Gertjan MEEUWS, et al.
LED Vertical Farming
Pink LEDs Grow Future Food with 90% Less Water
10,000 years after inventing agriculture, will we 7 billion take
this strange next step?
A Netherlands-based company called PlantLab has devised a method
for growing plants indoors using an unearthly pink-purple light
made by a combination of red and blue LED lights, instead of
Significantly, for a sustainable future anywhere on a planet with
7 billion already – and 9 billion by century’s end – this means we
could grow crops with 90 percent less water. Agriculture uses most
of the water around the world.
Nowhere is this need for managing on less water more crucial than
in the countries of the Middle East and Africa – from Saudi Arabia
and Israel, to Yemen and the Sudan – that face the threat of real
water scarcity already.
PlantLab has invented a way to grow plants under LED lights
indoors, with all the water recycled within the indoor environment
for reuse. Plants, it turns out, are not that dependent on using
the sun for photosynthesis. And they certainly don’t mind being
separated from their pests. And they are fine with 90 percent less
water, if they get it over and over again.
Importantly, in an age of peak oil, PlantLab has also found a way
to grow crops that eliminates the two ways that food is dependent
They have engineered the crops to be able to be grown using fewer
fertilizers – which are made from oil.
The second huge use of oil is in transporting food. But because
this indoor habitat can be replicated anywhere in the world,
regardless of climate or season – food would no longer rack up
unsustainable carbon miles on the way to your table.
Because these eerie new farms can be many stories high, crops can
be grown within cities, leaving the most possible land to work
naturally as nature’s utility, cleaning the air we breathe and the
water we drink, instead of being used for agribusiness that
pollutes our rivers with fertilizer runoff from agribusiness.
And, being indoors, away from their pests, there is no need for
pesticides. You can imagine how that might ultimately begin to
affect their evolution, if we change farming so much that we have
have generations of plants grown separated from their natural
pests in the open. We live in interesting times.
But PlantLab believes we must rethink food production to survive.
“In order to keep a planet that’s worth living on, we have to
change our methods,” says PlantLab’s Gertjan Meeuws in an
interview with the Associated Press.
The methods PlantLab is suggesting are revolutionary. The company
grows plants indoors, vertically stacking acres upon acres of
plants. They use LED lamps to grow the plants and water them with
a slow trickle that drains through the soil and is collected and
reused. The neon pink light of the lamps make the space look more
like a nightclub than an indoor farm.
Computers capture over 160,000 reports per second to determine the
exact amount, cycle, and color spectrum of light that’s optimal
for the plant, as well as water, so that no resource is wasted and
the plant is neither undernourished nor overexposed.
Plants convert light from the sun into energy through the process
of photosynthesis, but plants only need some parts of the sun’s
color spectrum. Blue and red LEDs can provide just the light a
plant needs, making the process more efficient and growing a
stronger, healthier plant.
LEDs and climate-controlled indoor farms not only use less energy,
less water, and less space than traditional agriculture; they also
reduce the unpredictability of our food supply. Indoor farms
aren’t at the mercy of droughts, torrential rains, unexpected
frosts, and pests. They reduce the danger of food shortages and
Apples from Chile, asparagus from Peru -- an average of six to 12
percent of every dollar we spend on food goes to transportation
Traditionally, most agriculture has been limited to large swaths
of land with rich soil, controllable pests, and a predictable
climate, but even under optimum conditions traditional methods of
agriculture drain our water supply, require intensive resources,
and produce a crop dependent on an undependable climate.
Until now, vertical greenhouses like AeroFarms Vertical Farming
have seemed a little impractical, because our one and only real
sun really needs to reach deep into each floor to ripen food
crops, but this unearthly pink agriculture would solve that.
But are we ready for such a drastic step?
The Independent, September 26
Shoots in the dark: Farming without sunlight
more efficient, reduces transport costs and won't fail because
of the weather. Is farming without sunlight the future of
Sunlight. It is the foundation of life on Earth, the daily
pacemaker of human existence and, with the exception of
geothermal, the basis for all energy consumed on our little
marble. Without it, Earth would be cold, dark, and unrecognisable.
Light's contribution to food is particularly important. Crop
plants use it to convert carbon dioxide and water into sugars and
oxygen, for eating and breathing respectively. It's our most
precious chemical reaction but, as global population diverges from
the planet's ability to feed it, one group of Dutch scientists
thinks we need a new approach. This approach isn't to meddle with
genes, or to plug extra fertiliser into nitrate-soaked soils. The
Dutch group, called PlantLab, have scrapped sunlight altogether.
"The plants look black," says Gertjan Meeuws, one of the
five-strong team. That's not because they're rotten or genetically
engineered, it's because they are bathed solely in blue and red
light – there is no green light in the PlantLab hanger for the
plants to reflect.
The hanger looks like something a character in Blade Runner might
have dreamt about. Huge sliding trays of leafy greens (blacks),
are tended by an army of robotic arms, and given, according to
Meeuws, precisely what they need to thrive. He and his team have
been studying plants since 1989, working to better understand
their needs and to make the growing process more efficient. They
are scientists and engineers, not just businessmen.
"Growing in an open field or greenhouse is not enabling plants to
maximise their potential," Meeuws says. "You have to look at our
system as taking two steps at once. Firstly, we grow plants in
totally controlled conditions – plant paradise as we call it. The
second step is placing these nurseries right at the end of the
supply chain, to produce around the corner from the consumer."
PlantLabs's controlled conditions are underpinned by some
interesting physics. Plants are green because they reflect green
light, meaning those specific wavelengths are not involved in the
process of photosynthesis. If you tried to grow a tomato plant
under a green light, it would die. In the process of reflection,
the plant heats up. Like humans, plants have a mechanism for
cooling down, but it costs energy which the plant would otherwise
use to grow.
"Plants have a very intelligent way of cooling themselves," Meeuws
explains. "They take up water through their roots and evaporate it
through their leaves. Energy is needed for evaporation, and this
energy is taken from the leaves, cooling the plant."
By giving the plants only blue and red light, PlantLab can avoid
heating its plants up unnecessarily, leaving more energy for
growth. The atmosphere in the underground hanger is completely
controlled for the same reason – to give plants the ideal
conditions for growth, rarely found in the real world.
Although there are technical kinks behind farming in the dark, the
potential benefits are broad: more nutritious produce, eradicated
air-miles, year- round access to fresh vegetables, in any
environment on earth. "We have been talking to people in winter
sport areas. In the seasons where those areas have the most
guests, they have no real fresh salads. It's a very interesting
idea to serve really fresh, just-picked salads right where the
consumers are," Meeuws says.
Human convenience factors are important, but not fundamental.
Water is fundamental, and it's one resource that PlantLab's
vertical farm does a very good job of conserving. Meeuws says that
PlantLab's system uses 90 per cent less water than conventional
open-field growing. The only water which ever leaves the facility
is in the form of plant matter for human consumption. The rest –
run off and evaporation – is collected and fed back into the
"Water savings are probably the most important part of our work,"
Meeuws says. "Water will be more important in the future than
Another benefit of growing indoors is the flexibility it allows
for the grower. Dixon Despommier, a microbiologist from Columbia
University and the blue-sky thinker behind the vertical farm, puts
it: "Let's say you have a breakdown in your growing system. When
is the next opportunity for an outdoor farmer? Next year. The
opportunity for an indoor farmer is tomorrow."
This agility is down to the increased number of available growing
hours for the indoor farmer. Meeuws gives a rough calculation: "In
our climate, there are maybe 1,000 or 1,500 growing hours a year.
When you go to the equator, they have a lot of sunlight, but it's
so hot that the plants can't breathe properly. In our system we
can give light to plants 24 hours a day, but it's usually 20
hours, to let them sleep."
Twenty hours a day, every day of the year amounts to 7,300 hours
of growing time, a five-fold improvement over relying on natural
light. Vertical farming comes with the bonus of easing the strain
on diminishing agricultural real estate, perhaps even allowing for
"re-wilding" of swathes of land previously dedicated to cucumbers.
But, as Kevin Frediani, puts it, "we're not there yet". Frediani
is the man behind VertiCrop, a vertical farming experiment
adjoined to Paignton Zoo in Devon, where he is the curator of
plants and gardens. His project, which has run for three years,
backs up PlantLab's numbers for water savings, which Frediani says
can be pushed as low as 4-6 per cent of conventional use.
Energy use is usually the number one concern among vertical
farming naysayers. Everyone knows the story of the tomatoes, grown
in British greenhouses and polythene tunnels, which, due to the
cost of heating, actually have a larger carbon footprint than
those shipped more than a thousand miles from Spain. Similar
concerns surround the idea of artificially lighting and heating
acres of underground crops.
The financial and energetic costs are big, but new technologies
can help. By growing the plants in an insulated environment,
temperature is easier and cheaper to control; polythene tunnels
and glasshouses are rubbish at keeping heat in or cold out.
A new generation of lightbulbs are answering the lighting question
too. Humanity has been stuck on the glowing strip of metal passing
an electric current since Edison made the idea a commercial
reality in 1879. New light sources – LEDs, high-pressure sodium
lamps and fluorescent bulbs – cost less to run, and in the case of
LEDs can deliver the exact colour of light which PlantLab
Technology aside, there is the issue of public perception. Another
step "away from nature", further removing ourselves from our
hunter-gatherer ancestors, might not be popular with some sectors
of the green contingent, but Meeuws has an answer for this too.
"We have to let technology come into our lives where it concerns
food production. A cell phone is normal, intensive care in
hospitals is normal, and accordingly technology will be normal in
order to save our world by producing food in a smart way."
Frediani's VertiCrop is one of the best examples of that "smart
way". If you head to dinosaur country, south-west England, you'll
find Frediani tucked away in the centre of Paignton Zoo,
surrounded by the whirring and dripping of the UK's first attempt
at growing vertical crops.
Made from re-purposed manufacturing line equipment which was
designed for making JCB engines, Frediani's farm consists of
multiple stacks of shelves which rotate around the room, sharing
the sun. While the system uses natural light rather than LEDs,
Frediani says it has shown that vertical farming is viable.
"As a pilot project, what it's demonstrated is that food can be
grown in urban areas that are higher density, and at a lower
embedded energy than we currently do growing it far away from
cities. If you can put your food supply into your packing house
and put your packing house into your distribution centre, and pack
all that into the building people are living in, there's got to be
an advantage in that," he says.
He compares Paignton's VertiCrop pilot to the earliest cars: "You
wouldn't want to drive at 4mph behind a man holding a red flag,
but you might drive a new Mercedes on modern highways – and it's
the same with this technology."
For the moment, he also has his doubts about LED-only growing. He
points to a beautiful crisp lettuce as it trundles by on its
carousel. "That red tinge only comes when you grow lettuce under
the full spectrum of natural light," he says. He adds that light
from current LEDs peters out after about 30cm, severely limiting
what can be done in an all-LED set-up.
But technology and knowledge tend to improve, and one day we may
know the exact absorption spectrum for each and every crop we
grow. Within five years, Frediani sees LEDs becoming good enough
and cheap enough to provide plants with all the light they need.
His set-up is pretty good right now, even if not on a commercial
scale. "Try a bit of rocket," he suggests. I nip a leaf off with
my thumbnail and bite. It's hot and crisp, perfect. My mouth
tingles, and we eat some more.
System and method for growing
a plant in an at least partly conditioned environment
Also published as: WO2010044662 // NL2002091 // MX2011003918
The present invention relates to a system for growing a plant in
an at least partly conditioned environment, comprising a
cultivation base for receiving a culture substrate with a root
system of the plant therein, root temperature control means which
are able and adapted to impose a predetermined root temperature on
the root system, and comprising lighting means which are able and
adapted to expose leaves of the plant to actinic artificial light.
The invention moreover relates to a method for growing a plant in
at least partly conditioned manner, wherein actinic light is
supplied to the plant and wherein a root temperature of a root
system of the plant is maintained at a desired value.
Such a system and such a method are applied on a significant scale
in the glass horticulture in greenhouses. An artificial climate is
created here in an at least substantially closed and conditioned
environment behind glass, and is adapted as far as possible to the
optimal growth conditions of the plant for cultivating. It is
hereby possible to grow plants in areas and seasons in which the
plant would not survive outdoors, or would at least not reach full
development. Furthermore, the production of the plant can
thus be precisely adapted to a desired harvesting time. It is thus
possible to estimate relatively precisely beforehand how much of
which plant will be ready, and when. If desired, the same product
can moreover be grown throughout the year and plants and flowers
at all stages of life can be cultivated.
In traditional glass horticulture sunlight is applied as the main
source of actinic light, i.e. optionally visible light of a
wavelength such that a plant response is thereby initiated or
influenced, such as a photosynthesis in the leaf or a determined
mode of growth. Sunlight moreover provides heat in the form of
infrared radiation, whereby an increased air temperature can be
maintained in greenhouses relative to an outside temperature. In
the absence of sunlight, such as particularly at night, heating is
possible in order to maintain such an increased air temperature,
while excessive entry of sunlight can be prevented during the day
by means of partial blinding and filtering, and the climate can
also be regulated by means of ventilation. All in all, a climate
in a greenhouse can thus be controlled within certain limits and
can be adapted to a desired growth development of a plant for
cultivation, which is further controlled by means of a controlled
dosage of moisture and nutrients, in addition to pesticides. An
additional component here is the root temperature. It has been
found that the growth of the plant can be influenced by control of
the root temperature. With a view hereto, root temperature control
means can be provided in order to maintain a root temperature
varying from the air temperature.
Classic glass horticulture does however also have drawbacks.
Firstly, the environment must be particularly taken into account
here. It costs energy to keep a greenhouse warm and, for some
plants, lighted day and night. It is therefore important to
regulate the energy management as efficiently as possible. Where
greenhouses are built in or close to densely populated areas, the
aspect of space is moreover an important factor. Traditional
greenhouses do after all require entry of sunlight and take up a
relatively large amount of expensive land area in these areas,
which could otherwise be employed for offices, house-building or
infrastructure. In order to address this problem, low-daylight, in
particular underground, daylight-free and multi-layer solutions
are being sought in order to enable multiple use of the same land
Because not only heat but also actinic light will in such a case
be supplied artificially, the energy management is even more of a
problem, and there is therefore a need for a cultivation of plants
which is as efficient as possible.
The present invention has for its object, among others, to provide
a system and method for growing a plant in an at least partly
conditioned environment which enable a further improvement in
In order to achieve the stated object, a system of the type
described in the preamble has the feature according to the
invention that leaf heating means are provided, which are able and
adapted to impose on the leaf of the plant a leaf temperature
varying from an ambient temperature. The system according to the
invention thus provides the option of a controlled evaporation and
carbon dioxide assimilation via the leaf by regulating a correct
amount of energy on the leaf, in addition to a controlled
lighting, both in respect of the amount of light and in respect of
spectral ratios, with a view to plant growth reactions, such as
blue/red and red/far-red ratios, and in respect of light spectra
necessary for specific reactions such as pigment formation, and in
addition to a control and optimization of the root pressure
activity. This all takes place in an at least partly conditioned
environment in which the climate can be controlled within narrow
limits in respect of, among other factors, an air humidity
balance, a room temperature and a carbon dioxide concentration as
well as water and nutrition for the plant.
The invention is based here on the insight that three factors are
essentially responsible for a successful plant development, i.e.
the photosynthesis, the sap flow in the plant pushed upwards under
the influence of a prevailing root pressure, and the carbon
dioxide assimilation through mainly the leaf system of the plant,
and that these three factors must at all times be adapted to each
other in order to actually realize an optimal plant growth. In
addition to the root temperature and the entry of actinic light, a
carbon dioxide assimilation management of the plant can also be
controlled by providing the leaf heating means in the system
according to the invention. Due to additional heating the stomata
in the leaf will open further, so enhancing entry of carbon
dioxide to the leaf and evaporation of moisture from the leaf.
This latter is particularly important if a sap flow in the plant
is stimulated by an increased root temperature, as this flow will
have to exit via the same stomata. Conversely, the leaf
temperature can be decreased at a lower sap flow in order to
prevent undesired plant dessication. All in all, the most
important climate parameters responsible for the development of
the plant can thus be controlled so that an optimal efficiency can
be realized in each of these components with a minimal energy
A particular embodiment of the system has the feature according to
the invention that the lighting means are able and adapted to emit
a lighting spectrum which can be adapted to an intended
photosynthesis and/or mode of growth of the plant to be
cultivated. The actinic light components necessary for the
development of the plant can thus be supplied only in precisely
sufficient intensity, while non-actinic components or an excess
can be avoided as far as possible in order to limit the overall
energy consumption of the system and/or possible harmful effect on
the plant development.
In a further particular embodiment the system according to the
invention is characterized here in that the lighting means
comprise a set of light-emitting diodes, these diodes being able
and adapted to emit radiation at different wavelengths and being
individually controllable, optionally in groups. Such so-called
LED elements produce substantially monochromatic light and are
obtainable for different wavelengths, particularly in the far-red,
yellow, green and blue visible part of the spectrum. A
photosynthetically active (PAR) spectrum which best suits the
concrete needs of the plant can thus be constructed, and
optionally modified, by combination and selection of individual
The leaf heating means can be formed per se in various ways,
although in a preferred embodiment the system according to the
invention is characterized in that the leaf heating means comprise
at least one heat source able and adapted to irradiate the leaf
with infrared radiation. Other than heating means which, wholly or
partially through guiding of an intervening medium, are capable of
heat-exchanging contact with the leaf, such a heat source enters
into heat-exchanging contact mainly through direct irradiation.
Not only does this result in a highly effective and efficient
heating of the leaf system, the intended temperature difference
with the environment contributing toward a desired widening of the
stomata is hereby also achieved in particularly effective manner.
In a further preferred embodiment the system according to the
invention is characterized here in that the lighting means and the
heat source are accommodated in mutually separated fittings in
order to thus exclude a possibly disruptive influence of an
inevitable heat dissipation in the heat source itself from the
conditioning sphere of the actinic light source. Although the root
temperature control means per se can also be realized in diverse
ways, a preferred embodiment of the system according to the
invention has the feature that the root temperature control means
comprise a closed conduit system for receiving therein during
operation a liquid flow with a controlled temperature, wherein the
conduit system is able and adapted to enter into heat-exchanging
contact with the culture substrate. Such a conduit system can for
instance be formed by a system of tubes or fins in or under the
culture substrate, in which a liquid flow meanders altematingly.
The root temperature can be uniformly controlled by thus heating
or cooling the culture substrate in which the root system is
received. A further embodiment of the system according to the
invention has the feature here that a control is provided between
the leaf heating means and root temperature control means which
imposes a mutual dependence on the leaf temperature and the root
temperature. In for instance a normal growth trajectory the leaf
temperature will thus follow, optionally in directly proportional
manner, a change in root temperature so that the assimilation
management keeps pace with a variation in the root pressure.
In order to achieve the stated object, a method of the type
described in the preamble has the feature according to the
invention that a carbon dioxide assimilation management of a leaf
system of the plant is also influenced, and that a supply of
actinic light, the root temperature and the carbon dioxide
assimilation management are adapted to each other. This method is
in line with the above described insight that the root
temperature, the supplied light spectrum and the carbon dioxide
assimilation management of the leaf are not separate entities but
will only arrive at the optimal result in mutual relation. The
method according to the invention provides the option of arranging
this mutual relation in the form of for instance a plant-dependent
and/or growth phase-dependent modification of these growth
In a particular embodiment the method according to the invention
is characterized in that the carbon dioxide assimilation
management is influenced by regulating a leaf temperature of the
leaf system so that it differs from an ambient temperature. The
above described system according to the invention is highly
suitable for an implementation of this method in that the leaf
temperature can hereby be regulated so that, if desired, it
differs from the environment, in addition to a control of the
other stated growth factors. In a further particular embodiment
the method according to the invention is characterized here in
that the supply of light, the root temperature and the leaf
temperature are adapted to each other depending on the plant.
For the purpose of an optimal photosynthesis and mode of growth of
the plant, a further particular embodiment of the method according
to the invention has the feature that actinic artificial light is
supplied with a spectrum adapted to an intended photosynthesis
and/or mode of growth of the plant. By thus specifically adapting
the mutual ratio and intensity of the various light components
which play a part in the photosynthesis and growth development of
the plant, a high yield can nevertheless be realized at a
relatively low total light intensity and energy consumption.
Within the context of the present invention a further particular
embodiment of the method according to the invention has the
feature here that the artificial light spectrum, a leaf
temperature of the leaf and the root temperature are controlled
individually of each other but in mutual relation, depending on
The invention will now be further elucidated on the basis of an
exemplary embodiment and an accompanying drawing. In the drawing:
figure 1 shows a cross-sectional partial view of a device in an
exemplary embodiment of a system according to the invention.
The figure is otherwise purely schematic and not drawn to scale.
Some dimensions in particular may be exaggerated to greater or
lesser extent for the sake of
clarity. Corresponding parts are designated as far as possible in
the figure with the same reference numeral.
The system shown in figure 1 makes use of a multi-layer
cultivation of plant 1 so as to enable the best possible use of an
available surface area. The plant is accommodated here in culture
trays 2 with a suitable culture substrate 3 therein, such as
earth, glass wool, rockwool or simply water, for the purpose of
receiving a root system 4 of the plant therein. Culture trays 2
are placed one above the other on beams 11 of a frame 10
constructed almost entirely from stainless steel. Any desired
number of such carriages 10 can thus be combined to form a
complete cultivation system in a conditioned environment, wherein
the plant is brought to full development in fully controlled
manner. Irrigation and fertilizing provisions (not further shown)
are arranged at or in carriages 10 in order to provide the plant
with sufficient water and the necessary nutrients.
Beams 11 of the carriages each comprise a closed conduit system 12
of a hose or tube which meanders at a regular pitch. In this
respect a system of successive hollow fins can optionally also be
applied as conduit system. This conduit system 12, through which a
heat-carrying medium such as water of a controlled temperature can
be guided in order to control a temperature of the root system,
forms part of root temperature control means. The heated medium
relinquishes heat during operation to for instance the beams,
which in turn conduct the heat via the culture trays to the
culture substrate with the root system of the plant therein.
Conversely, heat can also be extracted from the root bed by means
of a cooled heat-carrying medium. The root system is thus kept
more or less precisely at a desired root temperature during
operation according to the method described here. In order to give
this heat transport a more specific control, and thereby a more
efficient heat-exchanging capacity, the beams take a multi-layer
form with an insulating base 13 of foamed plastic such as
polyurethane foam or polystyrene foam, with a reflective top layer
14, for instance a reflective metal coating or an additional
intermediate layer provided with such a coating, followed by
conduit system 12 and thereon a metal plate 15, for instance of
stainless steel, having good thermal conductivity.
Each layer of cultivation system 10 is provided with an artificial
light source 20 in the form of a light fitting having therein
groups 21 of light-emitting diodes (LEDs), in addition to possible
other light sources 22 such as ultraviolet or infrared radiators.
The LED diodes in the first groups emit light at least mainly in
the visible part of the spectrum, in particular red, yellow, green
or blue light, while the second groups 22 add invisible components
such as infrared light and near-ultraviolet light thereto. Light
fittings 20 are provided with a control (not further shown) with
which the different groups and the elements within the groups can
be controlled selectively and individually in order during
operation to then adapt a specific spectral composition of the
emitted light to the requirements and type of the plant 1 being
cultivated. Because the beams are optically separated from each
other to a significant extent, a different spectrum can if desired
thus be supplied per beam in order to thus cultivate different
plants in combination with each other and provide each with an
optimal spectrum. The system is highly suitable here for
application in a low-daylight or even daylight- free environment,
such as for instance in an underground situation.
Further provided in the cultivation system are leaf heating means
30 in the form of infrared radiators which are disposed in layers
on either side on the shelves of the carriages. The infrared
radiators emit direct heat radiation in the direction of the leaf
of the plant and thus, if desired, increase a leaf temperature of
the leaf relative to the ambient temperature. The carbon dioxide
assimilation management of the leaf can thus be controlled to a
significant degree and particularly be adapted to the root
pressure of the sap flow in the plant which is produced by root
system 4. This because heating of the leaf results in a widening
of the stomata in the leaf, whereby they will be better able to
relieve surplus root pressure by allowing water to evaporate,
while a sufficient carbon dioxide assimilation required for the
photosynthesis, which is in turn activated and controlled using
the lighting means, nevertheless continues via these same stomata.
If on the other hand cuttings of the plant are taken, the leaf
system is however not heated, or at least heated less, at an
increased root simulation so as to thus limit evaporation and
ensure an excess of moisture on the cutting surface. All in all,
the main growth factors, i.e. the photosynthesis, the root
pressure and the carbon dioxide assimilation, can thus be
regulated individually in the system according to the invention,
and these factors are precisely adapted in mutual relation at each
stage of growth and for each plant in order to enhance optimum
growth and mode of growth.
Although the invention has been further elucidated above on the
basis of only a single exemplary embodiment, it will be apparent
that the invention is by no means limited thereto. On the
contrary, many other variations and embodiments are possible
without requiring a skilled person to depart from the scope of the
invention in a manner which is less obvious. The root temperature
control means can thus also comprise a conduit system directly in
the culture substrate which is in more or less direct
heat-exchanging contact with the root system. In the case of
cultivation on water or a watery substrate, such as glass wool or
rockwool, the root temperature can also be controlled by a
controlled control of the temperature of the water supplied
Use is made in the example of artificial light by means of
light-emitting diodes (LEDs), although within the scope of the
invention conventional incandescent growing lamps are also
suitable instead, and the invention can also be applied in full or
Use is made in the given example of multi-layer cultivation on
mobile carriages, although cultivation in a single layer and/or
cultivation in a fixed arrangement can also be envisaged within
the scope of the invention.
Within the scope of the invention the carbon dioxide assimilation
and moisture evaporation via the leaf system can be controlled and
adapted to particularly the root pressure. Instead of by means of
direct infrared lamps, this can also be achieved by means of
spiral filaments, heat panels or the like disposed close to the
leaf system. If desired, the leaf heating means, such as the
infrared radiators in the example, can further be integrated in
the same fitting as the artificial lighting means, for instance
for the purpose of saving space and/or ease of installation.
What is really important in the invention is that the growth
development of the plant is determined by the weakest link in a
chain of the most important growth factors, i.e. photosynthesis,
root pressure and carbon dioxide assimilation, and that all these
factors are controlled in mutual relation according to the
invention and, if desired, are artificially modified in order to
realize an optimal chain.