Why do desert plants need long roots?
Although surviving in the desert is difficult for humans, desert plants have evolved so that they can survive in all but the driest conditions. Many desert plants have adapted to the harsh environment by growing deep roots that can gather water from a metre (several feet) under the surface.
Without these long roots, these desert plants could not stay alive, nor could the wildlife that depends on them for food, drink and shade.
Desert plants have a variety of roots. Some have large spread-out root systems that takes up a space equal to several times the length of the plant itself. Other plants have deep roots with a few large tap roots that reach well into the earth. Other plants have a combination of both. Each type of desert root system has its own advantages and disadvantages.
Long roots for desert plants look similar to other roots, only more lengthy. The roots spread out from the base of the plant deep into the earth. Typically, the roots are larger than regular thread roots so that they absorb more water. Depending on the plant, the tap roots can reach anywhere from 60 or 90 cm (2 or 3 feet) under the surface of the ground to over 6 m (20 feet) for trees and other large plants and shrubs.
The plants grow deep roots to gather water that is far down under the surface of the earth. At such a deep level, the water evaporates from the desert heat much slower than it does closer to the surface. In some locations, there may even be groundwater present under the desert floor that can sustain plants with deep enough roots. The roots then gather this water and transmit it to the top of the plant so that it can accomplish photosynthesis to stay alive.
There are several benefits to a deep root system rather than a large surface root system. A deep root system helps the plants stay grounded in the soil through harsh winds and other adverse conditions. And the plant is not dependent on rainfall to get water for survival.
A deep root system is not the only way that a desert plant absorbs water. Many desert plants also have water absorption systems present in the stems or leaves of the plants, such as tiny hairlike fuzz on the surface of the leaves that helps prevent the evaporation of water. Plants typically have tiny pores in the stems and leaves of the plant called stomata. When these pores open, the plant looses water through evaporation. Some desert plants cope with this problem by having fewer stomata than non-desert plants.