Final answer:
Air is bubbled through the culture solutions to provide plants with oxygen for respiration and to circulate mineral salts for even distribution and absorption.
Step-by-step explanation:
The bubbling of air through the culture solutions in a plant growth experiment is necessary to ensure that the plants have a sufficient supply of oxygen for respiration, which is critical for their metabolism and overall growth.
Additionally, it helps to circulate the mineral salts and other nutrients in the solution, promoting an even distribution that can be readily absorbed by the plant roots.
Apart from oxygen, other gases such as carbon dioxide can also be supplied through aeration, which is essential for photosynthesis.