We took a geometric approach:
I think there are some benefits to having a flat-plane design. Depending on our vigor with construction, we can simply replicate triangular or trapezoid shapes, shingling them together to make a circular shape. This could prove to be a difficult endeavor, but if the class collaborates, we can execute a clean design.
Watering is an issue as well, because we have to be able to easily access our plant for watering without hitting the trough, giving skewed research data. The top housing of the plant should be the easier of the two parts, but I think for now our (or, at least my) concern is a more direct way to collect water in the "bladder."
Continuing with the geometric approach, a flat plane on the bottom would allow a more clear view of the water being yielded, taking advantage of gravity and focusing the water downward. The weight of the gasket at the bottom should make the reservoir hang in a sort of way, creating a ravine for the water to collect and feed out of the structure.
Any frame will have to be built from rigid materials, acrylic or wood. A downward coil (a sort of gravity condenser) could provide an aesthetic and closure to the device. I included a fabrication approach at the bottom left, and have started considering a circular design.