Hydrophilicity (botany)

from Wikipedia, the free encyclopedia

Hydrophilicity , also called hydrogamy or water bloom , describes the pollination of flowers by water as a transport medium for the pollen (water pollination ) or the adaptation of the plants to it. Hydrophilicity is a rare form of cross- pollination and only occurs in some aquatic plants . The pollination can take place below the water surface (hyphydrophilicity) or directly on or above the water surface (ephydrophilicity).

There is also the rain pollination the Ombrophilie (Ombrogamie) but what a chasmogame self-pollination is a wetted by rain bloom. This is not the same as ombrochory , the spreading of seeds by raindrops. Also different is the hydro kleistogamy where the flower remains closed.

Illustration of the large mermaid ( Najas marina ) with the flowers.

features

The following characteristics are common in water-pollinated plants:

  • The flowers are inconspicuous.
  • The flowers are unisexual ( dikline : monözie , diözie ).
  • Often come air fabric in front.
  • The - mostly thin - pollen wall is not wettable in the buoyant pollen grains .
  • The pollen grains are thread-like or the pollen tube germinates prematurely.
  • The scar has an enlarged surface.
  • There are only one or a few ovules per flower .

Hyphydrophilia

In the case of hyphydrophilic plants, pollination takes place below the water surface. The anthers open in the water. In some species, the pollen grains are thread-shaped, which makes it easier to find the stigma , for example in common seaweed ( Zostera marina ). In the whole genus of sea grasses ( Zostera ) the pollen grains are around 0.5 mm long and have no exine . In the case of the great mermaid ( Najas marina ), the pollen germinates into a tube in the dust bag. The flowers are small, inconspicuous and unisexual. The female flower usually has only one ovule . Also Ceratophyllum is pollinated under water, as some types of Callitriche .

Ephydrophilia

Illustration of the Canadian waterweed ( Elodea canadensis ) with flowers.

In the case of ephydrophilic plants, pollination takes place on or above the water surface. This form of pollination occurs, for example, in the frog-bite family . In the genera Vallisneria and Elodea , the male flowers separate from the plants and float on the water surface due to their air tissue ( aerenchyma ). In Elodea nutallii , the flowers open on the surface, the anthers release the buoyant pollen in tetrads onto the surface of the water. The female flowers are lifted to the surface of the water by stretching the hypanthium , where they develop their three sepals. The scars protrude into the water between the sepals. The sepals are water-repellent, so the water surface is lower here. Pollen tetrads that come near the female flowers are therefore attracted and thus reach the stigma.

In the case of Lagarosiphon , the pseudo waterweed, the pollen sticks to the anthers. These protrude horizontally from the flower, which drifts like a boat in the wind. If she comes near a female flower (which is built like Elodea's ), the boat tilts and the pollen-covered anthers brush against the stigma.

The male flowers of the ground nettle ( hydrilla ) also float on the water. They hurl the pollen, however, explosively, which flies up to 20 cm. In this case, only the inside of the flower cover of the female flowers is water-repellent, the outside is hydrophilic. The bell, which is open at the top, stands up to the edge in the water, the flower is only kept open by the surface tension of the water, the petals themselves are limp. This means that when there are waves, the flowers are closed and no water penetrates.

More examples of plants with hydrophilicity

literature

  • Peter Leins: blossom and fruit. Morphology, history of development, phylogeny, function, ecology. E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 2000, ISBN 3-510-65194-4 , pp. 207, 214-218.

Individual evidence

  1. ↑ Series of publications for vegetation science. Volumes 36–39, Federal Institute for Vegetation Science, Nature Conservation and Landscape Management , 2002, p. 152.

Web links