How do cacti store water in dry conditions?

Cacti are succulent plants that have evolved specialized adaptations to survive in dry conditions by storing water primarily within their stems.12

The internal structure of a cactus stem consists largely of thin-walled storage cells that contain mucilaginous substances, which help prevent the loss of moisture. To further minimize water loss, most cacti have leaves that are absent, greatly reduced, or modified into spines, which also serve to protect the plant and radiate heat.23

Additionally, many cacti utilize a specialized form of photosynthesis known as crassulacean acid metabolism (CAM). Unlike most plants, CAM plants keep their stomata closed during the hot, dry daylight hours to prevent transpiration, opening them only at night when the air is cooler and more humid to take in carbon dioxide. This temporal separation of carbon fixation allows these plants to thrive while requiring significantly less water than other species.14