Explain the half-leaf experiment.

(N/A) $\Rightarrow$ In this experiment,one half of a leaf is enclosed in a test tube containing cotton soaked in potassium hydroxide $(KOH)$,which absorbs $CO_{2}$,while the other half remains exposed to the atmosphere.
$\Rightarrow$ Test: After some time,the leaf is tested for the presence of starch using an iodine solution.
$\Rightarrow$ Observation: It is observed that the part of the leaf inside the test tube (deprived of $CO_{2}$) does not show the presence of starch,whereas the part exposed to the air tests positive for starch.
$\Rightarrow$ Conclusion: This experiment demonstrates that $CO_{2}$ is essential for the process of photosynthesis.