How do plants survive in the desert

All plants are covered by tiny pores called stomates, which allow plants to take in gasses for photosynthesis. However, these pores also allow water to be lost. Succulents have fewer stomates per cubic inch through which water can evaporate. In addition, succulents have a reduced surface area and, if they have leaves at all, they're thick and fleshy.

Many succulent plants also have a modified way of conducting photosynthesis. Other plants open their stomates during the day to take in carbon dioxide for photosynthesis. Many succulents, however, keep their stomates closed during the heat of the day and open them in the coolness of the night to take in carbon dioxide, which they store until the next day. Finally, because water is a scarce commodity in the desert, succulents have to protect themselves against thirsty animals.

That is taller than an story building. This can help slake the thirst of a full-grown mesquite, a shrub related to beans. But seedlings must find a different solution as they begin to sprout. Before a seed can take root, it must land in a good place to grow. Since seeds cannot walk, they rely on other methods to spread out. One way is to ride the winds.

Mesquite takes a different approach. Getting eaten helps the mesquite in a second way, too. The hard coating on its seeds also makes it difficult for water to get into them. And that is needed for a seeds to sprout.

Of course, to grow well, each mesquite seed still needs to land in a good spot. Mesquite usually grows best near streams or arroyos. Arroyos are dry creeks that fill with water for a short while after the rains. If an animal goes to the stream to have a drink and then does its business nearby, the mesquite seed is in luck. Instead, they lie in wait for rains — sometimes for decades.

Once enough rain does fall, the seeds will sprout. Now, they face a race against the clock. Those seeds must quickly send down deep roots before the water dries up. Steven R. Archer studies how this works. He is an ecologist at the University of Arizona in Tucson.

Most rain falls in short little bursts. Each might deliver just enough water to wet the top inch 2. It might last anywhere from a few minutes to an hour. Archer and his team wanted to see how two plant species respond to these pulses. In tests, the scientists doused seeds with varying amounts of water. They delivered it in varying numbers of pulses. Later, they measured how fast the seeds sprouted and grew roots.

They then soaked them with between 5. Mesquite seeds germinated quickly. They sprouted after 4. Acacia seeds, by contrast, took 7. The mesquite also grew deeper roots. For the plants that got the most water, the mesquite roots grew to an average depth of In both species, the roots grew longer with each additional 1 centimeter of water the plants received. The acacia grew more above ground; the mesquite put most of its energy into growing a deep root as fast as possible.

One study looked at a different type, honey mesquite P. Most young plants of this species that survived their first two weeks after germination went on to survive for at least two years.

Another common desert plant — the creosote bush — has adopted a different survival strategy. Still, the plant is a real desert survivor. The oldest creosote bush, a plant in California called the King Clone, is estimated to be 11, years old. It is so old that when it first germinated, humans were only just learning how to farm.

It is much older than the pyramids of ancient Egypt. Also known as Larrea tridentata , this plant is extremely common throughout large areas of the Sonoran and Mojave moh-HAA-vee deserts.

Touching them will leave your hands sticky. Like mesquite, creosote produces seeds that can grow into new plants. But this plant also relies on a second way to keep its species going: It clones itself. Phreatophytes are plants that have adapted to arid environments by growing extremely long roots, allowing them to acquire moisture at or near the water table.

These type of plants are usually and inaccurately referred to as perennials , plants that live for several years, and annuals , plants that live for only a season. Desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. Most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.

They bloom prodigiously for a few weeks in the spring, accounting for most of the annual wildflower explosions of the deserts.

Their heat- and drought-resistant seeds remain dormant in the soil until the next year's annual rains. Xerophytes The physical and behavioral adaptations of desert plants are as numerous and innovative as those of desert animals. Xerophytes, plants that have altered their physical structure to survive extreme heat and lack of water, are the largest group of such plants living in the deserts of the American Southwest. Each of the four southwestern deserts offers habitats in which most xerophytic plants survive.

But each is characterized by specific plants that seem to thrive there. The Sonoran Desert is home to an incredible variety of succulents, including the giant Saguaro Cactus, as well as shrubs and trees like mesquite, Paloverde, and Ironwood. The Chihuahuan Desert is noted for mesquite ground cover and shrubby undergrowth, such as Yucca and Prickly Pear Cactus.

Cactus, xerophytic adaptations of the rose family, are among the most drought-resistant plants on the planet due to their absence of leaves, shallow root systems, ability to store water in their stems, spines for shade and waxy skin to seal in moisture. Cacti originated in the West Indies and migrated to many parts of the New World, populating the deserts of the Southwest with hundreds of varieties, such as the Beavertail Cactus and Jumping Cholla.

Cacti depend on chlorophyll in the outer tissue of their skin and stems to conduct photosynthesis for the manufacture of food. Spines protect the plant from animals, shade it from the sun and also collect moisture. Extensive shallow root systems are usually radial, allowing for the quick acquisition of large quantities of water when it rains.

Because they store water in the core of both stems and roots, cacti are well-suited to dry climates and can survive years of drought on the water collected from a single rainfall. Many other desert trees and shrubs have also adapted by eliminating leaves -- replacing them with thorns, not spines -- or by greatly reducing leaf size to eliminate transpiration loss of water to the air.

Such plants also usually have smooth, green bark on stems and trunks serving to both produce food and seal in moisture. Phreatophytes, like the mesquite tree, have adapted to desert conditions by developing extremely long root systems to draw water from deep underground near the water table. The mesquite's roots are considered the longest of any desert plant and have been recorded as long as 80 feet. Botanists do not agree on the exact classification of the three mesquite trees: the Honey Mesquite, Screwbean Mesquite and the Velvet Mesquite, but no one disputes the success of their adaptation to the desert environment.