Plant growth device and plant growth method

Abstract

The present invention reduces cost without reducing yield.　This plant growth device, which uses artificial light to grow plants, comprises: a growing space for growing a plant; at least one light source panel for irradiating the growing space with artificial light; a cultivation tank in which a liquid fertilizer, which is a nutrient solution containing a fertilizer to be fed to the plant, is stored and at least a root of the plant is disposed; a measurement device for repeatedly measuring an amount corresponding to a fertilizer absorption amount of the plant; and an environment control device which, when the rate of decrease in the amount measured by the measurement device within a set period is larger than a threshold value, controls the growth environment for the plant to be changed to an environment where photosynthesis of the plant is suppressed.

Description

Plant growing device and plant growing method

[0001] The present invention relates to a plant growing device and a plant growing method for growing plants using artificial light.

[0002] Plant factories have been considered as a measure to increase agricultural production and realize stable harvests. In plant factories, the intensity of light irradiated on crops from an artificial light source for photosynthesis, the temperature, humidity, and carbon dioxide (CO ) in the plant growing space are controlled. ２ It is possible to control various parameters, such as the concentration of nitrogen, wind speed, and other environmental conditions, as well as fertilizer components for plant growth. This makes it possible to produce crops year-round, dramatically increasing crop productivity.

[0003] Patent Document 1 discloses a closed-type plant factory that cultivates plants by irradiating them with artificial light from light emitting diode (LED) light sources or the like, without using sunlight. In this closed-type plant factory, light is irradiated from the sides of the plants in close proximity, making it possible to cultivate vegetables that grow vertically and are tall, such as tomatoes and cucumbers.

[0004] Patent No. 5330162

[0005] Generally, outdoor plants grow in response to changes in the natural environment throughout the year. For example, beans flower and produce pods in response to changes in day length. By the time the pods are produced, the amount of photosynthesis also decreases. Regarding photosynthesis in agricultural crops, water, light, and CO ２ , and fertilizer are important factors.

[0006] In conventional artificial light cultivation, in order to maximize crop yield, the key factors for photosynthesis—water, light, and CO—are reduced. ２ The applicant believes that fertilizer is often oversupplied.

[0007] Therefore, the present invention provides a plant cultivation device and a plant cultivation method that can reduce costs without reducing yield.

[0008] One aspect of the present invention provides a plant growing device for growing plants using artificial light, the plant growing device comprising: a growing space for growing the plant; at least one light source panel for irradiating the growing space with artificial light; a cultivation tank for containing a liquid fertilizer that is a nutrient solution containing fertilizer to be given to the plant and in which at least the roots of the plant are placed; a measuring device for repeatedly measuring an amount corresponding to an amount of fertilizer absorbed by the plant; and an environmental control device for controlling the growing environment of the plant to change to an environment that suppresses photosynthesis of the plant when a rate of decrease in the amount measured by the measuring device within a set period is greater than a threshold value.

[0009] Another aspect of the present invention provides a plant growing device for growing plants using artificial light, the plant growing device comprising: a growing space for growing the plant; at least one light source panel for irradiating the growing space with artificial light; a cultivation tank in which at least the roots of the plant are placed; a measuring device for repeatedly and non-destructively measuring an electrical characteristic corresponding to a sugar concentration of a liquid in the tissue of the plant; and an environmental control device for controlling the growing environment of the plant to change to an environment that suppresses photosynthesis of the plant when a rate of decrease in the sugar concentration within a set period is greater than a threshold value.

[0010] Another aspect of the present invention provides a plant growing device for growing plants using artificial light, the plant growing device comprising: a growing space for growing the plant; at least one light source panel for irradiating the growing space with artificial light; a cultivation tank in which at least the roots of the plant are placed; a measuring device for repeatedly measuring electrical characteristics corresponding to the amount of fertilizer remaining in samples collected from the plant or from individual plants of the same variety as the plant grown in the same environment for the same period; and an environmental control device for controlling the growing environment of the plant to change to an environment that suppresses photosynthesis of the plant when a rate of decrease in the amount of fertilizer within a set period is greater than a threshold value.

[0011] One aspect of the present invention provides a plant cultivation method for cultivating a plant using artificial light, the method comprising: irradiating a cultivation space for cultivating the plant with artificial light; supplying a nutrient solution containing fertilizer to a cultivation tank in which at least the roots of the plant are placed; repeatedly measuring an amount corresponding to an amount of fertilizer absorbed by the plant; and controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant if the rate of decrease of the measured amount within a set period is greater than a threshold.

[0012] Another aspect of the present invention provides a plant cultivation method for cultivating a plant using artificial light, the plant cultivation method comprising: irradiating a cultivation space for cultivating the plant with artificial light; supplying a fertilizer to a cultivation tank in which at least the roots of the plant are placed; non-destructively and repeatedly measuring an electrical characteristic corresponding to a sugar concentration in a liquid in the tissue of the plant; and controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant when a rate of decrease in the sugar concentration within a set period is greater than a threshold.

[0013] Another aspect of the present invention provides a plant cultivation method for cultivating a plant using artificial light, the plant cultivation method comprising: irradiating a cultivation space in which the plant is grown with artificial light; supplying fertilizer to be administered to the plant to a cultivation tank in which at least the roots of the plant are placed; repeatedly measuring electrical characteristics corresponding to the amount of fertilizer remaining in samples collected from the plant or from individual plants of the same variety as the plant grown in the same environment for the same period of time; and controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant if the rate of decrease in the amount of fertilizer within a set period of time is greater than a threshold value.

[0014] According to an embodiment of the present invention, the plant growth environment can be controlled to change to an environment that suppresses plant photosynthesis during the seed filling and / or maturation stages of the plant. Even if photosynthesis is suppressed during the seed filling and / or maturation stages, the yield of plant seeds or rhizomes is not reduced, and costs can be reduced. Therefore, costs can be reduced without reducing yields in artificial light cultivation.

[0015] FIG. 1 is a schematic diagram showing an example of the general configuration of a plant growing device according to a first embodiment of the present invention. FIG. 2 is a perspective view of a cultivation unit of the plant growing device of FIG. 1. FIG. 3 is a front view of a light source panel of the cultivation unit. FIG. 4 is a longitudinal sectional view of the light source panel of FIG. 3. FIG. 5 is a longitudinal sectional view of a light source panel according to a modified embodiment of the embodiment of the present invention. FIG. 6 is a graph showing changes in the cumulative amount of fertilizer absorption by soybeans. FIG. 7 is a graph showing changes in the cumulative amount of fertilizer absorption by soybeans. FIG. 8 is a schematic diagram showing an example of the general configuration of a plant growing device according to a second embodiment of the present invention. FIG. 9 is a schematic diagram showing an example of the general configuration of a plant growing device according to a third embodiment of the present invention. FIG. 10 is a schematic diagram showing an example of the general configuration of a plant growing device according to a fourth embodiment of the present invention. FIG. 11 is a schematic diagram showing an example of the general configuration of a plant growing device according to a fifth embodiment of the present invention.

[0016] Various embodiments of the present invention will now be described with reference to the accompanying drawings, in which the drawings are not necessarily to scale and some features may be exaggerated or omitted.

[0017] The plant growing device according to the embodiment is placed in a plant factory. As shown in FIG. 1 , the plant growing device 1 according to the first embodiment has a number of cultivation units 2 arranged therein for growing plants. The plants to be grown are agricultural crops such as beans, but may also be other plants that perform photosynthesis. The plant factory in which the plant growing device 1 according to the embodiment is placed is provided with an air conditioning system 20. The air conditioning system 20 adjusts the environment of the area in which the plants are grown to a temperature, humidity, and carbon dioxide (CO ) suitable for plant growth. ２ ) concentration.

[0018] 1 and 2, the cultivation unit 2 of the plant cultivation device 1 according to the first embodiment has an upper portion 10, a cultivation tank 12 disposed below the upper portion 10, and a support panel 14 attached to the upper end of the cultivation tank 12. The upper portion 10 has a cultivation space 30 in which the stems and leaves of plants 200 grow (i.e., in which the plants are cultivated).

[0019] At least the roots (including the main root and lateral roots) of the plant 200 are placed in the cultivation tank 12, where the roots grow. The lower part of the stem of the plant 200 is also placed in the cultivation tank 12. The support panel 14 supports the plant 200.

[0020] The cultivation tank 12 is a container that contains a nutrient solution (liquid fertilizer) 16 containing fertilizer to be applied to the roots of the plants 200. A nutrient solution supply system 18 is connected to the cultivation tank 12, and the nutrient solution supply system 18 supplies the nutrient solution 16 to the cultivation tank 12.

[0021] The upper part 10 of the cultivation unit 2 has at least one light source panel 32 that irradiates the growing space 30 with artificial light Li. The light source panel 32 irradiates the plants 200 with artificial light Li from the side. In this embodiment, the upper part 10 includes two light source panels 32 that are vertically oriented and arranged parallel to each other. In this manner, the two light source panels 32 face each other, the growing space 30 is interposed between the two light source panels 32, and the two light source panels 32 irradiate the plants 200 with artificial light Li from both sides.

[0022] As shown in FIG. 2 , the light source panel 32 has a height X that is greater than the upper limit of the growth height of the plants 200, and a width Y that allows the artificial light Li to be applied substantially evenly and sufficiently to the plurality of plants 200 planted at intervals from one another. The distance Z between the two light source panels 32 is set large enough to allow the artificial light Li to be applied substantially evenly and sufficiently to each leaf of the plants 200. The distance Z is also set large enough to prevent damage to the plants 200 due to heat radiation from the light source panel 32. However, the distance Z is smaller than the quotient obtained by dividing the width Y by n+1 (n is the number of plants 200 in the growth space 30). Therefore, the distance Z is smaller than the width W of the light-emitting area of ​​the light source panel 32 that corresponds to one plant 200. The light-emitting area is the area where an LED chip, described later, is mounted.

[0023] The light source of the light source panel 32 may be, for example, a plurality of fluorescent lamps, a plurality of cold cathode fluorescent lamps, or a plurality of organic light-emitting diode (OLED) elements. However, in this embodiment, a plurality of light-emitting diode (LED) chips, which generate little heat, are used. As shown in FIGS. 3 and 4 , the light source panel 32 includes a flat substrate 33 serving as a support and a plurality of LED chips 34 arranged on the substrate 33. These LED chips 34 are of the same type. Therefore, when the same current and voltage are applied, these LED chips 34 emit artificial light Li with the same photon flux density. The LED chips 34 are arranged regularly (specifically, in a matrix) at equal intervals both vertically and horizontally. The LED chips 34 are mounted in a light-emitting region of the light source panel 32 having a height X1 and a width Y1.

[0024] The substrate 33 is provided with wiring (not shown) for lighting these LED chips 34. A light emission control device 44 (see FIG. 1) for simultaneously controlling the light emission of these LED chips 34 is provided outside the light source panel 32.

[0025] A plurality of ventilation holes 35 are formed in the light-emitting region of the substrate 33. The ventilation holes 35 are through-holes. Air controlled by the air conditioning system 20 is supplied to the growth space 30 through these ventilation holes 35, preventing the plants 200 from overheating due to heat dissipation from the light source panel 32 (note that the air controlled by the air conditioning system 20 may be supplied directly to the growth space 30). The ventilation holes 35 have the same size and are regularly (specifically, in a matrix) arranged at equal intervals vertically and horizontally. However, the ventilation holes 35 may have different sizes or may be arranged irregularly. Other measures may be used to cool the light source panel 32 in addition to or instead of the ventilation holes 35. For example, a heat dissipation member, a water-cooled pipe, or an air-cooled pipe may be in contact with the surface of the substrate 33 opposite the LED chip 34.

[0026] In order to increase the utilization efficiency of the artificial light Li in the cultivation space 30, it is preferable that the surface of the substrate 33 facing the LED chip 34 has a high light reflectivity. The substrate 33 is preferably formed from a light-reflecting material (e.g., a metal with a smooth surface). The surface of the substrate 33 facing the LED chip 34 may be coated with a light-reflecting paint.

[0027] 3 and 4 are merely examples. The size, number, and spacing of the LED chips 34 are not limited to those shown in the drawings, and the size, number, and spacing of the ventilation holes 35 are also not limited to those shown in the drawings.

[0028] The position of the light source panel 32 relative to the plant 200 and thus the cultivation space 30 is not limited, and for example, the light source panel 32 may be positioned above the cultivation space 30 so that the light source panel 32 emits artificial light Li from above into the cultivation space 30.

[0029] However, in order to make the illuminance as uniform as possible in the cultivation space 30, the growth of the leaves should be taken into consideration. When artificial light Li is emitted from above the cultivation space 30, the artificial light Li is blocked by the upper leaves at the stage when the plants 200 have many leaves, resulting in lower illuminance in the lower part of the cultivation space 30 and poor photosynthetic efficiency. Furthermore, when the plants 200 are densely grown, the growth of each individual plant varies.

[0030] Therefore, in this embodiment, the light source panel 32 is disposed on the side of the cultivation space 30 so that the light source panel 32 irradiates the plants 200 with artificial light Li from the side. Therefore, regardless of the growth stage of the plants 200, particularly the state of leaf growth, the illuminance can be made as uniform as possible between the upper and lower parts of the cultivation space 30. Furthermore, even when the plants 200 are densely grown, the artificial light Li can be supplied uniformly to each individual plant, thereby suppressing variation in growth among the individual plants.

[0031] The number of light source panels 32 may be one. However, in order to make the illuminance as uniform as possible on both sides of the plant 200, in this embodiment, as shown in Figures 1 and 2, two light source panels 32 face each other, the growth space 30 is interposed between the two light source panels 32, and the two light source panels 32 irradiate the plant 200 with artificial light Li from both sides. In this way, it is preferable to provide two light source panels 32, and in this case, the illuminance on both sides of the plant 200 can be made as uniform as possible, thereby improving photosynthetic efficiency.

[0032] In addition to the two light source panels 32, two more light source panels 32 may be provided at both ends of the light source panels 32 in the longitudinal direction (the direction of width Y). That is, four light source panels 32 may be provided around the periphery of the growth space 30, and the four light source panels 32 may emit artificial light Li into the growth space 30. However, in this case, plants 200 arranged near the ends of the growth space 30 in the longitudinal direction (the direction of width Y) will receive more artificial light Li than plants 200 arranged in the center of the growth space 30 in the longitudinal direction. In this case, if the amount of artificial light Li emitted from each LED chip 34 is large, the leaves of plants 200 arranged near the ends of the growth space 30 in the longitudinal direction may receive light with an intensity higher than the photosynthetic saturation light intensity, resulting in wasted light energy. Furthermore, growth may vary among individual plants. Therefore, it is preferable to provide only two light source panels 32, as in this embodiment.

[0033] In the embodiment, the substrate 33 of the light source panel 32 is a flat plate, but as shown in Fig. 5, the substrate 33 may be a corrugated plate. Fig. 5 is a vertical cross-sectional view of the light source panel 32, similar to Fig. 4. A corrugated plate can dissipate more heat generated by the LED chips 34 than a flat plate.

[0034] To cool the plants 200 in the cultivation unit 2, the nutrient solution supply system 18 or the cultivation tank 12 may be cooled by a cooling device.

[0035] 1, the plant cultivation device 1 further includes a fertilizer absorption amount measuring device 40 and an environmental control device 42. The fertilizer absorption amount measuring device 40 repeatedly measures the amount of fertilizer absorption of the plants 200 in the cultivation unit 2 at unit intervals (e.g., daily). In this embodiment, the fertilizer absorption amount measuring device 40 includes a sensor 40a, a liquid volume sensor 40b, and a fertilizer absorption amount calculation unit 40c.

[0036] The sensor 40a repeatedly (e.g., daily) measures the fertilizer concentration of the nutrient solution 16 in the cultivation tank 12. As the fertilizer concentration, the sensor 40a may measure the phosphate concentration that forms adenosine triphosphate, which is an energy component of the plant 200, or the nitrogen concentration that forms the protein of the plant 200. Alternatively, the sensor 40a may be a combination of a sensor that measures the phosphate concentration and a sensor that measures the nitrogen concentration. Alternatively, the sensor 40a may measure the electrical conductivity of the nutrient solution 16 in the cultivation tank 12. The fertilizer absorption amount calculation unit 40c, which will be described later, can calculate the fertilizer concentration of the nutrient solution 16 in the cultivation tank 12 from the electrical conductivity using, for example, a conversion formula.

[0037] The liquid volume sensor 40b repeatedly measures the amount of nutrient solution 16 supplied from the nutrient solution supply system 18 to the cultivation tank 12 at unit intervals (e.g., daily). The liquid volume sensor 40b may be, for example, a flow meter. Alternatively, the liquid volume sensor 40b may be a level gauge that measures the liquid level of the nutrient solution 16 in the cultivation tank 12. In this case, the liquid volume sensor 40b may report the amount of nutrient solution 16 that has decreased to the nutrient solution supply system 18, and the nutrient solution supply system 18 may maintain the liquid level of the nutrient solution 16 constant.

[0038] The fertilizer absorption amount calculation unit 40c is a computer processor. The fertilizer absorption amount calculation unit 40c repeatedly calculates the cumulative fertilizer absorption amount (the amount of fertilizer components absorbed by the plant 200) of the plant from sowing to the present every unit period (e.g., every day) based on the measurement results of the sensor 40a and the liquid volume sensor 40b. Alternatively, the fertilizer absorption amount calculation unit 40c may calculate the fertilizer absorption amount of the plant 200 per unit period (e.g., every day) based on the measurement results of the sensor 40a and the liquid volume sensor 40b. The fertilizer absorption amount calculation unit 40c may calculate the amount of phosphate absorbed by the plant 200, the amount of nitrogen absorbed by the plant 200, or both.

[0039] When the fertilizer concentration is constant, the cumulative amount of fertilizer absorption is calculated by multiplying the fertilizer concentration of the nutrient solution 16 obtained from the measurement results of sensor 40a by the cumulative amount of liquid absorbed by the plant 200 obtained from the measurement results of liquid volume sensor 40b. When the fertilizer concentration is constant, the amount of fertilizer absorption per unit period is calculated by multiplying the fertilizer concentration of the nutrient solution 16 obtained from the measurement results of sensor 40a by the amount of liquid absorbed by the plant 200 per unit period obtained from the measurement results of liquid volume sensor 40b.

[0040] When the fertilizer concentration changes, the cumulative fertilizer absorption amount A is calculated by the following formula: A = (C ２ *L ２ )-(C １ *L １ ) where C １ is the fertilizer concentration of the initial nutrient solution 16, and L １ is the amount of the initial nutrient solution 16. ２ is the fertilizer concentration of the final nutrient solution 16, and L ２ is the final amount of nutrient solution 16. When the fertilizer concentration changes, the amount of fertilizer absorbed per unit period is also calculated according to the above formula.

[0041] If the concentration of fertilizer in the cultivation tank 12 is always known, the sensor 40a is not necessary, and the fertilizer absorption amount calculation unit 40c can calculate the cumulative fertilizer absorption amount or the fertilizer absorption amount per unit period from the measurement results of the liquid volume sensor 40b.

[0042] The amount of fertilizer absorption measured by the fertilizer absorption amount measuring device 40 is notified to the environmental control device 42. The environmental control device 42 is a computer processor. The environmental control device 42 controls at least one of the air conditioning system 20, the light emission control device 44, and the nutrient solution supply system 18 based on changes in the measured amount of fertilizer absorption.

[0043] The environmental control policy based on changes in fertilizer absorption will be explained with reference to the graphs in Figures 6 and 7. The curves in Figure 6 show the change in cumulative fertilizer absorption when soybeans (variety: Hatsudaruma) are grown in a plant factory. The vertical axis represents the equivalent value of cumulative fertilizer absorption per four plants or per plant. Curve a shows the change in fertilizer absorption when five soybean plants in the growth space 30 are grown in a cultivation unit 2 in which artificial light Li is applied from the side by one light source panel 32. Curve b shows the change in fertilizer absorption when two soybean plants in the growth space 30 are grown in a cultivation unit 2 in which artificial light Li is applied from above by one light source panel 32. The amount of fertilizer absorption in the case of curve b is less than that in the case of curve a. This is because, as described above, when artificial light Li is applied from above, the artificial light Li is blocked by the upper leaves, resulting in poor photosynthetic efficiency of the lower leaves.

[0044] The growth stages leading up to maturity in photosynthetic plants can be divided into the pre-vegetative stage, mid-vegetative stage, flowering / pod number determination stage, seed filling stage, and maturation stage. During the pre-vegetative stage, plants actively photosynthesize, absorb nutrients, and develop lush branches and leaves. In soybeans, the mid-vegetative stage is the period of flower bud differentiation, and the flowering / pod number determination stage is the period when flower buds form and pods are produced. In outdoor environments, the flowering / pod number determination stage for soybeans varies depending on the conditions, but generally occurs approximately 70 days after sowing. Furthermore, the mid-vegetative and flowering / pod number determination stages are also periods when vegetative and reproductive growth occur simultaneously. During the seed filling stage, photosynthetic products (sugars) produced by photosynthesis are translocated to the seeds or rhizomes, causing the seeds or rhizomes to swell. The soybean seed filling stage varies depending on the conditions, but generally occurs 70 to 110 days after sowing. The maturity stage occurs when the seeds or rhizomes are fully ripe. In the case of soybeans, the maturity stage occurs when the seeds dry out. In outdoor environments, the maturity stage for soybeans varies depending on the conditions, but generally occurs between 110 and 150 days after sowing.

[0045] In a cultivation environment in a plant factory, plants typically develop faster than in an outdoor environment. In Figure 6, in the case of curve a, the increase in cumulative fertilizer absorption slowed down 44 days after sowing, and the increase in cumulative fertilizer absorption slowed even further 50 days after sowing. That is, the amount of fertilizer absorption per day decreased 44 days after sowing, and the amount of fertilizer absorption per day decreased 50 days after sowing. In the case of curve a, soybeans entered maturity 50 days after sowing. In the case of curve b, which shows a low amount of fertilizer absorption equivalent to when artificial light Li is irradiated from above on soybeans, a similar change in fertilizer absorption was observed earlier than curve a due to suppression of photosynthesis.

[0046] The curves shown in Figure 7 all show the change in cumulative fertilizer absorption when soybeans (variety: Sachiyutaka) are grown in a plant factory. The vertical axis is the converted value of cumulative fertilizer absorption per four plants or per plant. Curve c shows the change in fertilizer absorption when soybeans are grown at a continuous constant temperature. Curve d shows the change in fertilizer absorption when soybeans are grown by switching the temperature every 12 hours to simulate day and night. In both cases, artificial light Li was applied to the soybeans from above.

[0047] In the case of curve c, the increase in cumulative fertilizer absorption slowed down 50 days after sowing, and the increase in cumulative fertilizer absorption slowed down even further 70 days after sowing. In the case of curve c, the maturity period began 70 days after sowing. In the case of curve d, the increase in cumulative fertilizer absorption slowed down 48 days after sowing, and the increase in cumulative fertilizer absorption slowed down even further 73 days after sowing. In the case of curve d, the maturity period began 73 days after sowing.

[0048] Therefore, although the time when soybeans enter the seed filling stage varies depending on the growing environment, the amount of fertilizer absorption (in other words, the amount of fertilizer required) is significantly less during the seed filling stage than during the early vegetative growth stage, the middle vegetative growth stage, or the flowering / pod number determination stage. By monitoring the change in the amount of fertilizer absorption (a slowdown in the increase in cumulative fertilizer absorption, i.e., a decrease in the amount of fertilizer absorption per unit period), it is possible to recognize that soybeans have entered the seed filling stage. The same is thought to apply to other plants that perform photosynthesis. During the seed filling stage, the photosynthetic rate of plants slows down, so the factors for photosynthesis, such as light and CO2, ２, and the amount of fertilizer required decreases. Therefore, when a change in the amount of fertilizer absorption corresponds to the seed filling period of the plant, the above-mentioned environmental control device 42 (see FIG. 1) controls at least one of the air conditioning system 20, the light emission control device 44, and the nutrient solution supply system 18 to change the growing environment of the plant 200 to an environment that suppresses photosynthesis of the plant 200. Even if photosynthesis is suppressed during the seed filling period, the yield of the seeds or rhizomes of the plant does not decrease, and costs can be reduced.

[0049] The environmental control device 42 changes the growing environment to one that suppresses photosynthesis (i.e., determines that the plant has entered the seed-filling stage) when the rate of decrease in the cumulative fertilizer absorption amount per unit period (e.g., one day) during a set period is greater than a threshold value (i.e., when the rate of decrease in the fertilizer absorption amount per unit period during a set period is greater than a threshold value). Here, the "decrease rate" is the absolute value of the decrease rate, and the "threshold" is a positive value. The "threshold" corresponds to the seed-filling stage of the plant, varies depending on the type and variety of the plant and the growing environment, and is determined based on plant-growing experience. The "set period" does not have a predetermined start date but refers to the length of time. Taking measurement error into account, the "set period" is set longer than the unit period (e.g., one day). It is also known that the amount of fertilizer absorption by a plant changes depending on the phases of the moon, i.e., the gravitational force of the moon on the Earth. Therefore, it is preferable for the environmental control device 42 to adjust at least one of the threshold value and the set period according to the phase of the moon.

[0050] If the rate of decrease in the amount of fertilizer absorption per unit period within a set period is greater than a threshold, the environmental control device 42 may control the light-emitting control device 44 to at least one of reducing the amount of light emitted by the artificial light Li, shortening the irradiation time of the artificial light Li, and reducing the blue wavelength region of the artificial light Li. That is, changing the growing environment of the plant 200 to an environment that suppresses photosynthesis of the plant 200 may involve at least one of reducing the amount of light emitted by the artificial light Li, shortening the irradiation time of the artificial light Li, and reducing the blue wavelength region of the artificial light Li. The reduction in the amount of light emitted by the artificial light Li may be achieved by reducing the power supplied to each light-emitting source (e.g., LED chip 34) or by reducing the number of light-emitting sources that are turned on. In this case, the environmental control device 42 sends a command signal to the light-emitting control device 44, and the light-emitting control device 44 controls the light source panel 32 in accordance with the command signal. The reduction in the amount of light emitted can reduce costs. Furthermore, the reduction in the irradiation time can reduce costs.

[0051] Furthermore, costs can be reduced by reducing the blue wavelength range of artificial light Li. The wavelength range of light that contributes to photosynthesis is 400 to 700 nm. The shorter the wavelength of light, the greater the amount of energy per photon. In other words, for the same number of photons, short-wavelength light has a higher energy content, while long-wavelength light has a lower energy content. However, the amount of photosynthesis is correlated with the number of photons that hit the plant, not the amount of light energy. Therefore, for the same number of photons, long-wavelength light has a higher energy efficiency for photosynthesis than short-wavelength light. Furthermore, the power consumption required to generate short-wavelength light with a high energy content is greater than the power consumption required to generate long-wavelength light. Therefore, power consumption can be reduced by reducing the blue wavelength range of artificial light Li.

[0052] Three types of plant photoreceptors are known: phytochrome, cryptochrome, and phototropin. Phytochrome primarily responds to red and far-red light to perform photosynthesis, while cryptochrome and phototropin primarily respond to blue light to perform photosynthesis. Reducing the blue wavelength range of the artificial light Li suppresses photosynthesis by cryptochrome and phototropin, thereby changing the plant growth environment to one that suppresses plant photosynthesis. To reduce the blue wavelength range of the artificial light Li, the light-emitting control device 44 may replace the light source panel 32 being used with another light source panel. Alternatively, if the light source panel 32 has LED chips 34 with different emission wavelength ranges, the light-emitting control device 44 may stop the emission of the LED chips 34 that emit light in the blue wavelength range and continue or newly start the emission of the LED chips 34 that emit light in a longer wavelength range (e.g., the red wavelength range). Alternatively, if the light source panel 32 has OLED elements with different emission wavelength ranges, the light emission control device 44 may stop the emission of the OLED elements that emit light in the blue wavelength range and continue or newly start the emission of the OLED elements that emit light in the long wavelength range. However, it is not necessarily necessary to completely stop the emission of all light sources that emit light in the blue wavelength range, and the power supplied to those light sources may be reduced, or the number of light sources that are turned on may be reduced.

[0053] If the rate of decrease in the amount of fertilizer absorption per unit period within a set period is greater than a threshold, the environmental control device 42 may control the air conditioning system 20 to lower the temperature in the cultivation space 30, instead of or in addition to the above-mentioned control by the light-emitting control device 44. That is, changing the cultivation environment of the plants 200 to an environment that suppresses photosynthesis of the plants 200 may be achieved by lowering the temperature in the cultivation space 30. In this case, the environmental control device 42 provides a command signal to the air conditioning system 20, and the air conditioning system 20 lowers the temperature in accordance with the command signal. Lowering the temperature can reduce costs.

[0054] If the rate of decrease in the amount of fertilizer absorption per unit period within the set period is greater than the threshold, the environmental control device 42 controls the air conditioning system 20 to reduce the CO 2 in the air in the growing space 30 instead of or in addition to controlling the light emission control device 44 and / or the temperature.２ In other words, changing the growing environment of the plant 200 to an environment that suppresses photosynthesis of the plant 200 reduces the concentration of CO in the air in the growing space 30. ２ In this case, the environmental control device 42 sends a command signal to the air conditioning system 20, and the air conditioning system 20 reduces the concentration of CO in the air in accordance with the command signal. ２ Reduces the concentration of CO ２ The reduction in concentration can reduce costs.

[0055] If the rate of decrease in the amount of fertilizer absorption per unit period within a set period is greater than a threshold, the environmental control device 42 may control the nutrient solution supply system 18 to reduce the amount of top dressing, instead of or in addition to controlling the light-emitting control device 44 and / or the air-conditioning system 20. In other words, changing the growing environment of the plant 200 to an environment that suppresses photosynthesis of the plant 200 may reduce the amount of top dressing. In this case, the environmental control device 42 provides a command signal to the nutrient solution supply system 18, and the nutrient solution supply system 18 reduces the amount of top dressing in accordance with the command signal. The nutrient solution supply system 18 reduces the concentration of fertilizer in the nutrient solution 16, for example. Reducing the amount of top dressing can reduce costs.

[0056] In the first embodiment, when the rate of decrease in the amount of fertilizer absorption per unit period within a set period is greater than a threshold, the environmental control device 42 changes the cultivation environment to an environment that suppresses photosynthesis. However, the fertilizer absorption amount measuring device 40 may repeatedly calculate the product of the amount of nutrient solution 16 supplied from the nutrient solution supply system 18 to the cultivation tank 12 within a unit period and the electrical conductivity of the nutrient solution 16 every unit period (for example, every day), and when the rate of decrease in this product within a set period is greater than a threshold, the environmental control device 42 may change the cultivation environment to an environment that suppresses photosynthesis.

[0057] Next, a plant growing device 1A according to a second embodiment of the present invention will be described with reference to Figure 8. The plant growing device 1A has an intraplant fertilizer concentration measuring device 50 instead of the fertilizer absorption amount measuring device 40. The intraplant fertilizer concentration measuring device 50 measures the fertilizer concentration of the liquid inside the plant 200 that is actually being grown. In this embodiment, the intraplant fertilizer concentration measuring device 50 has a sensor 50a and an intraplant fertilizer concentration calculation unit 50b.

[0058] The sensor 50a is attached to a support bracket (not shown) and is positioned close to the plant 200 in the cultivation unit 2. The sensor 50a repeatedly measures an electrical characteristic corresponding to the fertilizer concentration of the liquid flowing through the plant 200 at regular intervals (e.g., daily). For example, the sensor 50a may have a probe needle (not shown) inserted into the plant's stem, and the probe needle may be used to measure the electrical characteristic (e.g., electrical conductivity or impedance) of the liquid flowing through the plant's vascular bundle. The individual plant to which the probe needle is inserted may be changed from time to time. The electrical characteristic corresponds to the fertilizer concentration of the liquid flowing through the plant's vascular bundle. Inserting the probe needle into the plant's stem is invasive (destructive) to the plant, adversely affecting its growth and possibly causing the plant to die. Therefore, the individual plant whose growth environment is changed by the environmental control device 42 to suppress photosynthesis may be different from the individual plant to which the probe needle is inserted. That is, the sensor 50a may measure the electrical properties of a liquid flowing through a different plant of the same variety as the target plant, but grown in the same environment for the same period of time. Alternatively, the sensor 50a may include an organic electrochemical transistor, which may be used to nondestructively (noninvasively) measure the electrical properties (e.g., electrical conductivity, capacitance, or impedance) of a liquid flowing through the plant's vascular tissue. In this case, the electrical properties correspond to the concentration of sugars (cellulose and sucrose) in the liquid within the plant's vascular tissue and also to the amount of fertilizer absorption. This nondestructive (noninvasive) method for plants does not adversely affect plant growth. Therefore, unless the target plant dies for some reason, the target plant, whose photosynthesis is suppressed by the environmental control device 42 through changes to its growth environment, is the same as the target plant.

[0059] The plant fertilizer concentration calculation unit 50b is a computer processor. The plant fertilizer concentration calculation unit 50b repeatedly calculates the fertilizer concentration of the liquid at unit time intervals (for example, every day) from the electrical characteristics of the liquid measured by the sensor 50a.

[0060] The fertilizer concentration calculated by the plant fertilizer concentration calculation unit 50b is notified to the environmental control device 42. If the rate of decrease in fertilizer concentration within a set period based on the change in the measured fertilizer concentration is greater than a threshold, the environmental control device 42 controls at least one of the air conditioning system 20, the light emission control device 44, and the nutrient solution supply system 18. The "decrease rate" is the absolute value of the decrease rate, and the "threshold" is a positive value. The "threshold" corresponds to the seed enlargement period of the plant, varies depending on the type and variety of the plant and the growing environment, and is determined based on plant growing experience. The "set period" does not have a predetermined start date but refers to a length of time. Taking measurement error into account, the "set period" is set longer than a unit period (e.g., one day). The environmental control device 42 preferably corrects at least one of the threshold and the set period according to the phase of the moon.

[0061] As in the first embodiment, the environmental control device 42 may control the light-emission control device 44 to at least one of reducing the light emission amount of the artificial light Li, shortening the irradiation time of the artificial light Li, and reducing the blue wavelength region of the artificial light Li. Instead of or in addition to the above-described control by the light-emission control device 44, the environmental control device 42 may control the air-conditioning system 20 to adjust the temperature in the cultivation space 30 and the CO 2 in the air. ２ The environmental control device 42 may reduce the amount of top dressing by controlling the nutrient solution supply system 18 instead of or in addition to controlling the light emission control device 44 and / or the air conditioning system 20. According to this embodiment, if the rate of decrease in the fertilizer concentration of the liquid actually flowing through the plant within a set period is greater than a threshold value, the plant growth environment can be changed to one that suppresses plant photosynthesis.

[0062] Next, a plant growing device 1B according to a third embodiment of the present invention will be described with reference to Figure 9. The plant growing device 1B has a remaining fertilizer amount measuring device 60 instead of the fertilizer absorption amount measuring device 40 and the plant fertilizer concentration measuring device 50. The remaining fertilizer amount measuring device 60 measures the amount of fertilizer remaining in a sample 61 collected from a plant 200 being grown in a cultivation unit 2. In this embodiment, the remaining fertilizer amount measuring device 60 has a sensor 60a and a remaining fertilizer amount calculation unit 60b.

[0063] The sensor 60a repeatedly measures an electrical property (e.g., electrical conductivity or impedance) corresponding to the amount of fertilizer remaining in the sample 61 at unit intervals (e.g., daily). The sample 61 includes at least one of the leaves and stems of the plant 200 grown in the cultivation unit 2. The amount of fertilizer remaining in the sample 61 corresponds to the amount of fertilizer absorbed. Collecting the sample 61 from the plant is invasive (destructive) to the plant, adversely affecting its growth and possibly causing the plant to die. Therefore, the individual plant whose photosynthesis is suppressed by changing the growth environment by the environmental control device 42 may be different from the individual from which the sample 61 is collected. In other words, the sensor 60a may measure the electrical property in the sample 61 collected from a different plant of the same variety grown in the same environment for the same period of time, but different from the plant whose photosynthesis is suppressed.

[0064] The remaining fertilizer amount calculation unit 60b is a computer processor. The remaining fertilizer amount calculation unit 60b repeatedly calculates the amount of fertilizer remaining in the sample 61 at unit intervals (for example, every day) from the electrical characteristics of the sample 61 measured by the sensor 60a.

[0065] The amount of fertilizer calculated by the remaining fertilizer amount calculation unit 60b is notified to the environmental control device 42. If the rate of decrease in the amount of fertilizer within a set period based on the change in the measured amount of fertilizer is greater than a threshold, the environmental control device 42 controls at least one of the air conditioning system 20, the light emission control device 44, and the nutrient solution supply system 18. The "decrease rate" is the absolute value of the decrease rate, and the "threshold" is a positive value. The "threshold" corresponds to the seed enlargement period of the plant, varies depending on the type and variety of the plant and the growing environment, and is determined based on plant growing experience. The "set period" does not have a predetermined start date but refers to a length of time. Taking measurement error into account, the "set period" is set longer than a unit period (e.g., one day). The environmental control device 42 preferably corrects at least one of the threshold and the set period according to the phase of the moon.

[0066] As in the first embodiment, the environmental control device 42 may control the light-emission control device 44 to at least one of reducing the light emission amount of the artificial light Li, shortening the irradiation time of the artificial light Li, and reducing the blue wavelength region of the artificial light Li. Instead of or in addition to the above-described control by the light-emission control device 44, the environmental control device 42 may control the air-conditioning system 20 to adjust the temperature in the cultivation space 30 and the CO 2 in the air. ２ The environmental control device 42 may control the nutrient solution supply system 18 to reduce the amount of top dressing, instead of or in addition to controlling the light emission control device 44 and / or the air conditioning system 20. According to this embodiment, if the rate of decrease in the amount of fertilizer in the sample collected from the plant within a set period is greater than a threshold, the plant growth environment can be changed to one that suppresses plant photosynthesis.

[0067] Next, a plant growing device 1C according to a fourth embodiment of the present invention will be described with reference to FIG. 10 . The plant growing device 1C is similar to the plant growing device 1A of the second embodiment ( FIG. 8 ), but includes a cultivation unit 2A and a fertilizer supply system 78 instead of the cultivation unit 2 and nutrient solution supply system 18. The cultivation unit 2A has the same upper portion 10 and support panel 14 as the cultivation unit 2, and includes a cultivation tank 72 containing culture soil 76 instead of the cultivation tank 12 containing the nutrient solution 16. The fertilizer supply system 78 supplies fertilizer to the culture soil 76 in the cultivation tank 72. The fertilizer supplied by the fertilizer supply system 78 may be liquid fertilizer, powdered fertilizer, or granular fertilizer. The plant growing device 1C also includes a water supply system 79. The water supply system 79 periodically supplies water to the culture soil 76 in the cultivation tank 72.

[0068] The plant growing device 1C has an in-plant sugar content measuring device 70. The in-plant sugar content measuring device 70 measures the sugar concentration of the liquid inside the plant 200 that is actually being grown. In this embodiment, the in-plant sugar content measuring device 70 has a sensor 70a and an in-plant sugar content calculation unit 70b.

[0069] The sensor 70a is attached to a support bracket (not shown) and is positioned adjacent to the plant 200 in the cultivation unit 2. The sensor 70a nondestructively and repeatedly measures electrical properties corresponding to the sugar (cellulose and sucrose) concentration of the liquid in the vascular tissue of the plant 200. The sensor 70a may be the same as the example of the sensor 50a in the second embodiment that includes an organic electrochemical transistor. Specifically, the sensor 70a uses an organic electrochemical transistor to nondestructively (noninvasively) measure electrical properties (e.g., electrical conductivity, capacitance, or impedance) of the liquid flowing through the plant's vascular tissue. In this case, the electrical properties correspond to the sugar (cellulose and sucrose) concentration of the liquid in the vascular tissue of the plant and also correspond to the amount of fertilizer absorption. This nondestructive (noninvasive) method for the plant does not adversely affect plant growth. Therefore, unless the individual plant being measured dies for some reason, the individual plant whose photosynthesis is suppressed by changing the growing environment by the environmental control device 42 is the same as the individual plant being measured.

[0070] The plant sugar content calculation unit 70b is a computer processor that repeatedly calculates the sugar concentration of the liquid at unit intervals (e.g., every day) from the electrical characteristics of the liquid measured by the sensor 70a.

[0071] The sugar concentration calculated by the plant sugar content calculation unit 70b is notified to the environmental control device 42. Based on the change in the measured sugar concentration, the environmental control device 42 controls at least one of the air conditioning system 20, the light-emitting control device 44, the fertilizer supply system 78, and the water supply system 79 if the rate of decrease of the sugar concentration within a set period is greater than a threshold. The "decrease rate" is the absolute value of the decrease rate, and the "threshold" is a positive value. The "threshold" corresponds to the seed development stage of the plant, varies depending on the type and variety of the plant and the growing environment, and is determined based on plant growing experience. The "set period" does not have a predetermined start date but refers to a length of time. Taking measurement error into account, the "set period" is set longer than a unit period (e.g., one day). The environmental control device 42 preferably corrects at least one of the threshold and the set period according to the phase of the moon.

[0072] As in the first embodiment, the environmental control device 42 may control the light-emission control device 44 to at least one of reducing the light emission amount of the artificial light Li, shortening the irradiation time of the artificial light Li, and reducing the blue wavelength region of the artificial light Li. Instead of or in addition to the above-described control by the light-emission control device 44, the environmental control device 42 may control the air-conditioning system 20 to adjust the temperature in the cultivation space 30 and the CO 2 in the air. ２ The environmental control device 42 may reduce at least one of the concentrations of sugar and fertilizer. Instead of or in addition to controlling the light-emitting control device 44 and / or the air-conditioning system 20, the environmental control device 42 may control the fertilizer supply system 78 to reduce the amount of top dressing. Instead of or in addition to controlling the light-emitting control device 44, the air-conditioning system 20, and / or the fertilizer supply system 78, the environmental control device 42 may control the water supply system 79 to reduce the amount of water supplied to the culture soil 76. According to this embodiment, if the rate of decrease in the sugar concentration of the liquid actually flowing through the plant within a set period is greater than a threshold, the plant's growing environment can be changed to one that suppresses plant photosynthesis. The sensor 70a is non-destructive (non-invasive) to the plant and does not adversely affect plant growth.

[0073] Next, a plant growing device 1D according to a fifth embodiment of the present invention will be described with reference to FIG. 11 . The plant growing device 1D is similar to the plant growing device 1B of the third embodiment ( FIG. 9 ), but includes a cultivation unit 2A and a fertilizer supply system 78 instead of the cultivation unit 2 and nutrient solution supply system 18. The cultivation unit 2A has the same upper portion 10 and support panel 14 as the cultivation unit 2, and includes a cultivation tank 72 containing culture soil 76 instead of the cultivation tank 12 containing the nutrient solution 16. The fertilizer supply system 78 supplies fertilizer to the culture soil 76 in the cultivation tank 72. The fertilizer supplied by the fertilizer supply system 78 may be liquid fertilizer, powdered fertilizer, or granular fertilizer. The plant growing device 1D also includes a water supply system 79. The water supply system 79 periodically supplies water to the culture soil 76 in the cultivation tank 72.

[0074] Like the plant growing device 1B of the third embodiment ( FIG. 9 ), the plant growing device 1D has a remaining fertilizer amount measuring device 60. The remaining fertilizer amount measuring device 60 measures the amount of fertilizer remaining in a sample 61 collected from a plant 200 being grown in the cultivation unit 2. The amount of fertilizer calculated by the remaining fertilizer amount calculating unit 60b of the remaining fertilizer amount measuring device 60 is notified to the environmental control device 42. Like the third embodiment, the environmental control device 42 controls at least one of the air conditioning system 20, the light-emitting control device 44, the fertilizer supply system 78, and the water supply system 79 based on the change in the measured amount of fertilizer when the rate of decrease in the amount of fertilizer within a set period is greater than a threshold. Like the first embodiment, the environmental control device 42 may control the light-emitting control device 44 to at least one of reducing the light emission amount of the artificial light Li, shortening the irradiation time of the artificial light Li, and reducing the blue wavelength region of the artificial light Li. Instead of or in addition to the above control of the light-emitting control device 44, the environmental control device 42 controls the air-conditioning system 20 to adjust the temperature and CO in the growing space 30. ２ or the concentration of fertilizer in the culture medium 76. Instead of or in addition to controlling the light-emitting control device 44 and / or the air-conditioning system 20, the environmental control device 42 may control the fertilizer supply system 78 to reduce the amount of top dressing. Instead of or in addition to controlling the light-emitting control device 44, the air-conditioning system 20, and / or the fertilizer supply system 78, the environmental control device 42 may control the water supply system 79 to reduce the amount of water supplied to the culture medium 76. According to this embodiment, if the rate of decrease in the amount of fertilizer in the sample collected from the plant within a set period is greater than a threshold, the plant's growing environment can be changed to one that suppresses plant photosynthesis.

[0075] Although the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the scope of the invention as set forth in the appended claims. Such changes, modifications and alterations are intended to be included within the scope of the invention.

[0076] For example, in the above embodiment, if the rate of decrease in the measured amount corresponds to the seed filling stage of the plant, the environmental control device 42 controls the plant's growing environment to an environment that suppresses photosynthesis. However, if the rate of decrease in the measured amount corresponds to the plant's maturity stage, the environmental control device 42 may also control the plant's growing environment to an environment that suppresses photosynthesis. Even if photosynthesis is suppressed during the maturity stage, the yield of plant seeds or rhizomes is not reduced, and costs can be reduced.

[0077] The fertilizer absorption amount calculation unit 40c, the plant fertilizer concentration calculation unit 50b, the remaining fertilizer amount calculation unit 60b, the plant sugar content calculation unit 70b, and the environmental control device 42 are not limited to computer processors. All or part of these may be executed by hardware instead of a processor, or may be executed by a programmable logic device such as an FPGA (Field Programmable Gate Array) or a DSP (Digital Signal Processor). The above embodiments may be combined as long as they are not inconsistent.

[0078] Aspects of the present invention are also described in the following numbered clauses: Clause 1. A plant cultivation device for cultivating plants using artificial light, comprising: a cultivation space for cultivating the plants; at least one light source panel for irradiating the cultivation space with artificial light; a cultivation tank for containing liquid fertilizer, which is a nutrient solution containing fertilizer to be given to the plants, and in which at least the roots of the plants are placed; a measuring device for repeatedly measuring an amount corresponding to an amount of fertilizer absorption by the plants; and an environmental control device for controlling the cultivation environment of the plants to change to an environment that suppresses photosynthesis of the plants when a rate of decrease in the amount measured by the measuring device within a set period is greater than a threshold.

[0079] Clause 2. The plant cultivation device according to Clause 1, characterized in that the measurement device has a liquid volume sensor that repeatedly measures the amount of liquid fertilizer supplied to the cultivation tank, and a calculation unit that repeatedly calculates the amount from at least the measurement results of the liquid volume sensor, and the environmental control device controls the plant cultivation environment to change to an environment that suppresses photosynthesis of the plant if the rate of decrease of the amount within a set period is greater than a threshold. In this case, the amount of fertilizer absorbed or an amount corresponding to the amount of fertilizer absorbed can be calculated from changes in the amount of liquid fertilizer, and the plant cultivation environment can be changed to an environment that suppresses photosynthesis of the plant if the rate of decrease of the amount within a set period is greater than a threshold.

[0080] Clause 3. The plant-growing device according to Clause 1, characterized in that the measuring device has a sensor that repeatedly measures an electrical characteristic corresponding to the fertilizer concentration of a liquid flowing through the plant or an individual plant of the same variety as the plant that has been grown in the same environment for the same period of time, and the environmental control device controls the plant-growing environment to change to an environment that suppresses plant photosynthesis if the rate of decrease in the fertilizer concentration within a set period is greater than a threshold. In this case, if the rate of decrease in the fertilizer concentration of the liquid actually flowing through the plant within a set period is greater than a threshold, the plant-growing environment can be changed to an environment that suppresses plant photosynthesis.

[0081] Clause 4. The plant cultivation device according to Clause 1, characterized in that the measuring device repeatedly measures electrical characteristics corresponding to the amount of fertilizer remaining in samples collected from the plant or from individual plants of the same variety as the plant that have been grown in the same environment for the same period of time, and the environmental control device controls the plant cultivation environment to change to an environment that suppresses plant photosynthesis if the rate of decrease in the amount of fertilizer within a set period of time is greater than a threshold. In this case, the plant cultivation environment can be changed to an environment that suppresses plant photosynthesis if the rate of decrease in the amount of fertilizer in the sample collected from the plant within a set period of time is greater than a threshold.

[0082] Clause 5. A plant cultivation device for cultivating plants using artificial light, comprising: a cultivation space for cultivating the plants; at least one light source panel for irradiating the cultivation space with artificial light; a cultivation tank in which at least the roots of the plants are placed; a measuring device for repeatedly and non-destructively measuring an electrical characteristic corresponding to the sugar concentration of a liquid in the tissue of the plants; and an environmental control device for controlling the cultivation environment of the plants to change to an environment that suppresses photosynthesis of the plants when the rate of decrease in the sugar concentration within a set period is greater than a threshold. In this case, the cultivation environment of the plants can be changed to an environment that suppresses photosynthesis of the plants when the rate of decrease in the sugar concentration of the liquid actually flowing within the plants within a set period is greater than a threshold.

[0083] Clause 6. A plant cultivation device for cultivating plants using artificial light, comprising: a cultivation space for cultivating the plants; at least one light source panel for irradiating the cultivation space with artificial light; a cultivation tank in which at least the roots of the plants are placed; a measuring device for repeatedly measuring electrical characteristics corresponding to the amount of fertilizer remaining in samples collected from the plants or from individual plants of the same variety as the plants grown in the same environment for the same period of time; and an environmental control device for controlling the plant cultivation environment to change to an environment that suppresses plant photosynthesis if the rate of decrease in the amount of fertilizer within a set period of time is greater than a threshold. In this case, the plant cultivation environment can be changed to an environment that suppresses plant photosynthesis if the rate of decrease in the amount of fertilizer in the sample collected from the plants within a set period of time is greater than a threshold.

[0084] Clause 7. The plant growing device according to any one of clauses 1 to 6, wherein the environmental control device controls the plant growing environment to change to an environment that suppresses photosynthesis of the plant by at least one of reducing the amount of light emitted by the artificial light, shortening the irradiation time of the artificial light, and reducing the blue wavelength range of the artificial light. Costs can be reduced by reducing the amount of light emitted. Furthermore, costs can be reduced by shortening the irradiation time.

[0085] Clause 8. The plant-growing device according to any one of clauses 1 to 7, wherein the environmental control device controls the plant-growing environment to change it to an environment that suppresses photosynthesis of the plant, thereby lowering the temperature within the growing space. In this case, lowering the temperature can reduce costs.

[0086] Clause 9. The plant-growing device according to any one of clauses 1 to 8, wherein the environmental control device controls the plant-growing environment to change it to an environment that suppresses photosynthesis of the plant, thereby reducing the carbon dioxide concentration in the air within the growing space. In this case, the reduction in carbon dioxide concentration can reduce costs.

[0087] Clause 10. The plant growing device according to any one of clauses 1 to 9, wherein the environmental control device controls the plant growing environment to change to an environment that suppresses photosynthesis of the plant, thereby reducing the amount of top dressing. In this case, reducing the amount of top dressing can reduce costs.

[0088] Clause 11. The plant growing device according to any one of clauses 1 to 10, wherein the at least one light source panel irradiates the plurality of plants with artificial light from the side. In this case, artificial light can be supplied evenly to individual plants, thereby suppressing variations in growth among individual plants.

[0089] Clause 12. A plant cultivation method for cultivating a plant using artificial light, comprising: irradiating a cultivation space in which the plant is cultivated with artificial light; supplying a nutrient solution containing fertilizer to be given to the plant to a cultivation tank in which at least the roots of the plant are placed; repeatedly measuring an amount corresponding to an amount of fertilizer absorbed by the plant; and controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant when a rate of decrease in the measured amount within a set period is greater than a threshold.

[0090] Clause 13. A plant cultivation method for cultivating plants using artificial light, comprising: irradiating a cultivation space in which the plants are grown with artificial light; supplying fertilizer to be given to the plants to a cultivation tank in which at least the roots of the plants are placed; non-destructively and repeatedly measuring an electrical characteristic corresponding to a sugar concentration of a liquid in the tissue of the plants; and controlling the cultivation environment of the plants to change to an environment that suppresses photosynthesis of the plants when a rate of decrease in the sugar concentration within a set period of time is greater than a threshold value.

[0091] Clause 14. A plant cultivation method for cultivating a plant using artificial light, comprising: irradiating a cultivation space in which the plant is cultivated with artificial light; supplying fertilizer to be given to the plant to a cultivation tank in which at least the roots of the plant are placed; repeatedly measuring electrical characteristics corresponding to the amount of fertilizer remaining in samples collected from the plant or from individual plants of the same variety as the plant that have been cultivated in the same environment for the same period of time; and controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant if the rate of decrease in the amount of fertilizer within a set period of time is greater than a threshold.

[0092] 1, 1A, 1B, 1C, 1D... Plant cultivation device, 2, 2A... Cultivation unit, 12... Cultivation tank, 16... Nutrient solution, 18... Nutrient solution supply system, 20... Air conditioning system, 200... Plant, 30... Cultivation space, 32... Light source panel, 40... Fertilizer absorption amount measuring device, 42... Environmental control device, 40a... Sensor, 40b... Liquid volume sensor, 40c... Fertilizer absorption amount calculation unit, 44... Light emission control device, 50... In-plant fertilizer concentration measuring device, 50a... Sensor, 50b... In-plant fertilizer concentration calculation unit, 60... Residual fertilizer amount measuring device, 60a... Sensor, 60b... Residual fertilizer amount calculation unit, 61... Sample, 72... Cultivation tank, 76... Culture soil, 78... Fertilizer supply system, 79... Water supply system, 70... In-plant sugar content measuring device, 70a... Sensor, 70b... In-plant sugar content calculation unit, Li... Artificial light

Claims

1. A plant cultivation device for cultivating a plant using artificial light, comprising: a cultivation space for cultivating the plant; at least one light source panel for irradiating the cultivation space with artificial light; a cultivation tank for containing liquid fertilizer, which is a nutrient solution containing fertilizer to be given to the plant, and in which at least the roots of the plant are placed; a measuring device for repeatedly measuring an amount corresponding to an amount of fertilizer absorbed by the plant; and an environmental control device for controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant when a rate of decrease in the amount measured by the measuring device within a set period is greater than a threshold value.

2. The plant cultivation device according to claim 1, characterized in that the measuring device has a liquid volume sensor that repeatedly measures the amount of liquid fertilizer supplied to the cultivation tank, and a calculation unit that repeatedly calculates the amount from at least the measurement results of the liquid volume sensor, and the environmental control device controls the plant cultivation environment to change to an environment that suppresses photosynthesis of the plant when a rate of decrease in the amount within a set period is greater than a threshold value.

3. The plant cultivation device described in claim 1, characterized in that the measuring device has a sensor that repeatedly measures electrical characteristics corresponding to the fertilizer concentration of a liquid flowing through the plant or an individual plant of the same variety as the plant grown in the same environment and for the same period as the plant, and the environmental control device controls the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant if the rate of decrease in the fertilizer concentration within a set period is greater than a threshold value.

4. The plant cultivation device described in claim 1, characterized in that the measuring device repeatedly measures electrical characteristics corresponding to the amount of fertilizer remaining in a sample taken from the plant or an individual plant of the same variety as the plant grown in the same environment for the same period as the plant, and the environmental control device controls the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant if the rate of decrease in the amount of fertilizer within a set period is greater than a threshold value.

5. A plant cultivation device for cultivating plants using artificial light, comprising: a cultivation space for cultivating the plant; at least one light source panel for irradiating the cultivation space with artificial light; a cultivation tank in which at least the roots of the plant are placed; a measuring device for repeatedly and non-destructively measuring an electrical characteristic corresponding to a sugar concentration of a liquid in the tissue of the plant; and an environmental control device for controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant if the rate of decrease in the sugar concentration within a set period of time is greater than a threshold value.

6. A plant cultivation device for cultivating a plant using artificial light, comprising: a cultivation space for cultivating the plant; at least one light source panel for irradiating the cultivation space with artificial light; a cultivation tank in which at least the roots of the plant are placed; a measuring device for repeatedly measuring electrical characteristics corresponding to an amount of fertilizer remaining in a sample taken from the plant or an individual plant of the same variety as the plant grown in the same environment for the same period as the plant; and an environmental control device for controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant if the rate of decrease in the amount of fertilizer within a set period is greater than a threshold value.

7. A plant growing device as claimed in any one of claims 1 to 6, characterized in that the environmental control device controls the growing environment of the plant to change to an environment that suppresses photosynthesis of the plant by at least one of reducing the amount of light emitted by the artificial light, shortening the irradiation time of the artificial light, and reducing the blue wavelength range of the artificial light.

8. A plant cultivation device as described in any one of claims 1 to 6, characterized in that the environmental control device controls the plant cultivation environment to change to an environment that suppresses photosynthesis of the plant, thereby lowering the temperature within the cultivation space.

9. A plant cultivation device as described in any one of claims 1 to 6, characterized in that the environmental control device controls the plant cultivation environment to change to an environment that suppresses photosynthesis of the plant, thereby reducing the carbon dioxide concentration in the air within the cultivation space.

10. A plant cultivation device as described in any one of claims 1 to 6, characterized in that the environmental control device controls the plant cultivation environment to change to an environment that suppresses photosynthesis of the plant, thereby reducing the amount of top dressing.

11. The plant growing device according to any one of claims 1 to 6, wherein the at least one light source panel irradiates artificial light from the side of the plurality of plants.

12. A plant cultivation method for cultivating a plant using artificial light, comprising: irradiating artificial light to a cultivation space in which the plant is cultivated; supplying a nutrient solution containing fertilizer to be given to the plant to a cultivation tank in which at least the roots of the plant are placed; repeatedly measuring an amount corresponding to an amount of fertilizer absorbed by the plant; and, if a rate of decrease in the measured amount within a set period of time is greater than a threshold value, controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant.

13. A plant cultivation method for cultivating a plant using artificial light, comprising: irradiating artificial light to a cultivation space in which the plant is cultivated; supplying fertilizer to be given to the plant to a cultivation tank in which at least the roots of the plant are placed; non-destructively and repeatedly measuring electrical characteristics corresponding to a sugar concentration of a liquid in the tissue of the plant; and, if a rate of decrease in the sugar concentration within a set period of time is greater than a threshold value, controlling the cultivation environment of the plant to be changed to an environment that suppresses photosynthesis of the plant.

14. A plant cultivation method for cultivating a plant using artificial light, comprising: irradiating artificial light to a cultivation space in which the plant is cultivated; supplying fertilizer to be given to the plant to a cultivation tank in which at least the roots of the plant are placed; repeatedly measuring electrical characteristics corresponding to the amount of fertilizer remaining in a sample taken from the plant or an individual plant of the same variety as the plant cultivated in the same environment for the same period as the plant; and, if the rate of decrease in the amount of fertilizer within a set period is greater than a threshold value, controlling the cultivation environment of the plant to change to an environment that suppresses photosynthesis of the plant.

Images