Mosquito ferns are very small plants, often less than 2.5 cm (1 inch) long, that float on the surface of still waters, sometimes becoming stranded on muddy banks. Their name is an allusion to the fact that the plants sometimes thoroughly cover the surface of a pond or other body of water, preventing mosquitoes and other insects from penetrating through to the water to lay eggs. The tiny leaves are in two alternating rows on either side of the stem and are divided into an upper green lobe and a lower white to transparent lobe. The sporangia (fern) are enclosed in small, structurally complex, globose structures known as sporocarps, with separate sporocarps formed containing either numerous microspores or a single megaspore. Both types of spores are globose (tetrahedral), but an average megaspore is 20 or more times larger than a microspore. The highly reduced gametophytes (gametophyte), which develop underwater, are mostly contained within the spore walls.

      Azolla is one of the most important ferns in agriculture. More money has been spent on its study and more scientific papers have been published involving this genus than on any other fern. Long ago, farmers in Vietnam and other parts of Southeast Asia discovered that rice fields in which mosquito ferns were released produced higher yields of grain. For centuries, families jealously guarded their individual strains of Azolla, keeping them alive in containers between plantings and inoculating the fields at the beginning of each crop cycle.

      The secret behind the use of mosquito fern as a “super fertilizer” is that within cavities of the green upper lobe of the leaves, there live colonies of a cyanobacterium ( blue-green algae), Anabaena azollae. These photosynthetic bacteria have the ability to transform atmospheric nitrogen into nitrate fertilizer. When individual plants of Azolla die, this nitrate fertilizer is released into the environment, where it becomes available to other plants. In addition to its use in rice fields, Azolla has been shown to benefit the cultivation of some other crops grown in paddies, such as taro. The plants have also been used in livestock and poultry feed.

      Scientists have bred numerous strains of Azolla in an effort to increase the efficiency of the nitrogen fixation and distribution cycles. Originally, these were from A. pinnata, the species used in traditional agriculture in Southeast Asia and native to the region. However, in the late 1970s, it was discovered that the American A. filiculoides also yielded good results and was more resistant to various diseases, so strains of this species have also been developed.

      Aside from their use in agriculture, mosquito ferns are sometimes cultivated in water gardens for their ornamental value.

George Yatskievych
 

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Universalium. 2010.

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Look at other dictionaries:

  • mosquito fern — plunksninė azolė statusas T sritis vardynas apibrėžtis Plūstinių šeimos pašarinis augalas (Azolla pinnata), paplitęs Afrikoje, Azijoje ir Australijoje. atitikmenys: lot. Azolla pinnata angl. ferny azolla; mosquito fern; water velvet šaltinis… …   Lithuanian dictionary (lietuvių žodynas)

  • mosquito fern — noun small free floating aquatic fern from the eastern United States to tropical America; naturalized in western and southern Europe • Syn: ↑floating fern, ↑Carolina pond fern, ↑Azolla caroliniana • Hypernyms: ↑aquatic fern, ↑water fern …   Useful english dictionary

  • large mosquito fern — šakotoji azolė statusas T sritis vardynas apibrėžtis Plūstinių šeimos dekoratyvinis augalas (Azolla filiculoides), paplitęs Šiaurės ir Pietų Amerikoje. atitikmenys: lot. Azolla filiculoides angl. azolla; large mosquito fern šaltinis Valstybinės… …   Lithuanian dictionary (lietuvių žodynas)

  • fern — fernless, adj. fernlike, adj. /ferrn/, n. any seedless, nonflowering vascular plant of the class Filicinae, of tropical to temperate regions, characterized by true roots produced from a rhizome, triangular fronds that uncoil upward and have a… …   Universalium

  • Fern — /ferrn/, n. a female given name. * * * Any of about 10,000–12,000 species (division Filicophyta) of nonflowering vascular plants that have true roots, stems, and complex leaves and reproduce by spores. Though ferns were once classified with the… …   Universalium

  • Fern — This article is about the group of pteridophyte plants. For other uses, see Fern (disambiguation). Ferns (Pteridophyta) Temporal range: Mid Devonian[1] Recent …   Wikipedia

  • mosquito plant — noun 1. or mosquito trap : an Asian vine (Cynanchum acuminatifolium) whose flowers sometimes entrap small insects 2. : a plant (as basil mint or pennyroyal) believed to be efficacious in driving away mosquitoes 3. : mosquito fern …   Useful english dictionary

  • floating fern — noun 1. small free floating aquatic fern from the eastern United States to tropical America; naturalized in western and southern Europe • Syn: ↑mosquito fern, ↑Carolina pond fern, ↑Azolla caroliniana • Hypernyms: ↑aquatic fern, ↑water fern …   Useful english dictionary

  • aquatic fern — noun ferns that grow in water • Syn: ↑water fern • Hypernyms: ↑fern • Hyponyms: ↑clover fern, ↑pepperwort, ↑pillwort, ↑Pilularia globulifera, ↑ …   Useful english dictionary

  • water fern — noun ferns that grow in water • Syn: ↑aquatic fern • Hypernyms: ↑fern • Hyponyms: ↑clover fern, ↑pepperwort, ↑pillwort, ↑Pilularia globulifera …   Useful english dictionary

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