Survival strategies of desert plants
Deserts receive less than 250 millimetres of rain a year, and the rain that does fall is often unpredictable. Plants that live in such environments have evolved a range of strategies to obtain water, store it and reduce its loss.
One group of plants avoids drought altogether. Annual wildflowers in many deserts survive dry periods as seeds, which can remain dormant in the soil for years. When heavy rain finally arrives, the seeds germinate, grow, flower and produce new seeds within a few weeks, completing their life cycle before the soil dries out again.
Other plants endure drought by storing water. Cacti and similar succulents have thick, fleshy stems that expand after rain and shrink as water is used. Their leaves are often reduced to spines, which lose far less water than broad leaves and also protect the plant from thirsty animals. Many succulents also use a special form of photosynthesis in which they open their stomata — the small pores through which gases enter and water escapes — only at night, when temperatures are lower and less water is lost.
A third strategy involves the roots. Some desert shrubs have extremely deep roots that reach groundwater many metres below the surface, while others spread shallow roots over a wide area to absorb light rain quickly before it evaporates. These different approaches allow several species to share the same area without competing directly for the same water.