CAM photosynthesis limits CO2 fixation to nighttime hours in order to (A) allow water to enter leaf spaces during the daylight h
ours.(B) open stomata only at night, limiting water loss because of heat and low humidity. (C) allow NADPH and ATP to enter leaf spaces.(D) limit the Calvin cycle reactions to nighttime only.(E) limit water uptake from the soil during daytime hours.
(B) open stomata only at night, limiting water loss because of heat and low humidity.
Explanation:
CAM plants are found in the regions characterized by very hot and dry environmental conditions. These plants reduce the water loss through transpiration by exhibiting CAM photosynthesis.
They open the stomata during night time when the air is cooler and rich in moisture. They take in CO2 during night time and fix it into the oxaloacetate which in turn is converted into malate and is stored in the vacuoles.
During day time, stomata remain closed to prevent water loss and the CO2 trapped during night time (released by decarboxylation of malate) enter the Calvin cycle.
As light intensity increases (distance between lamp and plant decreases) the volume of oxygen (or the rate of bubble production) increases. This indicates that the rate of photosynthesis increases with light intensity. However, at sufficiently high levels of light intensity, the rate oxygen evolution remains constant.
