Zosteraceae

Seagrass

The seagrass plants ( Zosteraceae ) are a small plant family of the order of the plantain -like ( Alismatales ). The only two to three genera with about 18 species thrive almost worldwide as a submersed aquatic plants in the salt water in coastal areas, but mainly outside the tropics.

  • 4.1 Notes and references

Description

Vegetative characteristics

Seaweed plants grow as mostly perennial, herbaceous plants, rarely are they annuals that form under water ( submerged ) in the seas " carpets ". They are anchored at their monopodial rhizomes with adventitious roots without lateral roots in the seabed. They look like grass, so you used for them as for some other growing marine species of frog spoon -like ( Alismatales ) the common name of seaweed.

The alternate and arranged in two rows leaves consist of leaf sheath and leaf blade, without petiole. In the leaf sheaths, their edges can touch; they are more durable than the leaf blades and decompose to form fiber bundles. The long, ribbon-like leaf blades are simple, linear, entire, and parallel-veined network without nerves. There are scales available to the leaf axils. The leaves have a persistent Basalmeristem that they can continue to grow from their base here. There are no stomata present.

Generative features

Seagrass plants are monoecious ( monoecious ) or dioecious ( dioecious ) getrenntgeschlechtig. There are formed on a more or less long inflorescence stem lateral or terminal inflorescences. The inflorescences have the usual for frog spoon-shaped structure: an inflorescence axis ( spadix ) that are included in a single bract ( spathe ) ( surrounded by it ). The flattened spadix has only one side many flowers. The flowers are often a cover sheet.

The always functionally unisexual flowers are reduced and have no perianth. The male flowers have only one stamen and the anthers opening longitudinally. The three-cell pollen grains have no apertures. The female flowers contain a superior ovaries, which consists of two carpels, but apparently consists of only one carpel. Each ovary contains only one sitting, hanging, orthotropic, bitegmische, pseudocrassinucellate ovule. Pollination is in the water by so-called thread pollen.

Are formed achänenähnliche seeded nut fruits. The seeds contain no endosperm, but a straight embryo with one seed leaf ( cotyledon ). The membranous seed coat ( testa) contains no Phytomelanine.

The chromosomes are 0.9 to 1.6 microns long. The basic chromosome numbers be x = 6, 9, 10

Dissemination

The three genera with about 18 species are distributed in temperate to subtropical areas in the coastal waters of the seas, so in cold, cool to warm, but hardly in tropical warm salt water. So they do not come off the Chilean coast with their cold ocean current but above on the east coast of South America. You are missing on the western shores of Africa, but ranging from East Africa to the Cape of Good Hope. You are lacking in the Caribbean. At the Chinese coast two genera and seven species occur and the North American coasts occur two genera and five species.

They grow on the seabed, including in the tidal area of the seas. For example, they grow throughout the North Atlantic and North Pacific. Stocks, there are also between Australia and New Zealand, also off the coast of East Africa to Madagascar line.

System

The Zosteraceae family was erected in 1829 by Barthélemy Charles Joseph Dumortier in analysis of Familles de Plantes, pp. 65-66. Type genus Zostera is L..

The Zosteraceae family contains only two or three genera with about 18 ( to 20) types:

  • Heterozostera ( Setch. ) Hartog: The approximately four species occur on the seashores mainly found in the southern hemisphere.
  • Phyllospadix Hook:. The five species occur on the coasts of the northern Pacific.
  • Zostera L.: The approximately twelve (up to 16) species on the coasts of the northern hemisphere (if sl and southern hemisphere ). After Jacobs & Les 2009 she also includes the species of the genus, and is divided into three subgenera: subg Zostera. Zostera, Zostera subg. Heterozostera and Zostera subg. Zosterella.

Swell

  • The Zosteraceae in APWebsite family. ( Section systematics and description)
  • The Zosteraceae at DELTA family. ( Description section )
  • Robert R. Haynes: Zosteraceae in the Flora of North America, Volume 22, 2000: Online. ( Description section )
  • Youhao Guo, Robert R. Haynes & C. Barre Hellquist: Zosteraceae. In: Wu Zheng -yi, Peter H. Raven & Deyuan Hong (eds.): Flora of China. Acoraceae - Cyperaceae. Volume 23, Science Press and Missouri Botanical Garden Press, Beijing, among others, September 2, 2010, ISBN 978-1-930723-99-3, pp. 106-108 ( online text is identical to the printed work, " Zosteraceae - Online "). (Section Description, systematics and distribution )
  • Leslie Watson, 2008: entry in the Western Australian flora. ( Description section )
  • SWL Jacobs & Les DH: New Combinations in Zostera ( Zosteraceae ) In: Telopea 12, 2009, pp. 419-423. ISSN0312 - 9764 Full Text PDF.
Ovary (botany) Cereal germ testa (botany)
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