taroking

I have experimented with banana seed germination for a few years now. What I did was to make three small germination chambers with heaters in them and placed them in a cool room. The chambers are on a timer, so I can fluctuate the times on high and low. The low temps are somewhat dependent on the weather, as its a passive cool room (like a wine cellar). I think there are temp. triggers for some sp. This may be cool temp triggers during the germination process, as Ive tried many different warm temps and combinations. Some trends have started to emerge with some sp. but some refuse to germinate at any temp regime. I thought of a temp gradient table, with cooling and warming, but they cost about 4K!!! I thought about making a rudimentary one, but the cooling part is a bit complicated. Any ideas?
Pat