Cactuses are thrifty plants that live in dry regions. They may not get much moisture where they live, but they manage to make the most of what they do get.
Since the cactus’s long roots lie close to the surface of the ground, they can catch water from desert rains. And since the roots have a cork-like bark covering them, they can absorb the water quickly.
Because the cactus has no leaves, its stems do the job of manufacturing food for the plant and of storing its water. And because these stems grow upward rather than out, not too much of the plant faces the direct drying rays of the sun. These broad stems have a great deal of room for storing the water and a thick covering for protecting it.
In addition, the plant’s sharp, pointed needles keep desert animals from sucking out this valuable liquid. However, cactus plants have saved the lives of thirsty people stranded in the desert.
A cactus plant only three feet tall may have roots spreading out to a length of ten feet across the desert!
This website helped me with my science assignment about plants in extreme environments.