Cactus Protective Adaptation

Succulence

• Succulency is a key adaptive feature common to all cacti and many other desert plants, including agave and aloe. According to the Arizona-Sonora Desert Museum, succulent plants store water in their stems, roots or modified leaves. These plants require some water throughout the year to survive, but they are able to save the water they get from small periods of rain to survive months of drought. The water chambers may also contain specialized cells or chemicals to prevent evaporation.

Needles

• The characteristic needles of cactus plants are adapted leaves that serve several critical protective functions. The needle-like leaves have a much smaller surface area than the broad leaves found on many plants in temperate climates. This prevents the sun and strong desert heat from scorching the plant's foliage. The needles also deter the many potential predators that are seeking a source of food or water in the desert.

Photosynthesis

• Many cactus species conduct photosynthesis differently than herbaceous plants, trees and shrubs. These plants process water and carbon dioxide through a process called crassulacean acid metabolism (CAM), which is a variation of standard photosynthesis. CAM requires as little as one-tenth of the water needed for normal photosynthesis, but the plant grows significantly slower as a result. Many CAM plants also have adapted stomates, pores on the surface of the needles, that close during the day and open at night. The plant stores the carbon dioxide and processes it with the water stored its in succulent chambers during the day.

Roots

• Most cacti have a sprawling root system that only penetrates the upper layer of the soil. This allows them to collect as much moisture as possible in a short amount of time, which is critical when there is only a day or two of rain in a season. According to the Arizona-Sonora Desert Museum, the roots of succulent plants rarely penetrate more than a few inches into the soil, with most of the roots within a few centimeters of the surface.