Re: In the process of plant respiration, where does the oxygen go?

The summary equation for cellular respiration is:

glucose + oxygen gas ----> carbon dioxide + water

The oxygen gas combines with hydrogen from the glucose to produce water. 
The oxygen is used in what is called either the Tricarboxylic Acid Cycle, 
Citric Acid Cycle, or Krebs Cycle. This cycle is discussed in detail in most 
biology and botany textbooks.


The summary equation for photosynthesis is often written as the reverse of that 
for cellular respiration, that is:

carbon dioxide + water  -----> glucose + oxygen gas 

In photosynthesis, the oxygen gas comes from the water.


Reference

Conn, E.E. and Stumpf, P.K. 1976. Outlines of Biochemistry. NY: Wiley.