Why is aerated water necessary?

Well, as you were probably told in cl, aerated distilled water is basically regular distilled water with a gas pumped into it. In terms of the benefits of this process; aerating distilled water with the air we breath supplies the water with increased amounts of oxygen, which provides life-forms dependant upon water with a bonus supply of oxygen with which they can breathe. This applies to your beetroots, which will help them remain turgid and grow faster from the increased supply of oxygen and possibly other gases as well. You can create a controlled experiment by using regular distilled water vs aerated distilled water and report the differences in beetroot development etc...