Growth and development of plants and vegetables is strongly influenced
by the quality and amount of light they receive, and the cycle of day
and night. Artificial lighting therefore plays a significant role in the
horticultural industry, where it enables producers to extend and control
the periods of plant growth. GE horticultural lamps allow growers to be
less reliant on daylight and improve their productivity.
PAR in relation to wavelength. Plants have different sensitivity to different
Photosynthesis Active Radiation (PAR, measured in micromole/sec) is essential
for plant growth. GE Lucalox™ PSL (PhotoSynthesis Light) high pressure
sodium lamps are designed to produce the best possible PAR performance
and this performance is covered by warranty.
Plants respond to light of varying colour. In general, red light causes
plants to become tall and “leggy” while blue light, when used alone, can
cause low, stocky growth. A proper balance of red and blue energy produces
plants that have normal growth and shape.
Effect of spectral range
Deleterious for growth.
Might have additive
effect to blue radiation.
Necessary for elongation control.
Less important in photosynthesis than red spectral range
for certain plants.
Optimisation is necessary because
unoptimised red portion will cause
Enhancement of flowering & stem
Blue only or green only irradiation
did not cause development.
Optimal growth was found when
the irradiation of the plants
contained 15-20% blue irradiation,
rest of the spectrum was balanced
with green and red irradiation.
High productivity requires the
dominance of the 600nm-700nm
red part in irradiation spectrum.
Saturation of the crop yield
was achieved with 60-65% red
irradiation, the rest of the spectrum
was balanced by blue and green
GE lighting for fruit
Growers of food plants find artificial light
just as important as it is for flowering plants.
Artificial light can improve the yield of a
crop, and its quality. And, as with flowering
plants, it enables growth to be timed to
meet market demands.
When an artificial lighting regime is applied
to food crops, these are some of the
- Plants can be used for over a longer period
- In winter, fruit can be produced with taste to match summer fruit
can start earlier
- Year-round cultivation is possible
It is therefore possible
for growers to enhance product quality and take advantage of marketing
opportunities throughout the year.
GE lamps can:
Extend day length
Extend growing season
Completely replace daylight
The relative length of day and night and
the seasons is important to plants. The
number of hours of darkness in a 24-hour
cycle is an important factor in determining
blossoming and growing time.
Night length triggers seed germination,
tuber and bulb formation, and other
growth characteristics such as colour,
enlargement of leaves and stem size and
shape. This rhythmic characteristic is called
photoperiodism and is of great value
Plants can be classified according to
Indeterminate or day-neutral
The perennial Chrysanthemum and the
Poinsettia, which flower in the autumn, are
examples of short-day (long-night) plants.
They fail to flower when the day length, or
period of light, is extended beyond a
Long-day plants, such as the China Aster
and Tuberous Rooted Begonia, flower only
with a day length longer than a critical
Day-neutral plants, such as the Rose and
Carnation are not limited by photoperiod.
Understanding these principles enables
commercial growers to use artificial light
profitably, so that flowering and vegetable
harvesting can be timed for markets.
Putting light into action
Short day length
The Perennial Chrysanthemum is a short
day length plant that will not flower when
the day is long (short night). To postpone
flowering, Chrysanthemum growers, instead
of lengthening the day, interrupt the night
for about four hours. This makes the night
appear short to plants, which then continue
to grow vegetatively instead of starting to
A more economical method of postponing
flowering of chrysanthemums is to apply
cycles of light, switching light on for 10
minutes and off for 50 minutes, for four
hours during the night, instead of applying
light continuously. This is cyclic lighting. It
is an effective way of growing flowers. If
lighting levels are higher then the grower
will see better stem and flower quality and
less opportunity for disease.
Long day length
The China Aster is a typical long-day
(short-night) plant. Long-day plants can
be brought to flower ahead of the normal
time by lengthening the day. Relatively low
intensities of light are enough to induce
flowering, when applied early in the morning
or at the end of the day. A dark-period
interruption - from a few minutes to a
few hours - as with other long-day plants,
effectively induces flowering just as it
inhibits flowering of short-day plants.
Poinsettias must have complete and
continuous darkness for about 12 hours a
day in order to flower. Even 1 minute of light
in the middle of the dark period will prevent
Tuberous Begonias flower only when daily
dark periods are short - less than 12 hours,
but they require long dark periods for best
production of tubers. Flowering of tomatoes,
however, is not influenced by photoperiod.
Plant colour and leaf formation
Photoperiod also influences plant responses
such as colour and formation of the leaves.
Coleus, for example, under continuous
lighting, produces dark red leaves with
bright green edges. Less than 10 hours of
light per day results in less sturdy plants
and paler colours. The tulip bulb is the main
source of food reserve, and the light is
needed mainly to develop the plants’ green
colour. Stems attain their greatest length if
grown under lighting.
GE lamp range
Lucalox™ PSL developed for greenhouse use
Other solutions include fluorescent and incandescent
GE High Intensity Discharge (HID), incandescent and fluorescent lamps
all have uses in horticulture.
HID lamps can be used for large area lighting either as a supplement
or total replacement for daylight. Standard incandescent lamps
are usually used for cyclic lighting both in greenhouses and outdoors.
Linear fluorescent lamps may be used to propagate bedding plants
in bench greenhouses. Compact fluorescent lamps can also be used,
mounted vertically, base up, in between plants.
HID lamps can be used for large area
lighting either as a supplement or total
replacement for daylight.
High Pressure Sodium (HPS)
Specially developed for greenhouses, GE’s
LucaloxTM PSL high pressure sodium (HPS)
range offers the twin benefits of stable
lumen maintenance and a full spectrum
content that promotes photosynthesis.
LucaloxTM PSL lamps provide an average 5%
Ceramic Metal Halide (CMH)
GE CMH lamps also have many benefits for
horticulturalists. With a stronger blue light
content, they favour seeding and vegetative
growth. They can be used in a mixed
scheme in which HPS and CMH are switched
or combined to give growers maximum
control over their crop. They have excellent
lumen maintenance characteristics.
Other lighting solutions
Standard incandescent lamps are usually used for cyclic lighting both in greenhouses and
outdoors. These lamps supply the relatively low levels of light needed, installation costs
are low, and light is rich in the red energy to which plants are sensitive for photoperiodic
Fluorescent lamps may be used to propagate bedding plants in bench greenhouses.
Mounted under the benches, they furnish light energy for propagation in areas that might
otherwise be used only for storage. Fluorescent lamps may also be used to extend day
length in small greenhouses.
For accurate control of periodicity and cycling, lamp types can be mixed. For example, high
intensity discharge lamps in overhead luminaires can be used to promote growth, with
incandescent lamps added for photoperiodic or cyclic control.
LucaloxTM PhotoSynthesis Lamp
Specially developed for greenhouses, LucaloxTM PSL high pressure sodium lamps offer the benefits of stable lumen and micromole
maintenance and a full spectrum content that promotes photosynthesis. Photosynthesis Active Radiation (PAR, measured in
micromole/sec) is essential for plant growth. LucaloxTM is available in three power strengths, 400W, 600W and 750W.
Simple light or lumen maintenance is not enough to create plant growth. Plants require
a certain radiation level to help with photosynthesis. The Lucalox™ PSL lamp has been
specially developed to provide stable lumen maintenance and increased PAR output.
Measured in micromole/sec, the increased PAR output of the Lucalox™ XO PSL lamp best
simulates natural daylight to maintain plant growth under artificial lighting conditions. The
PAR value of 400-750W LucaloxTM PSL products is on average 5% higher than the standard
GE LucaloxTM products.
As well as the scientific technology of light
output, reliability and performance have
also been key factors in the development of
the Lucalox™ PSL lamp range.
Robust construction, reliable starting
technology and improved lumen
maintenance ensure peace of mind
against early lamp failures and provide the
consistency demanded for perfect growing
Specially developed for greenhouses
Provide an average 5% additional PAR (Photosynthesis Active Radiation)
Stable lumen maintenance
400W, 600W and 750W
Superb performance and high reliability
– GE’s advanced sodium
resistant ceramic helps eliminate early failures to give a rated service
life of 10,000 hours for the LucaloxTM PSL products.
– In order to achieve
maximum performance, GE recommends lamp replacement when the Rated Service
Life is reached.
– The lamps use extra rugged monolithic arc tubes equipped
with GE Reliable Starting Technology which provides continuous high performance.
High xenon-fill gas delivers:
– extra light and PAR (Photosynthesis Active
– more resistance to mains voltage fluctuations.
Zirconium gettering system improves PAR maintenance that drives constant
and uniform plant growth.
The diameter of the frame wire in the lamp has been minimised to reduce
shading in the installation without affecting the robustness of the lamp.
Monolithic arc tube construction for durability and lumen maintenance.
Other lighting solutions
GE’s extensive lamps range includes many products which offer advantages to horticulture. These include incandescent reflector
lamps, fluorescent tubes and metal halide. Qualities such as energy efficiency and long life are inherent in all GE lamps. However,
there are other features that are beneficial to both horticultural luminaire manufacturers and to users. Following is a selection of
product highlights. However, there are many more and we will be pleased to advise about specific requirements.
T5 linear fluorescent
Linear fluorescent lamps are available in a
wide range of sizes, wattages and colours,
including daylight. The T5 range, at just
16mm diameter, delivers the light of much
larger wattage systems and make use of
GE’s Starcoat™ coating to provide unrivalled
colour rendering and lumen maintenance.
(CRI 85 and lumen maintenance, 94% at
40% rated life.)
The operating cost of these lamps is
relatively low and their Rated Average Life is
Available in two ranges, optimised for either
efficiency or output
Up to 104 lumens per Watt
High output range
Up to 7000 lumens
Both ranges offer:
Peak lumen output at 35°C for optimum light output within fittings
Designed for HF operation: higher lamp efficacy and lower ballast losses
BIAX™ compact fluorescent lamps have
the size advantage of incandescent lamps
with the energy saving and life benefits of
20% of the energy consumption of incandescent lamps
Up to 15 times longer life than incandescents
Variety of shapes and sizes, including reflector version
GE incandescent lamps have been
developed and researched over a century
and the current range represent stateof-
the-art lamps for commercial and
Incandescent lamps are commonly
available in a large variety of size, shape,
colour and wattage.
Long Life GLS lamps up to 2500 hours are
available from 40 to 100 Watts.
Extra Long Life GLS lamps up to 5000-6000 hours are available in 40 and
A full range of reflector lamps in a variety
of sizes with up to 3500 hours life including