In CAM plants, the source of carbon dioxide during the daytime is ________.

The correct answer is: Malic acid

• Correct option is C)
• Crassulacean acid metabolism is a carbon fixation pathway, that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide. The CO2​ is stored as the four-carbon acid malate, and then used during photosynthesis during the day. The pre-collected CO2​ is concentrated around the enzyme RuBisCO, increasing photosynthetic efficiency.