Why is cacti said to have sunken stomata?

Cacti are said to have sunken stomata to minimize water loss in their arid environments. By having stomata located below the surface of the epidermis, cacti reduce exposure to dry air and lower the rate of transpiration. This adaptation helps them conserve water while still allowing for gas exchange necessary for photosynthesis. Additionally, the surrounding air within the cavity can become more humid, further aiding in water retention.