Plant cultivation method, plant cultivation apparatus, and photosynthetic organism production method

Abstract

Provided is a plant cultivation method that can accelerate the growth rate of plants and that also can promote useful substance amount production. Performed in at least part of a cultivation period from seeding to harvest are irradiation with main light which is for photosynthesis and irradiation with additional light, radiation of which is possible in addition to the main light. From among additional signal light, the light intensity of which periodically changes, and additional moderate light, the light intensity of which changes more moderately than that of the additional signal light, the additional light includes at least the additional signal light.

Description

[Technical Field]

[0001] The present invention relates, for example, to a plant cultivation method, a plant cultivation apparatus, and a photosynthetic organism production method that promote plant growth and the production of useful components. [Background technology]

[0002] Crop growth is greatly affected by weather conditions. In field cultivation and greenhouse cultivation, when sunlight decreases, the amount of light energy necessary for photosynthesis becomes insufficient, and the growth rate of plants slows down. On the other hand, in plant factories that use artificial light, the lighting equipment and running costs for irradiating sufficient light energy are high, and improvements in profitability are desired. Therefore, there is a need for lighting technology that can promote the growth rate of crops in open field cultivation, greenhouse cultivation, and plant factories at low lighting costs. Patent Document 1 discloses an invention that can promote plant growth at low cost. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2019 / 031559 [Overview of the project] [Problems that the invention aims to solve]

[0004] The method described in Patent Document 1 involves irradiating plants with light that has a relatively low duty cycle under light conditions in which photosynthesis is not occurring. In the inventors' experiments, the results showed that the plants were damaged and altered by the relatively strong stimulus. Furthermore, there is the problem that the growth rate and the production of useful substances cannot be controlled independently.

[0005] The present invention aims to provide a plant cultivation method, a plant cultivation apparatus, and a photosynthetic organism production method that can accelerate the growth rate of plants and promote the production of useful substances. [Means for solving the problem]

[0006] The present invention provides a plant cultivation method, a plant cultivation apparatus, and a method for producing a photosynthetic organism having the following configurations.

[0007] (1) In at least a part of the cultivation period from sowing to harvesting, main light irradiation for photosynthesis and additional light irradiation for promoting photosynthesis of plants by said main light are performed, said additional light includes additional signal light whose light intensity fluctuates periodically, and additional relaxation light whose light intensity changes more gently than said additional signal light fruit, The first stage involves cultivation using the aforementioned additional light, The second stage includes stopping the irradiation of the additional light and performing cultivation. A plant cultivation method. (2) A plant cultivation apparatus irradiated with main light for photosynthesis of plants, wherein for said main light Promotes photosynthesis in plants an additional light source that performs additional light irradiation, and an irradiation light control unit capable of driving and controlling said additional light source, wherein said additional light source includes an additional signal light source that irradiates additional signal light whose light intensity fluctuates periodically, and an additional relaxation light source that irradiates additional relaxation light whose light intensity changes more gently than said additional signal light, wherein said additional relaxation light is irradiated together with said additional signal light death, The first stage of cultivation involves cultivation using the aforementioned additional light, The second stage of cultivation is carried out by stopping the irradiation of the additional light. A plant cultivation apparatus. (3) In at least a part of the cultivation period from sowing to harvesting, main light irradiation for photosynthesis and additional light irradiation for promoting photosynthesis of photosynthetic organisms by said main light are performed, said additional light includes additional signal light whose light intensity fluctuates periodically, and additional relaxation light whose light intensity changes more gently than said additional signal light. A method for producing a photosynthetic organism. Effects of the Invention

[0008] According to the present invention, it is possible to provide a plant cultivation method, a plant cultivation apparatus, and a photosynthetic organism production method that can accelerate the growth rate of plants and promote the production of useful substances. [Brief explanation of the drawing]

[0009] [Figure 1] This graph shows an example of a light-photosynthesis curve. [Figure 2] This is an explanatory diagram illustrating a comparison between pulsed light from prior art and additional signal light from the embodiment. [Figure 3] This diagram illustrates the flow of glucose produced by photosynthesis, from its distribution to the translocation pathway and secondary metabolic pathways. [Figure 4] This is an explanatory diagram illustrating signal light and relaxation light in a schematic manner. [Figure 5] This is a schematic diagram of a plant cultivation system. [Figure 6] This is an explanatory diagram showing the experimental results of Example 2 using images. [Figure 7] This flowchart shows the two-stage procedure for growing seedlings. [Figure 8] This is a schematic diagram showing a microalgae cultivation device used in a two-stage cultivation process. [Figure 9] This flowchart shows the two-stage process of growing Euglena. [Figure 10] This is a schematic diagram illustrating how additional light is emitted from a flying object. [Figure 11] (a) is an explanatory diagram showing the control of Example 8 by image, and (b) is an explanatory diagram showing the test section of Example 8 by image. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below.

[0011] <Plant cultivation method> <<Summary of the plant cultivation method in this embodiment>> Plants self-produce carbohydrates necessary for life maintenance and growth through photosynthesis. In photosynthesis, glucose (C6H 12 O6), a type of carbohydrate, is produced from the raw materials water (H2O) and carbon dioxide (CO2). Light energy is essential for the progression of the production reaction. Light energy is absorbed by a pigment assembly called a light antenna.

[0012] The present embodiment provides a plant cultivation method of additionally irradiating light whose intensity periodically changes in an environment where plants are grown by sunlight (natural light) or artificial light such as an LED. The added light stimulates the viability of the plant's DNA, thereby indirectly promoting photosynthesis. The added light is also referred to as "additional light" hereinafter. The additional light will be described later.

[0013] <<Plant Growth by Main Light>> Plants carry out photosynthesis and respiration simultaneously. Photosynthesis absorbs carbon dioxide and releases oxygen. Respiration absorbs oxygen and releases carbon dioxide. The carbon dioxide absorption rate in photosynthesis (unit: μmolCO2m -2 s -1 ) depends on light intensity (see Figure 1), but the amount of carbon dioxide absorbed in respiration does not depend on light intensity.

[0014] The difference between the carbon dioxide absorption rate (μmolCO2m -2 s -1 ) in photosynthesis and the carbon dioxide release rate (μmolCO2m -2 s -1 ) in respiration is the photosynthetic rate (μmolCO2m -2 s -1 ). The PPFD (photosynthetically active photon flux density, described later) at which the photosynthetic rate becomes zero is the light compensation point (Figure 1). The value of the light compensation point varies depending on the plant species.

[0015] Light intensity in photosynthesis is defined as the number of photons irradiating the leaf surface per unit area per second. This is called Photosynthesis Photon Flux Density, hereinafter abbreviated as PPFD.

[0016] When water and carbon dioxide are sufficiently supplied, glucose production increases proportionally to PPFD up to a certain saturation point. The light intensity at which glucose production saturates is defined as the photosynthetic saturation light intensity. To promote plant growth, light at approximately the photosynthetic saturation light intensity is necessary. The "light saturation point" in Figure 1 corresponds to the photosynthetic saturation light intensity.

[0017] When the amount of light irradiated falls below the photosynthetic saturation intensity, artificial light such as LED light may be used to compensate for the lack of light. This method of compensating for a lack of light is called "supplementary lighting." Supplementary lighting is a method that directly increases photosynthesis. It is also possible to refer to artificial light that directly increases photosynthesis as "supplementary lighting."

[0018] In this embodiment, sunlight (natural light) and artificial supplemental light are referred to as "primary light" for photosynthesis. This primary light is light that directly causes or increases photosynthesis. Primary light is light emitted from sunlight, LEDs, etc., and is the light that primarily carries out photosynthesis.

[0019] <<Growth promotion through additional light>> In this embodiment, supplementary light, different from the primary light, is artificially created and irradiated onto the plants. This supplementary light is referred to as "additional light." The irradiation of this additional light is carried out at predetermined times and for predetermined periods, as will be described in detail later. The additional light is light that indirectly promotes photosynthesis.

[0020] For example, in the plant cultivation method of this embodiment, sunlight or artificial light is used as the primary light for photosynthesis, and additional light is irradiated at any time during the cultivation period from sowing to harvest. The additional light is at least one of the following: light whose light intensity fluctuates periodically (additional signal light) and light whose light intensity changes slowly (additional relaxation light). In some cases, only additional signal light is irradiated as additional light.

[0021] The plant cultivation method of this embodiment is a method of plant cultivation in which this additional light is irradiated at any time of day, wherein the light intensity (PPFD) of the additional light is periodic, the period of variation is 8 μs or more and 200 μs or less, the wavelength of the periodic fluctuating light is 220 nm or more and 2000 nm or less, and the duty cycle of the periodic fluctuating light is 0.2 or more. These points will be described later.

[0022] The following explains the mechanism by which additional light with periodically changing light intensity (PPFD) promotes photosynthesis.

[0023] Plants are known to have a light accumulation function, accumulating the intensity and duration of sunlight exposure each day. When a decrease in PPFD (Photon Photon Diffusion Factor) in primary light is detected by this accumulation function, the DNA in the plant's chloroplasts sends a signal to increase chlorophyll production in the photoantenna. This increases light absorption and promotes photosynthesis.

[0024] In this embodiment, we utilize the differential function inherent in plants that detects the rate of change in light intensity. The most efficient way to stimulate the differential function of plants is with pulsed light (signal light) that repeatedly turns on and off at regular time intervals. This pulsed light (signal light) will be referred to as "additional signal light" below. Additional signal light is the light included in the additional light. In this embodiment, this additional signal light is irradiated onto the plant either alone or together with the additional relaxation light.

[0025] The additional signal light is insufficient to induce photosynthesis compared to the primary light. Therefore, the plant recognizes a temporary state of photosynthetic starvation. When DNA detects this starvation, it issues a command to increase chlorophyll production in order to absorb more light necessary for photosynthesis. Furthermore, the additional signal light triggers the DNA to issue commands to control the opening and closing of stomata, which are the entry and exit points for outside air, thereby increasing carbon dioxide absorption. As a result, the additional pulsed light irradiation increases the amount of light energy and carbon dioxide absorbed that are necessary for photosynthesis. In other words, in this embodiment, the additional signal light functions as a trigger signal to cause DNA to issue commands for increased chlorophyll production and stomatal opening and closing. This effect of the additional signal light is defined as the DNA trigger effect of the additional signal light.

[0026] The DNA trigger effect increases proportionally to the number of triggers per unit time, but does not depend on the strength of the trigger signal. If the time interval between trigger signals becomes too short, the DNA trigger effect decreases. In addition, the photosynthesis-promoting effect from additional light, including additional signal light, can be obtained regardless of the value of the primary light's PPFD.

[0027] Figure 2 shows a comparison between the pulsed light in the invention disclosed in the aforementioned Patent Document 1 (prior art) and the additional signal light of this embodiment. The graph on the left in Figure 2 shows the prior art, and the graph on the right shows this embodiment. The graphs on the left and right in Figure 2 show the time change of the number of photons incident on the leaf surface (representing the photosynthetic effective quantum flux density (PPFD)).

[0028] As shown in the left-hand graph of Figure 2, in the prior art, the pulse shape of the photon number (photosynthetic effective quantum flux density, PPFD) is rectangular, showing a steep rise and fall. In the left-hand graph of Figure 2, T represents the pulse period, and ΔT represents the pulse width. The period T is the minimum time during which the additional signal light blinks repeatedly, and the value of T is 2 μs. <T<500μsである。

[0029] The value of photon flux (photosynthetically active photon flux density, PPFD) satisfies 0.001 < PPFD < 4.0, and the unit of photon flux (photosynthetically active photon flux density, PPFD) is μmol·m -2 ·s -1 . The pulse duty ratio (ΔT / T) satisfies ΔT / T < 0.2.

[0030] In contrast, in the present embodiment shown in the graph on the right side of FIG. 2, the pulse shape of the additional signal light is trapezoidal, and exhibits gentler rising and falling edges compared to the pulses of the prior art. The period (fundamental period) of the additional signal light is T, the rise time of one pulse is ΔT1, the peak time is ΔT2, and the fall time is ΔT3. Among these, the light intensity during ΔT1 and ΔT3 changes over time. The slope of the time change during ΔT1 and ΔT3 may be the same between ΔT1 and ΔT3, or may be different. Furthermore, the slope during ΔT1 and ΔT3 may be changed in the middle of ΔT1 and ΔT3. Examples of forms in which the slopes during ΔT1 and ΔT3 are made different in the middle include forming the waveform in ΔT1 and ΔT3 into, for example, a curved shape (bow shape, arc shape, wavy shape, etc.), a step shape (step difference shape, staircase shape, etc.), and the like.

[0031] According to experiments conducted by the inventors, the photosynthesis promotion effect by the additional light is obtained when the period T of the additional signal light satisfies 8 μs < T < 200 μs. Furthermore, with respect to ΔT1 and ΔT3 before and after the peak time ΔT2, the effect is obtained when either one of them is 5 μs or less.

[0032] Pulsed light of the prior art (the rectangular wave light on the left side of FIG. 2) changes in intensity within a relatively short period of time, and thus acts as stress caused by light irradiation (light stress) on plants. In contrast, light such as the additional signal light of the present embodiment (the trapezoidal wave on the right side of FIG. 2) is light whose intensity periodically fluctuates similarly to the pulsed light of the prior art. However, since a period ΔT1 in which light intensity increases with a slope and a period ΔT3 in which light intensity decreases with a slope are added on the waveform, the change in light intensity is gentler compared to the prior art. Therefore, the light stress perceived by plants can be alleviated.

[0033] In the present embodiment, in addition to the above, additional relaxation light, which is light whose intensity changes more gradually than the additional signal light (on the left side of FIG. 2), is combined with the additional signal light in accordance with a desired photosynthesis promotion effect. As shown on the right side of FIG. 4, the additional relaxation light has a sinusoidal waveform, and its fundamental period is 1 ms or more. The period of the additional signal light satisfies 8 μs < T < 200 μs, and the fundamental period of the additional relaxation light is 125 to 2 times or more the period T of the additional signal light. The additional relaxation light can also be described as light exhibiting a waveform having a smaller rate of change related to intensity gradient (light intensity change rate) than the additional signal light. Furthermore, the additional relaxation light can also be described as light whose overall light intensity change rate is more gradual than that of the additional signal light, when compared with the additional signal light using a one-cycle waveform as shown in FIG. 4. The additional relaxation light is light for mitigating the influence of side effects of the additional signal light, whose intensity changes relatively abruptly, such as the inhibition of plant growth caused by strong light stimulation. Therefore, the temporal change in intensity of the additional relaxation light must be more gradual than the temporal change in light intensity of the additional signal light.

[0034] As described above, by irradiating plants with additional light obtained by combining additional signal light with additional relaxation light, light stress perceived by plants can be further mitigated compared to the case where the additional signal light is irradiated alone. That is, the additional light according to the present embodiment is light obtained by combining the additional signal light and the additional relaxation light, which can improve the light stress reduction effect of the additional light as much as possible.

[0035] The additional signal light is light that repeatedly turns on and off at an arbitrary cycle. The additional relaxation light is light with a substantially constant intensity. In the present embodiment, the additional relaxation light may sometimes contain a slight amount of ripple at a frequency of approximately 60 Hz.

[0036] The additional signal light of this embodiment is thought to reduce light stress on plants more effectively than the pulsed light of the prior art. However, by adding other forms of light (in this case, additional relaxation light) in addition to the additional signal light of this embodiment, the light stress that the additional light imparts to plants can be reduced more effectively.

[0037] To minimize photostress caused by additional signal light, it is desirable that the PPFD of the additional relaxation light be equal to or greater than that of the additional signal light. The wavelength ranges (wavelength bands) of the additional signal light and the additional relaxation light may be the same or different. In either case, there will be a photosynthesis-promoting effect. However, it is desirable that the wavelength bands of the additional signal light and the additional relaxation light have some overlap (at least some overlapping wavelength bands).

[0038] Plants are sensitive to temporal changes in light intensity. Therefore, when supplemental signal light and supplemental relaxation light are simultaneously shone on a plant, the plant preferentially detects photosynthesis caused by the supplemental signal light. This plant response is defined as the cocktail party effect in plant light detection.

[0039] When photosynthesis weaker than that induced by primary light occurs periodically, the plant recognizes this as a state of photosynthetic starvation, and its DNA signals the light antenna to synthesize chlorophyll. As a result, the efficiency of light utilization for photosynthesis improves, and the rate of photosynthesis increases even if the primary light (PPFD) of sunlight or artificial light remains constant. This increase in the rate of photosynthesis can also be observed when only supplemental signal light is irradiated.

[0040] The photosynthesis-promoting effect and a more stable growth-promoting effect can be achieved by superimposing additional relaxation light, which changes more slowly than additional signal light. Since additional signal light is light that provides a trigger signal to DNA, there are no restrictions on PPFD. On the other hand, it is desirable that the PPFD of the additional relaxation light be equal to or greater than that of the additional signal light.

[0041] Figure 3 illustrates the effect of pulsed light (additional signal light) on promoting biomass and useful substance production. As shown on the right side of the upper panel of the figure, additional signal light is irradiated onto plants (shown as leaves in Figure 3) in addition to primary light such as sunlight, promoting photosynthesis (indicated by the circled number 1). The increased glucose is then distributed under controlled distribution ratios to the translocation pathway (indicated by the circled number 2) used in basal metabolism for maintaining life, and to the secondary metabolic pathway (indicated by the circled number 3). In each pathway, glucose is converted into biomass and useful substances.

[0042] Thus, in addition to promoting photosynthesis, additional signal light has the effect of controlling the distribution ratio of glucose to the translocation pathway and secondary metabolic pathway.

[0043] The additional signal light may be irradiated at any time within the 24-hour period of a day, or at a predetermined time. The wavelength of the additional signal light may be any wavelength range from ultraviolet to infrared, not just visible light. Photosynthesis-promoting effects can be obtained in this wavelength range. Generally, shorter wavelengths result in a greater biomass increase effect, while longer wavelengths result in a greater secondary metabolism-promoting effect. In particular, light with wavelengths longer than 680 nm has a significant secondary metabolism-promoting effect.

[0044] The photosynthesis-promoting effect persists not only while the additional signal light is being applied, but also after the application is complete (promoting cultivation in high-speed growth mode). Therefore, by applying the additional signal light at any time from sowing to harvest, a growth-promoting effect can be obtained. Furthermore, the growth-promoting effect can be obtained even after the application is complete.

[0045] Furthermore, when additional signal light and additional relaxation light are irradiated simultaneously, the additional relaxation light mitigates the photostress caused by the additional signal light. In addition, each leaf has a top and bottom surface. Therefore, irradiating the same surface of the leaf (top or bottom surface) with additional light is desirable to maximize growth promotion.

[0046] When irradiating the same side of a leaf with additional signal light and additional relaxation light, the direction of irradiation does not necessarily have to be the same. For example, additional signal light and additional relaxation light may be irradiated from different directions onto the same leaf surface (upper or lower surface). However, to maximize growth promotion, it is desirable to irradiate the same side of the leaf with additional signal light and additional relaxation light.

[0047] The plant cultivation method according to this embodiment is effective for photosynthesis in all types of plants. Therefore, it can be applied to promoting the growth of leafy vegetables, root vegetables, flowers, fruit trees, seaweed, algae, and microalgae. Furthermore, it is effective for plant cultivation in fields, greenhouses, plant factories, smart cells (smart cell industry, biological material production), land-based aquaculture, on the sea surface, underwater, and in mountainous and hilly areas.

[0048] <Plant cultivation equipment 10> Figure 5 shows a schematic configuration of the plant cultivation device 10 according to this embodiment. The plant cultivation device 10 comprises a cultivation bed 12 for hydroponics or soil cultivation, a light irradiation unit 14 that irradiates light toward the cultivation bed 12, and an irradiation light control unit 16 that drives the light irradiation unit 14 to light up. The plant cultivation device 10 has a protective member 18 that covers the cultivation bed 12 and forms a cultivation chamber. The protective member 18 can be omitted.

[0049] The light irradiation unit 14 includes a main light source 20 that irradiates with main light and an additional light source 22 that irradiates with additional light. The main light source 20 and the additional light source 22 are individually driven and controlled by the irradiation light control unit 16 (current control in this case). In Figure 5, the main light source 20 and the additional light source 22 are shown side by side, but the light from the main light source 20 and the light from the additional light source 22 are irradiated toward the cultivation bed 12 via a similar path through a diffuser plate (which may also be a diffuser lens) not shown. The light from the additional light source 22 may be irradiated toward the cultivation bed 12 via an optical fiber not shown. An end-face emitting or side-emitting optical fiber can be used as appropriate.

[0050] The main light source 20 is continuously lit for a predetermined time and continuously emits the main light (also called "continuously irradiated light"). The main light source 20 can be an artificial light source such as an LED, fluorescent lamp, plasma lamp, mercury lamp, incandescent bulb, metal halide lamp, sodium lamp, or an electrodeless lamp or pulsed laser.

[0051] It is also possible to use sunlight as another primary light source. When using sunlight, it is possible to not use the primary light source 20 or to omit the primary light source 20. It is also possible to use sunlight and the light from the primary light source 20 in combination. In this case, the light from sunlight and the light from the primary light source 20 may be used interchangeably depending on conditions such as the time of day. Furthermore, it is possible to emit sunlight and the light from the primary light source 20 simultaneously.

[0052] The additional light source 22 includes an additional signal light source 24 and an additional relaxation light source 26. The additional signal light source 24 emits additional signal light, and the additional relaxation light source 26 emits additional relaxation light. The additional signal light and additional relaxation light constitute additional light (Figure 4).

[0053] In Figure 5, the additional signal light source 24 and the additional relaxation light source 26 are shown side by side. The additional signal light and the additional relaxation light are irradiated toward the cultivation bed 12 via a similar path through a diffuser plate (which may also be a diffuser lens) not shown in the figure. The additional light source 22 may be an integrated unit combining the additional signal light source 24 and the additional relaxation light source 26.

[0054] The additional light source 22 can emit light in the wavelength range of 220 nm to 2000 nm using the additional signal light source 24. The additional signal light source 24 can emit light of a wavelength suitable for the growth of the target plant, and various light sources such as LEDs, electroluminescent (EL), lasers, ultraviolet light, and infrared light can be used. Furthermore, it is desirable to use a light source that allows for easy pulse-on control for the additional signal light source 24. As the additional relaxation light source 26, various light sources such as cold cathode fluorescent lamps, monochromatic LED lamps, and LED fluorescent lamps driven by a power line (50 Hz or 60 Hz) can be used.

[0055] Although not shown in the diagram, the additional light source 22 may be equipped with a continuously emitting light source and a shutter placed in the optical path. In this case, the shutter intermittently blocks the optical path to form signal light. It is also possible to attach a wavelength limiting filter to the white light source to form light of the required wavelength. The shutter and filter may be provided for both the additional signal light source 24 and the additional relaxation light source 26.

[0056] The light irradiation unit 14 is installed on the ceiling or side walls of the protective member 18, or on the columns installed in the cultivation bed 12, etc. The light irradiation unit 14 illuminates the cultivation bed 12 in response to commands from the irradiation light control unit 16.

[0057] The light irradiation unit 14 can be equipped with multiple main light sources 20 and multiple additional light sources 22. In this case, multiple main light sources 20 and multiple additional light sources 22 can be arranged at different positions and with different irradiation angles. For example, multiple main light sources 20 and multiple additional light sources 22 can be arranged alternately. It is also possible to have multiple main light sources 20 and one additional light source 22 (or one main light source 20 and multiple additional light sources 22). It is also possible to install the additional light sources 22 so that light is irradiated onto the cultivation bed 12 from multiple directions. In this way, a more stable growth promotion effect can be obtained.

[0058] In this way, by providing multiple main light sources 20 and / or multiple additional light sources 22, it becomes possible to perform more precise light irradiation. Furthermore, by varying the arrangement and irradiation angles of the multiple light sources, the plants in the cultivation bed 12 can be uniformly irradiated with light, and uneven growth depending on the location can be suppressed.

[0059] The irradiation light control unit 16 drives the light irradiation unit 14 to light up based on the plant cultivation method of this embodiment. The irradiation light control unit 16 can drive only the main light source 20 to light up, drive only the additional light source 22 to light up, or drive both the main light source 20 and the additional light source 22 to light up simultaneously.

[0060] If the light irradiation unit 14 is equipped with multiple main light sources 20 and / or multiple additional light sources 22, the irradiation light control unit 16 can synchronize the illumination of the same type of light sources. Furthermore, if the cultivation bed 12 is divided into multiple blocks (test plots), the irradiation light control unit 16 can individually control the main light sources 20 and additional light sources 22 in each block.

[0061] The irradiation light control unit 16 may synchronize the main light source 20 and the additional light source 22 on a block-by-block basis, or it may synchronize the main light source 20 and the additional light source 22 of multiple blocks or all blocks. By synchronizing the additional signal light in the additional light source 22, the duty cycle of the additional signal light irradiated onto the plants can be accurately maintained.

[0062] Such a plant cultivation device 10 can be widely applied to various applications, including small cultivation kits for easy indoor cultivation in ordinary households, agricultural greenhouses, and large-scale plant factories with constructed cultivation rooms.

[0063] Here, an agricultural greenhouse can refer to an agricultural vinyl greenhouse in which a light-transmitting film is stretched across the entire surface of the greenhouse, or an agricultural glass greenhouse in which the film is stretched and spread across the entire inside surface of the glass windows. In an agricultural glass greenhouse, moisture-laden air in the cultivation space inside the greenhouse passes through the film and escapes to the outside of the greenhouse through the gaps between the glass windows and the frame of the glass windows. Therefore, even in an agricultural glass greenhouse, it is possible to suppress the temperature and humidity inside the greenhouse. The "light-transmitting" mentioned above refers to the property of allowing light necessary for growing plants to pass through during the day.

[0064] When an additional light source (in this case, additional light source 22) is installed inside an agricultural greenhouse, some of the additional light is reflected and diffused (reflective diffusion) by glass plates, resin plates, resin films, etc., which has the advantage of increasing the irradiation efficiency of the additional light. Similar effects of improving irradiation efficiency can be obtained in small cultivation kits and plant factories.

[0065] Furthermore, we can consider the effective direction of irradiation for additional light (additional signal light and / or additional relaxation light). Whether the additional light is irradiated from the same direction as the primary light or from a different direction, a growth-promoting effect can be obtained in either case. Moreover, if additional light is irradiated in areas where the primary light does not reach sufficiently (for example, the upper and lower surfaces of leaves in shaded areas, or the undersides of leaves in sunny areas), an even greater growth-promoting effect can be obtained.

[0066] Specifically, for plants with horizontally growing branches, such as grapes, additional light is shone from the ground upwards (including diagonally upwards). In this case, the amount of light reaching the underside of leaves (the side facing the ground) in the shade increases. As a result, photosynthesis is more vigorous compared to when no additional light is shone, and the grapes become sweeter. In this way, by setting the direction of the additional light according to the environment in which the plants are grown and the characteristics of the plants, plant growth can be promoted more effectively. For example, in tomato cultivation, it is also effective to install side-emitting optical fibers in the bushes to shone additional light.

[0067] <Comparison of Prior Art and This Embodiment> Table 1 below compares the prior art (technical matters disclosed in the aforementioned Patent Document 1) with the basic technical matters of the plant cultivation method according to this embodiment. [Table 1]

[0068] As shown in Table 1, the primary light source in both the prior art and this embodiment is sunlight and artificial light (such as LEDs). The period of the additional signal light is 8 μs to 500 μs in the prior art and 8 μs to 200 μs in this embodiment. The duty cycle of the additional signal light is restricted to 20% or less in the prior art, whereas there is no restriction in this embodiment.

[0069] Photosynthetic photon density (μmol·m) of additional signal light -2 ·s -1 In the prior art, there is a constraint of 0.001 to 4.0, whereas in this embodiment there is no such constraint. In the prior art, there is one type of light added to the principal light, while in this embodiment there are two types: additional signal light and additional relaxation light. In the prior art, the wavelength range is 400 nm to 500 nm, while in this embodiment it is 220 nm to 2000 nm.

[0070] The irradiation period in the prior art is the growth period after transplanting, while in this embodiment it is any period (including the entire period) from sowing to the seedling stage and the growth period. The period from sowing to transplanting is defined as the seedling stage, and the period from transplanting to harvesting is defined as the growth period.

[0071] The irradiation time during the day differs between the prior art, which uses nighttime hours, and this embodiment, which uses any time within the 24-hour day. The technical effect of the prior art is that it enables the promotion of growth and the increase of useful components, while this embodiment enables individual control of growth and the production of useful components.

[0072] Furthermore, although not shown in Table 1, in prior art, pulsed light provides a relatively strong stimulus to plants. Also, because the pulsed light wavelength range is limited to the blue wavelength range, it is difficult for the light to reach hidden leaves in situations where leaves overlap. Moreover, it is difficult to individually control growth and secondary metabolism (independently controlling growth rate and the production of useful substances).

[0073] In contrast, in this embodiment, the superposition of flashing light (additional signal light) and slowly changing light (additional relaxation light) results in less stimulation to the plants compared to the prior art. Furthermore, the plant cultivation method and plant cultivation apparatus 10 of this embodiment allow for individual control of growth and secondary metabolism. Individual control of growth and secondary metabolism is possible by changing the wavelength and light intensity of the additional signal light and additional relaxation light.

[0074] This embodiment is merely one example of how the present invention can be implemented, and the technical scope of the invention should not be interpreted as being limited by it. In other words, the present invention can be implemented in various forms without departing from its gist or its main features. <Various examples of plant cultivation methods>

[0075] Embodiments of the present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following description.

[0076] <Example 1> In Example 1, the effect of additional light irradiation on lettuce growth was investigated. First, lettuce seeds were sown in a water-soaked sponge and stored in a dark place for 3 days, then exposed to primary light for 7 days to grow seedlings. Next, these seedlings were transplanted into a hydroponic cultivation kit and grown for 28 days. During cultivation, the temperature was maintained at 22°C and the humidity at 40-50%. Hyponex (registered trademark: liquid fertilizer manufactured by Hyponex Japan Co., Ltd.) was used as liquid fertilizer, diluted 1000 times.

[0077] The lettuce was irradiated with two types of light: primary light and supplemental light. The supplemental light was a combination of supplemental signal light and supplemental relaxation light. Within a 24-hour day, the primary light was applied from 0:00 to 12:00, and the supplemental light was applied from 6:00 to 14:00. The PPFD (μmol·m³) of each light was measured. -2 ·s -1 The values ​​were: principal light 220, additional signal light 0.01, and additional relaxation light 0.01. The primary light was applied from the 3rd day after sowing until the 38th day, and the supplemental light was applied from the 10th day after transplanting until the 38th day.

[0078] In the following, the experiment in which plants were grown using only primary light will be referred to as the control (and may be abbreviated as "CNT" from now on), and the experiment in which additional light was applied will be referred to as the comparative experiment.

[0079] In this Example 1, the following three types of comparative tests, "1." to "3.", were conducted. 1. Comparative Test 1: Additional light with a wavelength range of 350 nm to 600 nm was irradiated. 2. Comparative Test 2: Additional light with a wavelength range of 600nm to 800nm ​​was irradiated. 3. Comparative Test 3: Additional light was irradiated in the wavelength ranges of 380nm to 500nm and 670nm to 1000nm.

[0080] In the comparative tests 1 to 3 described above, the parameters of the additional signal light were fixed to the following values. T=25μs, ΔT1=2μs, ΔT2=2μs, ΔT3=2μs Here, T, ΔT 1、 ΔT 2、 And ΔT3 is 、 This has the same meaning as explained for Figure 2.

[0081] The plants were harvested 38 days after sowing, and the wet weight of the harvested portion, excluding the roots, was measured. The wet weight ratio was calculated using the following formula (1). The wet weight was determined from the average value of 5 plants. [Yield wet weight ratio] = Yield wet weight of the test plot / Yield wet weight of the control (CNT) (1) The weight of ascorbic acid (vitamin C) per gram of harvested wet weight of lettuce was quantitatively analyzed using a high-performance liquid chromatography (HPLC) apparatus. The ascorbic acid ratio was calculated using equation (2). [Ascorbic acid weight ratio] = Weight of ascorbic acid in the test group / Weight of wet ascorbic acid in the control (CNT) (2) The total weight ratio of ascorbic acid contained in lettuce was calculated using the following formula (3). [Total weight ratio of ascorbic acid] = [Wet weight ratio of harvested produce] x [Weight ratio of ascorbic acid] (3)

[0082] Table 2 shows the calculation results for the harvest wet weight ratio, ascorbic acid weight ratio, and total ascorbic acid weight ratio in each comparative experiment. [Table 2]

[0083] According to Example 1, the results of the "harvested wet weight ratio" and "ascorbic acid weight ratio," which represent the ratio with the control (CNT), show that additional light irradiation has the effect of increasing the harvested wet weight of lettuce and the secondary metabolite, ascorbic acid. Furthermore, from the results of Comparative Test 1 and Comparative Test 2, it is shown that the shorter the wavelength of additional light irradiation, the more it increases the harvested weight, and the longer the wavelength, the more it increases secondary metabolism.

[0084] <Example 2> In Example 2, the effect of additional signal light irradiation on lettuce growth was investigated. First, lettuce seeds were sown in a water-soaked sponge and stored in a dark place for 3 days, then exposed to primary light for 7 days to grow seedlings. Next, these seedlings were transplanted into a hydroponic cultivation kit and grown for 10 days. During cultivation, the temperature was maintained at 22°C and the humidity at 40-50%. Hyponex (registered trademark: liquid fertilizer manufactured by Hyponex Japan Co., Ltd.) was diluted 1000 times and applied as liquid fertilizer.

[0085] The lettuce was irradiated with two types of light: primary light and supplemental light. Within a 24-hour day, the primary light was applied from 0:00 to 12:00, and the supplemental light was applied from 10:00 to 18:00. The primary light was applied for 20 days from sowing, and the supplemental light was applied for 10 days from sowing until transplanting. PPFD (μmol·m) of the main light -2 ·s -1The settings were set to 220 for the 10 days leading up to transplanting, and to 20 for the 10 days following transplanting. Additional light PPFD (μmol·m -2 ·s -1 For the additional signal light, the setting was 0.01, and the additional relaxation light was set to 0.02. Irradiation was carried out for 10 days from sowing. The parameters of the additional signal light were fixed to the following values. T=30μs, ΔT1=2μs, ΔT2=2μs, ΔT3=5μs

[0086] A comparative test (Comparative Test 1) was conducted under the following conditions. Comparative test 1: Additional light with a wavelength range of 400 nm to 600 nm was irradiated. The results of comparative experiment 1 showed no significant difference in wet weight at planting between the control (CNT) group and the group irradiated with additional signal light.

[0087] Figure 6 shows a comparison of the external appearance of lettuce harvested in Comparative Experiment 1. The lettuce on the left side of Figure 6 (experimental plot, irradiation during seedling stage) is from the experimental plot irradiated with primary light and additional light (additional signal light and additional relaxation light), while the lettuce on the right side of Figure 6 (control, no irradiation during seedling stage) is from the experimental plot irradiated with primary light only. The lettuce from Comparative Experiment 1 (left side of Figure 6) is significantly larger than the CNT (right side of Figure 6). The plants were harvested 20 days after sowing, and the wet weight of the harvested portion, excluding the roots, was measured. The harvested wet weight was determined from the average value of 5 plants. The wet weight ratio was calculated using equation (1) as explained in Example 1. In Comparative Test 1 of Example 2, the harvested wet weight ratio was 22 ± 0.1.

[0088] According to this embodiment 2, when additional light (additional signal light and additional relaxation light) is irradiated only during the period from sowing to transplanting, the PPFD subsequently increases to 20 (μmol·m³). -2 ·s -1 It was found that growth is promoted even under the main light source of ) The light compensation point for lettuce is PPFD = 20 (μmol·m²). -2 ·s-1 ) is approximately 20 (μmol·m³). Therefore, PPFD is 20 (μmol·m³). -2 ·s -1 Even when exposed to the primary light source, lettuce cannot grow sufficiently. This second embodiment provides evidence that the promoting effect persists even after additional light irradiation for a certain period of time.

[0089] <Example 3> In Example 3, the effect of the period of additional signal light (additional signal light period) on the growth of lettuce was investigated. First, lettuce seeds were sown in a water-soaked sponge and stored in a dark place for 3 days, then exposed to primary light for 7 days to grow seedlings. Next, these seedlings were transplanted into a hydroponic cultivation kit and grown for 28 days. During cultivation, the temperature was maintained at 22°C and the humidity at 40-50%. Hyponex (registered trademark: liquid fertilizer manufactured by Hyponex Japan Co., Ltd.) was diluted 1000 times and applied as liquid fertilizer.

[0090] The primary light was applied from day 3 to day 38 after sowing, and the supplemental light was applied from day 10 to day 38 after transplanting. Within a 24-hour day, the primary light was applied from 0:00 to 12:00, and the supplemental light was applied from 6:00 to 14:00. The PPFD (μmol·m³) of each light was measured. -2 ·s -1 The values ​​were 220 for the principal light, 0.15 for the additional signal light, and 0.01 for the additional relaxation light. The wavelength range of the additional signal light was 380 nm to 600 nm. The wavelength range of the additional relaxation light was 500 nm to 680 nm. In the control (CNT), only the principal light was irradiated. The PPFD of the principal light was 0.15 (μmol·m³). -2 ·s -1 )

[0091] In the comparative test, the PPFD of the additional signal light was set to 0.05 (μmol·m³). -2 ·s -1The temperature was fixed, and T was varied from 8 μs to 500 μs for comparative tests 1 to 6. The parameters of the additional signal light changed as follows: ΔT1 = 1 μs, ΔT2 = 1 μs, ΔT3 = (T-2) μs. The duty cycle of the additional signal light was 1.0. The PPFD of the additional relaxation light was 0.10 (μmol·m³). -2 ·s -1 It was fixed in place.

[0092] Table 3 shows the test results for Example 3. [Table 3]

[0093] This third embodiment revealed that the harvested wet weight of lettuce depends on the period of the additional signal light (see the values ​​in "Wet Weight Ratio"), and that T increases in the range of 8 to 200 μs. Furthermore, it was found that the greatest effect was obtained when T was in the range of 8 μs to 100 μs.

[0094] <Example 4> In Example 4, the effect of additional light irradiation on the growth of Euglena was investigated. Euglena gracilis was placed in a flask filled with a 1000-fold diluted aqueous solution of Hyponex®. The water temperature was maintained at 27°C. The initial concentration of Euglena was 1 μg / L. Four flasks were prepared, and the same amount of Euglena was placed in each flask. The Euglena was cultivated for 10 days.

[0095] Within a 24-hour day, the primary light was applied from 0:00 to 12:00, and the supplemental light was applied from 6:00 to 13:00. Additional light PPFD (μmol·m -2 ·s -1 The additional signal light was set to 0.001 and the relaxation light to 0.002. The parameters for the additional signal light were set to T=8μs, ΔT1=1μs, ΔT2=1μs, and ΔT3=1μs. Flask 1 was used as the control (CNT) test group, while flasks 2, 3, and 4 were used as the comparative test groups.

[0096] After 10 days of light irradiation, the size, number of individuals, and paramylon content of Euglena were measured. The population ratio was calculated using equation (4) below, based on the measurement results of the number of individuals and the paramylon content. The paramylon content ratio was calculated using equation (5) below. [Population ratio] = Number of individuals in the test plot / Number of control individuals (4) [Paramylon weight ratio] = Paramylon weight of the test group / Paramylon weight of the control group (5) The size of individual Euglena particles remained almost the same regardless of the test conditions.

[0097] Table 4 shows the parameters, population ratios, and paramylon ratios for the primary and supplemental lights. [Table 4]

[0098] In this embodiment 4, both the "number ratio" and the "paramylon weight ratio" increased compared to the control (CNT) in all comparative tests. Therefore, the additional light has the effect of promoting the growth of the microalga Euglena and paramylon synthesis. In Table 4, the PPFD of the primary light is indicated by "-" for comparative tests 4-1 to 4-3. The additional light is irradiated in addition to the primary light, and as mentioned above, the primary light was irradiated from 0:00 to 12:00 for comparative tests 4-1 to 4-3 in Table 4.

[0099] <Example 5> In Example 5, the effect of the presence or absence of additional light during the seedling stage of red perilla on its growth after transplanting to the field (field transplanting) was investigated. The seedling stage has the same meaning as explained in Example 2, and is the period from sowing to growing seedlings to a certain size. The field is a farm where cultivation is carried out using sunlight. The seedling stage lasted 10 days, and the field cultivation period lasted 60 days. During the seedling stage, a comparative experiment was conducted using a control group (CNT) irradiated only with primary light, and a control group irradiated with primary light and supplemental light. During the 24-hour day, primary light was applied from 6:00 AM to 6:00 PM, and supplemental light from 3:00 PM to 11:00 PM. After transplanting to the field, cultivation was carried out using only sunlight.

[0100] The harvest weight ratio and anthocyanin weight ratio were calculated from the harvest weight and anthocyanin pigment weight of red perilla using the following equations (6) and (7). [Yield weight ratio] = Yield weight of experimental plot / Yield weight of control plot (6) [Anthocyanin weight ratio] = Anthocyanin weight of the test group / Anthocyanin weight of the control group (7)

[0101] Table 5 shows the parameters for primary and supplemental light, harvest weight ratio, and anthocyanin weight ratio. [Table 5]

[0102] In field cultivation, red perilla seedlings that received additional light only during the seedling stage showed a 1.7 to 1.8 times increase in harvest weight and a 1.6 to 1.7 times increase in anthocyanin weight compared to control seedlings.

[0103] According to Example 5, additional light irradiation during the seedling stage of red perilla cultivation has the effect of promoting both growth and secondary metabolite synthesis when the plants are subsequently transplanted to the field and cultivated in the field using sunlight. For details on the promotion of growth, please refer to the results of each test under "Yield Weight Ratio" in Table 5. For details on the promotion of secondary metabolite synthesis, please refer to the results of each test under "Anthocyanin Weight Ratio" in Table 5. In Table 5, the PPFD of the primary light is indicated by "-" for comparative tests 5-1 and 5-2. Additional light is irradiated in addition to the primary light, and as mentioned above, primary light irradiation is also performed in comparative tests 5-1 and 5-2 in Table 5.

[0104] <Example 6> In Example 6, the effect of the presence or absence of mitigating light on lettuce growth was investigated. During the lettuce seedling stage, the seedlings were grown by irradiating them with only primary light for 10 days. Seedlings were transplanted into hydroponic cultivation kits, and a control test was conducted over a 28-day period with irradiation using only primary light, and a comparative test was conducted with irradiation using both primary and supplemental light. The cultivation environment for the lettuce was set to be the same as in Example 1. The wet weight ratio of the harvested lettuce was calculated using the same method as in Example 1. The parameters for the additional signal light were set to T=40μs, ΔT1=2μs, ΔT2=1μs, and ΔT3=2μs.

[0105] Table 6 shows the PPFD of the principal light at 10 (μmol·m³). -2 ·s -1 The parameters of primary and supplemental light and the ratio of harvested wet weight are shown. It can be seen that lettuce growth is significantly inhibited in an environment without restorative light. [Table 6]

[0106] Table 7 shows the PPFD of the principal light at 20 (μmol·m³). -2 ·s -1 The parameters of primary and supplemental light and the ratio of harvested wet weight are shown. This indicates that the presence of restorative light results in a 1.6 times greater growth effect compared to the control. [Table 7]

[0107] This embodiment 6 demonstrates that relaxation light has the effect of mitigating the photostimulation of signal light. In comparative test 6-1 in Table 6, the PPFD of the principal light is indicated by "-". Similarly, in comparative test 6-2 in Table 7, the PPFD of the principal light is indicated by "0". Additional light is irradiated in addition to the principal light, and as mentioned above, the principal light is also irradiated in Tables 6 and 7.

[0108] <Timing of additional mitigation light irradiation> As explained previously, additional light consists of at least one of additional signal light and additional relaxation light. Therefore, irradiation with additional relaxation light does not necessarily have to be done at the same time as with additional signal light. Even if additional relaxation light is irradiated after additional signal light (for example, immediately after or several hours later), the effect of promoting plant growth can still be obtained.

[0109] <Cultivation carried out in multiple stages> <<Seedling Growth>> According to the inventors' findings, additional light has the effect of promoting the growth of all types of plants. Therefore, irradiating a field with additional light may promote the growth of not only the target plants but also the non-target plants. In field cultivation, non-target plants are generally called weeds. In field cultivation, there is competition for survival between the target plants and weeds. If weeds proliferate, the growth of the target plants may be inhibited. To prevent this, it is best to divide cultivation into two stages: seedling cultivation and field cultivation.

[0110] First, in the first stage, additional light is irradiated during seedling growth (step (S)1 in Figure 7), and the seedlings are grown in high-speed growth mode (S2). Then, in the first stage, after the irradiation of additional light (S1) is completed, the seedlings are grown in high-speed growth mode (S2).

[0111] Here, "high-speed growth mode" refers to a state in which plant growth is promoted even after the irradiation of additional light has ended. In other words, as mentioned above, the photosynthesis-promoting effect continues not only while the additional signal light is being irradiated, but also after the irradiation is completed. Therefore, by irradiating with additional signal light at any time from sowing to harvest, a growth-promoting effect can be obtained. This is also supported by the aforementioned Examples 2 and 5.

[0112] Next, in the second stage, seedlings grown in high-speed growth mode are transplanted to the field (S3), and the seedlings are cultivated using only sunlight (or artificial light), which is the primary light source (S4). This allows for the preferential (selective) promotion of growth only among the target plants. In the example in Figure 7, S1 and S2 belong to the first stage, and S3 and S4 belong to the second stage.

[0113] <<Selective growth of beneficial phytoplankton>> In the aforementioned Example 4, it was shown that additional light irradiation is effective in promoting the growth of Euglena (a type of microalgae). Euglena is a type of phytoplankton.

[0114] More specifically, organisms that perform photosynthesis are generally classified as photosynthetic organisms. Photosynthetic organisms are organisms that convert light energy into a biologically usable form of energy (primarily chemical free energy) to grow. Photosynthetic organisms can be classified as shown in Table 8. [Table 8]

[0115] As described above, the plant cultivation method (photosynthetic organism production method) according to the embodiment of the present invention is effective for photosynthesis in all types of plants, including leafy vegetables, flowers, fruit trees, seaweed, algae, and microalgae. The plant cultivation method (photosynthetic organism production method) according to the embodiment of the present invention is also effective for root vegetables such as potatoes, carrots, burdock, and wasabi. Furthermore, the plant cultivation method (photosynthetic organism production method) according to the embodiment of the present invention is effective for plant cultivation in fields, greenhouses, plant factories, smart cells (smart cell industry, biological substance production), land-based aquaculture, the sea surface, underwater, and mountainous areas. In addition, it is possible to promote the growth of phytoplankton such as Euglena described in Example 4 by additional light irradiation. Furthermore, the plant cultivation device 10 shown in Figure 5 can be referred to as a photosynthetic organism cultivation device or a photosynthetic organism growth device. Furthermore, "growth" in relation to photosynthetic organisms can be rephrased as "production."

[0116] For example, bivalves such as clams and cockles feed on phytoplankton. Some phytoplankton, such as Noctiluca, Ceratium, and Chattonella, are poisonous. When bivalves eat such poisonous phytoplankton, the toxins accumulate in their bodies, making the shellfish toxic. In addition, Chattonella can attach to the gills of fish and suffocate them.

[0117] A diverse range of phytoplankton inhabit freshwater (lakes, rivers, etc.) and saltwater. When freshwater or saltwater is exposed to additional light, not only beneficial phytoplankton but also harmful phytoplankton can proliferate.

[0118] To cultivate only beneficial (non-toxic) phytoplankton for bivalves, it is effective to cultivate them in multiple stages (for example, two stages). First, in the first stage, beneficial, fast-growing phytoplankton are cultivated in a specific environment. In the second stage, beneficial phytoplankton are cultivated in freshwater or seawater.

[0119] In the first stage, additional light irradiation is used to switch only beneficial phytoplankton into a high-speed growth mode (high-speed proliferation mode). In the subsequent second stage, these phytoplankton are released into freshwater or seawater. Through this operation, non-toxic phytoplankton can be preferentially grown in freshwater or seawater from among the various types of phytoplankton.

[0120] Furthermore, by preventing the proliferation of unwanted phytoplankton, it becomes possible to prevent the occurrence of red tides and coral bleaching. These factors make it possible to prevent the decline (depletion) of fishery resources and even increase their numbers. Additionally, by dispersing the cultivated phytoplankton into freshwater or seawater, it becomes possible to accelerate the growth of fishery resources and promote their reproduction. Moreover, by utilizing the water purification function of fishery resources such as shellfish, it becomes possible to conserve and improve the aquatic environment.

[0121] Furthermore, when beneficial algae attach to coral, a symbiotic relationship develops between the coral and the algae, with the products of photosynthesis (photosynthetic products) providing nutrients to the coral. In other words, algae attached to the calcareous surface of the coral perform photosynthesis, and the photosynthetic products are supplied to the coral as nutrients. Therefore, irradiating the coral with additional light promotes the growth of the algae, and as a result, the coral's condition is maintained. By selectively cultivating beneficial types of algae and allowing them to attach to the coral, it becomes possible to protect the coral.

[0122] Furthermore, the growth of photosynthetic organisms through additional light irradiation can also be applied to soil algae. Soil algae mainly include cyanobacteria, green algae, diatoms, and red algae. Soil improvement can be achieved by irradiating soil algae with additional light and then scattering one or more selected types of soil algae onto the soil. In addition to soil algae, it is also possible to grow aquatic algae, as mentioned above, through additional light irradiation and then scatter them onto the soil to improve the soil.

[0123] <<Selective growth of microalgae>> The microalgae Euglena and Chlorella store the polysaccharides paramylon (β-1,3-glucan) and triacylglycerol, respectively, within their cells. Therefore, if Euglena and Chlorella are mixed in a cultivation pond, a new process of separating and purifying their respective stored substances becomes necessary. To avoid this, a technology is needed that allows for the selective cultivation of only one of the microalgae. To achieve this, culturing the microalgae in two stages is effective.

[0124] In other words, in the first stage, either Euglena or Chlorella is switched to a high-speed growth mode (high-speed proliferation mode). In the subsequent second stage, the rapidly proliferating microalgae are introduced into the cultivation pond. As a result, the number of microalgae in the cultivation pond will be dominated by the microalgae that were switched to the high-speed growth mode in the first stage.

[0125] <Microalgae growth device 30> Figure 8 shows a schematic configuration of a microalgae cultivation device (microalgae production device) 30 that can be used for the stepwise growth of microalgae. The microalgae cultivation device 30 is a plant cultivation device for cultivating microalgae and constitutes a plant cultivation system (or microalgae cultivation system). The microalgae cultivation device 30 in the example in Figure 8 is a preferred cultivation device for Euglena. The microalgae cultivation device 30 is capable of preferentially cultivating Euglena.

[0126] The microalgae cultivation apparatus 30 comprises a pre-chamber 32 for the first stage and a cultivation pond 34 for the second stage. The pre-chamber 32 is used to preferentially cultivate only specific microalgae. The pre-chamber 32 is equipped with a culture vessel 36, a water inlet pipe 38, a water outlet pipe 40, a main light source 42, an additional light source 44, and a partition wall 46, etc. In Figure 8, reference numeral 49 indicates the water surface of the culture solution 48 stored in the culture vessel 36.

[0127] As the primary light source 42, a light source device is used that can irradiate primary light in the culture solution 48 in the same way as the primary light source 20 in the plant cultivation apparatus 10 in the example of Figure 5. As the additional light source 44, a light source device is used that can irradiate additional light in the culture solution 48 in the same way as the additional light source 22 in the plant cultivation apparatus 10 in the example of Figure 5. The primary light source 42 and the additional light source 44 constitute the light irradiation section.

[0128] The main light source 42 is continuously lit for a predetermined time and continuously emits the main light (also called "continuously irradiated light"). The main light source 42 can be an artificial light source such as an LED, fluorescent lamp, plasma lamp, mercury lamp, incandescent bulb, metal halide lamp, sodium lamp, or electrodeless lamp.

[0129] It is also possible to use sunlight as another primary light source. When using sunlight, it is possible to not use the primary light source 42 or to omit the primary light source 42. It is also possible to use sunlight and the light from the primary light source 42 in combination. In this case, the light from sunlight and the light from the primary light source 42 may be used interchangeably depending on conditions such as the time of day. Furthermore, it is possible to emit (use) sunlight and the light from the primary light source 42 simultaneously.

[0130] The additional light source 44, although not shown in the figure, includes an additional signal light source and an additional relaxation light source. The additional signal light source emits additional signal light, and the additional relaxation light source emits additional relaxation light.

[0131] The main light source 42 and the additional light source 44 are individually driven and controlled by the irradiation light control unit 50 (current control in this case). The additional signal light source and the additional relaxation light source are also individually driven and controlled by the irradiation light control unit 50.

[0132] In the culture vessel 36, the culture medium 48 is circulating as indicated by arrow A. Equipment for circulating the culture medium 48 may be installed in the culture vessel 36.

[0133] In the culture vessel 36, a partition wall 46 separates the majority of the culture vessel 36 from the portion near the water drain pipe 40. The culture medium 48 mainly circulates inside the partition wall 46.

[0134] The water surface 49 of the culture solution 48 reaches the water discharge pipe 40, and the culture solution 48 flows into the water discharge pipe 40. The culture solution 48 flows through the water discharge pipe 40 and out into the aquaculture pond 34 for the second stage.

[0135] The second-stage aquaculture pond 34 is equipped with aquaculture containers 52 and a water-lifting pipe 54, etc. A water-lifting bucket 56 is installed below the tip of the water-lifting pipe 54. Reference numeral 59 indicates the water level of the culture medium 58 stored in the aquaculture containers 52. The water level 59 reaches the height of the water-lifting pipe 54.

[0136] In the aquaculture container 52, the culture medium 58 is circulating as indicated by arrow B. Equipment for circulating the culture medium 58 may be installed in the aquaculture container 52.

[0137] Although not shown in the diagram, a light-blocking member is installed between the anteroom 32 for the first stage and the aquaculture pond 34 for the second stage to block additional light. Various types of curtains can be used as the light-blocking member.

[0138] In this type of multi-stage cultivation, efficient aquaculture can be achieved by keeping the aquatic environment (e.g., salinity, nutrient levels, temperature, convection velocity, and degree of agitation) as similar as possible between each stage.

[0139] Furthermore, similar to the modified plant cultivation device 10 (Figure 5) described above, the light from the additional light source 44 may be irradiated into the culture medium 48 via an optical fiber. The optical fiber can be either end-emitting or side-emitting as appropriate. For example, a side-emitting optical fiber may be arranged around the inner wall surface of the culture container 36, and the additional light may be irradiated from the side of the optical fiber toward the inside of the culture container 36. Alternatively, for example, a side-emitting optical fiber may be placed in the center of the culture container 36, and the additional light may be irradiated from the side of the optical fiber toward the inner wall of the culture container 36.

[0140] <Example 7> The following describes an example using the microalgae growth apparatus 30. In this example, only the microalgae Euglena were placed in the culture vessel 36 (step (S) 11 in Figure 9), and the main light and supplemental light were irradiated (S12). Furthermore, the irradiation of the supplemental light was stopped, and the Euglena was switched to the high-speed growth mode (S13). Specifically, the irradiation of supplemental signal light and supplemental relaxation light was completed, and the Euglena was switched to the high-speed growth mode.

[0141] Next, a culture medium (water in this case) was continuously introduced into the culture vessel 36 for the first stage at a constant flow rate via the water introduction pipe 38 (S14). The amount of culture medium introduced was set so that the culture medium in the culture vessel 36 would be completely replaced in about 7 to 10 days.

[0142] As described above, a constant flow rate of culture solution was introduced into the culture container 36 from the water inlet pipe 38, and an amount of culture solution roughly equal to the inflow was flowed into the second-stage aquaculture pond 34 via the water discharge pipe 40. In this way, Euglena in high-speed growth mode was continuously introduced into the second-stage aquaculture pond 34. In the aquaculture pond 34, the culture solution 58 was discharged at a constant flow rate via the water lifting pipe 54, and the culture solution 58 containing Euglena was collected in the water lifting bucket 56 (S15). In the example in Figure 9, S11 to S13 belong to the first stage, and S14 and S15 belong to the second stage.

[0143] In this case, cultivation was carried out in the aquaculture pond 34 using only primary light. A primary light source may also be provided in the aquaculture pond 34.

[0144] At the start of cultivation, in the second stage cultivation pond 34, more than 20% of the organisms present were diatoms and chlorella in addition to Euglena. In this example, as the cultivation period (growth period) progressed, Euglena, which is in a high-speed growth mode, became dominant in cultivation pond 34. Furthermore, 20 days after the start of cultivation, more than 95% of the microalgae consisted of Euglena.

[0145] As explained above, the microalgae cultivation apparatus 30 of this embodiment was able to preferentially propagate only the specific microalga Euglena. However, it is not limited to Euglena; for example, if Chlorella is introduced into the pre-chamber 32 for the first stage, Chlorella will become the majority of microalgae in the cultivation pond 34 for the second stage. In addition, it is also possible to preferentially propagate only phytoplankton that are beneficial to fish and shellfish, in addition to the microalga Euglena and Chlorella.

[0146] Furthermore, experiments conducted by the inventors have shown that, in the two-stage cultivation described above, restricting the PPFD of the main light to approximately the light compensation point for only the last short period (e.g., 1-2 days) of the first stage significantly accelerates growth in the second stage. The inventors are currently conducting experiments with lettuce and Euglena.

[0147] This accelerated growth is thought to stem from the plant's survival instinct, as its DNA detects when the light dims or the exposure time shortens towards the end of the first stage, prompting it to issue an instruction to increase chlorophyll concentration.

[0148] More specifically, in cultivation where primary light irradiation is repeated daily at a constant PPFD value and for a constant irradiation time, if the primary light irradiation conditions are abruptly changed, the plant will take countermeasures against the environmental change. For example, if the intensity of primary light is abruptly reduced, the DNA will issue a command to increase chlorophyll production to compensate for the decrease in photosynthesis. Similarly, if the irradiation time is abruptly shortened, the DNA will also issue a command to increase chlorophyll production. By appropriately utilizing these defense responses to environmental changes, a greater growth promotion effect can be obtained.

[0149] When cultivating in two stages, rapidly lowering the PPFD value of the primary light source to, for example, the complementary focal point at any point during the first stage (including the end of the first stage) can significantly promote growth. Shortening the duration of primary light irradiation can also greatly enhance growth. Furthermore, rapidly changing the primary light irradiation conditions in the second stage can yield even greater growth promotion.

[0150] Regarding the increase in chlorophyll production, it is currently unclear whether (1) the chlorophyll in the chloroplasts themselves increases, resulting in an overall increase in chlorophyll, (2) the increase in chloroplasts results in an overall increase in chlorophyll, or (3) both of these are occurring. However, it is possible to consider that additional signaling light has the effect of increasing the number and size of chloroplasts.

[0151] The inventors hypothesize that additional light is highly effective in channeling photosynthetic products into primary and secondary metabolic pathways. Their reasons are as follows:

[0152] Generally, when light intensity is increased beyond a certain value, the rate of photosynthesis saturates. The reason for this saturation has traditionally been thought to be that the chemical reaction rate reaches its maximum value, and the reaction cannot be increased any further. However, the inventors now hypothesize that the saturation of photosynthesis may be due to a mechanism that slows down photosynthesis once sufficient photosynthetic products have accumulated.

[0153] If the additional light irradiation has the effect of increasing the rate at which photosynthetic products are transported through the primary and secondary metabolic pathways, then it would not be surprising if the rate of photosynthesis exceeded the saturation point. In other words, it can be strongly hypothesized that the additional light irradiation has the effect of increasing chlorophyll concentration and thus increasing the rate of photosynthesis, as well as increasing the rate at which photosynthetic products are consumed.

[0154] <Application to the production of photosynthetic organisms across a wide range of applications> Plants convert carbon dioxide, a cause of global warming, into oxygen through photosynthesis. Plants are at the top of the food chain. Therefore, promoting plant growth on a global scale can greatly contribute to the restoration of the global environment and to improving food self-sufficiency. In addition, by promoting the growth of photosynthetic organisms through the irradiation of additional light, decarbonization (reduction of carbon dioxide, decarbonization, carbon recycling, etc.) can be effectively promoted.

[0155] According to the various methods for producing photosynthetic organisms described above, the growth-promoting effect of additional light irradiation on photosynthetic organisms can be obtained even if the PPFD value of the additional light is only about one millionth of that of sunlight at the Earth's surface. The PPFD of direct sunlight is approximately 2000 (μmol·m). -2 ·s -1 ) and the PPFD on cloudy days is approximately 50-100 (μmol·m -2 ·s -1 )

[0156] Therefore, by appropriately selecting the emission intensity and light divergence characteristics (also called "light diffusion characteristics") of the additional light, even if an additional light source (having an additional signal light source and an additional relaxation light source) is installed (mounted) on an object (moving object) that is far away from photosynthetic organisms such as plants, the effect of promoting the growth of photosynthetic organisms can be obtained.

[0157] The aforementioned "moving objects" include various types of flying objects, ships, and land vehicles. Examples of flying objects include aircraft (including passenger planes carrying passengers), helicopters, drones, lunar surfaces, and spacecraft and satellites orbiting the Earth. Examples of ships include surface ships and underwater vessels. Examples of land vehicles include not only agricultural vehicles, but also livestock vehicles, environmental maintenance vehicles, and leisure vehicles (including golf carts). By irradiating these moving objects with additional light, the growth-promoting effect on photosynthetic organisms can be obtained.

[0158] By installing additional light sources on moving objects, it becomes possible to promote the growth of photosynthetic organisms that are widely distributed. Examples of photosynthetic organisms include plants that inhabit forests, mountain ponds, and grasslands, seaweed such as eelgrass and blue-green algae in the ocean and freshwater, and microalgae such as phytoplankton and Euglena. Furthermore, for example, if additional light is shone on a coral reef using a flying object or a ship, a large amount of algae can be attached to the coral. As a result, the coral can grow using the photosynthetic products of the algae as nutrients, enabling the protection and restoration of coral reefs.

[0159] By appropriately selecting the wavelength of additional light, it is possible to control the secondary metabolites contained in plants. As mentioned above (including in Example 1), shorter wavelengths increase the biomass-increasing effect (greater growth-promoting effect), while longer wavelengths increase the secondary metabolism-promoting effect. Therefore, by appropriately selecting the wavelength of additional light, it is possible to meet the needs of cultivation areas, such as those who want to significantly increase harvest weight or those who want to significantly increase nutritional content.

[0160] When installing an additional light source on a moving object, it is effective to combine the additional light source with a device that can adjust the light divergence angle (light divergence angle adjustment device). Examples of light divergence angle adjustment devices include optical focusing lenses and devices with a parabolic antenna-shaped mirror surface. By installing these light divergence angle adjustment devices and adjusting the light divergence angle, the illumination range of the additional light can be limited.

[0161] In particular, adjusting the light divergence angle is important when installing additional light sources in remote locations such as spacecraft or the lunar surface. This allows for targeted growth promotion even with additional light irradiation from a distance. Examples of locations for installing light divergence angle adjustment equipment include the vicinity of the additional light source, land or buildings (light relay points) between the additional light source and the cultivation area, and the vicinity of the cultivation area.

[0162] For example, a spacecraft orbiting at an altitude of several hundred kilometers above the Earth's surface moves with a period of approximately one and a half hours. Additional light could be continuously emitted from such a spacecraft. Alternatively, the additional light could be emitted only from above a specific location. Since geostationary satellites are located above a certain point in the Earth's surface, emitting additional light from a geostationary satellite allows for more precise control over the emission range of the additional light.

[0163] Figure 10 schematically shows an example of how a helicopter 60 irradiates plants 64 with additional light (in this case, additional signal light and additional relaxation light) 62 in a divergent manner. In Figure 10, the additional light is irradiated in a circular, magnified manner, but the method of irradiating with additional light is not limited to this. For example, it is also possible to irradiate a wide area by linearly scanning (back and forth scanning) the spot of additional light.

[0164] <Effects of plants by use> Additional light has the effect of promoting photosynthesis and facilitating the movement of photosynthetic products (photosynthetic products) into the primary metabolic pathway (primary metabolic pathway, pathway for primary metabolism) and the secondary metabolic pathway (secondary metabolic pathway, pathway for primary metabolism).

[0165] Plants are often used as food, medicine, and for their aromatic components. According to the various photosynthetic organism production methods described above, by irradiating plants with additional light in addition to primary light such as sunlight, it is possible to increase the production of food, specific medicinal components, aromatic components, and other substances.

[0166] For example, lettuce and other vegetables generally have a bitter taste that children dislike. In experiments conducted by the inventors, irradiating lettuce with additional signal light at wavelengths of 500nm to 600nm or higher suppressed the bitterness to an undetectable level. This is thought to be because the nitrogen components in the vegetables were converted into amino acids and glutamic acid. As a result, it is possible to reduce the number of consumers who dislike vegetables and increase vegetable consumption.

[0167] The same was true for cilantro. Japanese-grown cilantro is sometimes considered to have a stronger taste compared to Thai-grown varieties, for example. However, the stimulating effect can be suppressed by irradiation with additional light, thereby expanding the consumer base and consumption. As mentioned earlier, irradiation with additional light increases the sweetness of grapes. In the inventors' experiments, the sweetness of grapes was similarly increased more significantly by irradiation with additional signal light of wavelengths of 500nm to 600nm or higher.

[0168] Based on these findings, it is thought that additional light irradiation could potentially enhance the aroma and sweetness of, for example, green tea.

[0169] Seedlings that receive additional light for at least a portion of the seedling stage (seedlings grown in an environment with additional light during the seedling stage) exhibit sustained growth and metabolic product enhancement effects compared to seedlings that did not receive additional light. This is true whether cultivation is carried out using only primary light sources such as sunlight or white LED light after the additional light exposure, or whether primary and additional light exposure is used. For example, by simply applying additional light a few days before harvest and completing the exposure, it is possible to harvest vegetables with less bitterness or fruits with a stronger sweetness at a later date.

[0170] Furthermore, supplemental light also has the effect of increasing seed germination rates and the yield of good quality seeds. When plants are grown in an environment with supplemental light from germination to seedling stage, the promotion of growth and metabolite production is sustained compared to when supplemental light is not applied. This is true whether cultivation is carried out using only primary light after supplemental light irradiation, or whether primary light and supplemental light are used.

[0171] The additional signal light can control the weight of rice, wheat, and barley seeds, as well as the production of umami components such as glutamic acid, medicinal components such as beta-glucan, and pungent and aromatic components of herbs and cilantro.

[0172] Therefore, according to the various photosynthetic organism production methods described above, seedlings of lettuce, tomatoes, and rice that grow faster than conventional methods, fruits such as grapes and peaches with high sugar content, medicinal herbs rich in medicinal components, aromatic herbs with reduced spiciness, aromatic herbs rich in aromatic components, and plants such as Polygonum tinctorium and red perilla that contain many pigment components can be cultivated as annual herbs (annual plants).

[0173] To selectively increase the production of secondary metabolites found in plants, such as ascorbic acid (vitamin C), β-carotene (a precursor of vitamin A), polyphenols, and s-allyl cysteine, selective excitation of phytochrome, a protein receptor, is recommended.

[0174] Phytochromes exist in two types based on their protein aggregation structure: Pr and Pfr. The Pr type can be converted to the Pfr type upon photoexcitation. Conversely, the Pfr type can be converted to the Pr type upon photoexcitation.

[0175] Pr-type phytochrome has the effect of promoting the production of ascorbic acid, in particular, among secondary metabolites. On the other hand, Pfr-type phytochrome has the effect of promoting the production of secondary metabolites other than ascorbic acid, such as polyphenols, β-carotene, and s-allyl-cysteine, the medicinal component of garlic. By utilizing these properties, it becomes possible to control the production of secondary metabolites while promoting growth.

[0176] In addition to phytochrome, other protein receptors found in photosynthetic organisms such as plants include phototropin, which is involved in photochlorophyll transport, phototropism, and stomatal opening and closing, and cryptochrome, which is involved in flowering time and light-avoidance responses. By selectively exciting these protein receptors with additional signal light, it is possible to further precisely control growth rate and secondary metabolite production.

[0177] <Example 8> The following describes an example of the germination rate of plant seeds when exposed to additional light. In this example, the inventors sowed lettuce seeds in a water-soaked sponge. Cuts were made in the sponge, and one seed was placed in each cut (sown). These sponges were kept in the dark for two days, and then cultivated on a seedling shelf for seven days.

[0178] Seedlings were grown on the cultivation shelves using two types of samples: a control group that received only primary light, and an experimental group that received primary light plus additional signal light and relaxation light. Each control and experimental group had 30 sponges containing seeds (60 sponges in total). One seed was placed in each sponge.

[0179] A white LED was used as the primary light source. The primary LED was continuously lit for 14 hours from 8:00 AM, and then turned off for 10 hours. The PPFD of the white LED was 130 (μmol·m³). -2 ·s -1 I set it to ).

[0180] The wavelength of the additional signal light is 350 nm to 420 nm, and the PPFD is 0.005 (μmol·m). -2 ·s -1 The wavelength of the additional relaxation light was 350 nm to 420 nm, and the PPFD was 0.01 (μmol·m). -2 ·s -1 ) was.

[0181] The parameters for the additional signal light were set to T=30μs, ΔT1=2μs, ΔT2=3μs, and ΔT3=25μs. Both the additional signal light and the additional relaxation light were applied for 10 hours starting at 2 PM out of a 24-hour day.

[0182] Figure 11(a) shows a photograph of the germination status of the control group, and Figure 11(b) shows a comparative photograph of the germination status of the test group. Compared to the control group (Figure 11(a)), the lettuce in the test group (Figure 11(b)) has generally grown larger leaves.

[0183] The number of germinated seeds was 21 out of 30 in the control group (Figure 11(a)) and 27 out of 30 in the test group (Figure 11(b)). The yield rate (percentage of seeds that germinated in good condition) was 70% in the control group and 90% in the test group.

[0184] As a criterion for determining germination, we considered the seedlings to have germinated successfully if they had three leaflets. This is because we know that lettuce seedlings with two or fewer leaflets nine days after sowing do not grow well afterward.

[0185] According to this embodiment, additional signal light with a wavelength of 350 nm to 420 nm has the effect of promoting lettuce germination. Furthermore, by selling pre-germination seeds irradiated with additional signal light and additional relaxation light in addition to the primary light to consumers, it becomes possible to supply the seed market with seeds that germinate more abundantly on average.

[0186] <Acceleration and deceleration of growth> We have previously discussed the use of supplemental light irradiation to promote growth and metabolism. However, supplemental signal light with red wavelengths, for example, slows down growth rates and promotes secondary metabolite production. In other words, certain supplemental signal lights have the effect of suppressing the growth of photosynthetic organisms.

[0187] In recent years, large-scale lettuce farms and other agricultural businesses have been seeking to level out their harvest seasons. This is because a concentration of harvest seasons makes it difficult to secure workers (labor force).

[0188] Furthermore, in areas close to streetlights, so-called "light pollution" occurs, where weeds and rice plants grow more rapidly.

[0189] Furthermore, pyrethrum, being a short-day plant, begins to flower when the day length shortens. To delay this flowering, yellow or red light is shone on pyrethrum at night. This type of cultivation, which involves irradiating the plants with light, is called "electric lighting" or "electric lighting cultivation."

[0190] By increasing the wavelength of the additional light, it becomes possible to channel more photosynthetic products into the secondary metabolic pathway than the primary metabolic pathway. This property can be used to slow down plant growth.

[0191] For example, we can consider methods for producing photosynthetic organisms and cultivating plants that involve irradiating plants with additional signal light (additional signal light for growth acceleration) to promote growth in the early stages of growth, and irradiating them with additional signal light (additional signal light for growth slowing) to promote secondary metabolism as harvest approaches (late stages of growth).

[0192] By employing this method, it is possible to increase secondary metabolic components without changing the harvest weight. Furthermore, the amount of sugar can be reduced. This growth slowing method is particularly effective for leafy vegetables such as lettuce, komatsuna, and spinach, as well as vegetables such as cabbage, myoga ginger, and onions. Vegetables, including leafy vegetables, also contain sugars. Accelerating the conversion of sugars in vegetables to secondary metabolic components reduces the weight of the vegetables.

[0193] These methods for producing photosynthetic organisms and cultivating plants are a type of method that involves producing photosynthetic organisms in multiple stages or cultivating plants in multiple stages. In this case, it is possible to accelerate growth in the first stage and slow down growth in the second stage.

[0194] By employing these methods, it becomes possible to manufacture devices for accelerating growth (photosynthetic organism production devices, plant cultivation devices).

[0195] In the inventors' experiments, the effect of combining growth acceleration and growth deceleration on changing the cultivation period was approximately ±20%. Therefore, for example, if photosynthetic organisms are normally harvested after 4 weeks, growth acceleration makes it possible to harvest them in 3 weeks, and growth deceleration makes it possible to harvest them in 5 weeks. Furthermore, by combining growth acceleration and growth deceleration, it is also possible to harvest photosynthetic organisms in, for example, 4 weeks.

[0196] <Promoting cannabis growth> Irradiation with additional light is also effective for cannabis (an annual herbaceous plant of the Cannabis genus in the Cannabaceae family). Cannabis leaves and flower heads contain secondary metabolites such as tetrahydrocannabinol, which has pharmacological effects. Irradiation with additional light can increase the tetrahydrocannabinol content in cannabis. For cannabis leaves, similar to the red perilla in Example 5 described above, both leaf weight and the secondary metabolite content can be increased. It is assumed that approximately twice the amount of tetrahydrocannabinol can be purified compared to the control. The tetrahydrocannabinol content is calculated as leaf weight (1.6 times) × content (1.2 times).

[0197] <Improved Usability> For devices that provide additional light irradiation, such as the plant cultivation device 10 shown in Figure 5 and the microalgae growth device 30 shown in Figure 8, it is desirable to incorporate features to improve operability and ease of use from a user-friendly perspective.

[0198] For example, the operator (user) of the device inputs information about the photosynthetic organisms they wish to grow (such as their names) by operating a designated input unit. Examples of input units include mobile devices such as smartphones and tablet computers. Other examples of input units include dedicated control panels and notebook PCs (notebook personal computers).

[0199] The input results to the input unit are, for example, input to the irradiation light control unit 16 of the plant cultivation device 10 shown in Figure 5. The irradiation light control unit 16 searches for the identification information (ID information) of the input photosynthetic organism and refers to the irradiation condition information (irradiation condition information) associated with this identification information. Based on the referenced irradiation condition information, the irradiation light control unit 16 outputs a signal to drive the additional signal light source 24. The irradiation light control unit 16 also outputs a signal to drive the additional relaxation light source 26 as needed.

[0200] In another embodiment, the input unit can be an imaging device such as a camera, and photosynthetic organisms (plants, etc.) can be imaged using the camera. In this case, the irradiation light control unit 16 determines the type of photosynthetic organism imaged from the image information acquired by the camera. The determination of the type of photosynthetic organism can be performed by artificial intelligence that has obtained information on the determination criteria in advance through machine learning or the like.

[0201] The irradiation light control unit 16 refers to irradiation condition information linked to the identification information of photosynthetic organisms. Based on the referenced irradiation condition information, the irradiation light control unit 16 outputs signals to drive the additional signal light source 24 and the additional relaxation light source 26.

[0202] This method of identifying photosynthetic organisms and providing additional light irradiation tailored to those organisms can also be applied to the microalgae growth apparatus 30 shown in Figure 8. Furthermore, it can be applied to other types of photosynthetic organism production apparatuses, such as the plant cultivation apparatus 10 shown in Figure 5 and the microalgae growth apparatus 30 shown in Figure 8.

[0203] <Solving social issues by promoting the growth of photosynthetic organisms> The photosynthetic organism production method according to the embodiment of the present invention promotes the growth of photosynthetic organisms and enables the solution of various social problems. For example, it can shorten the period required for plant cultivation, thereby reducing the labor required for plant cultivation. Furthermore, it can reduce the burden on workers involved in cultivation. In addition, it can reduce the heating costs of greenhouses (agricultural greenhouses).

[0204] By reducing the burden on workers, it becomes possible to appropriately reallocate the workforce. This could contribute to resolving labor shortages and labor shortages.

[0205] Furthermore, compared to cultivation methods in plant factories, for example, where plants are constantly exposed to artificial light, the duration of light exposure can be shortened, reducing the amount of energy required to promote growth. In other words, as mentioned above, the photosynthesis-promoting effect continues not only while the additional signal light is being applied, but also after the irradiation is complete. Therefore, there is no need to constantly irradiate with additional light, and there are fewer time constraints. And by irradiating with additional light for a limited short period, growth can be promoted. Consequently, the amount of energy consumption required to promote growth can be reduced.

[0206] Furthermore, it is expected to have effects such as reducing energy costs for artificial light-based plant factories and improving productivity in solar-sharing agriculture.

[0207] Since the yield of vegetables and fruits will increase, it will be possible to obtain a large harvest from a small amount of seeds or seedlings. As a result, the food self-sufficiency rate of countries that implement the present invention can be improved, contributing to the resolution of food shortages and food crises.

[0208] Experiments conducted by the inventors (including those relating to each example) show that an increase in yield of at least 20% can be expected. When additional light is applied to plants that can be used as food, it is possible to increase food production by approximately 20%. Furthermore, some experiments have shown that the components of secondary metabolites increase by 1.5 to 2 times overnight. Therefore, it is possible to rapidly increase food production.

[0209] Furthermore, it enables more efficient plant cultivation, making it possible to grow plants even in countries and lands with unfavorable conditions for plant growth. As a result, the demand for transporting plants to regions and countries far from the cultivation area decreases. Consequently, food mileage decreases, and the costs of transporting and distributing plants can be reduced. Since these costs include the energy costs of transportation (aircraft, ships, and vehicles, etc.), the energy costs of transportation can also be reduced.

[0210] Furthermore, it promotes local production and consumption of plants, which in turn reduces transportation and distribution costs.

[0211] This technology will also enable more reliable and widespread plant growth promotion in desert greening efforts.

[0212] Plant growth requires a large amount of carbohydrates. Therefore, it becomes possible to cultivate low-carbohydrate plants. As a result, low-carbohydrate vegetables and other products can be provided to consumers, allowing them to maintain good health.

[0213] These factors make it possible to solve many social issues, such as reducing greenhouse gas emissions, securing resources, curbing deforestation, promoting sustainable agricultural development, realizing a green society, and achieving the SDGs (Sustainable Development Goals).

[0214] Furthermore, in recent years, various measures such as carbon taxes, emissions trading, credit trading, and carbon border adjustment measures have been considered by countries and the international community to achieve carbon neutrality. The growth of photosynthetic organisms through additional light exposure could stimulate discussions on these measures.

[0215] For example, Euglena, as described in Example 4 above, absorbs about 10 times more carbon dioxide than a forest over the same area. Furthermore, Euglena contains paramylon, which is also used in the refining of jet fuel. Additionally, with additional light irradiation, plants such as lettuce absorb about twice as much carbon dioxide as before. Therefore, the growth of photosynthetic organisms through additional light irradiation can significantly contribute to carbon neutrality and the realization of various policies.

[0216] Furthermore, the growth of photosynthetic organisms through irradiation with additional light enables the provision of a carbon dioxide absorber. The carbon dioxide absorber comprises at least a photosynthetic organism and an additional light irradiation device. The carbon dioxide absorber that performs additional light irradiation increases the absorption of carbon dioxide by the photosynthetic organism.

[0217] Even in a carbon dioxide absorber that performs additional light irradiation, photosynthetic organisms perform photosynthesis using main light such as sunlight. The additional light irradiation device includes an additional signal light irradiation unit and an additional relaxation light irradiation unit, and irradiates photosynthetic organisms with additional signal light or additional relaxation light according to the situation. Photosynthesis of photosynthetic organisms by main light is promoted by irradiation with additional light. In addition to the additional light irradiation device, the carbon dioxide absorber can be provided with a main light irradiation device that irradiates artificial main light.

[0218] Such a carbon dioxide absorber also functions as a carbon neutrality promotion device that promotes the achievement of carbon neutrality.

[0219] <Inventions Extractable from Embodiments and Examples> (1) In at least a part of the cultivation period from seeding to harvesting, irradiation with main light for photosynthesis (sunlight, artificial light, etc.) and irradiation with additional light that can be irradiated in addition to the main light are performed, A plant cultivation method, wherein the additional light includes at least the additional signal light among: additional signal light whose light intensity fluctuates periodically; and additional relaxation light whose light intensity changes more gradually than the additional signal light. (2) The light intensity of the additional light is lower than the light compensation point, The plant cultivation method according to (1) above. (3) The light intensity of the additional light is determined according to the plant to be cultivated, The plant cultivation method according to (1) or (2) above. (4) The fluctuation period of the light intensity related to the additional signal light (for example, 8 μs or more and 200 μs or less) is determined according to the type of the plant to be cultivated, The plant cultivation method according to (3) above. (5) The period of fluctuation in the light intensity related to the additional signal light is 8 μs or more and 200 μs or less. The plant cultivation method described in (4) above. (6) The period of fluctuation in the light intensity related to the additional signal light is 8 μs or more and 100 μs or less. The plant cultivation method described in (5) above. (7) The period of variation in the light intensity of the additional relaxation light is 1 ms or more. The plant cultivation method described in (5) or (6) above. (8) The period during which the additional light is irradiated is a part of the cultivation period from sowing to harvest (the period after transplanting, a part of the day, the 10 days from sowing to transplanting, the seedling stage, etc.) A plant cultivation method described in any one of the above items (1) to (7). (9) The period during which the additional light is irradiated is the seedling stage. The plant cultivation method described in (8) above. (10) A plant cultivation device (plant cultivation device 10, etc.) that is irradiated with primary light for plant photosynthesis (sunlight, artificial light, etc.), An additional light source (such as an additional light source 22) that emits additional light in addition to the main light, The system includes an irradiation light control unit (such as an irradiation light control unit 16) capable of driving and controlling the additional light source, The aforementioned additional light source, An additional signal light source (such as an additional signal light source 24) that emits additional signal light whose light intensity fluctuates periodically, A plant cultivation apparatus comprising at least the additional signal light source, and an additional relaxation light source (such as an additional relaxation light source 26) that emits additional relaxation light whose light intensity changes more gradually than that of the additional signal light. (11) A main light source (such as the main light source 20) that emits the main light, The plant cultivation apparatus described in (10) above. (12) The first stage of cultivation using the additional light, The plant cultivation method according to (1) above, comprising a second stage of cultivation in which the irradiation of the additional light is stopped. (13) The plant cultivation method described in (12) above, wherein the second step is performed by moving the plants from the place where the first step was performed to another location. (14) A method of cultivating plants as described in either (12) or (13) above, wherein the plant to be cultivated is selected from the group consisting of seedlings, phytoplankton, and microalgae. (15) The first stage of cultivation, in which cultivation is carried out with the additional light, The plant cultivation apparatus described in (10) above, which performs a second stage of cultivation by stopping the irradiation of the additional light. (16) The plant cultivation apparatus described in (15) above, wherein the second stage is performed by moving the plants from the place where the first stage was performed to another location. (17) A plant cultivation method according to any one of items (1) to (9) above, wherein the additional light is irradiated from a moving object (aircraft, helicopter, drone, lunar surface, spacecraft or satellites orbiting the Earth, ships, land vehicles, etc.) onto an area to be cultivated (an area where plants to be cultivated exist, etc.). (18) During at least part of the cultivation period from sowing to harvest, irradiation with primary light for photosynthesis (sunlight, artificial light, etc.) and irradiation with additional light to promote photosynthesis by photosynthetic organisms using the primary light, A method for producing photosynthetic organisms (such as plant seeds, seedlings, leafy vegetables, root vegetables, flowers, fruit trees, seaweed, algae, and microalgae), wherein the additional light comprises additional signal light whose light intensity fluctuates periodically and additional relaxation light whose light intensity changes more slowly than that of the additional signal light. Furthermore, the photosynthetic organisms to which this manufacturing method can be applied can be further subdivided from the perspective of agricultural products. In other words, this manufacturing method contributes to increasing the yield and production rate of these agricultural products. (18-1) Rice: Rice cultivated for consumption, rice for animal feed, rice for processing, rice unsuitable for consumption, rice for bioethanol production. (18-2) Grains and Cereals: Wheat, barley (six-row barley, two-row barley, hulless barley), corn (dried), grain sorghum, sorghum (sorghum, sorghum, sorghum, sorghum), and other grains and cereals {buckwheat, millet, barnyard millet, foxtail millet, oats, rye} (18-3) Legumes (dried): Soybeans, adzuki beans, peanuts (with shells), and other legumes {kidney beans (dried), peas (dried)} (18-4) Leafy and stem vegetables: Asparagus, cabbage, broccoli, lettuce (salad lettuce, loose-leaf lettuce, red leaf lettuce, ssam lettuce), spinach, Chinese cabbage, bean sprouts, komatsuna, shiso, garland chrysanthemum, mizuna, bok choy, bamboo shoots, green onions, chives, onions, garlic, and other leafy and stem vegetables {rakkyo, cauliflower, myoga ginger, mitsuba, celery, loose-leaf tsukena, rapeseed blossoms, parsley, fuki, seri, daikon radish sprouts, udo, tara no me, sakegi, gyouja ninniku, asatsuki, edible chrysanthemum, wasabi, Brussels sprouts, and other vegetables whose leaves or stems are eaten (including those whose flowers, buds, or bulbs are eaten)} (18-5) Fruiting vegetables: Melon, watermelon, strawberry, bell pepper (colored bell pepper), cucumber, eggplant, tomato (cherry tomato), sweet corn (fresh), pumpkin, edamame (not dried), green beans (not dried), snow peas (not dried), snap peas, other fruiting vegetables {okra, paprika, shishito pepper, bitter melon, winter melon, white melon, chili pepper (undried), bottle gourd, broad bean, green pea} (18-6) Root vegetables: carrots, turnips, radishes, ginger, burdock, lotus root, yams (Japanese yam, wild yam, Chinese yam, Japanese yam, ginkgo yam, Tsukuneimo), taro (shrimp yam), other root vegetables (excluding bulbous vegetables), lily bulbs, radishes, and other root vegetables not classified elsewhere (those mainly eaten for their roots or tubers). (18-7) Root vegetables: Potatoes, sweet potatoes (18-8) Fruits: Avocado, banana (unripe), pineapple, mandarin orange (Unshu mandarin), orange (navel orange), lemon / lime, grapefruit, other citrus fruits {Shiranui (Dekopon), pomelo, Iyokan, Natsumikan, yuzu, Hassaku, Ponkan, Kiyomi, Hyuganatsu, Sudachi, kumquat, Tankan, Kabosu, Seminole, grapes, apple (small apple, crabapple), cherry, peach (nectarine), pear (Japanese pear, Western pear, Chinese pear), persimmon, plum, kiwifruit, chestnut, other fruits (Japanese plum, mango, fig, loquat, ginkgo nut, akebi, sansho pepper, black pepper, vanilla berries, nuts, walnuts (in shell), blueberries, olives) (18-9) Flowering plants: Chrysanthemums (cut flowers), lilies (cut flowers), roses (cut flowers), lisianthus (cut flowers), carnations (cut flowers), cut branches {acacia, plum, cherry, bamboo, camellia, quince, shikimi, sakaki, etc. (including flowering plants, plants with fruit, and branches and leaves)}, other cut flowers (statice, gerbera, baby's breath, alstroemeria, gentian, orchids, stock, delphinium, sweet pea, tulip, gladiolus, cut leaves), orchids, flowering trees {bonsai, acacia, hydrangea, plum, maple, oleander, conifers, bamboo} * **Amphicarpa species, azaleas, roses, forsythia, etc. (woody plants, including those that are cold-hardy and those that are not cold-hardy and grown for their flowers or fruits)**, * **Ornamental plants {Asparagus species, bromeliad species, ferns, cissus species, ficus species, palms, yucca, etc. (herbaceous plants and non-cold-hardy woody plants)}, * **Other potted plants (cyclamen, cacti, succulents, begonias)**, * **Flowering trees and shrubs (including seedlings), garden tree seedlings, street tree seedlings, garden trees and street trees)**, * **Other flowering plants {Bulbs, turf, ground cover plants (vines, bamboo, dwarf bamboo, herbaceous plants, woody plants), flowerbed seedlings}** (18-10) Craft crops: rapeseed, sesame, coffee beans (unroasted), tea (fresh leaves), cocoa beans, sugar beets, sugarcane, tobacco leaves, konjac, cotton (seed cotton, ginned cotton, raw cotton, raw cotton), other craft crops {hops (fresh and dried), rush, textile raw materials (hemp, jute, etc.), papermaking raw materials (mulberry, paperbush, etc.), oil-producing seeds (sunflower seeds, camellia seeds, cottonseed, etc.), medicinal raw materials (ginseng, licorice, ouren, etc.), essential oil and fragrance raw materials (peppermint, etc.), dye raw materials (indigo, safflower, etc.), persimmon leaves, and other non-tea raw materials (excluding wheat, buckwheat, and other items classified elsewhere), natural rubber (latex, etc.) (18-11) Other agricultural products: Pasture and silage crops {pasture grass (fresh and dried), rice for whole crop silage (green corn, sorghum, etc.), mulberry} (19) Seedlings grown by the photosynthetic organism production method described in (18) above. (20) Seeds irradiated with the additional light by the photosynthetic organism production method described in (18) above. (21) Phytoplankton grown by the photosynthetic organism production method described in (18) above. (22) Microalgae grown by the photosynthetic organism production method described in (18) above. (23) A carbon dioxide absorption device that carries out the photosynthetic organism production method described in (18) above. [Industrial applicability]

[0220] The plant cultivation method and photosynthetic organism production method of the present invention are effective for open-field cultivation, greenhouse cultivation, and plant factory cultivation. Since it has a growth-promoting effect on all plants that perform photosynthesis, it can be used to improve production efficiency and reduce production costs for leafy vegetables such as lettuce, perilla, and basil, fruit trees such as strawberries, grains such as rice and wheat, seaweed such as wakame, and green algae such as monognathus and Euglena. [Explanation of Symbols]

[0221] 10:Plant cultivation equipment 12:Cultivation bed 14: Light-irradiating section 16: Irradiation light control unit 18: Protective component 20: Main light source 22: Add a light source 24: Added シグナル light source 26: Add a mild light source 30: Microalgae growth device 42: Main light source 44: Add a light source 50: Irradiation light control part

Claims

1. During at least a portion of the cultivation period from sowing to harvest, primary light for photosynthesis and additional light to promote photosynthesis by the primary light are provided. The additional light includes an additional signal light whose light intensity fluctuates periodically, and an additional relaxation light whose light intensity changes more slowly than that of the additional signal light. The first stage involves cultivation using the aforementioned additional light, A plant cultivation method comprising a second stage in which cultivation is carried out by stopping the irradiation of the additional light.

2. The light intensity of the additional light is less than that of the light compensation point. The plant cultivation method according to claim 1.

3. The light intensity of the aforementioned additional light is determined according to the plant being cultivated. The plant cultivation method according to claim 1 or 2.

4. The period of fluctuation in light intensity related to the aforementioned additional signal light is determined according to the type of plant being cultivated. The plant cultivation method according to claim 3.

5. The period of fluctuation in the light intensity related to the additional signal light is 8 μs or more and 200 μs or less. The plant cultivation method according to claim 4.

6. The period of fluctuation in the light intensity related to the additional signal light is 8 μs or more and 100 μs or less. The plant cultivation method according to claim 5.

7. The period of fluctuation in the light intensity of the additional relaxation light is 1 ms or more. The plant cultivation method according to claim 5 or 6.

8. The period during which the aforementioned additional light is irradiated is a part of the cultivation period from sowing to harvesting. A method for cultivating plants according to any one of claims 1 to 7.

9. The period during which the aforementioned additional light is irradiated is the seedling stage. The plant cultivation method according to claim 8.

10. A plant cultivation device that irradiates plants with primary light for photosynthesis, An additional light source that irradiates additional light to promote plant photosynthesis using the aforementioned primary light, The system includes an irradiation light control unit capable of driving and controlling the additional light source, The aforementioned additional light source, An additional signal light source that emits additional signal light whose light intensity fluctuates periodically, The system includes an additional relaxation light source that emits additional relaxation light whose light intensity changes more gradually than that of the additional signal light, The additional relaxation light is irradiated together with the additional signal light, The first stage of cultivation involves cultivation using the aforementioned additional light, A plant cultivation apparatus that performs a second stage of cultivation, in which the irradiation of the aforementioned additional light is stopped and cultivation is carried out.

11. A main light source that emits the aforementioned main light is provided, The plant cultivation apparatus according to claim 10.

12. The second step is performed by moving the plant from the location where the first step was performed to another location. The plant cultivation method according to claim 1.

13. The object to be cultivated is selected from the group consisting of seedlings, phytoplankton, and microalgae. The plant cultivation method according to claim 1 or 12.

14. The second step is performed by moving the plant from the location where the first step was performed to another location. The plant cultivation apparatus according to claim 10.

15. The additional light is irradiated from the moving object onto the area to be cultivated. The plant cultivation method according to claim 1.

16. During at least a portion of the cultivation period from sowing to harvest, irradiation is performed with primary light for photosynthesis and additional light to promote photosynthesis by photosynthetic organisms using the primary light, The method for producing photosynthetic organisms includes additional signal light whose light intensity fluctuates periodically and additional relaxation light whose light intensity changes more slowly than that of the additional signal light.

17. A carbon dioxide absorption device for the photosynthetic organism production method of Claim 16.

Images