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LED lights cause unexpected results

May 1, 2012

University Relations

Nancy Tarnai
907-474-5042
5/1/12

In late March, Meriam Karlsson, a horticulture professor at the University of Alaska Fairbanks, gazed at rows and rows of cheery sunflowers with a look of puzzlement.

When doing research, things don’t always go as predicted and this was one of those times. On Jan. 9 Karlsson planted Sunny Smile dwarf sunflowers as part of a lighting experiment in the new School of Natural Resources and Agricultural Sciences greenhouse on the west ridge of campus.



Half the plants were placed under red or blue light-emitting diode lamps at 14 days and the other half joined the first batch at 24 days. “They all flowered at the same time,” Karlsson said. “It’s not what I expected.” Another surprise was she had thought that the blue LED lights might cause delays in flowering but that was not the case.

“Everyone says it’s so critical to have the right light initially,” Karlsson said. With this experiment she learned that it might be OK to use LEDs, which are more energy efficient than high-pressure sodium lamps, to start flowers or seeds.

Basking in the 72-degree greenhouse, the perky sunflowers looked exactly the same, no matter what lighting treatment they received. “Next time we will leave them under different lights and let them stay until they flower and see if there are differences,” Karlsson said.

Her research is spurred by the increasing interest in LED lights. Overseeing a graduate student research project, Karlsson saw that plants such as lettuce and black-eyed Susans reacted differently when placed under red or blue LED lights. “They didn’t flower as fast,” she said.

Of course the best light is natural, full spectrum light, which has all the lengths and colors of light waves but since that isn’t possible in a Fairbanks winter, artificial light is required. While the standard has been high-pressure sodium lights, new research is touting the advantages of LEDs. One factor is that sodium lights don’t have a blue range, which is important for certain processes in plants. Without the blue rays, the plants look different.

The plants’ pigment reacts to light and chlorophyll is used in photosynthesis. “If you just look at plants they are very efficient,” Karlsson said. “The most effective light for photosynthesis is red and blue but there are more things going on in plants than photosynthesis. Other pigments absorb the green and orange.”

While sunflowers are a beautiful addition to any landscaping scene, Karlsson ponders some broader aspects. “I wonder about the nutritional value of food grown under certain lights,” she said. “NASA has been looking at this.

“LED is a completely different technology,” Karlsson said. “It’s monochromatic light. It may be red or blue, or even orange. There is a peak of light quality and nothing in between. What happens after the plant absorbs these wave lengths of light?” In addition to energy savings, another advantage of LEDs is they don’t give off a lot of heat, so they can be placed closer to the plants.

Karlsson’s fascination with growing things began at an early age on her family’s farm in Sweden, where barley, oats, hay and potatoes were grown. “I was always interested in plants and crop production,” she said. “But I thought those crops were kind of boring.” When choosing her career, Karlsson decided to go the horticulture route rather than agronomy. She earned a doctorate in horticulture at Michigan State University, where she first got interested in studying the effects of lights on plants.

After coming to Alaska her focus on lighting increased. “Up here light is really important,” she said. “It’s fascinating to me the long days in the summer and the short days in the winter. Nobody knows why plants grow so well in 24 hours of light; they really shouldn’t.”

In the lettuce and black eyed Susan study, lights used were red, blue, red and blue and a multi-colored light with red, blue, orange and white. “If you worked under those you would go crazy,” Karlsson said. “You would see spots and it’s hard to tell if the plants need water or not.”



Working in the just completed greenhouse attached to Arctic Health Research Building is fun, Karlsson said. “You can do so many things with the shade and lighting via computer.” While being interviewed, Karlsson took a call from a technician in California who monitors the temperature and lighting in the greenhouse via computer. “We have to figure out the light levels because it changes every day,” Karlsson said.

“Spring has challenges because it is sunny and warm but it is still cold out. We work closely with Link 4 in California.”

Karlsson is convinced greenhouse manufacturers should use Fairbanks as a testing ground. “If they can make it work here it would work anywhere in the U.S.,” she said.

And she firmly believes Alaska should step up its agricultural research. “We should do much more,” she said. “We have unique conditions in lighting and temperature variations. We can do a lot the rest of the world could learn from. We can be more productive here because we have excellent growing conditions and we don’t have to fight many pests and diseases that are devastating to crops in other areas.”

Note to readers: It’s that time of year when you can reserve a plot in the Fairbanks Community Garden. Visit , or call Lara Lotze at 457-8216, lara@alaska.net for all the information you need to get growing! Plot rental is $35, which includes water and tools.