8th grade plant science projects

I need a science project. I would like it to be with plants because i think they're easy to measure. My teacher wants our projects to be a little more sophisticated. Anybody have any ideas? I have the entire summer to do it so time isn't a problem. Any suggestions?

Well what does your science class cover? Is it an 8th grade biology course?
And what exactly does "sophisticated" mean, in regards to your project.

Anyways, you can try something like the effects of different colors of light on plant growth.