Species of the week

Meet Welwitschia mirabilis, a plant that produces and lives only with two leaves of continuous growth throughout its life cycle.

Common name: Desert octopus or platypus plant

Scientific name: Welwitschia mirabilis

Class: Gnetopsida

Order: Welwitschiales

Family: Welwitschiaceae

Genus: Welwitschia

Longevity: It´s estimate that can live until about 1500 – 2000 years.

Size: 1,2 already registered


Description

Welwitschia mirabilis is a monotypic species confined along the southwest coast of Africa, a narrow bank of the Namib, from the northern Kuiseb River to Cabo Negro in Angola, classified as one of the most extreme deserts in the world. This is a rare plant and represents the only species of the genus Welwitschia.

This plant consists of a non-branched, limited growth, turnip-like stem surrounded by a border of photosynthetic and meristematic green tissue. It has a large, relatively shallow root and produces only two perennial and opposing leaves from the two seed cotyledons, which grow throughout the plant’s life cycle, since they have basal meristems. These leaves can reach about 6 meters when adult, and become ragged at top, as they grow. Also, they are specialized in water absorption.

Welwitschia mirabilis survives in very severe places where the annual rain is frequently lower than 25 mm and where the coastal fog extends up to 50 mm.

Distribution

Welwitschia mirabilis is a Holocene species, that range along the southwest African coast, namely in Angola and Namibia.

Habitat

Welwitschia mirabilis is a species adapted to desertic environments or with precipitation levels extremely low.

Reprodution

W. mirabilis is a dioecious plant, therefore, have the female and male parts separated. The females contain tapered and larger cones and the male contain smaller cones in an inflorescence form.

This species is currently classified as a gnetophyta, a division of green plants that produce seeds (spermatophytes) but without true flowers. Its pollination is carried out mainly by the wind, which transports the pollen grain, which has an aerodynamic form, like a rugby ball.

Its inflorescences arise from the meristematic tissue of the trunk on the adaxial side, but occasionally also on the outermost side of the leaf.

 

Its seeds present wing-like structures, which allow their dispersion. These seeds can measure about 3.6 x 2.5 cm, including wings and 1.2 x 0.6 cm without wings, and germinate efficiently in 11 to 21 days after a rain equivalent to 25 mm. Below this, the seeds do not germinate.

Ecological Importance

In some areas, Welwitschia mirabilis is the dominant perennial vegetation present and can serve as a source of food and water for various animals, including ungulates such as oryx, rhinoceros and zebra.

Social use

Welwitschia mirabilis is often cultivated in botanical gardens.

Curiosities

  • Welwitschia mirabilis is the plant with the largest leaf of all plant kingdom.
  • This plant is famous for its longevity and for the number of leaves produced in its life cycle.

    Sources

    Wetschnig, W., & Depisch, B. (1999). Pollination biology of Welwitschia mirabilis HOOK. f.(Welwitschiaceae, Gnetopsida). PHYTON-HORN-39, 167-184.

    Henschel, J. R., & Seely, M. K. (2000). Long-term growth patterns of Welwitschia mirabilis, a long-lived plant of the Namib Desert (including a bibliography). Plant Ecology150(1), 7-26.

    Bornman, C. H. (1972). Welwitschia mirabilis: paradox of the Namib Desert. Endeavour31(113), 95-99.

    Bornman, C. H. (1972). Welwitschia mirabilis: paradox of the Namib Desert. Endeavour31(113), 95-99.

    Google

     Arkive