Final answer:
Bromothymol blue is used in aquatic plant experiments as a pH indicator to visualize changes related to photosynthesis and respiration, helping students infer which processes are dominant.
Step-by-step explanation:
The purpose of bromothymol blue as an indicator in experiments with aquatic plants is to help visualize the pH changes in the water, which reflect the metabolic processes taking place. When conducting experiments to understand plant physiology, bromothymol blue can shift in color depending on the pH level of the solution. This shift in color is due to the acid-base equilibria in the solution. Specifically, in an aquatic plant experiment, the color change can indicate whether photosynthesis or cellular respiration is occurring. During photosynthesis, plants consume carbon dioxide and produce oxygen, leading to a rise in pH and a shift towards a blue color. Conversely, during respiration, carbon dioxide is produced, which can lower the pH and change the indicator towards yellow. By observing the color changes associated with bromothymol blue, students can draw conclusions about whether aquatic plants are primarily photosynthesizing or respiring under various conditions.