Azolla

Big Algenfarn ( Azolla filiculoides )

The algae ferns ( Azolla ) belong to the family of Schwimmfarngewächse. Previously they were placed in a separate family Algenfarngewächse. It consists of seven species that are native to the tropics.

Features

Algae ferns are 0.5 to 15 cm wide, driving on the water surface plants. They spread by stolons and can overgrow the water surface over a large area. Its root hair reaches a few inches down, but are not anchored in the ground. Therefore, ferns algae occur only in standing or slow- flowing waters.

The nitrogen-fixing cyanobacteria algae ferns ( azollae Anabaena, Nostoc azollae ) in Blatthöhlungen. This symbiosis is used in rice cultivation: Azolla grows on the rice fields and contributes according to its composting to a supply of nitrogen at. In addition, a dense growth of Azolla prevents the development of many mosquito species, which is advantageous in areas where malaria occurs.

Algae ferns are used as ornamental plants in garden ponds or aquariums, and have spread to many parts of the world. Some of them have developed into a " weed ". In Germany, this applies to the type Azolla filiculoides, which is run as a " naturalized neophyte " by the Federal Agency for Nature Conservation. The weevil Stenopelmus rufinasus been successfully used for biological control.

It is believed that in the Arctic repeatedly running over several hundred thousand years bloom of a Algenfarns had removed much carbon dioxide from the atmosphere. This Azolla event meant that in the Eocene 49 million years ago the earth cooled strong and the global climate was transferred from a warm period in the still existing ice age, with constant ice at both poles.

Species

The genus Azolla include the following types:

Asian tropical species

  • Japanese Algenfarn ( Azolla japonica Franch. & Sav. )
  • Big Algenfarn ( Azolla filiculoides Lam. )
  • Pacific Algenfarn ( Azolla pinnata R. Br ) (also comes in Africa )

African Style

  • African Algenfarn ( Azolla nilotica Decne. Ex Mett. )

American species

  • Small Algenfarn ( Azolla caroliniana Willd. )
  • Mexican Algenfarn ( Azolla mexicana Presl )
  • Leaved Algenfarn ( Azolla microphylla Kaulf. )
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