I like that you went through with this idea. we need to plant this thing and get it going. Experiment time.
The idea of evaporation and saturation as a generator for mobility is a beautiful one, that I think will work to rotate the vessel. the plant response to this environmental flux will be interesting, since both root and shoot development is partially gravitropic. Please post pictures as the spinach germinates so we may settle our bets as to how this works. I love the experimentation in your project, and it is exciting to see that experimntaiton with materials translate into your concept for a larger scale term project!