who first proposed that oxygen is liberated in photosynthesis comes from water and not from carbon dioxide?

 Hill in 1937, Ruben and Kamen in 1941 proposed that Oxygen(or O₂) is liberated in photosynthesis comes from water and not from Carbon dioxide(or CO₂).

Some thing more about this question that:

Hill in 1937 demonstrated 'photolysis of water by isolated chloroplasts' in the presence of suitable electron acceptor.

Ruben and Kamen in 1941 demonstrated that the oxygen given out during photosynthesis is from water by using O¹⁸ isotope.

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