2013-06-20

Bees Like LED Grow Lights

Solid state lighting has shown that it can aid photosynthesis and plant growth. Now we know it can help plant pollinators, too.

Last month, we discussed research out of Purdue on the effect of LED lighting on the growth of tomato plants. Now meet Valoya, a Finnish maker of LED lighting for agricultural applications. It conducts research on plant growth and how LED light affects it, both at its own facilities and at those of universities and commercial growing operations.

Their stated goals for their research are to make more effective LED lighting for the purpose of growing plants, and to provide benefits to their customers. Valoya says they have a database and software called LightDNA(TM), in which customers can search and research plant species and the light spectra that work best with them. A word of caution, though. The quality of the research may or may not meet the standards of published science. I didn't see an indication on Valoya's site that they submit research to peer-reviewed journals, though their university-affiliated customers and partners may do so.

For the bees
Valoya set up equipment to watch the hives of bumblebees that pollinate tomato plants for PlantResearch of Made, Netherlands. Using high-speed cameras, the company filmed bumblebees entering and exiting the hives in separate greenhouses lit by conventional high-pressure sodium (HPS) lights and by Valoya's LED lights using its AP67 light spectrum.

The experiment was carried out in January, when the sun doesn't rise at the facilities until around 8:00 a.m.

Bumblebee count on a typical day, between 4:00 a.m. (lights on) and 7:00 a.m., in greenhouses
lit by Valoya AP67 LEDs (left) and by HPS.
(Source: Valoya)

The chart shows bee activity resulting from turning on the lights at 4:00 a.m. The green bars represent the number of bees leaving the hive; the red bars represent bees returning. The bees living under HPS light showed little activity until the sun began to provide natural light. They simply didn't see the sodium light. Under LED light, bee activity picked up promptly when the lights went on.

Bumblebees have trichromatic vision. They can see light in three areas of the spectrum: UVB, blue, and green. These frequencies are not present in HPS light, but they are in Valoya's AP67 spectrum.

Valoya says on its site that AP67, which is designed to encourage vegetative growth and flowering, is "strong on far-red (about 18 percent of the total radiation) and has no UV radiation." The light appears pinkish to human eyes. The company also offers a spectrum called AP67S ARCH for environments in which growing plants coexist with people. This spectrum includes an additional component of green light and appears warm white to humans.

I haven't heard of any research investigating other qualities of LED-grown plants (nutrients, flavor, texture, etc.) compared with those grown in natural light. What have you seen?

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— Keith Dawson , Editor-in-Chief, All LED Lighting