WHEN REDS & BLUES COLLIDE
BLUE LIGHT
A dramatically smaller fraction of
the type of light plants use is blue
light. Though just as much of the
visible spectrum is considered blue
(400-500 nm in wavelength) as
red, plants need only a small
percentage of the total
light received to be blue
for effective plant growth.
As little as 1% blue light
increases photosynthesis
rates and shoot dry matter
compared with plants
grown under red light
alone. Some blue light is
absorbed by chlorophyll,
but some is also absorbed
by chryptochromes.
Cryptochrome response
to blue light has been
shown to be involved
in stomatal control and
stem elongation of plants.
Specifically, with exposure
to higher percentages of
blue light, plants tend to
become more compact and
flower earlier in some species.
The Effects of Blue Lights on Lettuce
This image shows two heads of lettuce of the
same variety and age. Both were grown in the
same growth chamber, but under different light
treatments. On the left, a treatment of 50% red
and 50% blue light was applied for two weeks.
On the right, a treatment of 100% red was
applied for two weeks. The presence of blue light
resulted in a more compact, richly pigmented
lettuce head, while the absence of blue light
resulted in stretched-out leaves that are almost
completely green. When grown outdoors, this
variety of lettuce more closely resembles the
darkly colored head than the green one.
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Maximum Yield USA | October 2015