How do cactus plants adapt to their habitats?

Cactus plants adapt to their extreme habitats by specializing body parts and functions. For example, the roots concentrate on anchoring the plant and on capturing nutrients and water from the soil. The stem concentrates on processing and storing water, nutrient solutions, and energizing starches and sugars. It also concentrates on controlling breathing, gas exchanges, and water loss through its pores, or stomata. It concentrates too on the photosynthetic interaction with sunlight. And the modified leavesconcentrate on directing moisture down to the ground, to be taken in by the cactus' roots.

They have prickles to protect themselves.