How do we know the oxygen released in photosynthesis comes from water?

Hello! The answer to your question is: O18 is a heavy isotope that was used as a tracer, and only when the H20 was the source of O18 would the O2 released be labled with the isotope.

I really hope this helped you! c:

Predator instincts is what causes it

Mechanical energy from wind nonrenewable resource