Question

Stomata of CAM plants
A) Are always open
B) Open during the day and close at night
C) Open during the night and close during the day
D) Never open

Answer 1

Hint: Stomata are the tiny pores that help in gaseous exchange in the plants. CAM plants show Crassulacean acid metabolism. In these types of plants carbon dioxide intake is done during the night and carbon fixation occurs during daylight. It is mostly observed in desert plants.

Complete answer:
The tiny pores present in leaves for the exchange of gases and water are called stomata. CAM photosynthesis is the carbon fixation pathway that evolved in some plants as an adaptation in arid conditions. CAM stands for Crassulacean acid metabolism. This metabolism was first discovered in plants of the family Crassulaceae. The stomata of the plants which show this pathway remain close during the day to reduce evapotranspiration. The opening of stomata in these plants occurs at night to collect carbon dioxide and allow it to diffuse to the mesophyll cells. Carbon dioxide is stored in the form of malic acid in vacuoles at night. Malic acid is transported to chloroplasts where it again converts into carbon dioxide. It is used during photosynthesis during the day time. RubisCo helps in carbon fixation and increases photosynthetic efficiency. CAM is mostly observed in fleshy plants having low surface-to-volume ratio. Succulents mostly perform this metabolism.
From the above information we know that stomata of CAM plants open during the night and close during the day.

So, the correct answer is option C.

Note: Not all the succulents are CAM plants, exceptions are there like halophytes that are adapted to salty soils. CAM plants are mostly found in dry, desert habitats. These plants include about 20,000 species in about 40 families which is equivalent to 8 percent of all land plants. Examples of CAM plants: jade plant, Aeonium, Echeveria, Kalanchoe, pineapple, Spanish moss, cacti, orchids and wax plant.