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Waterless horizons
Plants need water to survive. Desert plants have developed characteristics to counteract the lack of water.
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Hot deserts cover 1/3 of the surface area of our continents. Their aridity makes them some of the most hostile environments on the planet.
In the course of their evolution, the desert plants have adapted to these extreme conditions.
On some plants, therefore, the leaves, the main areas of evaporation and water loss, have become smaller.
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Other plants can survive for years as seeds. The slightest drop of rain makes them germinate, flower and produce new seeds in a few days, before the drought returns.
Adapting to the desert environment has taken millions of years, for let us not forget that the ancestors of these plants lived in environments where water was abundant.
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Tonnes of water in the desert
Some desert plants are just like sponges, soaking up the minutest drop of humidity.
Cacti and succulent plants live in the deserts. These plants can absorb vast quantities of water through their roots which go deep into the ground or branch out over a wide area.
The water is stored in the spongy tissues (because similar to a sponge) in the leaves, roots or stems - this is whatsucculence means.
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Some cactuses can thus store up to 5 or 6 tonnes of water in their tissues.
Although their origins are different, the agaves, the American cactus, the spiny aloes of Africa and the cactus-like euphorbia are all succulents. This shows clearly the convergence of the various plant families towards identical adaptation during their Evolution.
Bien qu’ayant des origines différentes, les agaves, les cactus américains, les aloès africains et les euphorbes cactiformes possèdent la succulence. Ceci montre bien qu’il y a au cours de l’Évolution convergence de différentes familles végétales vers une même adaptation.
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Preserving stored water
Most plants lose 95% of the water they drawup through their roots. How can they keep this water? Desert plants have a few solutions.
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Some desert plants have very small leaves, limiting water loss.
Thus the cactus spines are all that remain of the ancestral leaves.
Some plants no longer have leaves, like the euphorbia. Photosynthesis takes place through the stems in this case.
Lithops, living stones, can limit how much of their surface is exposed to the sun.
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These plants have a root capable of pulling into the ground. It draws the plant more or less deeply into the ground depending on the harshness of the drought conditions.
Plants like the fenestraria have translucent windows that focus the light on a specific area.
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