Welwitschia

Welwitschia Mirabilis
Welwitschia Mirabilis


Name

Welwitschia [Welwitschia mirabilis]

Introduction:

'It is out of the question the most wonderful plant ever brought to this country, and one of the ugliest.' This was the response of the Regius Keeper of the Royal Botanic Gardens, Kew, in 1863 when presented with a plant of Welwitschia mirabilis. Welwitschia mirabilis plants are unusual for their large, strap like leaves that grow continuously along the ground. During its entire life, each plant produces only two leaves, which often split into many segments as a result of the leaves being whipped by the wind. Carbon-14 datings of the largest plants have shown that some individuals are over 1500 years old.

Description:

The Welwitschia mirabilis is a dioecious perennial plant with short stem and taproot. Beyond that, the plant is often described as 'bizarre', 'weird', or 'unlike any known plant on earth'. Its short, woody, unbranched stem is surmounted by 2 strap-shaped leaves that grow from a basal meristem throughout the life of the plant, becoming twisted and frayed with the passing centuries.

Stomata occur on both leaf surfaces. The woody stem widens with age to become a concave disc up to a meter across, from which grow small ramified branch systems that serve only to bare pollen and seed cones. The branched reproductive shoots arise near the leaf bases. Red pollen cones, resembling those of Ephedra, appear in groups of 2-3 on each branch. Normally, only one seed develops within each cone and is dispersed by wind.

Leaf characteristics:

The leaves are the longest-lived in the plant kingdom, they are evergreen, a single pair and generally broad and flat. The broadest unbroken leaf measures 179 sm. This particular leaf was 6 meters long of which 3.15 meters were living tissue. The surface that this leaf covers helps the plant to survive at a temperature on the soil as high as 65 'C. It keeps the soil under the plant cool and moist. The leaves grow annually an average 13.8 sm. Therefore the plant can produce up to 150 metres of leaf tissue over a growth period of 1000 years.

The leaves are on average 1.4 cm thick. The leaves that lay on the sand surface also prevent wind erosion. Even under gale force conditions the broad leaves remain rigid and immobile. Absorption of water through the stomata must be regarded as very interesting; this characteristic of the leaves has ensured the species survival. The stomata remains open until the fog has lifted and although much of the water that has condensed on the leaves runs off the direct intake of a proportion of this water takes place. Unlike other plants the stomata is open under foggy conditions and closes when it is hotter. This ensures that no water is evaporated during the heat of the day.

Location:

The Welwitschia is endemic to the Namib Desert, which is one of the world's oldest deserts with extreme arid conditions stretching in the western part of Namibia along the coast up to the southwestern part of Angola. The area receives no rainfall during some years and averages fewer than 100 mm per year. Most specimens are found within 80 km of the coast in a fog belt, suggesting that the fog is an important moisture source. Leaves typically grow at a rate of 8-15 cm/yr on mature plants, some of which have been found with leaves measuring 1.8 m wide and 6.2 m long, suggesting potential ages of 500-1000 years.

Most of the observations are done on the Welwitschia Fl?che, a desert plain, about 50 km east of Swakopmund and east of the confluence of the Khan and Swakop rivers.

History:

The first Welwitschia plant was discovered by Austrian botanist Friedrich Welwitsch (1806-1872) in 1860 in the Namib desert in the southern part of Angola. The plant was named after Friedrich in recognition of his successful botanical research and because he found and collected it first.

Dr. Friedrich Welwitsch (1806-1872):

Friedrich Welwitsch was born in Austria where he worked for some time as a theatre critic. Later he fled to Portugal where he started to work as a plant collector.
Several years later he was sent to Angola by the Portuguese government where he made over 5000 collections during 12 years in the country. Some were completely new to science at that time and contained large amount of useful information.

When he returned from Angola Welwitsch decided to settle in London to stay close to the Natural History Museum and the Royal Botanical Gardens. He worked there until his death in 1872. After his death the Portuguese Government (who funded his collections) took the executors of his estate to court to try to retrieve the collections. After a long court battle, which lasted 3 years a compromise was reached - the Portuguese Government got the first set of duplicates and the Natural History Museum received the second set. Dr. Friedrich Welwitsch is buried in Kensal Green Cemetery in London. His tombstone is decorated with an engraving of Welwitschia.

Field Notes

It was once thought that a bug that lived on the Welwitschia plant ? known as the Welwitschia Bug [Probergrothius sexpunctatis] ? was responsible for the pollination of the plant but this has since been rejected. The Welwitschia Bug is not a beetle as some think but a true bug. It feeds on the sap of the Welwitschia plant.



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