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Welwitschia mirabilis - The strangest succulent plant in the world

Welwitschia mirabilis - The strangest succulent plant in the world


Welwitschia mirabilis
the strangest succulent plant in the world

There Welwitschia mirabilis it is a plant that we find in south-western Africa, in the desert areas of the Kalahari and the Namib, between Angola and Namibia. It is the only species of the order Welwitschiales and the family of Welwitschiaceae.

It is a gymnosperm (such as the cicas, the Gingko biloba, cypresses and conifers in general) and grows where there are fogs, within 25 - 120 km from the coast, along a strip of about 1000 km, which goes from the Kuiseb River, in Namibia, to Moçamedes, in Angola.

It is a perennial plant with two huge non-deciduous leaves that completely comes out of the traditional life patterns of sub-desert plants. This is because it is not a desert plant, but it is an incredible adaptation of a forest tree to an arid climate.

There Welwitschia mirabilis belongs to a group of very ancient plants that had their maximum diffusion 135-205 million years ago, when deserts were rainforests. They can be considered to all intents and purposes the last trees of a prehistoric forest.

It was first discovered by Friedrich Martin Joseph Welwitsch (hence the name), an Austrian physician and naturalist who discovered the Welwitschia, near Cabo Negro in Angola, on September 3, 1859.

Charles Darvin called it the platypus of the vegetable kingdom (note 1).

It has a very short and massive stem and two huge ribbon-like leaves that live all their life and grow fraying in contact with the scorching desert soil.

The Welwitschia mirabilis they grow non-stop, 10-20 cm per year. They could theoretically reach one meter and a half in width and an indefinite length, but in their continuous movement the tips, touching the ground, burn and then fray and over time break into many strips along the ribs. leaves that grow perpetually. A meristematic tissue continuously produces new cells and in its long life this plant produces at least 1,000 m2 of leaves!

Each individual can live up to 2,000 years.

The leaves of the Welwitschia mirabilis they are hard, leathery, lack the waxy coating typical of many desert plants and offer the sun a huge surface, as if the plant abounded with water.

As for stomata, one might think that we have very few of them, thinking about the losses related to photosynthesis in the desert. On the contrary, they count over 250 per mm2, on both sides, more than most plants. A memory, perhaps, of the life spent, millions of years ago, in the rainforests. They are thought to have maintained this characteristic because the more stomata there are, the more water they can absorb in the morning. Then, during the day, when the air becomes very hot and dry, the stomata close. In fact the Welwitschia mirabilis adopts CAM metabolism (Crassulacean Acid Metabolism), first discovered in a group of succulents, the Crassulaceae. In practice, the plant opens its stomata at night or at dawn, when it is cool and carbon dioxide can enter without the wind and heat taking away too much water. CO2 is retained in organic acids and is subsequently transformed with the sun into sugars and starches. Amazing!

They are dioecious plants that is to say there are plants that bear only female flowers and plants that bear only male flowers.

As for pollination, this is entrusted to the wind, but in practice an insect, the Probergrothius sexpunctatus, which lives almost in symbiosis with the Welwitschia mirabilis. It spends most of its life sucking female cones, and favoring their infection by microscopic fungi, thus helping to ensure that of the theoretical 10,000-20,000 seeds per plant, only 20-200 per year are saved. The seeds, once formed, do not go very far from the mother plant but fall close to it. However, since the water and food resources are very scarce, the young plants do not compete with the mother plant and organize themselves to grow at a certain distance. In fact the seeds are covered with powerful germinative inhibitors (to remove them it takes at least 25 mm of rain, continuous or concentrated in 2-3 days) and the Probergrothius sexpunctatus, causing the death and fall of most of the seeds, almost all of them dissolve at the base of the mother plant. In short, the surrounding soil is soaked with anti-germinative substances and in this way the birth of other plants is impossible and only the seeds that have fallen away from the mother plant will be saved.


Note 2

Pollination takes place between November and March. After which the female cones swell, the scales rise and the seeds are dispersed by the wind. The seeds, rich in proteins and carbohydrates, are extremely hygroscopic and can wait up to 3 years to germinate, waiting for the environmental conditions to allow it.

The roots of the Welwitschia mirabilis they stretch several meters into the ground and are as deep as the width of the plant. They perform an important reserve function and absorb, with their lateral ramifications, the water that filters into the subsoil. It has also been observed that the huge carrot-shaped roots emit toxic substances into the soil.

In short ... we are dealing with a great masterpiece of nature.

Note
1. The platypus is considered a mix of duck, beaver, otter and scorpion: the duck for the beak and webbed legs, the beaver for the tail and the otter for the body and coat. The scorpion because the males are also poisonous. On the heels of the hind legs they have stinging spurs that they can use to attack any enemy with poison. The reproduction of the platypus is almost unique. It is one of only two mammals to lay eggs (the other is the echidna).

2. Image licensed under a Creative Commons Attribution-Share Alike 3.0 Unported license by Bries

Online bibliographic sources: Monano Nature Encyclopedia


Video: Welwitschia mirabilis