Is this the experiment you’re referring to? I found a couple different articles that hinted at a similar point though:
- Economic Analysis of Greenhouse Lighting: Light Emitting Diodes vs. High Intensity Discharge Fixtures
- http://onlinelibrary.wiley.com/doi/10.1111/php.12233/full
Very true, and given the fact that evolution produces some unusual adaptations, I wouldn’t be surprised if there was some benefit to a fuller set of wavelengths.