AP BIOLOGY

Detailed explanation-1: -CAM plants such as cacti and Opuntia ficus–indica achieve their high water use efficiency by opening their stomata during the cool, desert nights and closing them during the hot, dry days.

Detailed explanation-2: -The majority of CAM plants are found in hot, dry, very arid regions with little water. CAM plants undergo photosynthesis. Therefore, the stomata of such plants only open at night and remain closed throughout the day in order to prevent excessive water loss through transpiration.

Detailed explanation-3: -Stomata in CAM plants open during the dark period and close during light period. Behavior of stomata in CAM plants is part of an adaptive mechanism evolved by plants that grow in hot and dry environments to conserve water (Lee and Assmann, 1992).

Detailed explanation-4: -The opening of stomata through night time is a physiological alteration to prevent loss of water through transpiration.-Sedum, Kalanchoe, Pineapple, Opuntia are some examples of CAM plants. These plants also carry out double carbon dioxide fixation.

Detailed explanation-5: -Their stomata remain open during the night. This is done because they tend to minimise the rate of transpiration. It is the characteristic feature of CAM plants. These plants fix carbon dioxide during the night but form sugars only during the day when RuBisCO is active.