Sticking a router inside a tiny faraday cage isnt what how we live under wifi. The RF waves push through, move out and dissipate. Putting a plant embryo in a tiny faraday cage next to a powerful microwave RF emitter isnt the same as putting it in a room. Id imagine its like a RF echo chamber in there, and those vibrations would effect the incredibly tiny process involved in gowning a plant from a seed. A better experiment would have been adding a third box with no faraday cage and see how normal background wifi in a school effects the growth compared to one inside a faraday cage, ill bet there is no noticeable difference. If cell and wifi caused cancer and tumors we would see significant rise in them over the last 20 years. We dont see that at all anywhere, despite kids falling asleep with cell phones on their faces.