The World Foliage Plant Industry - Acta Horticulturae

Prof. Roar Moe, co-convener and responsible
for the scientific program (left) and
Prof. Hans R. Gislerød, convener (right) in
national costumes. Photo by Randi Setrom
Brunborg, UMB.
greenhouses. However, in growth chambers
fluorescent tubes are still necessary for some
species in order to obtain a normal growth
habit.
Commercial use of supplemental light for cut
flowers and vegetables in Norway started in the
late 1980’s. In the last decade, the improvement
in light-emitting diodes (LED) and cold
cathode fluorescent lamps (CCFL) has opened
new opportunities related to improve growth
and plant quality by light quality manipulations.
By increasing the light intensity (photosynthetic
photon flux), light quality seems to play a less
important role for plant growth. The light
intensity used for plant growth today in
Norway ranges from 50 to 300 mol m -2 s -1 for
the different crops, stage of development and
growers. The lowest level of supplementary
light is applied to some foliage plants and plant
species within Gesneriaceae. The main part of
the pot plants and cut flowers are given a supplementary
lighting of 100-150 mol m -2 s -1 .
For roses and cucumber, the light intensity is up
to 300 mol m -2 s -1 . The lighting period is usually
20 hours a day except in the growth period
when short-day-plants are exposed to short
days. For roses, we are working on 24 h
lighting. The results show that the growth rate
is linear with increasing daily light integral, and
at the same time, the incidence of powdery
mildew can be significant reduced.
Maihaugen, a famous open-air museum. A
total of 140 participants from 23 countries
attended the symposium.
The scientific programme comprised the following
topics:
1. Introduction to Horticultural Lighting. New
Developments.
2. Biological Aspects of Lighting on: a)
Photosynthesis, Growth/Yield and Product
Quality; b) Integrated Optimization of Light
and Other Growth Factors; c) Light
Regulated Plant Growth and Development.
3. Biological and Technical Aspects of Lighting:
a) Regulation of Plant Morphogenesis,
Flowering and Quality; b) Photoperiodic
Lighting.
4. Technical and Economical Aspects of
Lighting.
Following is the list of plenary speakers from
different parts of the world: A.H. Halevy (Israel),
E. Heuvelink (The Netherlands), R. King
(Australia), T. Kozai (Japan), E. Runkle (United
States), C. Mènard (Canada) and J. Aaslyng
(Denmark). In total there were 34 oral presentations
and 66 posters and exhibitions on various
aspects of lighting at the symposium. Some of
the highlights of the symposium are summarized
below.
Mobile Lighting
In the last light symposium held in Canada in
November 2000, ‘mobile lighting’ was the ‘in
thing’ and it was supposed to be the future. At
the light symposium in Lillehammer there were
presentations on research with mobile lighting
on pot plants and cut flowers. They all showed
that mobile lighting had the same effect or less
on growth compared to static lighting. This was
true for production, photosynthesis and in a
simulation model.
Interlighting
When growing cucumber or tomato with a
high wire system, the light intensity decreases
Coffee break and poster discussion. Photo by Randi Setrom Brunborg, UMB.
rather quickly downwards in the canopy due to
shelf-shading. This is true even if a high irradiance
of 200-300 mol m -2 s -1 is applied at
the top of the plants. This question was addressed
by giving a part of the light between the
plants. The results presented indicated that in
some experiments there was a better efficiency
in using interlighting in combination with top
lighting, while in some cases there were no differences
in yield of cucumbers. However, interlighting
improved fruit quality.
Light-Emitting Diodes (LED)
Light-Emitting Diodes (LED) have been in the
market for several years, but have not reached
any commercial value in greenhouse production
because of their high cost and low efficiency.
However, improved technology has increased
their efficiency and reduced the cost. The general
opinion was that in 5-10 years this lamp type
will also be important in commercial production.
Today this lamp is used in specialized production
and research; there were several papers
dealing with the topic.
Light Integration/Light Use Efficiency
Natural light is still the most important for plant
growth and will probably be so for most crops
in the future. There was a discussion on specialised
plant production in growth rooms with
only artificial lighting. The main questions
addressed were related to efficient use of artificial
light in addition to natural light for increasing
production and quality.
The cost of energy is steadily increasing. This
raises the question on the use of light together
with other climatic factors in the most optimal
way. The general rule says 1% increase in light
gives 1% increase in growth/yield and still
seems to be about right when the light level is
far below the saturation point of photosynthesis
and growth. An interesting observation was
to let the temperature increase as the sunlight
increased during the day and decrease at other
times of the day to maintain the average daily
LIGHT SYMPOSIUM
The “Light symposium” was held at the
brightest time of the year that gave the participants
a chance to celebrate the mid-summer
night in the traditional Lillehammer way at
ISHS • 34