HABITAT—HOW DRY I AM
Many succulents thrive in desert habitats that are far too hot and dry for other plants. In some places, rain may fall just once or twice a year, and during drought, a plant may go two years or more without a shower—and survive! Many succulents have shallow roots that spread like a wide net around the plant, to make the most of even small amounts of rain.
Other adaptations help a succulent conserve water, too. A thick, waxy layer called the cuticle provides a barrier that protects the soft, water-storage tissue inside. And for some species, hairs or spines help shade leaves or stems from the sun and insulate the plant from some of the effects of drying winds.
To photosynthesize, plants need sunshine—and carbon dioxide (CO2), which they take from the air through tiny pores—called stomata—in their leaves. But while open stomata bring carbon dioxide in, they also let water vapor out. So, when they sun's not shining, stomata close to conserve water.
Many succulents protect themselves further from water loss by working in the relative coolness of night; stomata open at night to take in CO2, and close during the hot, dry daytime, to conserve water loss. This requires a special adaption, though, because photosynthesis requires sunshine. These succulents have a way to rearrange CO2 molecules and store them overnight. When the sun comes up, the stomata snap shut, and the photosynthesis-engine starts, powered by the stored CO2.