LED Spectra - John Dunn, Consultant, Ambertec, P.E., P.C.

The illustration below shows some light source spectral distributions that were presented by Cree, Inc. at an LED seminar in March of 2010. Clearly (no pun intended.), the contours of intensity versus wavelength differ profoundly from one light source versus another.

 

Interestingly, to the normal human eye, all three of these spectra yield a light by which most people are comfortable for reading and even for room lighting.

However, I am struck by the use of LED for plant lighting. See Grow lights or any of a whole lot of websites that advertise LED lighting for plants.

Would plants that normally grow well in sunlight still do well under the spectral content of LEDs? I honestly don't know the answer to that, but the question does arise in my thinking.

An item in a recent Scientific American suggested that if there were plant life on an extra-solar planet whose sun differed in its light spectra from that of our own sun, that the said plant life would be tailored to make optimum use of that alien light and would therefore be quite different from earthly vegetation.

Therefore, would LED lighting bring about significant changes in LED illuminated plants?

"The Day of the Triffids" anyone?

Comments

[John Dunn]

This professional daylily hybridizer delivered a lecture last year at The Long Island Daylily Society and announced that he'd placed much of his plant stock under LED lighting. I had to wonder just how much of a financial risk he might be taking if the plants reacted badly to the LED specral content versus getting exposure to the sun or to more conventional plant lights.

I don't think he understood what I was trying to say.

[George Storm]

Unsurprisingly, given the importance of horticulture and the cost of heating/lighting greenhouses, there has been significant research on this topic.
It is clear that earthly chemistry is more important than the spectrum of the sun in determining the use that plants make of incoming radiation.

You can find some information on photosynthesis requirements at http://assets.sylvania.com/assets/documents/FAQ0074-0605.844b0c66-0b11-44c1-b6b5-32218c3e6d08.pdf
Unfortunately, this spectrum can confuse some pollinators, so different lamps may be required when plants are in flower.

BTW - even if their spectrum were somewhat better for the plants (unlikely) LED lamps seem like an expensive way of lighting them - at least at the present stage of development

[Roy Plant]

If not done already, an interesting research paper would be on the qualitative food production of various plants with light wavelength variation as a parameter

[Nathan Taylor]

The LED based grow lights I have seen are tailored to deliver the particular wavelengths that plants (in general or possibly specific plant types) grow best under. While your diagram is true of light from "white" LEDs the gaps can be filled in with additional LEDs of varying wavelength. AlInGaP based LEDs can provide much of the red deficiencies seen in your chart.