Cactus plants surprise many people with their ability to survive and thrive in the world’s harshest climates. Cactus plants are mostly found in deserts where no one knows when it rained last and when it will rain next. We’ll know that plants need water to grow and thrive. But it’s amazing those cacti thrive without rain and can survive up to 200 years. How’s that possible?
Cacti have all kinds of adaptations that enable them to survive with minimal or no water. These plants have devised several ways to collect and store as much water as possible when it rains. They also have various ways to ensure they don’t waste the water they’ve collected. The water storage and preservation tactics start from their long and spread-out roots to the needle-like spines.
Cacti plants need water to survive, just like other plants. If you’re wondering how they get water despite their dry climates, read this article to learn some of their water retention and collection tactics.
Cactus Plants Modify Their Roots to Collect and Store Water
While the deserts are known to be dry and dusty, the areas also experience rains once in a while. Cactus plants have their roots a few inches below the ground to help them absorb as much water as possible. Their roots are shallow and widely spread to enable them to collect water even from light rains.
These plants also develop some temporary roots that absorb extra water during rainy days. These roots can spout from the cacti in just two hours whenever it rains. They get to work as soon as they sprout. When it stops raining, the temporary roots dry up and fall from the main roots to reduce water loss.
All the roots transport the water they’re able to absorb to the main plant for storage. Some large cacti plants, such as the saguaro cactus, can store up to 4200 pounds of water during the rainy seasons. They can survive with this water for the next couple of seasons until it rains again.
Other cacti plants grow very long roots called taproots. The roots go deep underground to get moisture from the soil so that the plant can survive the long drought. The taproot also ensures the plant gets firm anchorage, so the plant isn’t washed away by soil erosion or rainstorms. Cacti plants that develop the taproots include Mexican cereus and saguaro.
Apart from the roots that help the cactus absorb water, some cacti also have succulent roots that store food and water. An example of such a cactus is the Arizona queen of the night or the Cereus greggii. These cacti plants have enlarged roots to serve the storage purpose. The roots of these plants can go up to 27 kilometers. The enlarged parts of these roots are called the xylem tissue.
Other cacti plants decrease their water loss by detaching themselves from the ground. This is because the plant sometimes has more moisture than the ground to extend that it risks losing water to the ground.
Cacti don’t have aerial or adventurous roots because these kinds of roots tend to encourage water loss.
Cactus Grow Spines Instead of Leaves to Minimize Water Loss
Cactus plants don’t develop leaves, or even if they do, the leaves are very tiny, and you’ll barely see them from a distance. Most cactus plants have spines instead of leaves. In most cacti, you’ll notice small bumps known as areoles. This is where the spines spout from.
But how do these plants carry out essential processes such as photosynthesis without the leaves? Cacti use their stems to conduct photosynthesis. Because of the plenty of sunshine in the desert, the stem of cacti plants has no trouble accessing the sunlight needed for photosynthesis.
The reason why cacti spout spines instead of leaves is to avoid water loss through evaporation. The spines of the cactus also create a buffer that traps air. By trapping air, the plants restrict airflow, which in turn prevents them from losing water.
Another function of the spines in the cactus is providing shade that shields the plant from extreme sunlight, leading to water loss. The spines are densely populated in the plant that they provide enough shade that the plant needs.
Believe it or not, the spines of cacti also serve water collection purposes. Some deserts are so dry that they might not experience any rain for many seasons. But such deserts also experience heavy fog in the morning. Once this dew settles on the spines, it turns to water which then drops to the ground. The roots of the cacti then absorb this water to help in nourishing the parent plant.
The spines also deter animals that might come to steal the water already collected by the cacti. So, these spines are also a form of security detail for the plant.
Cactus Preserve Water for as Long as Possible
Because the rains are unpredictable in the desert, cacti don’t waste the little water they get. The plants have gotten good at water storage, which has worked so well for their desert survival. Their water storage techniques start right from their shape.
The cells of these plants develop a stiff outer layer known as a cell wall. The cell wall keeps the plant strong and prevents them from exploding when they’re full.
The plants have a very fleshy stem that gives them many volumes to store enough water collected during the rainy periods. Other cacti have their stems coated with a thick wax that they utilize for their waterproofing purposes. The wax keeps water inside the plant long enough.
Other cacti grow ridges and ribs on the stems. The ribs and stems allow the plant to expand to accommodate as much water as possible.
With so many ways of storing water, cacti plants can survive and thrive in the desert for many years without rain. Many plants will die with prolonged drought, but this will not happen with cacti. The plants are known to hold on to their water even after it dies. You’ll find the stem of dead cacti still filled with water even after getting cut from the main plant.
Cactus Plants Avoid Evaporation by Having Stomata on the Stem
Many plants have their stomata on the leaves, which encourage their carbon dioxide intake. These plants need carbon dioxide gas for food manufacturing. As the plant takes in carbon dioxide, it loses oxygen. This process also encourages a lot of moisture loss.
To avoid losing too much moisture and oxygen in the process, most cacti plants only carry out the photosynthesis process at night. This is the time when the temperatures are cooler, and the plants won’t lose moisture. They also open their stomata only at night to avoid losing too much water.
Cacti also have very small stomata, which are hidden deep into the tissues. They’re not exposed to the surface, as this will encourage water loss.
Cacti Know How to Keep Away Other Animals from Their Water
Because many cacti plants are good at water collection and storage, many desert animals also depend on their water for survival. But the cacti don’t give up their water so easily. They have their ways of deterring these animals from drinking their water.
One of the ways the plants deter desert animals from their water is through the use of spines. However, some very desperate animals are capable of going past the spines to quench their thirst.
Cactus Cortex Is Modified to Store Water
The cortex is yet another way that cacti use to store water. The cortex has two categories. The inner section is used for storing water, and the outer section for photosynthesis.
The outer layer also allows the plant to absorb carbon dioxide, which foresees the photosynthesis process.
The inner layer of the plant has several collapsible cells for water storage. It stores enough water, which keeps the plant healthy and hydrated all day, even in the driest months. These cells also portray fewer chloroplasts which are elastic and flexible. This allows the cell to expand and allows enough water absorption. The cell of the inner cortex walls is also thin and flexible, so they can easily fold to avoid water loss.
Cacti plants survive the harsh climate conditions in so many ways. They’re so used to their survival tactics that the plant won’t survive when you change the climate they’re used to. If you plan to plant some cacti in your garden, you have to mimic their growth conditions for them to survive. For instance, you should not give them too much water as they’ll lack where to store the excess and rot instead.
Some will rather collect dew than rainstorms. Allowing them to survive from the dew can sometimes prove fruitful than watering. Make sure you give them well-drained soil, so they never get soggy. If you cannot provide the environment almost the same as their natural habitats, you better not grow then as they’ll die on you.