How do cacti adapt to survive in a desert?

Cacti have the following adaptations that help them to survive in a desert.
1. The cactus plant has an extensive root system with numerous root hairs that go deep into the soil in search of water.
2. The leaves are modified into spines and coated with a cuticle to prevent the loss of water through transpiration.
3. The stomata are few, sunken in pits.
4. The stem is thick and fleshy for conserving water.