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Re: The Environment
Oxygen and photosynthesis
With respect to oxygen and photosynthesis, there are two important concepts.
Plant and cyanobacterial (blue-green algae) cells also use oxygen for cellular respiration, although they have a net output of oxygen since much more is produced during photosynthesis.
Oxygen is a product of the light-driven water-oxidation reaction catalyzed by photosystem II; it is not generated by the fixation of carbon dioxide. Consequently, the source of oxygen during photosynthesis is water, not carbon dioxide.
Therefore the really big, old trees use lots of oxygen, ok it is offset by the fact they produce it during the day but during the night they still use oxygen, but cant produce it.
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