Using LEDs to manipulate plant growth, characteristics

With the ability to deliver specific light wavelengths
with LED lights, growers, retailers and consumers could eventually manipulate
the scent, color, flavor, postharvest life and other characteristics of
ornamental and edible crops.

By David Kuack

Both ornamental and edible plant growers are using
supplemental lighting. Some use light to control photoperiod. Others use
supplemental light to hasten plant development by increasing the rate of

What if you could use light to increase the flavor,
aroma, color intensity, insect and disease resistance and postharvest life of
edible crops? What if you could use light to increase the fragrance, color
intensity, insect and disease resistance, flower timing and postharvest life of
ornamental flowering plants? Sound like science fiction? Read on.

Talking to plants

Kevin Folta, interim chair and associate professor of the
Horticultural Sciences Department at the University of Florida, said the
fundamental idea of using light to manipulate plants is an old one.

“We’ve known for a long time that light can affect
photosynthesis, but we are now starting to understand how light can regulate specific
plant responses,” Folta said. “It’s no big surprise that light could manipulate
something like flavors or any other aspect of plant metabolism.”

Working with other scientists at the university’s
Institute for Plant Innovation, Folta said
initial research indicates red, far red and blue light are the three major
wavelengths that affect volatile accumulation in plants. The researchers have
studied the impact of light wavelengths on strawberries, blueberries, tomatoes
and petunias.

“Volatiles are the chemicals that contribute to the aroma
and flavor that are released,” Folta said. “Volatiles are the chemicals that
are emitted that allow you to smell and taste a piece of fruit. These are the
compounds that are really important in providing flavor to fruit and

University of Florida associate professor Kevin Folta and other
scientists at the university’s Institute for Plant Innovation are
studying the impact specific light wavelengths can have on
plant characteristics.
Photo by Tyler Jones, UF/IFAS Photography  

 Folta said similar changes could be made to flowering
plants by manipulating the light wavelengths that the plants are exposed to.

“For ornamentals we could affect aromas, colors and
flower timing by changing the light environment—the specific wavelengths,” he
said. “It would be possible to synchronize an entire greenhouse of plants to
flower at the same time just by flipping a switch. By understanding the light
spectrum and how a plant sees it, it could allow us to manipulate how a plant

“It’s almost like we can talk to the plants. It’s a
language that is essentially a vocabulary of light wavelengths and that we can
use to influence how a plant grows.”

Focused on LEDs

Folta said all of the research being done involves the
use of LED lights.

“LEDs allow us to deliver very precise amounts of
specific wavelengths,” he said. “LEDs allow us to mix the light conditions
precisely. We can pick and choose the light we want to use.”

Folta said one of the ways different light wavelengths
could be used is to customize what the final fruit, vegetable or flower would
look, taste and smell like.

“For example, maybe we could put the plants under blue
light for a few days and then switch to far red and then red. We know that such
sequential treatments allow us to bump up the pigments, then the nutrients and
then the flavors,” he said. “This treatment could change the way we grow, ship
and sell crops, as well as how consumers store them at home.

“All plant traits are a combination of genetics and the
environment. The genetics are already in place to make a quality fruit,
vegetable or flower, so the LEDs allow us to manipulate what’s already there.
We can tweak the environment with the LEDs to alter plant characteristics.
Maybe an LED light would be placed in a box of roses. When a consumer opens the
box there would be this incredible aroma released.”

Folta said the research has tremendous potential for both
edible and ornamental crops.

“This research would probably have happened a longtime
ago, but LED lights were prohibitively expensive,” he said. “Now that the cost
of LEDs and narrow band width lighting is becoming more affordable, we realistically
see LED arrays being used in greenhouses to manipulate the way plants grow.”

Endless potential

Although the initial research has focused on changing the
taste of fruit and vegetables, Folta said the use of light could easily be
expanded to manipulate other plant characteristics.

Kevin Folta said growers may eventually be able to synchronize
an entire greenhouse of plants to flower at the same time just
by flipping a switch for LED lights.
Photo by Tyler Jones, UF/IFAS Photography

“There is an increasing body of research literature that
indicates some of the compounds emitted by plants and their fruit deter insects
or deter fungal growth,” he said. “It may be possible that we could affect
insect and disease resistance. For example, by using LED lights we could change
the metabolic profile of the plant so that poinsettias would be more resistant
to whitefly. This might be done by stopping production of plant compounds that
attract whiteflies, or producing compounds that scare them away or even better
than that may attract a predator of the whitefly.

“What we are doing is manipulating the plant metabolism
or changing it in ways that we don’t necessarily understand 100 percent yet,
but we know we can do it.”

An example of one of the results of the research he
doesn’t completely understand has occurred with strawberry plants.

“In the lab we have exposed strawberry plants to LED
lights and they don’t get spider mites,” he said. “We don’t know if there is
something that the LEDs are doing to change the development of the spider mite.
Or the light maybe doing something to the plant that causes it to produce a
chemical the spider mites don’t like so they choose to go to a different plant.
This is something that we still need to test.”

Folta said most of the previous research that involved
the same type of plant process manipulation involved inserting a gene, spraying
a chemical or other types of treatments that were labor intensive and required
other inputs.

“Now we are looking at basically flipping a switch to
turn on a low energy device,” he said. “Adding value at a low cost would be a
great thing for the horticulture industry.”

For more: Kevin
Folta, University of Florida, Horticultural Sciences Department, (352) 273-4812

David Kuack is a freelance technical writer in Fort
Worth, Texas;

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