Question

If a photosynthesising plant, releases oxygen containing more than the normal amount of ${}^{18}O$, it is concluded that the plant has been supplied with ______________.

• A. $C_6{H}_{12}{O}_6$ containing ${}^{18}O$
• B. $H_{2}O$ containing ${}^{18}O$
• C. $C{O}_2$ containing ${}^{18}O$
• D. Oxygen in the form of ozone

Answer 1

The correct option is B $H_{2}O$ containing ${}^{18}O$

In light reaction, the energy of the light is used to' split water', stripping a pair of electrons from it and causing the two hydrogen to be lost as a hydrogen molecule, thus generating molecular oxygen. Since the evolution of oxygen during photosynthesis takes place due to the splitting of water, more amount of oxygen evolution means more supply of water to a plant.