Why is KOH solution kept in the test-tube inside the airtight conical flask while doing the experiment of respiration of seeds?

KOH is a chemical that is used to absorb carbon dioxide.

During respiration, the germinating seeds release Carbon Dioxide (CO₂). Germination is a process where the growth of the seeds begins. The KOH solution kept in the test tube inside the airtight conical flask absorbs the released Carbon Dioxide by the seeds. This creates space in the conical flask and an equal volume of the water rises in the tube. Hence this shows seeds are respiring and CO₂ gas is evolved in the process of respiration.