Isotopes popularly known to have been used in the study of photosynthesis are

Explain the experiment of $T$. $W$. Engelmann $(1843 - 1909)$.

The fact that oxygen released during photosynthesis comes from water was proved by $O^{18}$ isotope experiments conducted by:

Two plants $A$ and $B$ are supplied with $CO_2$ with $H_2O^{18}$ and $CO_2^{18}$ with $H_2O$ respectively. Which of the following plants releases $O^{18}$ type oxygen in photosynthesis?

What does the experiment of two leaves explain in the context of photosynthesis?

$PGA$ as the first $CO_2$ fixation product was discovered in photosynthesis of