Kazimiera
09-20-2013, 06:59 PM
http://i1.trekearth.com/photos/27608/welwitschia1a.jpg
This succulent plant can live up to 1,500 years and is only found in a strip of land in the Namibia Desert comprising part of Namibia and Angola. It can survive on moisture from fog and dew.
It consists of 2 leaves that grow continuously, a stem base and roots. It is thought to be a relic from the Jurassic Period and it has changed very little since then.
Taxonomy
Welwitschia mirabilis is a perennial plant that grows up to 2 metres high. It has a taproot that is elongate, usually branching near the apex.
The woody, unbranched stem often splits into 2 lobes with an obconical shape - a conical shape but with a downwards-pointing apex. The apex growth of the stem stops at an early stage giving this peculiar and unique habit.
It has just 2 opposite, entire, simple leaves with continuous basal growth. The leaves are up to 9m long and 2m wide, tearing lengthways into strips and wearing away at the tips. The texture is leathery and the pair of leaves is parallel-veined.
It is a dioecious plant, so male and female cones are produced on separate plants:
salmon-coloured male strobili are oblong, cone-like structures that are 1–4cm long, 5–7mm wide, and on a pedicel 2–5 mm long, with bracteoles1–3mm long
female strobili are larger than male strobili - 3.5–8cm long, 2–3cm wide, with outer bracteoles 5mm long and inner bracteoles 8mm long
This plant's seeds are 3.5cm long and 3cm wide, white to creamish white with persistent papery winged bracteoles.
Distribution
Welwitschia mirabilis is limited in distribution to the desert or desert margin along the south-west coast of Africa. This land strip is about 1000 kilometres long and stretches from the Kuiseb River, just south of Walvis Bay in Namibia (latitude 20–24°S), to the Nicolau River in Angola (latitude 15–16°S).
While some dispersed populations are found 200 kilometres inland, the majority of specimens are situated within 80 kilometres of the coast.
http://www.nhm.ac.uk/resources-rx/images/1049/welwitschia-mirabilis-map-88291-1.gif
Ecology
Based on this plant’s distribution, it is thought that fog is an important source of water.
Its habitat is extremely arid - annual rainfall is 10–100mm during the summer, but some years there is no rain at all.
This plant grows on gravel or rocky ground and has a long taproot to take underground water. The fog contributes with about 50mm dew a year.
This plant can stand extreme temperature fluctuations between 7°C at night up to 50°C during the day.
Biology
Welwitschia mirabilis flowers from mid-summer to autumn.
Both the male and the female cones produce nectar which is 50% sugar to attract insects.
The female cone has exposed stigmas that exude the nectar and the male cone possesses a modified stigma-like structure to produce it.
Beetles are commonly thought to pollinate this plant, however considering the distance between individual plants it has also been suggested that hornets may be involved in its pollination.
Female cones reach maturity nine months after fertilisation, during the spring months.
Seed germination depends directly on rain - rain must fall for several days and in great quantity for the seeds to germinate.
The arid conditions and other factors such as fungal infection and small animals eating the seeds can lead to seed loss.
Once the plant becomes established, it can live up to 1,500 years.
Source: http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/economic-impact/welwitschia-mirabilis/
http://i1.trekearth.com/photos/17939/huge_welwitschia_mirabilis.jpg
http://www.esu.edu/~milewski/intro_biol_two/lab_3_seed_plts/images/welwitschia.jpg
http://farm4.staticflickr.com/3607/5806505497_99930561be_z.jpg
http://www.eduvideoafrica.com/wp-content/gallery/drought-adapted/welwitschia-female2.jpg
This succulent plant can live up to 1,500 years and is only found in a strip of land in the Namibia Desert comprising part of Namibia and Angola. It can survive on moisture from fog and dew.
It consists of 2 leaves that grow continuously, a stem base and roots. It is thought to be a relic from the Jurassic Period and it has changed very little since then.
Taxonomy
Welwitschia mirabilis is a perennial plant that grows up to 2 metres high. It has a taproot that is elongate, usually branching near the apex.
The woody, unbranched stem often splits into 2 lobes with an obconical shape - a conical shape but with a downwards-pointing apex. The apex growth of the stem stops at an early stage giving this peculiar and unique habit.
It has just 2 opposite, entire, simple leaves with continuous basal growth. The leaves are up to 9m long and 2m wide, tearing lengthways into strips and wearing away at the tips. The texture is leathery and the pair of leaves is parallel-veined.
It is a dioecious plant, so male and female cones are produced on separate plants:
salmon-coloured male strobili are oblong, cone-like structures that are 1–4cm long, 5–7mm wide, and on a pedicel 2–5 mm long, with bracteoles1–3mm long
female strobili are larger than male strobili - 3.5–8cm long, 2–3cm wide, with outer bracteoles 5mm long and inner bracteoles 8mm long
This plant's seeds are 3.5cm long and 3cm wide, white to creamish white with persistent papery winged bracteoles.
Distribution
Welwitschia mirabilis is limited in distribution to the desert or desert margin along the south-west coast of Africa. This land strip is about 1000 kilometres long and stretches from the Kuiseb River, just south of Walvis Bay in Namibia (latitude 20–24°S), to the Nicolau River in Angola (latitude 15–16°S).
While some dispersed populations are found 200 kilometres inland, the majority of specimens are situated within 80 kilometres of the coast.
http://www.nhm.ac.uk/resources-rx/images/1049/welwitschia-mirabilis-map-88291-1.gif
Ecology
Based on this plant’s distribution, it is thought that fog is an important source of water.
Its habitat is extremely arid - annual rainfall is 10–100mm during the summer, but some years there is no rain at all.
This plant grows on gravel or rocky ground and has a long taproot to take underground water. The fog contributes with about 50mm dew a year.
This plant can stand extreme temperature fluctuations between 7°C at night up to 50°C during the day.
Biology
Welwitschia mirabilis flowers from mid-summer to autumn.
Both the male and the female cones produce nectar which is 50% sugar to attract insects.
The female cone has exposed stigmas that exude the nectar and the male cone possesses a modified stigma-like structure to produce it.
Beetles are commonly thought to pollinate this plant, however considering the distance between individual plants it has also been suggested that hornets may be involved in its pollination.
Female cones reach maturity nine months after fertilisation, during the spring months.
Seed germination depends directly on rain - rain must fall for several days and in great quantity for the seeds to germinate.
The arid conditions and other factors such as fungal infection and small animals eating the seeds can lead to seed loss.
Once the plant becomes established, it can live up to 1,500 years.
Source: http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/economic-impact/welwitschia-mirabilis/
http://i1.trekearth.com/photos/17939/huge_welwitschia_mirabilis.jpg
http://www.esu.edu/~milewski/intro_biol_two/lab_3_seed_plts/images/welwitschia.jpg
http://farm4.staticflickr.com/3607/5806505497_99930561be_z.jpg
http://www.eduvideoafrica.com/wp-content/gallery/drought-adapted/welwitschia-female2.jpg