Cacti / Desert Succulents
NPS Photo/Cookie Ballou
Cacti and succulents, such as agaves, yuccas, and ocotillo, are xerophytes—plants that possess highly adaptive characteristics that allow them to thrive in bone-dry conditions. Forced to survive by conserving water, these plants have evolved into uniquely shaped characters, with atypical characteristics. Cacti and desert succulents are often confused because of their spiny appearance, but each has its own set of distinct traits.Cacti and succulents use a photosynthesis process called Crassulacean Acid Metabolism or CAM. Minute pores in the plant's skin surface—called stomata—open only at night. Carbon dioxide is absorbed through these minute openings and chemically stored as an organic acid. Much less stored moisture is lost by the plant's use of this nightly process. During the day, carbon dioxide is internally released from the acid and made available to the plant. The trade-off in this delayed system of photosynthesis is that cacti and succulent species generally grow very slowly.