Plants in desert do not have leaves. Which of the following are replaced by their leaves?

The desert is a harsh, unforgiving environment. It is just as hazardous to plants as it is to animals. Temperatures swing wildly between extremes in a desert.The most extreme form of this adaptation is found in the desert plants like cacti, whose stems and leaves have been reduced so much that only spines remain. These spines also can shade the plant, helping it conserve even more moisture. With cacti, the primary photosynthetic activity has been moved to the stalk, the main body of the plant and away from the leaves.