That spectrometer thing was cool. I am making one tomorrow. I am confused. Do the different wavelengths of light do different things to the plant? A leafy plant grown with lots of blue light is an example. If that is true.
You could build a lot of LED lights a few hundred of them, each a different wavelength. Grow identical plants under all the different individual wavelengths.

I guess my question comes down too...
We know plants use some wavelengths more efficiently than others but do the different wavelength contribute to different growth characteristics?
My experiment would tell you but it is not very practical. I do not know any other way to figure it.