Lemnoideae

Several dwarf and duckweed

The duckweed plants ( Lemnoideae ) are a subfamily within the arum family ( Araceae ). In other surveys, however, they are treated as a separate family Lemnaceae and also at a higher taxonomic level classified differently than shown here. The duckweed plants different species of aquatic plants are summarized: Lemna, Spirodela, Landoltia, Wolffia and Wolffiella. Three of them are also represented by species in Central Europe.

Common to all is that it is only a few millimeters large " flakes " (more precisely, sprout limbs ) is lacking a division into stem and leaf. They swim floating on the surface of water bodies, inhabit this often in masses and they can completely cover. This floating carpets are colloquially often referred to as duckweed.

Genera and species

In this subfamily, there are five genera with about 37 to 38 species:

• Genus duckweed ( Spirodela Schleiden ): There are two or three duckweed species: Vielwurzelige duckweed, frequent root - duckweed, European duckweed ( Spirodela polyrhiza (L.) Schleiden ): It is the only species of the genus, which is found also in Central Europe.
• Spirodela intermedia W.D.J. cook

• Genus dwarf duckweed ( Wolffia Horkel ex Schleid. ): Of the approximately five to eleven dwarf duckweed species: Rootless Duckweed Dwarf, ducks lens ( Wolffia arrhiza Horkel ex CFHWimmer ): It is the only species of the genus, which is found in Central Europe.
• Wolffia borealis ( Engelm. ex Hegelm. ) Ex Landolt Landolt & Wildi
• Wolffia brasiliensis Weddell
• Wolffia columbiana Karst.
• Wolffia globosa ( Roxb. ) Hartog & Plas

• Genus duckweed ( Lemna L.): About nine to 13 species belong to the duckweed Lemna genus; five are also in Central Europe: Small duckweed, small duckweed ( Lemna minor L. )
• Duckweed, cross - duckweed, water - immersion lens ( Lemna trisulca L.)
• Hunchback Duckweed, Humpback duckweed ( Lemna gibba L.)
• Petite duckweed ( Lemna minuta Humb. , Bonpl. & Kunth ) ( an American Neophyte )
• Red Duckweed, red duckweed ( Lemna turionifera Landolt )

• Lemna aequinoctialis Welw.
• Lemna obscura (Austin ) Daub
• Lemna perpusilla Torr.
• Lemna Valdiviana Phil

• Genus Landoltia Les & Crawford: with only one kind that does not occur in Europe: Landoltia punctata ( G.Meyer ) Les & Crawford ( Syn: Spirodela punctata ( GFWMeyer ) CHThompson )

• Genus Wolffiella Hegelmaier: with at least three types, they are lacking in Europe.

General

The species of duckweed plants drive usually in mass societies at the surface ( Lemna trisulca also submerged ) of standing, rather nutrient-rich waters. Air chambers in their offspring members to give them the necessary lift. During the summer months can be covered smaller to medium ponds and ponds entirely with a green carpet swimming very quickly the entire water surface. Either dominance of a single species or stocks are companies from several species are observed. With the hanging threads down root nutrient salts are taken from the open water.

By covering all water surfaces duckweed affect the rest of life significantly: It penetrates very little sunlight in the water body is a thing among other things, prevents the growth of diving foliage plants and complicates the exchange of oxygen. At the same time, the water warms less or only delayed, so that ( for example, the tadpoles the alternating hot and Anura ) develop on the outside temperature -dependent species is slow and grow. The large biomass production of dying in the autumn sprout members also contributes to the siltation of the watercourse. All too lush growth of duckweed plants indicates a rich to excessive nutrient supply of the water. This is often caused by direct or diffuse pollution from agriculture with.

Duckweed multiply either remain connected to the mother plant or become self-employed mainly asexually by budding, in the laterally growing shoots. Only rarely small, inconspicuous flowers are monoecious pronounced. In autumn the plants store starch, and then falls to winter on the frost -free base form or winter buds. In addition, they also use Hydroepizoochorie by the whole small plant of animals is kidnapped. This enables them to tap into new habitats.

Duckweed plants are used worldwide by fish, higher animals and also of human beings as food and are the fastest growing higher plants worldwide. As a food, they are especially valued because they contain all essential amino acids ( in dry weight up to 43% proteins, also up to 6 % fat and 17% carbohydrates). They also possess the ability to bind significant amounts of nitrogen and minerals from waste water.