wageningenupdate - Wageningen UR

‘The influence of light
is a complex system,
which we have to learn
to understand again’
translated into higher production. The plant
develops less rapidly and its leaves curl because
of the unnatural color proportions. This results in
the absence of any increase of production, by
definition. The influence of light is a complex
system which we need to learn to understand
again.”
In the past years, there have been many tests
with LED light, by growers and LED suppliers as
well as by Wageningen UR. The experiences differ
and many new discoveries require further
research. That is taking place abundantly.
Wageningen UR plays an important role in it.
LED LIGHT
The technology
behind LED
LED is an abbreviation of
light-emitting diode. It is an
electronic chip consisting of
two minute layers of semiconductors.
One layer is charged
positively, the other negatively.
As soon as a current
runs through the diode, the
excess of electrons in the
negative layer wants to fill the
holes in the positive layer.
The electrons have too much
energy to fit into the hole and
the excess energy is emitted
in the form of light. The color
of the light depends on the
used semiconductor material.
LEDs generally work on
low-voltage current and have
a long life. They are rumored
to be energy-efficient, but
that is only partially true.
A very well-known and a very
energy-efficient application is
the on/off light on electronic
equipment. The new
generation of LEDs does well
as light source in for example
traffic lights and flashlights.
With growth light, it is
important to convert
electricity in as many photons
(light particles) as possible.
At the moment, LEDs do that
less efficiently than the gas
discharge lamps commonly
used in greenhouses.
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On the left, Wim van Ieperen, on the right, Leo Marcelis
with in the background a made-to-measure LED lighting
unit for research purposes
Night and Day
Part of the research addresses the question as to
how plants function in light of different wavelengths.
Basic knowledge about light colors is
available. In the past, extensive investigations took
place into the effect of small differences in the
composition of red light. The ratio between
wavelengths in the red part of the spectrum
controls different processes in the plant. It tells the
plant how close it is to another plant, for instance.
Based on that, it will grow higher or, in contrast,
remain relatively compact. The effects of blue light
were investigated before. The difference is that this
used to be done by means of filters. Van Ieperen: