A cactus is a member of Kingdom Plantae’s Cactaceae family. Cacti are the most commonly found species of flora around the deserts.
While the desert vegetation mostly has non-flowering plants due to the unbearable conditions such as extreme temperature and lower precipitation, cacti are the only flowering plants in the ecosystem.
Cacti are mostly confused with succulents, but there are some differences between the two.
While succulents may simply be plants with fleshy stems, cacti have areolas and spines as distinguished characters.
Numerous adaptations have allowed cacti to survive in the arid and semi-arid climates of deserts for centuries.
Here’s how the parts of a cactus plant have adapted to the desert over the years.
Various species of cactus produce different root systems according to their needs. There are three most common types of roots found in the most popular species of cactus:
Such roots sprout when there’s an extensive need for a large surface area for water absorption and rapid water transportation from roots to stem.
These types of roots can be seen mostly during rains as the little precipitation is a rare chance of capturing moisture, and the absorption of water from the soil to the root is time-consuming.
After absorbing water, these temporary roots die, hence the name. This removal of temporary roots helps the plant in holding onto the moisture.
Cacti with shallow root systems may take in as much rainwater as they can and can also access minute amounts of humidity that may be present at the surface owing to dewy mornings or foggy evenings.
Desert vegetation, such as cacti, frequently grows close to riverbeds. These regions, whether dry or wet, typically include a substantial amount of groundwater sources, aiding plants with deep roots in withstanding the heat.
The main purpose of the taproot is to enable the cactus to delve deeper into the moist subterranean soils. The taproot can penetrate up to five feet of earth.
Desert storms are ubiquitous in deserts and can cause the vegetation to detach from their soil.
A deep taproot system helps anchor the plant to its soil as the roots widely hold a large surface area, making the extreme climatic conditions fail to cause harm.
The stem is the most evolved and essential part of a cactus plant.
Over the years, the cactus’ stems have changed to become more adapted to the arid and semi-arid climate of the desert and help the plant survive.
Underneath the epidermis of a cactus lies a cortex. The cortex is a thin layer with an important purpose.
Its water-holding cells act as a water reservoir thanks to the cell’s flexibility and permeability.
These water-holding cells have a gooey substance called mucilage within them. The substance helps the water adhere to it and stores the water efficiently.
The water storage protects the water from evaporation. This water then comes in handy during the drought season.
The cells also collapse and release water effectively when needed during low precipitation seasons.
The thick inner layer of cells, xylem, and phloem, help the stem of a cactus in enduring the long-term harsh climatic conditions by storing the water within the cells.
Phloem cells allow the storage and transportation of plant food and minerals.
Xylem cells and other cells in the inner cortical layer also provide the stem with a sturdy shape that keeps the plant standing tall without losing itself amidst the unbearable heat and low precipitation.
The pleated surface of a stem also indicates the presence of leaves. However, this pleated surface, made up of tubercles, allows the process of water storage to work efficiently.
The surface of a tubercle increases the volume for the storage and retention of water as these areas expand without bruising.
Once the water leaves the stem, the surface area of these tubercles reduces, saving the plant from being exposed to sunlight. This is called the Accordion Effect.
The extreme temperatures are detrimental to the growth and survival of the cactus.
However, temperature regulation becomes easy once water is stored in the stem.
While the temperature outside the plant will cause a hike in the internal temperature of the plant, water stored within the plant helps fight these conditions back through thermal inertia.
This property of water also keeps the plants from freezing during the cold, windy nights, and even when the daytime heat dissipates; plants survive due to the remaining heat in the water stored within.
There’s an extensive debate amongst the botanist community whether spines are cacti leaves in their evolved form or just another part of the plant.
The functions of a leaf, along with its internal structure, are quite different from the hard spines made mainly of dead cells.
The shape, size, and color of spines vary from plant to plant. Some may be short and wooly, while others may have a hair-like appearance.
The Desert ecosystem has numerous species roaming around in the food search. These animals may find their way toward a cactus due to its green color.
Since the green tissue in a cactus is vital but limited, it must be protected from predators.
Spines help such predators to keep at bay. The spines are clustered and usually needle-like, pricking the predators whenever they try to harm the plant.
Spines are located on the outermost layer of a cactus and therefore interact with the environment.
Whether it’s rain, mist, or some other water source, spines collect the droplets and let them flow towards the roots of the cell.
Every drop of water is stored as it comes in handy when survival becomes tough.
Spines disrupt the airflow, forming a layer of air called a microclimate that protects against temperature variations and faster absorption brought on by warm air currents or wind.
Cactus’s exposure to the extreme sunlight of the desert can cause irreparable damage to the plant’s surface, bleaching out the chlorophyll responsible for food production and dehydrating the plant.
The UV rays also harm the plant’s DNA, which can prove detrimental to its growth and survival.
Spines, though small in size, provide shade to the plant through their large number and light color reflecting the sunlight.
Numerous cacti produce varied species of flowers depending upon the pollinators.
However, the arid and semi-arid climate of the desert doesn’t necessarily invite traditional pollinators.
While hummingbirds, butterflies, and bees are found in the desert, bats are lesser-known pollinators for cacti.
The cacti-produced flower for bats typically opens their buds in the evening and night as that’s when the bat’s population takes over.
Apart from that, these flowers aren’t brightly colored as bats use their ears for hunting their targets. The flowers do have sweet nectar to attract pollinators.
Pollination is a crucial part of the survival of cactus species. Like every organism on this planet, cacti reproduce and grow to keep the ecosystem balanced.
The spine and flower development nodes in the cactus are called areolas.
They come in various shapes but are often spherical and covered in hair or thorns because that is the only area they can develop.
The growth of spines and flowers is essential for cacti as they serve different purposes for the plant’s survival, as discussed.
Areolas are the only parts that can produce them. The location of areolas also matters for the plant’s protection and self-defense.
Other Features of Cacti that Help in Survival
While a cactus evolved with regards to its parts serving it to help in survival during the extreme conditions of the desert, here are some other features or characteristics of a cactus plant that help in adaptation:
Desert cactus show unique growth habits and patterns that allow the plant to grow in different types of shapes.
The purpose of adapting the shape to the environment is to increase the volume of the plant.
The long, columnar cells present in the stems of a cactus allow maximum volume for the storage of water.
The cells are also responsible for imparting strength to the stem to survive windy storms.
Despite having a shape to maximize volume, a cactus’s surface doesn’t allow the plant to be exposed to a lot of heat, saving the plant from UV damage.
Desert cactus lack the leaves that serve as the vegetative growth accelerators, which reduces the amount of green tissue capable of photosynthesis.
They consequently grow slowly. For numerous reasons, slow metabolism is considered one of the most crucial cactus adaptations for survival in the desert arid and semi-arid climates, where conditions are challenging and unpredictable.
Survival in Limited Resources: Cacti’s ability to adapt and live with minimal resources greatly benefits their development because desert areas frequently possess poor plant nutrition and inadequate rainfall.
Conservation of Energy: Cacti can strive to maintain the structures and behaviors that aid in their survival rather than focusing their energy on producing the vegetation that other plants require to sustain their more explosive growth.
Cacti are one of the most unique and evolved flora around the world. The plant’s adaptation to the harsh climatic conditions of the desert has allowed the plant species to survive for centuries.
The limited water supply has made cacti more self-reliant, while the extreme weather conditions have increased the plant’s resilience.
The parts of a cactus have unique characteristics that aid in water absorption, storage, and retention, which are crucial for the plant’s survival.
A unique root system allows the plant to stay rooted, whereas the stem holds the sturdy structure and nutrients in its cells.
Where the areolas give birth to spines and flowers, the spines act as protection from predators while flowers allow pollination.
The shapes and metabolism of the cactus are also unique, allowing the plant to keep adapting and evolving with the changing climate.