The fumes from the scorching sun saturate the desert sands with a submissive heat. Blistering and burning this barren landscape brutally. One can picture the often-cliched scene of an empty desert landscape, the hot wind blowing a ball of dried plant debris across the ground, whilst a raven or vulture circles above. Besides for the rocky outcrops and hills in the distance, the area is absent of any recognizable life. But, look closer, and you’ll notice a thriving tree or community of unconcerned shrubs sunbathing in this solitude. Those are the survivalists and succulents that fascinate many plant enthusiasts and naturalists. How do these little wonders maintain a population in places on this planet that even the hardiest of species struggle to stomach? These plants are specialists in succumbing the unfavorable conditions and adapt to not only survive but sustain themselves to satisfaction.
There are many such plants of the desert that stand out. Below is a short description of some really peculiar and persistent plants that have evolved to overcome the harsh reality of very little rain, extended periods of extreme heat and more.
Types of adaptations
Phreatophytes – Is a type of plant that produces a long, extended root system that penetrates vertically into the ground, to reach the water table deep below. The purpose here is to absorb water that is trapped underground, as the conditions above may be unfavorable (dry deserts and arid regions). It comes from the word ‘phreatic zone’, meaning zone of saturation. They are a good indication as to where potable groundwater can be found.
What are Xerophytes?
Xerophytes – Is a type of plant that has adapted to survive in areas that have little to no water. They are suited for arid, dry regions like a desert or even an ice-covered area like the poles. Typically they are able to converse and store large amounts of water over extended periods. The opposite of a xerophyte is a mesophyte.
Xerophytes can adapt both morphologically and physiologically.
- Reduction of surface area – Thin, broad leaves have a greater water loss than thick, spiky or needle leaves. Examples of plants that have reduced their surface area are cacti, which often don’t have leaves, only spikes. Xerophytes often have fewer leaves or fewer branches than other plants.
- Reduction of air flow
- Reflectivity – the color of the plant, shape or waxy/hairy covering of the leaves can reflect sunlight.
- Drought deciduous – Plants that drop their leaves during periods of drought to conserve energy and reduce transpiration.
- Dormancy – A plant will cease to grow or reproduce until conditions become favorable to do so.
- Succulence – Able to store water in its trunk, roots, stem or leaves.
- Crassulacean acid metabolism (CAD) – An adaptation where plants keep their stomata shut during the day, and open during the night to take in carbon dioxide.
- Epicuticular wax
- Seed specialization – Seeds are encased in a thick covering or able to withstand long periods of drought until rain falls.
Anastatica Hierochuntica (True Rose of Jericho)
The Rose of Jericho is an extremophyte found growing in regions around the Middle East and Sahara desert. A.hierochuntica displays tolerance to extreme heat, low nitrogen, and salts in the soil, of which is characteristic of the area.
After the wet season, the plant curls up into a ball, drying out. During this process the plant’s leaves retract and fold in, encapsulating and protecting the seeds.This ball unfolds when the next rain period arrives, exposing and releasing the seeds, which germinate within a few hours around the mother plant. These seeds are hardy and can remain dormant for many years during periods of drought.
This process of curling and uncurling is repeatable and happens each season. And thus has received the name “resurrection plant”.
Tiny masters of disguise, Lithops are dwarf succulents found growing naturally in Southern Africa. They have two fleshy leaves fused together, with just the flattened roof of each showing above the ground. The two leaves taper down to form a root. Lithops are often referred to as “living stones” because of their mimicry to the rocky gravel and granite it grows in. The window of the plant ( the two flat tops of the leaves that appear above ground ) are often grey, brown or translucent with speckled dots or lines, making it very difficult to see without a trained eye.
During flowering, the bud emerges from between the two leaves. The flowers are typically white or yellow and come out at noon on a sunny day. ‘Lithops’ is derived from the Greek lithos meaning stone-like or stone appearance. These plants range in size from a few millimeters to 4-6 centimeters. In the wild one might find them growing in a cluster. During the period after flowering (winter to early summer ), the old body or head gradually shrivels and dries up, while the growth of the new body is accelerated by drawing nutriment from the old one which usually ends up as nothing more than a paper-thin shell tightly enveloping the new growth(s). These two new baby leaves grow up and become the new Lithop.
The Welwitschia mirabilis is a highly-specialized gymnosperm found growing along the Namib Desert. The plant grows between 100 to 150km from the coast. Welwitschia is referred to as a “living fossil” and is a true survivor of this arid landscape, and can reach an age of up to an astonishing 2000 years.
The rainfall in the area is both infrequent and few, with as little as 10 mm of rain during the wet season. In some years, no rain falls at all. The Welwitschia has adapted to this harsh environment by having large, broad leaves which capture as much moisture from the area during the night’s fog. The plant also puts out a lingering taproot, that absorbs any water deep underground.
During one of David Attenborough’s visits to the country, he noted this wonderful species and it’s remarkable characteristics:
“Further inland, one of the oddest of all plants manages to survive largely on dew. Welwitschia is related to the conifers and the cycads and consists of just two long strap-like leaves that sprout from a central swollen trunk only a few inches high. The leaves grow continuously from their base and become very long indeed. They would doubtless be even longer were it not for the desert winds which, blowing them back and forth, frays the ends into tatters. Even as it is, these leaves may be twenty yards long and lie curled in untidy heaps around the stunted trunk. They collect droplets of dew and channel them down runnels into the ground where the water is absorbed and stored in an immense conical taproot.” (Attenborough 1995:267)
The first European to describe the plant, Friedrich Welwitsch, was so overwhelmed by the curious shape and size of the plant that he was left speechless. The world ‘mirabilis’ means marvelous in Latin. Another interesting distinction is the fact that the plant has only two leaves, of which are the original ones formed as a seedling. The largest plant recorded was found standing at 1.8m high with a width of around 9m.
Yucca is a genus native to the Americas and Caribbean. These shrubs and trees have evergreen, durable rosettes of sword-shaped leaves. They grow frequently in dry and hot arid parts and have adapted in several ways to survive the conditions. Some Yucca species have thick, waxy skins that prevent water loss. Some have oily coatings on their leaves that help trap water. Whilst others shed their leaves during droughts to conserve energy.
Yucca brevifolia is the largest plant species of the genus Yucca and is commonly referred to as the Joshua Tree. It grows natively in the semi-arid regions of the Mojave desert. This is the smallest, but driest, desert in North America.
In the mid-19th century, traveling Mormons encountered the tree in the Mojave desert. The limbs of the plant branching upwards reminded them of a biblical tale, the one in which Joshua reaches his hands out in prayer to the heavens.
The seedlings grow rapidly over the first few years, but generally, the plant is slow-growing and long-lived. The Joshua Tree can live for hundreds of years, with some reaching thousands of years of age.
There are plants in the Atacama Desert that use their roots for little more than anchorage. They need no soil and endure purely off the moisture available in the air. Besides for the North and South Pole, this desert is the driest place on Earth. Barren yet beautiful, this strip of flat, inhospitable land travels along the coast of Chile. Despite its harsh environment, the area is home to an array of interesting life.
The Tillandsia, a genus of flowering plants belonging to the Bromeliaceae, is prominent throughout South and Central America. Tillandsia, more commonly recognized by their alias “air plant”, are epiphytic, and take in their nutrients through their leaves, as opposed to their roots. They are found living on other plants or on rock displays or sandy slopes.
5 species of Tillandsia grow in the Atacama Desert. These air plants use their adaptations to survive; through a combination of their specialized leaf scales obtaining moisture from the coastal fog, and utilizing Crassulacean acid metabolism (CAM). These plants thrive under extreme conditions which are beyond the tolerance limits of other typical plant species.
Tillandsia leaves are covered in specialized hairs called trichomes, which reflect sunlight. Thus retaining moisture more efficiently and giving the plant that gray/silver color. The trichomes are responsible for the uptake of water to the plant.
Great Basin Bristlecone Pine (Pinus longaeva)
Strong winds, shallow, rocky soils, long winter periods and extreme cold are some of the conditions that these antediluvians have faced for ages. The famous, and equally mighty, bristlecone pine grows along the subalpine mountains of Western United States. It grows in scattered, often isolated groves below the tree line. It thrives in conditions where the soil and climate would often deter other species of plant. The bristlecone pine is drought-resistant and has adapted to the extreme conditions in the region. These traits have allowed the plant to endure even death itself, with species alive today aging over 4000 years! Thus being recognized as the oldest living species on Earth. It has also been noted, dead trees, because of the durability of the wood, are still preserved next to living ones, of which some have been dated to have been as old as 7000 years.
On average, species of the Great Basin bristlecone pine found growing on the north slopes of the White Mountains, in California, have an age of 2000 years. As the tree ages, it is not uncommon for only parts of the plant to remain alive, with a single section of tissue being attached to the root system. One can observe this through the almost barren appearance of the tree, with the exception of one or two branches having greenery.
The bristlecone pine is an example of nature’s grandest diversity, with each tree being twisted and carved into its own unique and unforgettable character. These trees are as old as mankind’s first written words and endure patiently for future generations we’ll never know.