The 'Discoverers' : The
Welwitschia plant is named after the Austrian botanist Dr. Friedrich Welwitsch
(1806-1872) who first 'discovered' the plant near Mocamedes in
South-West Angola in 1860 while working for the Portuguese Government.
On completion of his contract he took up residence in London, England.
The Africa explorer painter Thomas Baines trekked through
Namibia in 1861 and made sketches of the plant which were later
sent to London. The plant was first named Tumboa bainesi. Baines wrote of
his first sighting of the plant being in one of the sandy ravines
running into the Swakop River.
"In its sandy bed we came upon a bulbous
plant with four leaves, fourteen or sixteen inches wide, and, when
perfect, nine or ten feet long, lying in a cross upon the ground. The
ends were withered and curled up, and in the centre was an assemblage of
small stems six inches long, each bearing on smaller stems from three to
five greenish-crimson substances, of an elongated ova three inches long
and three quarters of an inch thick, and marked with scales like a fur
cone. On this plant I found a number of red, or red and yellow field
bugs, and captured some of them for preservation, beside making an
outline of the plant itself, intending to colour it from some of the
specimens we expected to see to-morrow."
The
priority of Dr. Welwitsch was eventually recognized and the plant given
the name Welwitschia mirabilis.
The Welwitschia mirabilis is a unique and
protected plant (CITES Appendix ll): that still invites a
considerable amount of research. The plant only grows two leaves during
its entire lifetime. The bunches of leaves seen on older plants are
actually splits of the original leaf pair. Apart from Cacti and
succulents most desert plants are xeromorphic having spiny leaves with a
small surface area. However the Welwitschia has long, wide and relatively thin
leaves, similar to plants found in climates that experience regular rains. The leaves
have up to 22,000 stomata (small pores) per sq cm combined on both upper
and lower leaf surface which are used for the exchange of gases in the
photosynthesis. In contrast to other leafed plants
these stomata remain opened during foggy or wet conditions and absorb
moisture. When hot conditions are being experienced these stomata close
to reduce the evaporation of plant fluids. The root system reaches
depths of 2 to 3 meters and can grow laterally as much as 30 meters
across.
Water
Intake: Rainfall in the Namib is limited and ranges from 20mm in the
coastal belt to 120mm further inland, per year. Moisture from the early
morning fogs produced by the cold Benguela (sea) Current for about 300
days per year add about another 50mm of moisture per year.
Temperatures experienced in the Namib can fall to near
freezing point on a cold winters night. Daytime temperatures of the gravel
surface can reach 70 Celsius, and the Welwitschia leaf ends spilt and become
burnt.
Reproduction - Some Facts: The Welwitschia
is a 'gymnosperm' meaning naked seed and being the name for any vascular
plant not having flowers. e.g. Cycad, Ginkgo, Conifers, Yew. Gymnosperms include the most ancient of the living
seed plants and appear to have descended from the early fern-like plants
dating from the Devonian Period (408.5 to 365.5 million years ago). The flowering plants that we are familiar with are Angiosperms,
and they first appeared in the mid-Jurassic Period, about 175 million
years ago. The seeds of gymnosperms are not enclosed within the
ovule as with flowering plants.
The Male
reproductive system comprises of six
stamens each having an anther and a pistil. The stamens reach 'maturity'
between during September and October when they secrete an insect
attractant.
Pollination: The
latest research by the Gobabeb Training and Research Centre is of the
considered opinion that owing to the large size, weight and 'stickiness'
of the
Welwitschia pollen it is unlikely that the desert
winds play any roll in the pollination process and that a variety of
wasps and other flying insects are responsible for carrying 'the load'
from one plant to the other.
The Female is
unlike any other known plant insomuch that fertilization occurs within
the pollen tube and not the embryo-sac.
The seeds develop on the
surface of the scale like leaves of the female cones. A female plant can
produce between 10,000 to 20,000 seeds having winged
segments which are used for dispersion by the winds. In consideration of the environment, quantities of this
magnitude would be required for the species to survive, let alone
flourish. Recent studies estimate that 0.1% of seeds dispersed will
take root.
The
Welwitschia Bug: There's a good chance that
you will see these bugs busying themselves on and around the cones
of the female plants. They are not a beetle, but a bug, and have the
rather exotic name - Odontopus sexpunctatis. The larger ones in the
upper left hand photograph are adults, while the smaller red coloured bugs
are still in the nymph stage. These are known as Pyrrhocorid bugs
and feed by sucking the sap of the Welwitschia Plant. Contrary to popular belief these bugs
play no part in the pollination of the plant.
Other Life Forms: The Welwitschia having wide and
long leaves offers a welcoming refuge for many desert dwellers.
Birds, chameleons, lizards, scorpions, snakes along with a variety
of small mammals and insects can be found under the leaves of a
larger plants, so take care, enjoy the experience and
don't touch.
|
Adult bugs with nymphs |
The Welwitschia Plains |
The Big Welwitschia |
The Big Welwitschia stands approximately 1,4 meters tall and its'
leaves spread to a diameter of about 5meters. Exact aging of the plant
is difficult. The detail board at the site gives the age as being in
excess of 1500 years old. However recent studies show that the plant
could be twice as old. The longevity of the plants indicates an
unusual resistance to disease. However, you may find some that have recently
become 'infected' by a fungus growth.
Tour Part 1 - Moon-Landscape
Acknowledgements and further reading: GV1,
P1, P2, T4, T5
