Welwitschia is a monotypic genus In biology, a genus is a low-level taxonomic rank (a taxon) used in the classification of living and fossil organisms, which is an example of definition by genus and differentia. The term comes from Latin genus "descent, family, type, gender", cognate with Greek: γένος – genos, "race, stock, kin" of gymnosperm Once an authoritative and major classification level in the plant kingdom, the gymnosperms form today a rather heterogeneous group of seed-bearing plants that includes conifers, cycads, Ginkgo and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of plant Plants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants, bryophytes, ferns and fern allies. As of 2004,, composed solely of the very distinct Welwitschia mirabilis. It is the only genus of the family Welwitschiaceae, in the order Welwitschiales, in the division Gnetophyta The plant division Gnetophyta or gnetophytes consists of three genera of woody plants grouped in the gymnosperms. The living Gnetophyta are in the genera Gnetum , Welwitschia (family Welwitschiaceae), and Ephedra (family Ephedraceae). The plant, which is considered a living fossil Living fossil is an informal term for any living species of organism which appears to be the same as a species otherwise only known from fossils and which has no close living relatives. These species have all survived major extinction events, and generally retain low taxonomic diversities. A species which successfully radiates (forming many new,[1][2] is named after the Austrian botanist Friedrich Welwitsch who discovered it in 1859. The geographic distribution of Welwitschia mirabilis is limited to the Namib desert The Namib Desert is a desert in Namibia and southwest Angola that forms part of the Namib-Naukluft National Park. The name "Namib" is of Nama origin and means vast within Namibia Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March 1990 following the Namibian War of Independence. Its and Angola Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city. The exclave province of Cabinda has a border with the Republic of the Congo and the.
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Biology
Welwitschia grows from a short, thick, woody trunk, with only two leaves In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. As an evolutionary trait, the flatness of leaves works to expose the chloroplasts to more light and to increase the absorption of carbon dioxide at the expense of water loss. In the Devonian period, when carbon that continuously grow from their base, and a long, thick taproot A taproot is an enlarged somewhat straight to tapering plant root that grows vertically downward. It forms a center from which other roots sprout laterally. After germination, the cotyledons A cotyledon , is a significant part of the embryo within the seed of a plant. Upon germination, the cotyledon may become the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the flowering plants (angiosperms). Species with one cotyledon are called monocotyledonous (or, " grow to 25–35 mm in length, and are followed shortly afterward by the appearance of two permanent leaves. These leaves are produced opposite of the cotyledons, and continue to grow throughout the entire life of the plant. They eventually grow to a length of 2–4 m and usually become split into several strap-shaped sections, thus sometimes disguising the origin from only two leaves. After these appear, two cotyledonary buds appear; in these, the growing tip dies, causing elongation of the buds. Growth continues sideways, which forms the obconical growth of the stem. The species is dioecious, with separate male and female plants. Fertilization Pollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Pollen grains, which contain the male gametes to where the female gamete(s) are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself. The receptive part of the carpel is called a, that is, the transfer of the pollen from the male to the female strobili A strobilus is a structure present on many plant species consisting of leaf-like, sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but many botanists restrict the use of the term cone to the woody seed strobili of conifers. Strobili are characterized by a central axis (anatomically a stem) surrounded, is carried out by insects that are attracted by "nectar" produced on both male and female strobili.[3]
The age of the plants is difficult to assess, but they are very long-lived, living 1000 years or more. Some individuals may be more than 2000 years old.[citation needed]
The plant absorbs water through structures on its leaves, harvesting moisture originating from dew The Distant Early Warning Line, also known as the DEW Line or Early Warning Line, was a system of radar stations in the far northern Arctic region of Canada, with additional stations along the North Coast and Aleutian Islands of Alaska, in addition to the Faroe Islands, Greenland, and Iceland. It was set up to detect incoming Soviet bombers during that forms during the night.
It is possible that W. mirabilis uses crassulacean acid metabolism Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway present in some plants. These plants fix carbon dioxide during the night, storing it as the four-carbon acid malate. The CO2 is released during the day, where it is concentrated around the enzyme RuBisCO, increasing the efficiency of photosynthesis. The (CAM) photosynthesis; if this were true, W. mirabilis would be the only known gymnosperm to do so. However, the evidence is contradictory.[4]
Although considered endangered due to its very slow growth and despite the fact that older plants are often sought by collectors, a fair number of plants exist in the wild. The plants living in Angola Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city. The exclave province of Cabinda has a border with the Republic of the Congo and the are better protected than the plants in Namibia Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March 1990 following the Namibian War of Independence. Its, owing to the relatively high concentration of land mines The name originates from the practice of mining, where tunnels were dug under enemy fortifications or forces. These tunnels were first collapsed to destroy fortifications above, and later filled with explosives and detonated. Land mines generally refer to devices specifically manufactured for this purpose, as distinguished from improvised in Angola, which keep collectors away[citation needed].
The species grows readily from seed A seed ( /ˈsiːd/ ) is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant. The formation of the seed completes the process of reproduction in seed, which may be purchased from specialty seed dealers. The seed must be kept moist for the first couple of weeks and exposed to as much heat and light as possible during this time. Seeds collected from the wild are often heavily contaminated with spores of the mold Aspergillus niger Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food. It is ubiquitous in soil and is commonly reported from indoor environments, where its black colonies can be, which causes them to rot shortly after they germinate. Seeds from the Kirstenbosch National Botanical Garden in Cape Town Cape Town is the second-most populous city in South Africa, and the largest in land area, forming part of the City of Cape Town metropolitan municipality. It is the provincial capital and primate city of the Western Cape, as well as the legislative capital of South Africa, where the National Parliament and many government offices are located. The, South Africa Coordinates: 29°02′46″S 25°03′47″E / 29.046°S 25.063°E The Republic of South Africa is a country located at the southern tip of Africa, with a 2,798 kilometres coastline on the Atlantic and Indian Oceans. To the north lie Namibia, Botswana and Zimbabwe; to the east are Mozambique and Swaziland; while Lesotho is an independent, or other cultivated sources are much cleaner and less likely to rot.[citation needed]
Scientific classification
The taxonomic placement of Welwitschia has changed many times with the development of new classification systems (see Flowering plants: History of classification The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Together with gymnosperms, they are the only extant groups of seed-producing plants, but they can be distinguished from the gymnosperms by a series of synapomorphies (derived characteristics). These characteristics include flowers,). Most botanist have treated Welwitschia as a distinctly monotypic genus In biology, a genus is a low-level taxonomic rank (a taxon) used in the classification of living and fossil organisms, which is an example of definition by genus and differentia. The term comes from Latin genus "descent, family, type, gender", cognate with Greek: γένος – genos, "race, stock, kin" in a monotypic family or even order. The Angiosperm Phylogeny Group The Angiosperm Phylogeny Group, or APG, refers to two international groups of systematic botanists who came together to try to establish a consensus view of the taxonomy of flowering plants that would reflect new knowledge in angiosperm relationships based upon molecular systematics studies. Three papers resulted from these collaborations,, a leading authority in plant systematics Biological systematics is the study of the diversification of life on the planet Earth, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees . Phylogenies have two components, branching order (showing group relationships) and branch length (showing amount of evolution), places Welwitschia miribilis in its own family in the gymnosperm Once an authoritative and major classification level in the plant kingdom, the gymnosperms form today a rather heterogeneous group of seed-bearing plants that includes conifers, cycads, Ginkgo and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of order Gnetales Gnetum is a genus of about 30-35 species of gymnosperms, the sole genus in the family Gnetaceae and order Gnetales. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms they possess vessel elements in the xylem. Some species have been proposed to have been the first plants to be insect pollinated as they occur in.[5]
Heraldry
The plant figures as a charge In heraldry, a charge is any emblem or device occupying the field of an escutcheon . This may be a geometric design (sometimes called an ordinary) or a symbolic representation of a person, animal, plant, object or other device. In French blazon, the ordinaries are called pièces while other charges are called meubles (i.e. "mobile"; this in the national coat of arms of Namibia, as well as that of Westelike Rugby Subunie.
Gallery
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The largest known Welwitschia, nicknamed "The Big Welwitschia", stands 1.4 m tall and is over 4 m in diameter |
Female plant |
Detail photograph of male plant and cones |
Detail photograph of female plant and cones |
See also
References
- ^ Flowering Plants of Africa 57:2-8(2001)
- ^ A. Lewington & E. Parker (1999). Ancient Trees: Trees that Live for a Thousand Years. Collins & Brown Ltd.. ISBN The International Standard Book Number is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, now Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W.H. Smith and others in 1966 1-85585-704-9.
- ^ Wetschnig W, Depisch B (1999). "Pollination biology of Welwitschia mirabilis HOOK. f. (Welwitschiaceae, Gnetopsida)". Phyton-Annales Rei Botanicae 39: 167.
- ^ Winter K, Schramm MJ (1986). "Analysis of Stomatal and Nonstomatal Components in the Environmental Control of CO2 Exchange in Leaves of Welwitschia mirabilis". Plant Physiology 82 (1): 173. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1104/pp.82.1.173. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 16664987.
- ^ Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 http://www.mobot.org/MOBOT/research/APWeb/
External links
| Wikimedia Commons has media related to: Welwitschia |
- Gymnosperm database: Welwitschia
- Ecology & Evolutionary Biology Conservatory
- The Welwitschia Page: photos of Welwitschia in the wild
- Welwitschia mirabilis
Categories: Endangered species | Flora of Angola | Flora of Southern Africa | Gnetophyta | Living fossils | Monotypic plant genera
