WHEN REDS & BLUES COLLIDE
L
ight is all around us every day.
We can see it and manipulate it
to a certain extent, but what exactly
is it? Scientific literature says light
behaves as both a wave and a particle,
and wavelength information can
tell us about the energy contained
within light. The human eye perceives
different wavelengths of light as
different colors, and multiple waves of
light can be produced by the same light
source, leading to separate waves being
perceived as one combined color. The
particle nature of light emerges when
light differentiates into discrete packets
An effective LED grow
light should include
LEDs in the blue and red
range. Including green
LEDs can make plants
appear more natural to
the human eye, but does
not always offer significant
advantages for growth.
Including far-red light has
a number of applications
that many growers are
currently investigating.
Including white light can
make visual identification
of disease symptoms
easier, and make it more
comfortable to look at
plants with the naked eye.
of energy called photons. Beams of
light are described by referring to
individual wavelengths, a.k.a. colors or
energy, and intensity, a.k.a. counts of
individual photons per unit time.
HOW DO PLANTS SENSE LIGHT?
To understand how different
types of lights affect plants, a basic
understanding of photosynthesis is
required. Photosynthesis is, in broad
terms, the process used by plants or
other photosynthetic organisms to
convert light energy into chemical
energy. First, light reaches the plant
surface. Some wavelengths of light
are reflected (bounced) off the plant,
some are transmitted (shine all the
way through the plant) and some
are absorbed. The apparent color of
plants is determined by the light that
is reflected away. The reflected light
has little to do with photosynthesis,
since most of the energy is directed
away from the plant. Some wavelengths
of light are captured by chlorophyll,
which are green pigments within
special structures called chloroplasts
inside of plant cells. Ultimately, this
light energy is used to convert carbon
dioxide and water into carbohydrates
to fuel growth processes and release
oxygen into the environment.
Chlorophyll pigments are better at
catching some wavelengths of light
than others, so not all light is efficiently
absorbed. While chlorophyll is the most
abundant light-absorbing compound
found within plants, it is not the
only material sensing and absorbing
incoming energy. Over the past several
decades, researchers have been able to
isolate other light-sensing compounds
within many plants, and identify what
kind of light they are most responsive
to. Phytochromes are one such family
of compounds, which are sensitive to
red and far-red ratios. Another group of
compounds called cryptochromes are
compounds that sense light at the other
end of the visible spectrum, in the blue
and ultraviolet ranges. Plants exposed
to each of these ranges of light in the
electromagnetic spectrum can stimulate
a variety of physiological changes as
they grow and develop.
The electromagnetic spectrum contains visible light, radio waves, X-rays and more. The visible
portion of the spectrum, measured in nanometers, makes up only a small portion of the total.
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Maximum Yield USA | October 2015