- Also called:
- tumboa
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- Welwitschia
welwitschia
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What is welwitschia?
The Welwitschia (Welwitschia mirabilis) is a unique gymnosperm plant belonging to the family Welwitschiaceae. It is the only living genus in its family. This unusual plant is found exclusively in the Namib desert of southwestern Africa, near the coasts of Angola and Namibia.
Welwitschia has a deep taproot and a short, broad stem. A pair of leaves grow continuously throughout the plant's life, reaching about 3 meters in length, and are maintained by basal meristem. Some Welwitschia specimens are estimated to be between 1,500 and 2,000 years old. The species is now protected by law due to past over-collection, and some sources list it as endangered.
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Where does welwitschia grow naturally?
The Welwitschia is a unique gymnosperm plant, the only member of the family Welwitschiaceae. It is native to the Namib desert of southwestern Africa, near coastal Angola and Namibia, and extends inland approximately 150 km (90 miles).
Welwitschia has a deep taproot and only two permanent leaves that can reach about 3 meters (nearly 10 feet) in length, which are continuously eroded by wind and sand. Some specimens are estimated to be between 1,500 and 2,000 years old. The plant is now protected by law due to over-collection in the past, and some sources list it as an endangered species.
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What does a welwitschia plant look like?
The welwitschia plant, Welwitschia mirabilis, has a unique appearance. It has a deep taproot and a short, broad, cone-shaped stem, most of which remains hidden by its two leaves.
The plant produces only two permanent, broad, and straplike leaves that grow continuously throughout its life. The leaves are kept to a length of about 3 meters (nearly 10 feet) through constant erosion at the tips. In older plants, the leaves split and fray so much that they appear to be many leaves instead of just two. The male and female cones grow in a ring above the leaves.
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How long can a welwitschia plant live?
The Welwitschia is a very long-lived gymnosperm plant found only in the Namib desert of southwestern Africa. Some individual Welwitschia specimens have been estimated to be 1,500 to 2,000 years old. The plant has a deep taproot and two permanent leaves that grow continuously throughout its life.
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How does welwitschia survive in harsh desert environments?
The Welwitschia is a unique plant that survives in the harsh Namib desert of southwestern Africa through several adaptations. It has a deep taproot that can extend several meters into the ground to access water sources unavailable to other plants.
Welwitschia's two permanent leaves are sustained by a basal meristem, with growth at the base adding 8 to 15 cm of tissue per year. The leaves can capture water from the desert's morning fog, though this hasn't been definitively proven. Additionally, carbon dioxide uptake occurs during daylight hours via open stomata, causing significant water loss through transpiration, which cools the leaf surface.
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Why is welwitschia considered unique among plants?
The Welwitschia is considered unique because it is unlike any other known plant in the world and is the only member of the family Welwitschiaceae. It is geographically restricted to the Namib desert of southwestern Africa.
Welwitschia has a deep taproot and a short, broad stem from which a pair of leaves grow throughout the plant's life. These leaves are kept at about 3 meters (nearly 10 feet) in length by constant erosion at the tips. Some specimens are estimated to be 1,500 to 2,000 years old.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
welwitschia, (Welwitschia mirabilis), unusual gymnosperm plant that is the sole member of the gnetophyte family Welwitschiaceae. Welwitschia is found only in the Namib desert of southwestern Africa near the coast of Angola and Namibia as well as inland to about 150 km (more than 90 miles). It is the most geographically restricted gnetophyte species and is unlike any other known plant in the world. Some individual specimens have been estimated to be 1,500 to 2,000 years old. The species has suffered from being overly collected for firewood and museum specimens in the past, and it is now protected by law. Some sources list it as an endangered species.
Welwitschia somewhat resembles a large turnip. The plant has a deep taproot, which may extend downward for 1.5 metres (about 5 feet) or more before it divides into numerous thin roots. Given the aridity of the Namib, an area that frequently receives less than 25 mm (1 inch) of rain per year, it is thought that the taproot must be able access a supply of water not available to other plants of the desert. The cone-shaped stem, some 60 to 120 cm (about 25 to 50 inches) in diameter and projecting about 30 cm (12 inches) above the ground, is a short broad crown. It is often branched into three growing points and mostly hidden by the plant’s pair of straplike leaves.
The permanent pair of broad flat leaves grow throughout the life of the plant but are kept at about 3 metres (nearly 10 feet) in length by erosion by the hot sand at the tips. The leaves are perpetuated by the basal meristem at the rate of 8 to 15 cm (3 to 6 inches) per year. The leaves become split and frayed in old plants, often appearing as many leaves instead of two. A leaf of one giant was reported to have an unbroken width of 1.8 metres (6 feet) and a length of 6.2 metres (20 feet), of which 3.7 metres (12 feet) were living tissue. Other than these, the only leaves produced during the plant’s life are a pair of cotyledons (seed leaves), which generally wither less than 18 months after the seed germinates, and a pair of inconspicuous scalelike leaves that protect the stem tip.
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It is not known for certain how a plant with gigantic leaves such as welwitschia can exist in a desert and carry on photosynthesis if the stomata (pores) of a leaf remain open during the heat of the day. It is thought that water from the desert’s roughly 100 days of brief morning fog may accumulate on the leaves and enter them, although the process has never been proved. Carbon dioxide has been shown to be taken up during the daylight hours through open stomata, leading to a tremendous loss of water by transpiration for the purpose of cooling the leaf surface.
As in other gymnosperms, reproduction is by cones rather than flowers. The staminate (male) and ovulate (female) cones grow in a ring above the leaves. The staminate cones are morphologically complex, and each scale encloses a flowerlike complex consisting of six stamenlike structures bearing the microsporangia and surrounding a rudimentary nonfunctional ovule. These reproductive organs are associated with a small series of scales superficially similar to the perianth of flowering plants. The ovulate cones are simpler, with each scale subtending a single ovule and two small scales.