How Does a Cactus Survive in the Desert?

The science behind how a cactus can thrive in the desert while other plants can't is amazing

The ability of the cactus plant to survive in the desert with no water plus harsh weather conditions all – year round baffles many people. I carried out some in-depth research on this topic in my quest to understand this mystery. I compiled this article based on scientific facts, and I’m happy to share the information with you. 

How does a cactus manage to survive in a hostile desert climate? The cactus plant survives in the desert by using the adaptation technique. This plant’s leaves, roots, and stems have adapted to the desert to enable it to absorb, and conserve water.

The science behind how a cactus can thrive in the desert while other plants can’t is easy to understand. Read on to understand better how the plant adapts into the desert environment.

The cactus plant’s adaptation techniques

The cactus plant is one of the few easily recognizable plants on the planet. The plant is a staple of many cartoons due to its unique features. There are over 2000 species of this plant scattered in deserts all over the globe. 

Human beings have utilized some species of this plant for centuries for their medicinal value and as a source of food. This plant can also serve as a great garden or house plant. 

The plant attracts tourists in the desert each year, with its unusual shapes and beautiful blossoms.  The plant is a native of Africa, America, Australian, and Europe, and many different species exist in the desert environment.  

A cholla cactus bearing fruits.
The plant attracts tourists in the desert each year, with its unusual shapes and beautiful blossoms. 

It is astonishing how the cactus can live for up to 200 years in the hot desert climate, right? Thanks to its adaptation capabilities, the plant is not only able to survive but thrive in the environment. 

Characteristics like spines, shallow roots, stomata on the stem and waxy skin make the plant a reservoir despite the harsh climate.

1. Spines instead of leaves

The plants don’t have real branches or leaves, like other plants. Instead, cacti have modified leaves known as spines. The branches of the cactus plant have small bumps known as areoles, and this is where the thorns sprout from the plant. 

This brings about the question of how the plant can carry out photosynthesis without leaves. Well, the plant’s stems are what conduct photosynthesis for these plants compared to other plants where the leaves are what carry out the procedure. 

Therefore, cactus doesn’t need leaves to photosynthesis the way other plants do. The added advantage of that is the desert has plenty of sunshine so it’s easy for the stems to have access to sunlight. 

The spines play a significant role when it comes to avoiding water evaporation. 

So, how does the cactus carry out photosynthesis during the summer?

During the summer, most desert shrubs droop and stop photosynthesis. Not the cactus plant. The plant continues to manufacture food, and that’s the reason you’ll see the cactus standing tall even during the hot summer months. 

Cactus in a pot.
Cactus spines

2. The roles that spines play in a cactus’s survival

Air trapping to reduce moisture loss

The spines create a buffer that traps air around the spine. The air trapping is necessary for restricting airflow; otherwise, the water might escape from the plant in the process.  

The buffer contains moist air, and this plays a vital role in preventing water from evaporating from the plant in the hot desert heat.

Water collection for survival

The Chilean Atacama Desert is one of the driest deserts on earth. However, this desert experiences heavy fog in the early morning hours. The locals refer to the heavy dew as “camanchaca.”

Once dew from the fog settles on the spine, it liquefies into the water and then drips on the ground below. The cactus roots then absorb this water to help nourish the plant and keep it alive.

The spines also have a hierarchical groove structure. The unique grooves that help the cactus plants collect water. 

Shade provision to avoid the hot desert sun

The cactus spine may look like it can’t offer much shade because it has a thin radius. However, the needles have a dense population with a single plant having thousands of them, and this is for a reason.

The dense population serves the purpose of covering as much surface area as possible.  Therefore, the shade that these spines provide adds up to protect the plant from losing water.

Close up image of a cactus with spines.
The cactus spine provide shade to the plant

Protection from predators

The desert is full of herbivorous animals that would love to munch away on the plants. The spines are prickly and can pierce through the skin, the reason why they are excellent for keeping these animals at bay.

3. Shallow root systems for quick water absorption

The desert experiences rains from time to time. The cactus plants have shallow roots that absorb water from the ground. 

The plant also grows temporary roots when the ground becomes damp with the goal for absorbing plenty of water during the rains. It only takes about two hours for a cactus plant to grow these roots.  After the rains stop, the roots dry up. 

In addition to roots that are close to the ground for maximum water absorption, the roots are also extended to enable them to cover a large area.  After water intake, the roots then transport this water to the stems for storage.

Some plants like the saguaro cactus can store up to 4200 pounds of water.

4. Stomata on stem to discourage evaporation

Are you wondering how it’s possible for the cactus to store water in the hot desert weather that could otherwise encourage evaporation? 

Well, here is how. 

Every plant has stomata on the leaves for carbon dioxide intake. Together with sunlight and water, plants use the gas to manufacture food in a process known as photosynthesis. 

As a plant inhales carbon dioxide, it also exhales oxygen and in the process loses a lot of moisture. Moisture loss shouldn’t be a big deal in plants that grow in climates that have regular rain, but for the cactus plants that grow in the desert, this is a different story. 

Desert plants need to conserve as much water as possible for survival during times where there’s no rain. Remember that it only rains once in a long while in the desert. 

For this reason, the plants only carry out the photosynthesis process at night. Temperatures are much cooler at night.  

Photosynthesis needs sunlight. So how is the plant able to carry out the process if the stomata are only one during the night when there is no sunlight?

 Since it’s hot in the desert during the day, the cactus plant’s stomata only open up at night when temperatures are cooler, hence fewer chances of water loss. Scientists refer to the process of night photosynthesis as crassulacean acid.

The stomata’s opening and closing work like clockwork. By dawn, the pores close, and automatically open at night. 

To further avoid water loss, the cactus stomata is very small. In addition, it’s found deep in the tissue as opposed to the surface, which would otherwise cause water loss. 

5. Stem water storage

The stem usually has thick skin than that of regular leaves, and this is why cactus uses it as a reservoir. Since a desert experiences sporadic rain, the feature allows the plant to store water for lengthy amounts of time, before the next rainfall. 

A cholla cactus.
The stem usually has thick skin than that of regular leaves, and this is why cactus uses it as a reservoir.

6. Waxy skin for water retention

The plant’s surfaces have a waxy skin. This skin covers most of the leaves, apart from the stomata since the plant needs inhalation and exhalation of carbon dioxide and oxygen. This wax helps to avoid water evaporation. 

The wax also helps to keep the plants cool in the hot climate. Else the plant would dry out, due to extreme heat. 

7. Expandable stems for maximum water intake

To enable the plants to store as much water as possible during the rainy season, the cactus has an expandable stem. These stems expand to allow as much water intake as possible for use during the days when there’s no rain. 

If you were to cut up the plant, you would notice that it resembles an accordion. The structure allows channeling of water to various parts of the plant.

These stems shrink as the plant continues to use up the water in anticipation for the next rainy season.  

8. Short growing season for water conservation

Unlike most plants that grow continuously, the cactus has periods where it stops growing. Growth requires a lot of water, which is already limited in the plant’s habitat.

For this reason, the plants only grow for a season, then pauses for a while, before the next growing season. It’s no wonder that the cactus plants grow slowly, but stay alive longer than most plants.

9. Spherical shapes to reduce surface area

The plant’s body assumes a sphere, especially during seasons where it has stored a lot of water. The sphere shape reduces the plants surface area, which means that only a small part gets sunlight exposure, avoiding dehydration. 

10. Thick tissue for maximum water storage

Due to evolution, the plants have formed a thick layer of plant tissue. The dense tissue is essential for water storage and retention deep within the plant. 

Cactus plant with fruits.
Cactus spherical shapes and thick tissue for maximum water storage

Related Questions

What does a cactus need to survive? Cactus is one of those low maintenance plants that need close to nothing to survive. If you’re considering using this unique for landscaping purposes, lal you need to do is plant it in dry soil, place it in direct sunlight and water it regularly. Avoid water logging by creating drainage in potted plants and avoid too much watering during cold seasons.

How much water does a cactus need to survive? Watering your plant once a week should be enough. Some seasons are cold, which means less watering. Before you water, check about half an inch of the topsoil layer. If the layer is dry, then your plant needs water. To ensure that you don’t water too much or too little, water until the drainage holes begin to leak water. 

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