Desert plants have evolved specializations to survive the lack of water in the arid regions. Annuals can complete their entire life cycle during the brief rainy periods in deserts. Some perennials store water within their stems and leaves. Succulents minimize water loss by closing their stomata during the day when the temperatures soar under the hot desert sun, opening them at night to take in CO₂. During prolonged periods of drought some plants may keep their stomata closed both day and night.

      Some succulents have a reduced surface to volume ratio, developing a globose shape like the barrel cactus. While we generally think of the cactus family (Cactaceae) when discussing succulents, other plant families, including Euphorbiaceae and Asclepiadaceae, have species with shape characteristics adapted for water storage.

      Instead of forming a tree with a solid core of xylem, many stem succulents have a woody support network with large parenchymatous gaps where large volumes of water can be stored.

      The root system of many succulents consists of a very deep taproot as well as "rain roots" that may only grow to a depth of 5 centimeters but extend laterally for several meters.

      Many succulents lack foliage leaves or only produce leaves when water is available. Cacti can be distinguished from other succulents by the presence of areoles. An areole is thought to be a modified lateral bud, or axillary short shoot with lateral appendages homologous to leaves modified as spines. An areole is generally borne on the adaxial surface or apex of a podarium, a modified leaf base.

      The podaria of some species have become fused into vertical ribs that cover the entire surface of the plant. The barrel cactus provides a good example of this type of ribbing. The ribs form an accordion shape that allows the plant to expand and increase the volume of water it can hold. The plant may lose up to 80% of the water it stores. As the stem loses water, it folds inward at the "valleys" between the podaria, and its volume decreases, minimizing the surface area exposed to direct sunlight.