What are the adaptations of desert plants?
Deserts are areas that have a hot, dry climate and receive little rainfall. Plants that grow in such areas have unique adaptations that help them survive the harsh conditions of the desert.
The desert plants adapt themselves by changing their physical structure or by altering the growth phases in their life cycle.
Let us study the mechanisms through which plants adapt themselves to the desert climate.
Adaptations of Desert Plants
Plants adapt themselves to the desert conditions through the following mechanisms -
- Storing water
- Altering their physical structure
- Growing when conditions are favorable
Adaptations of Xerophytes
Xerophytes are desert plants that have modified their physical structure to cope with the arid conditions of the desert.
Plants that can store water are called succulents. Succulent plants store water in fleshy leaves, stems or roots and efficiently use the stored water as and when needed by the plant.
Rainfalls in the desert areas are sparse and occur for a short time. Therefore the plants should have the ability to absorb large quantities of water in a short time.
Succulent plants have an extensive shallow root system to absorb large amounts of water in a short time.
To prevent the stored water from escaping through evaporation, the leaves of the succulent plants adapt themselves in the following ways -
- few stomata (openings) through which water can evaporate
- reduced surface area of the leaves from which water can evaporate
- the absence of leaves
Succulent plants are toxic or have spines to protect themselves from the thirsty animals in search of water.
Adaptations of Phreatophytes
Phreatophytes are desert plants that depend solely on underground water. These plants have a network of long roots that reach deep down to the water table from which the plants absorb water for their existence.
Examples of Phreatophytes – Mesquites (Prosopis sp), Salt cedar (Tamarix gallica), Sarcobatus vermiculatus, Willow (Salix) Cottonwood (Populus), saltgrass (Distichlis stricata) and Baccharis.
The roots of the Mesquite has been measured up to a length of 80 meters and is considered to be the longest among desert plants.
Adaptations of Desert Perennials
Desert perennials are plants that survive by becoming dormant during drought conditions and start growing when water becomes available for plant growth. For example, the Ocotillo plant is a desert perennial that becomes dormant during drought conditions.
After a rainfall, the Ocotillo absorbs the available water and sprouts leaves to start the process of photosynthesis and then flowers within a few weeks.
Once the flower becomes a fruit and the seeds are dispersed the Ocotillo plant does not die but sheds its leaves and becomes dormant till the next rainfall. The stems of the Ocotillo plant have a waxy coating to conserve water during dormancy.
Perennials are plants that survive for two or more growing seasons.
Adaptations of Desert Annuals
Desert annuals are plants that adapt to the desert conditions by completing their lifecycle when there is sparse rainfall, and then all the parts of the plant die.
The desert annuals grow, flower produces seeds and then die. The seeds lie dormant till the conditions are favorable for growth. The seeds germinate towards the end of summer before the start of winter and require a minimum of one inch of rainfall for the seeds to start germinating.
Examples of Desert Annuals - Desert sunflower (Geraea canescens), Mexican Gold Poppy (Eschscholtzia Mexicana), Lupine (Lupinus sparsiflorus), Owl Clover (Castilleja exserta), Desert Sand Verbena, Desert Paintbrush, and Mojave Aster.
Other Adaptations of Desert Plants
Teddybear Chola Cactus (Cylindropuntia bigelovii)
The Teddybear Chola cactus has short, sharp spines arranged in clusters around the stem. Each cluster has 7 – 15 spines. These clusters cast shades to protect the cactus from the intense heat. The spines are pale yellow in color.
Grizzlybear Prickly Pear Cactus (Opuntia erinacea)
Old Man Prickly Pear Cactus has spines that are 1 – 7 inches long and are white or pale yellow in color. The short spines are thick, and the long spines on the mature cactus are thin, hair-like and shadows the cactus from the harsh sun.