Flora's Life : in Hot Deserts
There are many saguaro cacti in hot deserts
Plants in the hot deserts have developed important adaptations for them to be able to live in them.
Hot desert plants have adaptations that allow them to live in their hot, dry environment. Some desert plants have extremely long roots that can reach water 50 feet (15 m) or more below ground. Other desert plants have a network of roots that spread out just below the surface of the ground. These roots are able to quickly absorb water from dew or an occasional shower.
Desert plants have other adaptations, such as tiny leaves or no leaves at all. This prevents a lot of water from being lost through transpiration. Desert plants with few or no leaves have green stems, and most or all of their photosynthesis occurs in their stems.
Plants, regardless of the biome where they are found, are called annuals if they live for only one year or growing season, and perennials if they live for many years. Some desert perennials are drought-deciduous, meaning they sprout leaves only during the rainy period, then drop them when it gets dry. Other desert perennials die back above ground during droughts (a time when there is a lack of rain), but their roots are still alive. Water in the roots of these plants keeps them alive until the next rain, when the plant will quickly send up shoots above ground. Desert perennials are among the oldest plants in the world, with some living many thousands of years. This age refers to the age of the root from which stems grow when there is enough moisture.
In hot deserts, a heavy rain generally occurs yearly, but in cold deserts, it rarely rains. For example, several hundred years may pass before it rains in the cold Atacama desert. After a hard rain, many deserts will suddenly be in bloom. This is because the seeds of many annual desert plants germinate (begin to grow) after a hard rain. Within only a few days, the plant has fully grown and a flower with seeds has been produced. But most of these fast-growing plants don't last long, and some don't even grow each year. Instead the seeds remain dormant (alive but inactive) until the necessary amount of rain has fallen. Scientists have found dormant seeds hundreds of years old that were still able to germinate. Since annual implies yearly, desert annuals are more accurately called ephemerals, which means they are short-lived. If their seeds were to sprout without enough water available to keep them growing, they would die. This doesn't generally happen because the seeds are covered with a protective coating that is washed off only by a hard rain. Once the chemical protective coating is washed off, the seed sprouts.
Some hot desert plants, such as the saguaro cactus, found only in the Sonoran desert, have a pleated or folded surface, much like an accordion. During wet periods, this folded surface expands, allowing the plants to hold a great deal of water. Plants in any biome that have thick and fleshy stems or leaves designed to retain water and reduce evaporation are called succulents. Succulents also have these hard leaves for them to handle the extreme temperatures from day to night in the desert. They also have a hairy structure to help reflect the heat from the sun.