How Are Cactus Adapted To Survive In A Desert?

Introduction

Cactus are very distinct plants found in extremely hot environments such as deserts. In fact, no other plants are able to tolerate the extreme heat and the lack of water in these environments. So how do cactus survive in deserts?

The Adaptations

Unlike other plants, a cactus has special adaptations in its roots, leaves as well as stems, enabling it to thrive in hot and dry environments. A brief of these adaptations are as follows:

Spines

If you could take a closer look at a cactus, it does not have any structures resembling leaves. Instead, the leaves are modified into spines, which emerge from small bumps on the plant known as an areole. Hence, the process of photosynthesis is not carried out by the leaves – instead the stems perform this process. And since cacti are predominantly found in deserts, it is easy for the stem to have access to sunlight.

Moreover, the spines prevent excess evaporation, since water is rather hard to come by in a desert. Additionally, the spines also trap air – which restricts airflow and prevents evaporation. Another important function that the spines perform is collecting dew from the early morning fog. The collected dew liquified into water and drips to the ground below. This water is then absorbed by the plant. The desert also has herbivores that might be tempted to feed on the succulent flesh of the cactus. The spines deter these animals from doing so.

Roots

Cacti have shallow and wide fibrous roots close to the surface to quickly absorb rainwater. The desert is a dry place but it does experience rainfall occasionally. To collect rainwater from the ground, these plants have shallow roots that usually cover a large area. Moreover, cactus roots also show temporary growth spurts during the rains – often growing within a span of two hours. After the rains, these temporary roots wither away. Root hairs grow quickly when there is rain to increase the surface area of absorption and later die when the ground dries up.  Some cacti have a taproot in addition to fibrous roots, that grows deep underground and is of several times the length of the plant height above the ground. Taproots absorb water present deep underground.

Deep-layer Stomata

Cacti have stomata that is found deep in the tissue as opposed to the surface. Moreover, the stomata opens at night, in a type of photosynthetic adaptation called Crassulacean acid metabolism (CAM). This, coupled with the deep-layer stomata significantly reduces water loss, which is paramount in a desert environment.

Thick and Expandable Stem

Cactus have succulent stems. Stems in cactus are comparatively thicker than other plants, hence it is able to store water in stems – specifically in collapsible water-storage cells. The stems can also expand considerably to store more water. They are green and perform photosynthesis.

Waxy Skin

A waxy layer covers most of the plant’s surface (except for the stomata). This helps the plant to avoid excess evaporation as well as retain moisture.

Short Growing Season

Constant growth requires a large amount of water and in environments like deserts water is very scarce. Hence, cacti have a short growing season compared to other plants. In fact, the plants grow for one season and stop before resuming growth on the next season. Moreover, cacti grow much slower than other plants, but they do live longer.

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Further Reading:

• Adaptation – Meaning, Plant & Animal Adaptations
• Photosynthesis ☀️ (Definition, Process, Stages & Significance)
• Discover the Scientific Name of Camel