Parts of the cactus. The structure of a cactus helps the plant survive in dry climates. Most cactuses have thick, fleshy stems with waxy skin. The stem holds water, and the skin keeps the water from evaporating. In addition, the surfaces of many cactuses can expand and contract like an accordion to accommodate the changes of water content in the stem.
Cactuses have extremely long roots.
The roots grow close to the surface to collect as much water as possible for storage. After a heavy rain, they can absorb a large amount of water for the plant. The spines of a cactus protect the plant from being eaten by animals. Spines may be long or short and soft or sharp. They may have straight or hooked tips.