FR2545320A1 - Hothouse plant growth method - Google Patents

Abstract

The method improves the growth of plants in a hothouse etc., thdse being placed on a flat horizontal surface. They are then illuminated by a moving overhead source, and which remains in a horizontal plane parallel to the surface. The rays from the source have a wavelength of between 380 and 800 nanometres, pref. between 450 and 750 nanometres, and the source is moved to a regular pattern so that the plants are intermittently illuminated.

Description

 The present invention relates to a method for improving the growth of plants in greenhouses and climatic cells by subjecting them to intermittent lighting.

 For the purposes of this text, we mean by greenhouses and climatic cells X 'all enclosures in which we artificially recreate, partially or wholly, the conditions specific to the cultivation of plants, in particular the conditions of temperature, humidity and lighting.

 The use of greenhouses and climatic cells makes it possible to grow plants outside their usual growing season, for example in winter, while the usual growing season is spread, generally, over the spring / summer period.

 To achieve this, it is of course necessary to recreate inside the greenhouses or climatic cells the optimal conditions suitable for ensuring satisfactory development of the plant, in particular the conditions of temperature, humidity and appropriate lighting. The conditions to be used will of course be very different, depending on whether one wishes to cultivate crops of temperate climate, such as wheat or crops of tropical or subtropical climate such as cotton or soybeans.

 If the establishment of appropriate conditions, with regard to temperature and humidity, does not present insurmountable difficulties, it is not the same with the establishment in greenhouse and climatic cell of the conditions of somewhat appropriate, especially when you want to recreate the lighting conditions necessary for the cultivation of tropical or subtropical plants. Indeed, the lighting system must then satisfy several very restrictive conditions: - it must provide plants with lighting that can reach, if necessary is (that is to say, depending on the crop), very high values, reaching and even passing 100,000 Lux at plant level, - the lighting must be distributed very evenly over the growing area - the lighting system must be placed at a sufficient height, above the growing area, so that it does not hinder either the growth of the plants, or the manipulations necessary for their cultivation, - finally, in the in the case of greenhouses, the Lighting system must obscure the entry into the greenhouse of external sunlight as little as possible.

 For this, we usually use a set of fluorescent tubes fixed to the upper part of the greenhouse or the climatic cell, these tubes being parallel to each other, contiguous to each other and located in the same horizontal plane> at very short distance the of each other, so as to constitute together a light source of rectangular shape, the vertical projection of which on the lower part of the greenhouse or of the cliiaatic cell represents the surface to be lit. As an indication to light a ground surface of en x 6m we use 180 fluorescent tubes of 215 watts each, located 0.90m above the area in which the plants will be placed. The main drawback of this system is that despite the use of a large number of tubes, it is difficult to obtain an illumination (luminous flux) reaching 40,000 Lux at plant level, which is completely insufficient when it is desired to cultivate tropical or subtropical plants. Another drawback of this system is that it requires a large number of fluorescent tubes and therefore entails, on the one hand, a significant investment and, on the other hand, also a very significant energy consumption. itself significant heat release inside the greenhouse or climatic cell and it is therefore necessary to provide a larger temperature regulation installation to maintain the latter at the desired value. Finally, with such a system, in the case of a greenhouse, the sunlight is almost completely obscured and therefore the light of external origin is totally unused.

 The replacement of the tubes by more powerful lamps, such as for example discharge lamps, whose unsteady pulse can be of 1,000 and even 2,000 watts does not give any satisfaction either because then problems of lack of uniformity arise. lighting and even in this case, it is hardly possible to obtain more than 50,000 Lux at plant level. The drawbacks mentioned above and relating to the consumption of energy and the dissipation of this energy in the form of heat inside the greenhouse or the enclosure exist of course also when using lamps in place of fluorescent tubes. Due to these insufficiencies of lighting in greenhouses or climatic cells, we observe that plants cultivated under such conditions have in general a different aspect from those cultivated in open field, in the optimal conditions relative to these plants: those cultivated in the greenhouse or climatic cell are very often damaged, more fragile and less green than those grown in the open field. These differences are particularly troublesome when it is desired to test in the greenhouse or climate cell pesticide products intended for agriculture and which will therefore, as a general rule, be used for treatments carried out in the field; it is especially necessary for such experiments that greenhouse trials are as similar as possible to field trials.

 An object of the present invention is to remedy the drawbacks of known techniques.

 Another object of the invention is to promote to the maximum the phenomena of photosynthesis in plants.

 Another object of the invention is to develop to the maximum the ability of plants to assimilate carbon dioxide from the air and to produce oxygen.

 Another object of the invention is to produce plants in the greenhouse whose growth is as close as possible to growth in the open field, as regards size, size, vigor, branching (branching), budding, flowering.

 Another object of the invention is to produce plants with a high chlorophyll content.

 Another object of the invention is to provide a method of growing plants in a greenhouse using equipment that is as simple as possible and that consumes a minimum of energy.

 Another object of the invention is to provide a method of cultivating plants in which the light energy incident on the leaves is distributed in a homogeneous manner, whatever the inclination of the leaves and whatever the situation of the leaves on the plant (outside or inside the foliage).

 Another object of the invention is to avoid as far as possible non-visible radiation, especially ultraviolet radiation. Indeed, in addition to the dangers that such radiations create against people occupying plants, these radiations are often the cause of degradation of the agrochemicals applied to plants which annihilates the beneficial effect of these products and disturbs the experiments if they are experiments.

 Other objects and advantages will emerge during the description which follows.

 It has now been found that these aims can be achieved by the method of the invention.

 This process is therefore a process for improving the growth of plants in greenhouses or climatic cells and it is characterized in that - the plants are arranged on a substantially flat and horizontal surface, - the plants are lit using a mobile light source located above the plants and remaining in a substantially horizontal plane parallel to the surface where the plants are arranged - the light source mainly comprises radiations of wavelength between 380 nanometers and 800 nanometers> preferably between 450 and 750 nanometers, - the light source moves above the plants in a regular movement so as to create intermittent lighting at the plant level.

 Various methods of carrying out the process of the invention can also be carried out.

 According to an advantageous modality, the plants are arranged on a surface of substantially rectangular shape and the light source is also in the shape of a rectangle, one of the dimensions of which is substantially equal to one of the sides of the zone of substantially rectangular shape to be lit. .

 Also advantageously, the light source moves in a direction parallel to one of the dimensions of the rectangular area to be lit (the light source having a dimension common with the other side of the area to be lit).

 In practice, during its movement, the extended light source gradually illuminates all the points of the substantially rectangular horizontal surface along which the plants are arranged.

 The light source preferably moves in a regular movement at constant speed, either in one direction or in another. It can be a back and forth movement.

 In the case where the surface to be lit, which is rectangular, would in fact be made up of a succession of rectangles which can form a closed circuit, the light source could then move along each of these rectangles and also travel through it. even a closed circuit. In such a situation, for a given rectangle to be lit, the light source moves above it always in the same direction.

 As indicated above, the extended light source generally comprises several lamps. These lamps are advantageously arranged inside a reflective casing of substantially rectangular section.

 FIG. 1 schematically illustrates an embodiment of the invention according to which an extended light source, constituted by a reflective casing (1) in which are disposed 4 discharge lamps of 1,000 watts each (2), shown in dotted lines at 1 he interior of the casing moves in the direction represented by the arrows, above the bench seat (3), of substantially rectangular shape, on which the plants to be cultivated will be arranged (not shown in FIG. 1). The extended light source is moved in a uniform back-and-forth motion, first from an extreme position A to the opposite extreme position B, then from B to A, etc.

 For reasons of simplification, we have not shown in Figure 1 the electrical connection means for conducting the electric current to the lamps, nor the mechanical means for moving the light source. In practice, it can advantageously provide for this two guide rails located above the longitudinal dimensions of the bench seat (3) and install rollers at the two longitudinal ends of the housing (2) so that this housing can be move on these guide rails in the direction indicated.

FIG. 2 represents another embodiment, according to which the reflective casing (1), located above the bench seat (3), is movable in the directions represented by the arrows, comprises 10 discharge lamps of 1,000 watts each represented dotted. The light source, consisting of the lamps and the housing, moves in a uniform movement from A to
B then from B to A in a back and forth movement. I1 is of course possible to use a higher or more limited number of lamps than that shown in Figures 1 and 2 and the invention should therefore not be limited to only the devices shown in these figures.

 As is well understood from the exemplary embodiments illustrated by these figures, the method according to the invention makes it possible to sweep in a regular manner the entire rectangular horizontal surface mentioned above by providing it very uniformly with the amount of desired lighting.

 The distance between the plane in which the light source moves and that of the rectangular horizontal surface on which the cultures are placed can be determined according to the power of the light source and the desired light flux at the level of the plant. Thus, by way of indication, for a distance between planes of 1.6 m, the light source represented in FIG. 1 brings, at each passage, 50,000 Lux to the plant situated at its vertical, whereas that represented by FIG. 2, more especially intended for a climatic cell, brings to the passage nearly 100,000 Lux.

 In the case of a greenhouse, it will be observed that such a system produces only a very weak concealment of the external light which can therefore be advantageously used in addition.

 The speed of movement of the light source can be chosen within wide limits, however, it has been observed that, whatever the plants cultivated, the best results have been obtained for speeds ranging from 2m / min to 8m / min and preferably for the speed of 4m / min.

 The periodicity of passage of the light source can also vary within wide limits, it is advantageous however to effect a passage of the light source above each plant per period of 45 seconds to 3 minutes, preferably one passage per period 1 to 2 minutes.

 The following examples, given without limitation, illustrate the invention and show how it can be implemented.

Example 1
For a greenhouse test, a light source of 4 x 1,000 watts is used as shown in FIG. 1. The deflector (1) (or lampshade), serving as a lamp holder is equipped, on these two ends, with casters (not shown) allowing it to move, in the direction shown by the arrows on horizontal rails (not shown), located 1.6 m above the long sides of the seat (3) whose length is 6m .

This light source only emits radiation in the visible range.

 On this bench one sows in terrines seeds of wheat, mustard and soya which one maintains under the usual conditions of temperatures and hygrometry.

The lamps are on. The light source moves back and forth over the bench at the speed of 4m / min from 7 a.m. to 9 p.m. hall is off the rest of the time. After 35 days under these conditions, it is observed that the plants obtained have an appearance quite similar to that of the same plants obtained in the field.

Example 2
Example 1 is reproduced by growing bean plants in pots under lighting from the start of sowing seeds.

 Half of the bean plants are subjected to intermittent lighting (mobile light source) as in Example 1. The other half is subjected to identical lighting from the point of view of the light source but not intermittent (fixed light source) .

 After 15 days, 15 guilles are taken from each of the two bean populations and the chlorophylls A and B are extracted with a water / acetone mixture and then these chlorophylls are assayed by spectrophotometry.

 It is found that plants with fixed lighting contain 0.67 mg of chlorophyll per gram of bean leaf while plants with mobile lighting contain 0.89 mg / g, ie approximately 33 X more.

Example 3
Example 1 is reproduced with various kinds of plants by making a comparative experiment with plants subjected to fixed lighting by my lamps.

15 days after the start of the experiment, the following observations are made on beans and soy beans
The average size of plants obtained under mobile lighting is reduced by 35% compared to the size of plants obtained under fixed lighting. your plants obtained under mobile lighting are therefore shorter but more vigorous, very green and similar to those obtained in the open field; the plants obtained under fixed lighting are, on the contrary, etiolated, that is to say that they have an excessive size and thinness; moreover, they have a strong tendency to lodging, the stem not having enough vigor to stand straight.

Soy :
The average size of plants obtained under mobile lighting is reduced by 25 X compared to plants obtained under fixed lighting. But these plants obtained under mobile lighting are more vigorous and have a port or maintenance as well as a color similar to that of plants obtained in open field
Panisse (echinochloa crus galli)
Gerinination or emergence is obtained in 4 days after sowing under mobile lamps, and in 8 days after sowing under fixed lamps.

Claims (9)

1) Method for improving the growth of plants in greenhouses or climatic cells characterized in that - the plants are arranged on a substantially flat and horizontal surface - the plants are lit using a mobile light source located above plants and remaining in a substantially horizontal plane parallel to the surface oA are arranged the plants - the light source mainly comprises radiation of wavelength between 38a manometers and 800 manometers preferably between 450 and 750 manometers - the light source moves over the plants in a regular movement so as to create intermittent light at the level of the plants. 2) A method according to claim 1) characterized qn that the plants are arranged on a surface of substantially rectangular shape and the light source is also in the shape of a rectangle, one of the dimensions of which is substantially equal to one of the sides of the area of substantially rectangular shape to be lit. 3) Method according to one of claims 1 or 2) characterized in that the light source moves in a direction parallel to one of the sides of the rectangular area to be illuminated, the light source having a common dimension with l other side of the area to be lit. 4) Method according to one of claims 1 to 3) characterized in that, during its movement, the extended light source gradually illuminates all the points of the substantially rectangular horizontal surface along which the plants are arranged. 5) Method according to one of claims 1 to 4) characterized in that the light source moves at constant speed. 6) Method according to one of claims 1 to 5) character in that the light source moves in a back and forth movement. 7) Method according to one of claims 1 to 5) characterized in that the area to be lit consists of a succession of rectangular areas. 8) Method according to claim 7) characterized in that the light source travels in a closed circuit. 9) Method according to 11 one of claims 1 to 8) characterized in that the light source passes over the plants once per period of 45 seconds to 3 minutes. lO) Method according to claim 9) characterized in that the light source passes over the plants once per period of 1 to 2 minutes.