Explanation:

Hardness and Wax coatings on leaves prevent water loss through evaporation, which in the hot desert can cause loss of water from both the surface and the inside of leaves. Leaves are also smaller on desert plants, further reducing the possibility for water loss.

Many plants in the desert conserve water by not having any leaves at all. Cacti are the most prolific of this plant type. Many cacti have spines in place of leaves, which conduct photosynthesis and catch dew when the climate is right. These small structures also reflect light, further reducing water loss. During heavy rains, cacti will grow temporary root systems and absorb water. They will then shed the roots when the ground has dried.