Cacti can survive in arid environments thanks to their adaptability. Their specific structure, with thick skin and tissues capable of storing water, allows them to withstand drought by retaining moisture and limiting water loss.
Cacti have particular shapes, perfectly adapted to drought, such as their thick and fleshy stems. This shape allows them to store a lot of water, a perfect reserve for managing long periods without rain. They generally do not have traditional leaves; these are replaced by spines. Less beautiful perhaps, but effective in minimizing transpiration and discouraging potential predators. Their green color comes from the presence of chlorophyll directly in the stem, directly ensuring photosynthesis without the need for leaves. But that's not all: their rounded or cylindrical shape reduces the surface exposed to the scorching sun while limiting water loss. Clever, isn't it?
Cacti have become survival experts thanks to their special cells capable of swelling like sponges when it rains. This internal, gelatinous pulp filled with mucilage acts as a sort of water reservoir. The thick stem of a cactus can hold up to 90% water: when rain falls, it quickly absorbs and stores everything for tough times. Some species also have a waxy layer on their skin, a waterproof barrier that prevents the stored water from evaporating easily. No need to look far; an internal reserve is always handy in the middle of the desert.
To minimize water loss, cacti use a clever system: CAM photosynthesis. Basically, they open their stomata only at night to absorb carbon dioxide without sweating under the scorching daytime sun. When day arrives, these openings remain closed, and the cactus calmly uses the CO₂ accumulated overnight for photosynthesis. Clever, right? Additionally, they have a thick, waxy cuticle that acts as a sort of protective barrier, preventing water from escaping too easily. Another little trick: cacti limit their exposed surface area with their compact, cylindrical shape. Less surface means less transpiration, so more water is retained. Not bad for a plant that grows in places where it hardly ever rains!
Under a cactus, it's like a secret network: behind their seemingly simple appearance, their roots are extremely clever. Most cacti have a vast shallow root system, very extensive horizontally but not deep. As a result, at the slightest drop of rain, they quickly absorb a maximum of water before it evaporates under the blazing sun. Some types of cacti go even further with a central taproot that is long and very deep, capable of reaching hidden moisture far underground. These taproots allow them to find deep water reserves, a useful bonus when the surface becomes too dry. In terms of roots, cacti also manage their timing: during severe drought periods, their fine roots can dry out in a controlled manner, thus reducing their needs and conserving resources. As soon as water returns, they quickly regenerate and resume their activities fully.
Cacti adapt their biological cycle to the harsh periods of the desert. For example, flowering and fruiting occur quickly during rainy periods, when water is available. When conditions become tougher, they slow down their growth and enter a sort of pause called dormancy. This rhythmic cycle, alternating rapid growth during wet periods and rest during dry periods, allows them to conserve their resources and increase their chances of survival in these hyper-arid environments.
There are about 1,750 different species of cactus in the world, all native to the Americas (with one exception, Rhipsalis baccifera, which is also found in Africa and Madagascar).
Some giant cacti like the Saguaro can absorb and store up to 750 liters of water, allowing them to survive for several months without rain.
The spines of cacti not only serve to defend against herbivores, but they also help limit water loss by reducing air circulation around the surface of the plant.
Many species of cacti perform CAM photosynthesis: they open their stomata only at night to absorb CO₂, which significantly reduces water loss during the daytime heat.
In general, watering every 2 to 4 weeks is more than enough for indoor cacti, depending on the season and the room temperature. In winter, the frequency of watering can be significantly reduced or even suspended to match the cactus's dormant period.
Yes, in theory, all sufficiently mature adult cacti can produce flowers, but some species only bloom after several years of growth. Appropriate environmental conditions, including light, temperature, and humidity, greatly influence their ability to flower.
Most cacti are perfectly adapted to strong direct sunlight. However, if a cactus that was previously grown indoors is suddenly moved to full outdoor sun, it can suffer from burns. Therefore, acclimatization should be gradual.
Of course, most cacti can easily be propagated from cuttings. To do this, simply take a clean cutting, let it dry for a few days to form a callus (to prevent rot), and then plant it in well-draining, slightly moist substrate.
A cactus that is lacking water may show signs such as a shrinking or sagging stem, wrinkled skin, and sometimes a loss of its classic green tone, replaced by a grayish or yellowish hue. Watering lightly and gradually helps the cactus recover.
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