Laminaria digitata
The kelp ( Laminaria digitata ) is a Braunalgenart of the order Laminariales. It forms on the coasts of the North Atlantic stocks extended ( Tangwälder ) and is also present in the North Sea and Baltic Sea. It is used commercially for the production of alginate.
- 6.1 Notes and references
Description
The kelp is a handsome, multi-annual Tang of palm like habit, which can be more than 2 meters long. The sporophyte is attached with a strong claw-like holdfast ( rhizoids ) on rocky ground. Above it, the thallus is divided into a stick ( Cauloid ) and a sheet-like surface ( Phylloid ) and has differentiated tissue.
The stem is flattened, elastic and has a smooth surface, which is usually free of epiphytes. The length of the stem reaches populated depending on the water depth about 20 to 40 cm, its diameter is about 2 cm. It consists of a cortex and a central body, run in the real pathways. The brown to dark brown, leathery, rough Phylloid with a length up to 1.5 m and a width up to 50 cm is divided finger-shaped and widens without Ausrandung immediately above the stalk.
The oar differs from similar Palmentang ( Laminaria hyperborea ) by its flattened, flexible, smooth stem and the leaves are darker surface with gradually broadened leaf base. In addition, the rhizoid is not tapered.
Deciduous
The Journal of Fingertangs is renewed every year. Stored in the old deciduous reserve materials are transported to the growth zone to early winter. With increasing light grows in the spring of the leaf grass-roots approach a new Phylloid, where the last year's sheet still seated until the beginning of May, while it degenerates at the ends.
Development
When kelp is a generational change occurs with two very different generations. The visible is the diploid sporophyte Tang. From June to October, the tubular sporangia are formed on the Phylloid at irregular darker spots ( sori ). In each sporangium produced by meiosis 32 mobile zoospores. These grow to the haploid gametophyte, which consists of microscopic, branched hyphae. Triggered by blue light and low temperatures, the eggs and sperm are formed here. The spermatozoids are attracted by the pheromone Lamoxiren of the egg. After fertilization, the zygote sets and germinates into a young sporophyte. The young plants are fertile for the first time with two or three years.
Ecology
The growth optimum of the Fingertangs is ( 5) 10 to 17 ° C, the species is therefore adapted to cold temperate seas. In the extremely hot summers of 2003 and 2006, no meiospores were released at Helgoland, although sori were present. Therefore, the observed decline in many areas of the kelp is considered as a result of global warming
Sea urchins of the genus Strongylocentrotus, which have multiplied en masse after overfishing can erode the entire holdings Fingertangs and completely destroy, so that all that remains is the bare ground. The Grey top shell ( Gibbula cineraria ), the Banded Grübchenschnecke ( Lacuna vincta ) and the isopod Idotea granulosa eat the kelp. Compared to vegetative structures, since they prefer the Sori and also frequently occur in masses, they can strongly affect the propagation of Fingertangs.
Occurrence
The kelp is common off the coasts of the North Atlantic. In Europe it is found from Iceland and Spitsbergen to Spain and the Canary Islands. It occurs on a suitable substrate in the North Sea and Baltic Sea, for example, in Helgoland. He also grows Greenland and on the Atlantic coast of North America to Cape Cod
He settled the upper sublittoral and forms on rocky ground dense Tangwälder, or lower " Tangwiesen ". In the North Sea it grows to 1.5 m depth below the low water line. At very low water level, the stocks can also be momentarily free.
System
The first description of Fingertangs was made in 1762 by William Hudson under the name Fucus digitatus (In: Flora anglica, p 474). John Vincent Felix Lamouroux set the type 1813 in the genus Laminaria (In:. Essai sur les genres de la famille the thalassiophytes non Articulees Annales du Muséum d' Histoire Naturelle, Paris 20, p 42). This is the type species of the genus Laminaria ( lectotype ).
Laminaria digitata for Synonyms (Hudson ) JVLamouroux are Fucus digitatus Hudson, Gigantea digitata (Hudson ) Stackhouse, Hafgygia digitata (Hudson ) Kützing and Saccharina digitata (Hudson ) Kuntze. As more synonyms apply Laminaria apoda Postel & Ruprecht, Laminaria conica Bory de Saint -Vincent, Laminaria cucullata (Le Jolis ) Foslie, Laminaria ensifolia Kiitzing, Laminaria flexicaulis Le Jolis, Laminaria intermedia Foslie, Laminaria latifolia C.Agardh, Laminaria phycodendron De la Pylaie and Laminaria stenophylla ( Harvey ) J.Agardh.
Laminaria digitata belongs to the family Laminariaceae within the order of Laminariales.
Use
Previously, the alluvial or harvested at low tide algae were used as fertilizer. In the Middle Ages, the incineration of the algae ( kelp) of economic importance, in order to extract alkalis, which were needed for the soap and glass production. Later, the Tangveraschung came again to produce iodine to blossom. The iodine content of the Fingertangs 0.25 and 5% of the dry matter.
Today oar in France (Brittany ) is harvested for the production of alginate. For 2005, a harvest of 75,000 t is specified.
In Ireland and France kelp is also used to a lesser extent for the production of Tang vegetables. The content of minerals and trace elements, especially potassium ( 0,116 mg per g dry weight) and calcium ( 10.05 mg per g dry weight ) is higher than in most edible land plants. However, the protein content is relatively low, at 8-15 % of dry matter.
Swell
- P. Korn man P.H. Sahling: seaweed from Helgoland - Benthic green, brown and red algae. Biologische Anstalt Helgoland, Hamburg 1983, ISSN 0017-9957, pp. 144-149. (Sections description, Deciduous, development, occurrence, use)
- Wolfram Braune: seaweed. A color guide to the benthic green - brown and red algae of the oceans. Ruggell: Gantner, 2008, ISBN 978-3-906166-69-8, pp. 194-195. (Sections Description, occurrence, use)