H2O + hv -> OH + H
H(atmos) ---heat---> H space
OH + OH -> H20 + O
With photosynthesis the production
of free oxygen is accelerated from:
CO2
+ H2O ----sunlight---> 'CH2O' + O2
But energy can also be released from carbohydrates by
respiration:
'CH2O'
+ O2 -----> CO2 + H20 (+energy)
thus depleting free oxygen.