Out there in the wild, cacti have braced the desert conditions for many years. But I’m sure you know that, right? If not don’t worry, you will today!
Extreme temperatures. Little rainfall. Odd climate patterns.
Cacti plants know exactly how to maneuver around them. They relish in them. If it’s any plant that is capable of adapting to their environment, the cactus plant is just that.
So, how are they able to do this? How have they been able to put in places known to be a death sentence for most plants? What makes cactus plants different?
Obviously they’ve been able to develop specialized features but what are they?
They’re not like the average plant growing in places where water is an everyday thing. They’ve adapted to especially take advantage of the little rainfall in their natural habitat.
Continue reading about these adaptations below and let us know what you think, some of them you might already know but there’s others than are quite cool!
Leaves are Reduced to Spines on a Cactus
Spines are one of the most notable features in cactuses.
Instead of having leaves, the stems are covered in a number of these prickly structures. You know, the spiky little fellas that they have, ouch! They guard against desert herbivores but that’s not important for now. (Maybe a future article, let us know!)
Here’s how a cactus is adapted to saving water by having spines. It’s quite interesting…
- The spines are made up of dead cells at a mature age. This means they don’t take up water as it would have been the case if they were alive. Just one less part for the plant to worry about right?
- They trap air around the plant. This air provides a thin cover over the plant preventing water loss by evaporation and transpiration.
- The spines, with their numerous number, add up to provide a considerable amount of shade for the plant. Such an adaptation lowers the temperature of the cactus surface which further reduces water loss.
- In instances of fog/mist, the spines condense it into water droplets that fall off to the base of the plant where they are absorbed immediately – courtesy of the nature of the roots as you’ll see below.
To ensure you know how to properly handle the thorns on a cactus, check out this article here.
Cactus have a Highly Specialized Root System
Cacti roots differ from those of other plants in a number of ways and these are in themselves adaptations to better survive the desert terrain.
- They’re shallow and widespread to take advantage of any light rains in the desert. That means they can absorb quite an amount of water within the shortest time.
- They can grow new tiny roots very fast when it rains. These contribute to more rapid absorption of water. The roots also dry up quickly so they don’t turn out to be another burden for the plant.
- The root cells have a very high concentration of salts. An essential adaptation which translates to a higher water absorption rate.
In some specific cacti species, the roots are also used as water storage organs. In this case, the plant will have a taproot larger than itself for this sole purpose.
The Stem of a Cactus is Well-Equipped to Store Water
For a majority of cacti, the stems are the main water storage organs. And, they have particular adaptations, not just to store but also to retain the water. Have a look at them:
Cacti have varied shapes that contribute immensely to water storage and retention capabilities. Cylindrical and spherical shapes are adapted to bring about a low surface area to volume ratio which reduces water loss to the atmosphere. These shapes also reduce the heating effects of the sun.
In other words, cactus plants have a lower than average evaporation rates.
Particular cacti have specific features on their stems. For instance, the ribs and flutes on a species, like the rounded ball cactus stem, enables it to easily shrink during the prolonged desert droughts and expand when it rains.
Shrinking is an adaptation that ensures there is just a small surface area hence reducing water loss.
Expanding gives the stem enough room to take up as much water as possible.
Wax on Cacti
The stems and spines of any cactus plant have a layer of thick wax. The functionality behind this is so that cacti can stop any water loss as much as possible.
With the thick layer of wax mixed with the ability to shrink and expand, the wax serves as a multifunctional purpose. It helps the cacti retain as much water in as possible without allowing the sun, or the idea of evaporation, to affect cacti as much as it would with your average plant.
Short Growing Seasons and Long Periods of Dormancy
Cacti grow only during the short rainy seasons and stay dormant for the long dry months of the desert.
This adaptation ensures water efficiency as the stored water is only used in very vital processes such as photosynthesis. Development of new cells and tissues (water-intensive) is confined to periods of rain when water is aplenty.
Photosynthesis occurs in the leaves during the day for most plant species. But not for a good deal for cacti.
This vital process is carried out in the stems (as the cacti are devoid of leaves) at night. Such an adaptation ensures the plant loses very little water as its stomata are only open at this time when temperatures are at the minimum.
Water is a valuable commodity to lots of organisms but its value increases probably hundreds of times in a desert setting. Every drop counts. Cacti get this all very well. So they try to keep as much of it as it’s possible through an array of adaptations.
And that’s how they’ve been able to thrive in them deserts for years.
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Happy planting! 🌵