App note from Würth Elektronik on why plants evolved to use far-red wavelengths and why it is essential for them. Link here (PDF)
The light requirement of plants is now known to be far more complex than originally thought leading to the development of numerous LED technologies that produce a variety of different light spectra, both monochromatic and polychromatic.
Far-red encompasses wavelengths 700 – 800 nm, a region of light that is on the edge of visibility in humans. However, these wavelengths have been proven to result in faster growth, increased biomass and better sensory characteristics (e.g. smell, taste, texture, color).
from Dangerous Prototypes http://bit.ly/2Fc3YT7