Usually plants take CO2 and release oxygen during day (due to photosynthesis) and they take O2 and release carbon dioxide during night as a result of respiration.
But it has been found that Peepal tree (scientific name Ficus religiosa) releases oxygen 24 hours a day. How is it possible that a plant releases oxygen throughout day and night? Don’t they carry out respiration?
It is all because of CAM pathway of photosynthesis. CAM pathway is one among the three pathways – C3 pathway (Calvin cycle), C4 pathway and CAM pathway (Crassulacean Acid Metabolism) adopted by plants for carbon fixation in photosynthesis.
C3 and C4 are common among land plants and among these two C3 is the most common. C3 and C4 plants keep their stomata open during day time for taking carbondioxide for photosynthesis and release oxygen and during night they carry out respiration and release carbon dioxide.
CAM pathway can be seen in desert plants and epiphytes (plants that lives on other plants). Unlike C3 and C4 plants these plants keep their stomata closed during day and open it during night for carbon fixation and release oxygen. They do it so, to prevent loss of water due to sunlight. So, CAM plants release oxygen during night.
Inspite of being land plant Peepal tree can release oxygen during night also, because it is a hemi –phyte in its native i.e the seeds germinate and grow as an epiphyte on other trees adapting CAM pathway of photosynthesis and when the host tree dies, they establish on the soil and then switch to C3 pathway of photosynthesis.
So, Peepal tree can either release oxygen or not during night totally depends on whether it is an epiphyte or not.