CAM photosynthesis and sunken stomata are the adaptations of plants living in

CAM (Crassulacean Acid Metabolism) photosynthesis is an adaptation found in many plants that live in arid or semi-arid environments like deserts. This type of photosynthesis allows plants to conserve water by opening their stomata at night and closing them during the day. During the night, the plants absorb carbon dioxide and convert it into organic acids, which are stored in vacuoles. During the day, the stomata are closed to prevent water loss through transpiration, and the organic acids are used in photosynthesis to produce glucose.
Sunken stomata are another adaptation found in plants that live in arid or semi-arid environments like deserts. In these plants, the stomata are located in deep pits or cavities on the surface of the leaves. This adaptation helps to reduce water loss from the leaves by transpiration. 
Plants living in tropical rainforests, temperate grasslands, and tundra environments do not typically have these adaptations as these environments are not as water-limited as deserts.