WO2003037068A1

WO2003037068A1 - A method of accelerating the growth of plants and a light source for use in the acceleration of the growth of plants

Info

Publication number: WO2003037068A1
Application number: PCT/DK2002/000723
Authority: WO
Inventors: Leif Erik Wraae
Original assignee: H.G.W.- Electric Aps
Priority date: 2001-10-31
Filing date: 2002-10-31
Publication date: 2003-05-08
Also published as: DK200101604A; EP1450595A1

Abstract

With a view to accelerating plant growth a method and a light source are used for illumination in that the light is emitted at a number of discrete wavelengths, eg. 435 nm, 451 nm, 660 nm and, if desired, 638 nm. The wavelengths 435 nm and 451 nm are used for splitting off hydrogen from H2O whereas the wavelength 660 nm, and if desired 638 nm, are used for photosynthesis. Furthermore, the light is emitted with a given number of photons. By the method and use of the light source according to the invention it is ensured that only useful light is provided to the plants since light at the wavelengths which are not useful to the biological processes of the plants will not be present. In other words, the plants will not have to absorb unnecessary light, which the plant will have to absorb when generating heat and with a subsequent need for cooling, without any useful effect on the growth.

Description

A METHOD OF ACCELERATING THE GROWTH OF PLANTS AND A LIGHT SOURCE FOR USE IN THE ACCELERATION OF THE GROWTH OF PLANTS

The invention relates to a method for stimulating biological processes for accelerating the growth of plants by illuminating the plants for stimulating the biological processes.

The invention also relates to a light source for use in the acceleration of the growth of plants.

The background of the invention is a realisation of the fact that much of the light provided to plants does not really have any useful effect on the acceleration of plant growth.

So far it has been held that a measured absorption across a wavelength region is an expression of the activity of the plants. In other words, all the light absorbed by the plant is considered useful to its growth.

However, this may be questioned since plants will necessarily have to absorb all the light provided having the effect that some of the light will either have to be reflected or pass through the plant. Most of the light, however, is left in the form of heat in the plant with the result that the plant will require cooling by eg. water.

It has accordingly been recognised that it is sufficient to use the part of the light spectrum which notoriously has a real physical function to the plant.

Any plant will absorb a quite specific and useful part of a light spectrum, determined by the requirements of the plant to be capable of performing particular biological functions. All other light than the light required by the plant for its biological functions may be considered bothering to the plant, i.e. light which it will have to accept energy-wise, but will have to deal with temperature-wise, i.e. cool or reflect.

Many suggestions for the acceleration of plant growth have been described in literature.

The common feature of these suggestions is that they focus on the application of light emitted in spectral bands.

As an example, reference may be made to JP 10000022 A suggesting the application of a set of fluorescent lamps emitting light in given spectral bands.

Furthermore, reference is made to US patent no. 5012609 describing a light fixture for plants emitting light in three wavelength band ranges of 620 - 680 nm, 700 - 760 nm and 400 - 500 nm, respectively.

Finally, US patent no. 4109414 describes a method whereby plants are illuminated in narrow spectral bands during night periods.

It is now an object of the invention to provide a method for the acceleration of the growth of plants which is more efficient than hitherto seen.

The object of the invention is achieved by a method of the kind described in the introduction to claim 1 which is characterised in that the plants are illuminated at at least two discrete wavelengths, each of which is useful to the specific biological processes of the plants, in that the energy at the discrete wavelengths is set such that the number of photons at the discrete wavelengths is adapted to a specific biological process. This will ensure that the plants are only illuminated by useful wavelengths used for specific biological processes at energy levels such as to optimise the number of photons emitted at a given wavelength for the acceleration of their growth.

By fixing the number of wavelengths at three or four as disclosed in claim 2, it is possible to select discrete pairs of wavelengths where one pair is particularly suited for splitting off hydrogen from water, whereas the other pair is particularly suited for performing the photosynthesis.

Tests have demonstrated, as further disclosed in claim 4, that particularly suitable, discrete wavelengths for the acceleration of plant growth are selected in the ranges of 429 - 436 nm, preferably 435 nm, 449 - 453 nm, preferably 451 nm, 636 - 640 nm, preferably 638 nm, and 658 - 662 nm, preferably 660 nm.

For further optimising by illumination for the acceleration of plant growth it is advantageous, as disclosed in claim 5, if the number of photons at 638 nm is lower than the number of photons at the other wavelengths.

As disclosed in claim 6, it is advantageous to use the light at the wavelengths 435 nm and 451 nm for the specific biological processes consisting in splitting off hydrogen from H₂O and OH for use in the subsequent photosynthesis.

In this manner it will be possible to split off hydrogen from H₂O at 451 nm and to split off hydrogen from OH at 435 nm and accordingly at energy levels which will ensure that the number of photons given off is as high as possible.

It is advantageous, as disclosed in claim 7, that the light at the wavelength 660 nm, and possibly at 638 nm, is used for photosynthesis.

As mentioned, the invention also relates to a light source.

This light source is of the kind described in the introduction to claim 8 and is characterised in that the light source is composed of a number of light sources emitting light at each their discrete wavelength and that the light emitted from the individual light sources is emitted with a pre-determined number of photons.

Finally, as disclosed in claim 9, it is advantageous that the number of light sources is at least two and emits'light at the discrete wavelengths 435 nm, 451 nm, 660 nm and, if desired, 638 nm.

Summing up, the following advantages are achieved by applying the principles of the invention:

a) The plants are not bothered by energy which they cannot utilise being equivalent to improved and faster growth. b) Easier control of growth conditions such as raising compact plants, flower inductions, heavier stems etc. c) Less energy consuming. d) Higher yield per m² of cultivated area.

For further explaining the principles of the invention the following should be noted:

A plant has to "interpret" the light in quite a certain manner, namely in such a manner that it is not the energy which is interesting to the plant, but rather the number of photons at a given wavelength. This is due to the fact that in order for the plants to utilise the light properly, two parameters of the light must be met, and more precisely, the light must be adapted to the molecules of the absorbing vital function in terms of resonance and, moreover, the energy must overall be adapted to the ionisation levels in the function itself.

It is also conceivable that the angle of the light relative to the plant cell should be correct since the light must fall thereon perfectly in order that the functions can be carried out in the most perfect manner. This is emphasized by the fact that plants have a phototropism (turning of the leaf angle at right angles to the light source (the sun)) controlled by certain parts of the light (blue colours) so that the cells will be turned towards or away from the light depending on the accuracy of the light.

Accordingly, by analysing the functions that plants have to carry out, a minimum spectrum is obtained, which a light source must contain.

On this background it is possible to develop an optimum light source, which may for example consist of two light sources, where one is adapted to control the compact shape of the plants whereas the other makes the plants grow.

In this manner it is moreover possible to avoid the use of chemicals, such as retardants, and to compensate for nature's inability to provide the "right" light.

By controlling the reciprocal light emission of the light sources, it is possible to control the plant growth so that the plants get the shape or properties desired.

A light source developed in consideration of the requirements of the plants will also save energy in that a conventional light source emitting 100W/m² would be replaceable by a light source emitting 10W/m^2, since it is only necessary to provide useful energy at the desired discrete wavelengths, which the plants require biologically.

Finally, it should be noted that while light is today measured in terms of energy, i.e. lux, there will be a need for measuring the light in terms of number of photons (μE/m²s or μMol/m²s).

Claims

PATENT CLAIMS

1. Method for stimulating biological processes for accelerating the growth of plants by illuminating the plants for stimulating the biological processes, c h ar-acterised in that the plants are illuminated at at least two discrete wavelengths, each of which is useful to the specific biological processes of the plants, in that the energy at the discrete wavelengths is set such that the number of photons at the discrete wavelengths is adapted to a specific biological process.

2. Method according to claim 1, characterised in that the number of wavelengths is three or four.

3. Method according to claims 1 -2, characterised in that the light at the discrete wavelengths is emitted with a given number of photons.

4. Method according to claims 1 - 3, c h a ra cte r i s e d in that the discrete wavelengths are selected in the ranges of 429 - 436 nm, preferably 435 nm, 449 - 453 nm, preferably 451 nm, 636 - 640 nm, preferably 638 nm, and 658 - 662 nm, preferably 660 nm.

5. Method according to claim 4, characterised in that the number of photons at 638 nm is lower than the number of photons at the other wavelengths.

6. Method according to claims 1 -5, characterised in that the light at the wavelengths 435 nm and 451 nm is used for the specific biological processes consisting in splitting off hydrogen from H₂O and OH for use in the subsequent photosynthesis.

7. Method according to claims 4-6, characterised in that the light at the wavelength 660 nm, and possibly 638 nm, is used for photosynthesis.

i 8. Light source for use in illuminating plants for accelerating the growth thereof, ch a racte ri sed in that the light source is composed of a number of light sources emitting light at each their discrete wavelength, and that the light emitted from the individual light sources is emitted with a predetermined number of photons.

9. Light source according to claim 7 or 8, characterised in that the number of light sources is at least two and emits light at the discrete wavelengths 435 nm, 451 nm, 660 nm and, if desired, 638 nm.