First, there is no hard and fast rule concerning the relative production and consumption of oxygen. Plants can only produce Oxygen when light is available hence they do not produce it at night. Further, the only other requirement to produce Oxygen is the availability of water (this is where the oxygen comes from). In fact plants can't turn off Oxygen production and if they run out of water the "motor" will burn out. It is a little like running an engine without oil. So plants produce Oxygen independently of their needs.
On the other hand plants consume oxygen based upon their needs. Parts of the plant that are actively growing (in the tips) will use relatively more oxygen than they produce whereas mature leaves that are not growing will produce more oxygen that they use.
On the other hand plants consume oxygen based upon their needs. Parts of the plant that are actively growing (in the tips) will use relatively more oxygen than they produce whereas mature leaves that are not growing will produce more oxygen that they use.
