Welwitschia
Encyclopedia
Welwitschia is a monotypic genus
of gymnosperm
plant
, composed solely of the very distinct Welwitschia mirabilis. The plant is commonly simply known as Welwitschia in English. It is known locally as !kharos or khurub (Nama
), tweeblaarkanniedood (Afrikaans
), nyanka (Damara), or onyanga (Herero
), among others. It is the only genus of the family Welwitschiaceae and order Welwitschiales, in the division Gnetophyta
. The plant, which is considered a living fossil
, 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
within Namibia
and Angola
.
that has been variously described as long and short. Bornmann appears to have investigated the matter more intimately at first hand than most authors, and describes the root system as "rather shallow and simple, consisting of a tapering taproot with one or more non-tapering extensions, some pronounced lateral roots, and a network of delicate spongy roots." He offers the guideline that the roots extend to a depth roughly equal to the span of the living leaves from tip to tip.
After germination, the cotyledon
s grow to 25–35 mm in length, and are followed shortly afterward by the appearance of two permanent leaves. These leaves are produced at right angles to the cotyledons, and continue to grow throughout the entire life of the plant; they are the only leaves that the plant will bear, because the stem is acephalous; its apical meristem
dies after the first two leaves are produced. Those two leaves
grow continuously from a basal meristem
in the plant's terminal groove. They eventually grow to a length of 2–4 m and usually become split, frayed and shredded into several well-separated strap-shaped sections by the distortions of the woody portions surrounding the apical slit, and also by wind and adventitious external injuries. The growth of the leaves outstrips that of the cotyledons after about four months, after which the growing tips of the two cotyledons die, but their bases continue to grow sideways. That lateral growth leads the obconical extension of the stem which produces the terminal groove from which the leaves grow.
The species is dioecious
, with separate male and female plants. Fertilization
, that is, the transfer of the pollen from the male to the female strobili
, is carried out by insects — mostly flies
and infrequently wasps and bees — that are attracted by "nectar" produced on both male and female strobili.
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.
The plant absorbs water through structures on its leaves, harvesting moisture originating from Namib desert morning fogs
that blow in during the night, comprising the main source of water for much of the desert life.
It is possible that W. mirabilis uses crassulacean acid metabolism
(CAM) photosynthesis; if this were true, W. mirabilis would be the only known gymnosperm to do so. However, the evidence is contradictory.
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
are better protected than the plants in Namibia
, owing to the relatively high concentration of land mine
s in Angola, which keep collectors away .
The species grows readily from 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
, which causes them to rot shortly after they germinate. Seeds from botanical gardens, or other cultivated sources are much cleaner and less likely to rot. It is suggested that the seeds might contain a germination inhibitor that prevents germination until the substance has been leached out by plentiful water. This is a common strategy among desert plants and is consistent with the observation that one commonly encounters communities of Welwitschia plants of apparently more or less the same age. It is reasonable to suspect that they had germinated at about the same time during unusual episodes of wetness in the desert.
in a monotypic family or even order. Most recent systems place Welwitschia mirabilis in its own family Welwitschiaceae in the gymnosperm
order Gnetales. The order Gnetales is most closely related to the order Pinales
, which includes pines, spruces, larches and firs The species is sometimes given the name Welwitschia bainesii to honour its co-discoverer, Thomas Baines
.
in the national coat of arms of Namibia
, as well as that of Westelike Rugby Subunie.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of gymnosperm
Gymnosperm
The gymnosperms are a 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 their seeds...
plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
, composed solely of the very distinct Welwitschia mirabilis. The plant is commonly simply known as Welwitschia in English. It is known locally as !kharos or khurub (Nama
Nama language
The Khoekhoe language, or Khoekhoegowab, also known by the ethnic term Nàmá and previously the now-discouraged term Hottentot, is the most widespread of the Khoisan languages. It belongs to the Khoe language family, and is spoken in Namibia, Botswana, and South Africa by three ethnic groups, the...
), tweeblaarkanniedood (Afrikaans
Afrikaans
Afrikaans is a West Germanic language, spoken natively in South Africa and Namibia. It is a daughter language of Dutch, originating in its 17th century dialects, collectively referred to as Cape Dutch .Afrikaans is a daughter language of Dutch; see , , , , , .Afrikaans was historically called Cape...
), nyanka (Damara), or onyanga (Herero
Herero language
The Herero language is a language of the Bantu family . It is spoken by the Herero people in Namibia and Botswana...
), among others. It is the only genus of the family Welwitschiaceae and order Welwitschiales, in the division Gnetophyta
Gnetophyta
The plant division Gnetophyta or gnetophytes consists of three genera of woody plants grouped in the gymnosperms. The living Gnetophyta consists of around 70 species across the three genera Gnetum , Welwitschia , and Ephedra .The gnetophytes differ from other gymnosperms The plant division...
. The plant, which is considered a living fossil
Living fossil
Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records...
, is named after the Austrian botanist Friedrich Welwitsch
Friedrich Welwitsch
Friedrich Martin Josef Welwitsch was an Austrian explorer and botanist who in Angola discovered the plant Welwitschia mirabilis...
who discovered it in 1859. The geographic distribution of Welwitschia mirabilis is limited to the Namib desert
Namib Desert
The Namib Desert is a desert in Namibia and southwest Angola that forms part of the Namib-Naukluft National Park, the largest game reserve in Africa. The name "Namib" is of Nama origin and means "vast place"...
within Namibia
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...
and Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the 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...
.
Biology
Welwitschia grows from a short, thick, woody trunk with a thick taprootTaproot
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.Plants with taproots are difficult to transplant...
that has been variously described as long and short. Bornmann appears to have investigated the matter more intimately at first hand than most authors, and describes the root system as "rather shallow and simple, consisting of a tapering taproot with one or more non-tapering extensions, some pronounced lateral roots, and a network of delicate spongy roots." He offers the guideline that the roots extend to a depth roughly equal to the span of the living leaves from tip to tip.
After germination, the cotyledon
Cotyledon
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...
s grow to 25–35 mm in length, and are followed shortly afterward by the appearance of two permanent leaves. These leaves are produced at right angles to the cotyledons, and continue to grow throughout the entire life of the plant; they are the only leaves that the plant will bear, because the stem is acephalous; its apical meristem
Meristem
A meristem is the tissue in most plants consisting of undifferentiated cells , found in zones of the plant where growth can take place....
dies after the first two leaves are produced. Those two leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
grow continuously from a basal meristem
Meristem
A meristem is the tissue in most plants consisting of undifferentiated cells , found in zones of the plant where growth can take place....
in the plant's terminal groove. They eventually grow to a length of 2–4 m and usually become split, frayed and shredded into several well-separated strap-shaped sections by the distortions of the woody portions surrounding the apical slit, and also by wind and adventitious external injuries. The growth of the leaves outstrips that of the cotyledons after about four months, after which the growing tips of the two cotyledons die, but their bases continue to grow sideways. That lateral growth leads the obconical extension of the stem which produces the terminal groove from which the leaves grow.
The species is dioecious
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
, with separate male and female plants. Fertilization
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
, that is, the transfer of the pollen from the male to the female strobili
Strobilus
A strobilus is a structure present on many land plant species consisting of 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...
, is carried out by insects — mostly flies
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
and infrequently wasps and bees — that are attracted by "nectar" produced on both male and female strobili.
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.
The plant absorbs water through structures on its leaves, harvesting moisture originating from Namib desert morning fogs
Namib Desert
The Namib Desert is a desert in Namibia and southwest Angola that forms part of the Namib-Naukluft National Park, the largest game reserve in Africa. The name "Namib" is of Nama origin and means "vast place"...
that blow in during the night, comprising the main source of water for much of the desert life.
It is possible that W. mirabilis uses crassulacean acid metabolism
Crassulacean acid metabolism
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. The stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide...
(CAM) photosynthesis; if this were true, W. mirabilis would be the only known gymnosperm to do so. However, the evidence is contradictory.
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
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the 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...
are better protected than the plants in Namibia
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...
, owing to the relatively high concentration of land mine
Land mine
A land mine is usually a weight-triggered explosive device which is intended to damage a target—either human or inanimate—by means of a blast and/or fragment impact....
s in Angola, which keep collectors away .
The species grows readily from seed
Seed
A seed 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...
, 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
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...
, which causes them to rot shortly after they germinate. Seeds from botanical gardens, or other cultivated sources are much cleaner and less likely to rot. It is suggested that the seeds might contain a germination inhibitor that prevents germination until the substance has been leached out by plentiful water. This is a common strategy among desert plants and is consistent with the observation that one commonly encounters communities of Welwitschia plants of apparently more or less the same age. It is reasonable to suspect that they had germinated at about the same time during unusual episodes of wetness in the desert.
Scientific classification
The taxonomic placement of Welwitschia has changed many times with the development of new classification systems (see Flowering plants: History of classification). Most botanists have treated Welwitschia as a distinct monotypic genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
in a monotypic family or even order. Most recent systems place Welwitschia mirabilis in its own family Welwitschiaceae in the gymnosperm
Gymnosperm
The gymnosperms are a 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 their seeds...
order Gnetales. The order Gnetales is most closely related to the order Pinales
Pinales
The Order Pinales in the Division Pinophyta, Class Pinopsida comprises all the extant conifers. This order was formerly known as the Coniferales....
, which includes pines, spruces, larches and firs The species is sometimes given the name Welwitschia bainesii to honour its co-discoverer, Thomas Baines
Thomas Baines
Thomas Baines was an English artist and explorer of British colonial southern Africa and Australia. Born in King's Lynn, Norfolk, Baines was apprenticed to a coach painter at an early age...
.
Heraldry
The plant figures as a chargeCharge (heraldry)
In heraldry, a charge is any emblem or device occupying the field of an escutcheon . This may be a geometric design or a symbolic representation of a person, animal, plant, object or other device...
in the national coat of arms of Namibia
Coat of arms of Namibia
The coat of arms of Namibia is the official heraldic symbol of Namibia. Introduced at the time of independence in 1990, it superseded the earlier coat of arms used by the South African administration of the territory.-History:...
, as well as that of Westelike Rugby Subunie.