Photosynthesis?
Design an art piece that uses natural processes, in which you are the orchestrator but not the maker. What wacky ways are artists using science and nature to make art? Creating portraits out of photosynthesis, growing icicles, electrifying flowers, using heartbeats to generate a light show....among other things. Scale it down a bit to something do-able with the resources you have and design your own nature-ly...