JPH0325123B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a plant growing method and apparatus for promoting plant growth in an artificial environment, and particularly relates to light and CO ₂ concentration. [Prior Art] New plant growing methods and systems have been devised to promote plant growth and produce plants industrially by controlling plant growing environmental conditions. Plants generally produce organic matter (photosynthesis) based on water and _CO2 in their leaves, and when light energy is added, part of which is consumed as energy for maintaining the individual, and the rest is used in leaves, roots, etc. It is distributed and accumulated in the organs, and each organ grows. It is possible to significantly promote the growth of these plants by controlling environmental conditions such as light, CO ₂ concentration, and temperature, which has the effect of dramatically increasing land productivity. This made it possible to produce plants in factories. In this case, it would be possible to save energy by using sunlight as a light source, but the amount of light fluctuates due to seasonal weather changes, and environmental conditions such as temperature and humidity change accordingly. The reactions of plants below are complex, making year-round planned production of plants difficult. In addition, a huge amount of air conditioning costs were required to create certain environmental conditions, which resulted in the problem of being uneconomical. Therefore, with the aim of year-round planned production, efforts have been made to promote plant growth by using artificial light sources of constant intensity instead of sunlight. In this case, it is easy to control other environmental factors to a constant condition, but there is a problem that the lighting power is enormous and it is not economical. [Summary of the Invention] This invention was made to eliminate the drawbacks of the conventional methods as described above. By simultaneously irradiating low-intensity light from the circumferential direction of the plant and maintaining the CO ₂ concentration higher than the atmospheric concentration, the growth of the plant can be promoted at extremely low illuminance. The purpose is to provide a method and apparatus for growing plants. [Embodiments of the Invention] Hereinafter, the present invention will be explained in more detail with reference to the drawings. It is well known that increasing the light intensity of the growing environment is an effective method for promoting plant growth. 1st
The figure shows the apparent photosynthetic rate (relative value) and illuminance (Klux), which are indicators of growth rate, using salad vegetables as an example.
This shows the relationship between This is a method in which the plant body is irradiated with light from above, and the temperature is 20°C and the humidity is
80%, CO ₂ concentration is 1200 ppm, and photoperiod is 12 hours. As is clear from the figure, plants generally have a limit point (light saturation point) at which the photosynthesis rate does not increase even if the illuminance is increased, and in order to promote growth, the illuminance near this light saturation point must be maintained. Irradiation is considered to be effective. When light is irradiated from above as in the conventional method, the light saturation illuminance on salad vegetables is approximately 20 Klux, as shown in Figure 1. For example, set the illuminance to 20Klux,
When the day length is 24 hours and other conditions are the same as those shown in Figure 1 above, salad greens will grow approximately 20 times their weight in 10 days. The main purpose of this invention is to promote the growth of plants at an illuminance lower than the light saturation illuminance by simultaneously irradiating light from the circumferential direction. The relationship between plant growth and environmental factors is complex;
These relationships are not fully clarified, and efforts are being made to investigate these relationships. As plants grow, the number and size of their leaves increase, and they even become deciduous. Under these conditions, when the plant is irradiated with light from above as in the past, the light absorption rate of the leaves is as high as 80 to 90%, so the light intensity within the community has a significant distribution. Especially in the lowest leaves, photosynthesis is significantly reduced due to the decrease in light intensity, and eventually the plant dies. Therefore, the conventional method of irradiating light from above for growth in such clusters of fallen leaves is not effective in terms of the productivity of plants, as the efficiency of light energy use is low. Furthermore, for example, if light is irradiated from both sides of a leaf, it is only a matter of speculation how the growth of leaf clumps will occur, but it is likely that the light-receiving area will increase and the rate of photosynthesis will be accelerated as a result. . Therefore, it is considered that irradiating the plant body with light from all directions is effective for growth in the above-mentioned leaf litter. FIG. 2 is a configuration diagram showing a plant growing apparatus used in an experiment to demonstrate this invention. In the figure, 10
Reference numeral 1 denotes a cylindrical outer cylinder of a plant growing chamber, the inner circumference of which is formed of a reflective material 102 such as Al, and an artificial light source 103 is installed along the reflective material 102. Reference numeral 104 denotes an inner cylinder made of glass, which together with the outer cylinder 101 constitutes a double cylindrical plant growth chamber. The plant body is planted in a cultivation pot 105 fixedly installed in an inner cylinder 104, and an artificial light source 10
It grows when irradiated by 3. At this time, the plant body was irradiated with light from the circumferential direction, and it was confirmed that uniform illuminance was obtained in all directions and locations within the cylinder 104, except for the upper and lower ends of the cylinder. Heat dissipation of the artificial light source 103 is performed by the cooler 10
It is removed by cold air from 6. In addition, the inner cylinder 1
The air introduced into the cylinder 1 is adjusted in advance to a predetermined temperature and humidity by the air conditioner 201.
The air is introduced from the lower part of the air conditioner 04, discharged from the upper part, and returned to the air conditioner 201 by the blower 1, thereby circulating. CO ₂ is injected from a CO ₂ inlet 2 provided in the middle of the circulation path by a CO ₂ generator, for example a CO ₂ cylinder (not shown). The circulation passage is also provided with a fresh air inlet 3 and an outlet 4 to renew a portion of the circulating air. At this time, CO ₂ is supplied so as to maintain the CO ₂ concentration in the circulating air at a predetermined value, and the CO ₂ concentration is adjusted by the amount of CO ₂ supplied. The air conditioner 201 is composed of a cooler 202, a water spray section including a spray nozzle 203 and a packed bed 204, and a heater 205.
After being cooled by a cooler 202 using a water heater 6, water in a storage water tank 207 is sent to a spray nozzle 203 by a pump 5, humidified by a packed bed 204, and then heated by a heater 205 to maintain a predetermined temperature and humidity. adjusted to. On the other hand, 301 is a nutrient solution with a predetermined concentration, which is kept at a predetermined temperature by a liquid constant temperature bath 302, and is pumped into the cultivation pot 1 by a pump 6.
After being sent to 05, it returns to tank 303. 7 is an air pump, and the nutrient solution 301 is aerated by this air pump 7 to maintain a sufficient amount of dissolved oxygen. Using the above plant growing device, we change the illumination from 3 Klux to 15 Klux, taking salad vegetables as an example.
The relationship between the weight (g) and the number of growing days (days) was investigated. Figure 3 shows the results. At this time, the CO ₂ concentration is 1200ppm, the air temperature is 20℃, the temperature of the nutrient solution 301 is 21℃, the relative humidity is 80%, the wind speed is 0.5 m/sec or less, the nutrient concentration is 1.2 mm, pH 5 to 6.5, day The longest time was 24 hours. Furthermore, a fluorescent lamp and an incandescent lamp were used as the artificial light source 103. As is clear from this figure, contrary to the conventionally predicted results, from 3Klux
It was found that no difference was observed in the growth rate (relationship between the weight of salad greens and the number of growing days) at each illuminance at 15 Klux, and the salad greens grew to approximately 20 times the weight in 10 days. As a result, it was found that this method can promote plant growth as well as in the conventional method even at a low illuminance of 3 Klux, which is approximately 1/7 of the light saturation illuminance (20 Klux) when irradiated with light from above. The economic problem, which was the biggest problem in factory production of plants, has been solved, and it has become possible to produce plants year-round in a planned production manner, resulting in extremely large practical effects. In the experiment shown in Figure 3, the CO ₂ concentration was set at 1200 ppm, but it is practical to set it in the range of 500 to 2000 ppm, which is several times the CO ₂ concentration in the atmosphere (around 3000 ppm), and is economical and growth rate. It is a good idea to consider this when choosing. The above shows that by continuously irradiating the plant with light from all directions and raising the carbon dioxide concentration higher than that in the atmosphere, high-speed cultivation can be achieved even with unconventional low-intensity light, resulting in power savings. Ta. Here, the effects of the above invention will be further explained in detail. The table shows the photosynthetic rate of salad vegetables, light intensity,
These are the results of a similar experiment with different day length and carbon dioxide concentration.

[Table] When considering practical plant production, the efficiency of lighting power must be considered first, but at the same time, growth rate is also important. If the growth rate is low, the number of cultivation days will be longer, and if you try to increase a certain amount of production,
As the cultivation area increases, equipment costs become excessive. As is clear from the table, increasing the illuminance increases the photosynthetic rate under all conditions, but the efficiency is higher under low illuminance. This means that lower illuminance increases the efficiency of lighting power for production, but increases the number of cultivation days. Furthermore, we will look at the effect of day length and carbon dioxide concentration under strong and weak light. That is, the effect of increasing photosynthesis due to the addition of carbon dioxide gas is more pronounced under weak light at any day length. Furthermore, it can be seen that the rate of decline in photosynthesis rate due to longer day length is smaller in weak light. From the above results, the effect of adding carbon dioxide gas and irradiating with low-intensity weak light becomes even clearer. In addition, although Fig. 3 shows the case of salad greens, other plants may be used, and depending on the plant, the light saturation illuminance and the effective illuminance when irradiated simultaneously from the circumferential direction will differ, and as a result of taking these into consideration, It seems that an illuminance of 1/7 to 1/2 of the light saturation illuminance is sufficient. In addition, in the above plant growing device, the plant growing chamber 10
1,104 is assumed to be cylindrical, but the same result will be obtained even if it is spherical or rectangular. Further, although the artificial light source 103 is used as a light source, sunlight may also be used. In this case, the same effect can be obtained by arranging a light reflecting plate or using an optical fiber. Furthermore, in the present invention, the circumferential direction originally means all of the front, rear, left, right, and upper and lower sides of the plant, but it is sufficient to irradiate at least from the front, rear, left, and right, and from above. [Effects of the Invention] As described above, according to the present invention, 1/7 of the light saturation illuminance when light is irradiated only from above the plant body.
By simultaneously irradiating the plants with ~1/2 low-intensity light from the circumferential direction and keeping the CO ₂ concentration higher than the atmospheric concentration, the growth of the plants can be promoted with extremely low illuminance. There is an effect that can be done.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the relationship between the apparent photosynthetic rate of salad vegetables and illuminance when light is irradiated from above, Fig. 2 is a configuration diagram showing the plant growing device of the present invention, and Fig. 3 is a diagram showing the relationship between the apparent photosynthetic rate of salad vegetables and illuminance when light is irradiated from above. The relationship between the weight of salad greens and the number of growing days when irradiated at the same time from illuminance 3 to
It is a characteristic diagram shown about 15Klux. In the figure, 101 is the outer cylinder of a double cylindrical plant growth chamber, 102 is a reflective material, 103 is an artificial light source, and 10
4 is an inner cylinder, 105 is a cultivation pot, 201 is an air conditioner, 301 is a nutrient solution, and 2 is a CO ₂ injection port.

Claims (1)

[Claims] 1. In a plant growing method that promotes plant growth by controlling at least light and CO ₂ concentration among environmental conditions, 1 of the light saturation illuminance when light is irradiated only from above the plant body. Simultaneously irradiate the above plants with low-intensity light of 7 to 1/2 from at least the front, back, left, right, and upper directions, and raise the CO ₂ concentration to a level higher than that in the atmosphere.
A plant growing method characterized by maintaining the concentration between 500 and 2000 ppm. 2. A light-transmissive inner container in which a plant to be grown is stored, an outer container arranged around the outer periphery of this inner container and whose inner peripheral surface is made of a reflective material, and a container provided inside this outer container. 1/7 to 1/2 of the light saturation illuminance when the above plant is irradiated with light only from above.
a light source that simultaneously irradiates low-intensity light from the circumferential direction of the plant, and a means for supplying CO ₂ into an inner container in which the plant is housed, and keeping the CO ₂ concentration higher than the atmospheric concentration. A plant growing device equipped with