What would be an interesting topic to do an investigatory project about botany?

You should do a test to see if plants are affected by the brain waves from the human body. to do this get a polygraph machine and test on 5 different plants and if you want to do more see if the bacteria in your mouth reacts if you get hurt . This is an A+ project.

Tropisms...Plants respond to their environment, but we don't take note because they aren't moving fast enough for us. The way they respond to light, water gravity and touch are really cool and I am sure you could get a lot of info on it. Another neat subject: Invasive species of plants...they're everywhere and the chemical warfare going on in the soil is amazing. One plant will chemically change the soil making it unfit for other plants. Good luck with your project!