Question

in photosynthesis source of oxygen is water not carbon dioxide give reason

Answer 1

(i) It was previously assumed that the source of oxygen in photosynthesis was CO2 and not H2O molecules. (ii) According to recent studies, oxygen is evolved from water and not from CO2. (iii) It was proved by the use of radioactive elements For example, the water containing heavy oxygen (H2O18) was supplied to the leaves in place of natural osygen, (H2O16). (iv) On observation it was found that oxygen evolved in photosynthesis was heavy oxygen 18O2 and not the natural oxygen. (v) Now, the heavy isotope of carbon dioxide (C14O2) was supplied to the plant. (vi) Thus, it showed that in photosynthesis, oxygen is evolved from water molecules and not from carbon