Philips Horticulture Lamps

The role of light in the growth and development of plants.

Plant growth(photosynthesis) is not

then determined bylux or energy, but

by the photons fromthe blue to red

(400–700 nm) part of the spectrum.

This is called growthlight!

Forthe human eye, light is the visible part of
electromagneticradiation. Most lighting products
aredeveloped for human application. Forthese
purposes,the intensity of visible light is expressed
in lux.Lux is a photometric unit and is based on
the averagesensitivity of the human eye.
The sensitivity is maximized at green/yellow
(555nm) and declines towards longer (red)
and shorter (blue) wavelengths.A lux meter
is correctedfor this specific eye sensitivity.
Forhorticulture, natural daylight (global radiation)
is in mostcases measured in terms of energy
(Jor W) with a solar meter.Thismeter is generally
positionedon top of the greenhouse.The value
of globalradiation is important for climate and
humiditycontrol in the greenhouse.
GrowthLight
Plantshave a completely different sensitivity for
colorsof light than the human eye. For plant
growth,it is important to define light as small
lightpar ticles,also called photons or quantum.
The energy contentof photons is different
dependingon wavelength (color of light). Forone
W of energy,almost twice as many red photons
can be producedcompared to blue. In addition to
this,plants are most efficient using the red part of
the lightand less efficient using the green and
blue part.In fact, we are dealingwith a plant
sensitivitycurve for growth light.
Micromoland PPF
Research,both at universities and applied
researchstations, has demonstrated that therate
of photosynthesisis determined by the amount of
photonsbetween 400–700 nm. In scientific terms,
this growthlight is called Photosynthetic Photon
Flux(PPF) and is the onlyreliable measureto clarify
ifa light source is suitablefor photosynthesis.The
higherthe PPF value per Watt,the more efficient
thelight source for plantgrowth.This is the reason
whyPhilips specifies the PPF value in micromols
per second(µmol/s) for all its light sources for
horticulturaluse. Philips Green Power and
AgroliteXT lamps are specially developed for
maximumgrowth light and for this reason,are
amongthe most efficient light sources available
forhor ticulture.
Lightsensitivity curve of the human eyeLightsensitivity curve of the human eye
400 450 500 550 600 650 700 750
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Wavelength(nm)
RelativeEyeSensitivity
300 400 500 600 700 800
1.0
0.8
0.6
0.4
0.2
0
Wavelength(nm)
RelativeQuantumEfficiency
Lightsensitivity curve of plantsLightsensitivity curve of plants
Lightsource as protonemitter
Lightparticles
orphotons(= growth light)
Photosynthesis
Growthlight
Carbon
dioxide
Water
Glucose
PhotosynthesisprocessPhotosynthesisprocess
555
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