Method of Applying Plant Growth Promoter

Abstract

To provide application methods of plant growth promoters capable of efficiently and stably producing plants in hydroponics.SOLUTION: The application method of a plant growth promoter of the present invention is an application method of a plant growth promoter in hydroponics, the method comprising: impregnating a water-retaining carrier with a hydroponic culture solution to prepare a solid medium that is a water-retaining carrier that holds the hydroponic culture solution (S1); putting a mixed solution of a hydroponic culture solution and a plant growth promoter containing a substance involved in plant growth promotion into a tray (S2); and placing the solid medium in the tray with the mixed solution (S3).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a method for applying a plant growth promoter.

Background Art

[0002] In recent years, there has been a demand for the development of technologies for efficiently and stably producing plants in plant factories. For example, as a method for enhancing plant production, a method of inoculating a plant with a plant growth promoter containing a substance related to plant growth promotion (hereinafter also referred to as a plant growth promoting substance) has been disclosed (see Patent Document 1).

[0003] Further, for example, as a method for suppressing a reduction in the yield of plants, a method for suppressing plant growth inhibition or contamination (for example, contamination by algae) has been disclosed (see Patent Document 2). Patent Document 2 discloses a method of covering the upper surface of a carrier arrangement hole for fitting and supporting a carrier in which a plant body (also referred to as a plant) is planted in a hydroponic cultivation plate with a light-shielding sheet having a slit at a portion located directly above the carrier arrangement hole to shield the hydroponic culture solution from light.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the technology described in Patent Document 1 is applied to the initial stage of plant cultivation in hydroponics (hereinafter referred to as the germination process), there is a problem that, for example, algae tend to grow. Further, when the technology described in Patent Document 2 is applied to the germination process, since the amount of light required for plant growth is insufficient due to the leakage light from the slit of the light-shielding sheet, there is a problem that the plant cannot grow to the extent of pushing open the slit. Therefore, it is difficult to say that these technologies can efficiently and stably cultivate plants in hydroponics.

[0006] Therefore, the present disclosure provides a method for applying a plant growth promoter that can efficiently and stably cultivate plants in hydroponics.

Means for Solving the Problems

[0007] A method for applying a plant growth promoter according to an aspect of the present disclosure is a method for applying a plant growth promoter in hydroponics, comprising preparing a solid medium which is a water-retentive carrier impregnated with a hydroponic culture solution, putting it into a mixing solution tray of the hydroponic culture solution and a plant growth promoter containing a substance involved in promoting the growth of the plant, placing the solid medium in the tray into which the mixing solution has been put, sowing the seeds of the plant on the solid medium, and then 、before germination of the seeds of the plant and until the first transplantation applying the plant growth promoter thereto.

Effects of the Invention

[0008] According to the method for applying a plant growth promoter of the present disclosure, plants can be efficiently and stably cultivated in hydroponics.

Brief Description of the Drawings

[0009]

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[0010] (Knowledge underlying the present disclosure) In recent years, due to global abnormal weather or natural disasters, the yield of agricultural crops has fluctuated, hindering the stable supply of food to people. Therefore, the development of technologies for stably producing plants such as agricultural crops is required. As one such technology, for example, plant factories have attracted attention. In a plant factory, depending on the type of plant, environmental conditions such as air conditioning in the growing space of the plant are controlled in a partitioned space where the plant is cultivated, so that it is possible to stably produce plants such as agricultural crops regardless of natural disasters such as abnormal weather or natural disasters, seasons, or locations. On the other hand, plant factories have a problem of low profitability because equipment costs and running costs such as electricity bills are high. In order to solve this problem, it is necessary to improve the production efficiency of plants in plant factories. Therefore, as one method for improving the production efficiency of plants, the development of technologies for promoting the growth of cultivated plants is required.

[0011] For example, as a method for promoting plant growth, there is a method of inoculating a plant with a plant growth promoter containing a substance involved in promoting plant growth (so-called plant growth promoter). For example, Patent Document 1 discloses a method of applying oxidized glutathione to the underground part of leafy vegetables (specifically, the part of the leafy vegetable plant that is in contact with the soil or medium and is not exposed to the air) during the seedling raising period from at least the day of germination to the 12th day.

[0012] However, when the technique described in Patent Document 1 is applied in the initial cultivation process in hydroponics (for example, the seedling raising period from at least the day of germination to the 12th day), while the growth of the cultivated plants is promoted, the growth of unnecessary algae such as green algae is also promoted, resulting in the drawback that algae grow on the culture medium.

[0013] Algae utilize nutrients such as nitrogen and phosphorus contained in the hydroponic culture solution and grow on the culture medium. When a plant growth promoter is contained in the hydroponic culture solution, algae utilize the plant growth promoter and its growth (in other words, proliferation) is promoted. Thus, the growth of algae not only increases the cleaning cost of the cultivation device, but also causes adverse effects such as the growth of the cultivated plants being hindered because the composition of the hydroponic culture solution changes as algae absorb the nutrients contained in the hydroponic culture solution.

[0014] In order to suppress the growth of algae in hydroponics, it is considered effective to suppress the photosynthesis of algae. For example, Patent Document 2 discloses a method of covering the upper surface of a carrier arrangement hole that fits and supports a carrier (also referred to as a medium) in which a plant body is planted in a hydroponic plate with a light-shielding sheet having a slit at a position directly above the carrier arrangement hole to shield the hydroponic culture solution.

[0015] However, the technique described in Patent Document 2 is applied after a plant body (here, a seedling) with roots grown on a solid medium (so-called medium) after germination is transplanted into a hydroponic cultivation device. For example, when the technique described in Patent Document 2 is applied in the initial cultivation step (so-called germination step) in hydroponic cultivation, the amount of light required for plant growth is not sufficient due to the light leakage from the slit of the light-shielding sheet, so the plant cannot grow to the extent of pushing open the slit. As described above, the germination step is the seedling raising period from germination to cotyledon expansion. If the amount of light required for plant growth is not sufficient during this period, the cotyledons or stems will not grow to the extent of pushing open the slit. Therefore, it is difficult to apply the technique described in Patent Document 2 in the initial cultivation step in hydroponic cultivation.

[0016] The growth of algae occurs on the lower surface of the water-retaining carrier (so-called medium) containing the hydroponic culture solution facing the tray, but particularly easily occurs on the surface exposed to light by the light source. Furthermore, when a plant growth promoter is added to the hydroponic culture solution, the growth of algae is also promoted, so the growth of algae is promoted. Therefore, generally, in the germination step, the application of the plant growth promoter is not actively carried out.

[0017] As a result of intensive studies to solve the above problems, the present inventors prepared a solid medium containing a hydroponic culture solution in a water-retaining carrier and a tray containing a mixed solution of a hydroponic culture solution and a plant growth promoter, and found a method of setting the solid medium in the tray. Thereby, the plant growth promoter is not contained in the exposed surface of the solid medium, and the plant growth promoter is contained in the range absorbed from the roots when the roots of the plant grow on the solid medium after germination. It has been found that the growth of algae on the exposed surface of the solid medium is suppressed and the growth of the germinated plant is promoted.

[0018] Therefore, according to the method for applying the plant growth promoter of the present disclosure, even when the plant growth promoter is applied during the germination process of the plant, the amount of algae generated on the medium surface (in other words, the exposed surface of the solid medium) can be suppressed to the same level as when the plant growth promoter is not added, so that the growth of algae can be suppressed. Further, according to the method for applying the plant growth promoter of the present disclosure, since the growth of the plant can be effectively promoted, the plant can be cultivated efficiently. As a result, in hydroponic cultivation, plant production is enhanced and the harvest of the plant increases. Therefore, according to the method for applying the plant growth promoter of the present disclosure, plants can be produced efficiently and stably in hydroponic cultivation.

[0019] Hereinafter, embodiments will be described with reference to the drawings.

[0020] Note that each of the embodiments described below shows comprehensive or specific examples. The numerical values, materials, steps, order of steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, components not described in the independent claims indicating the most general concept are described as optional components.

[0021] Also, each drawing is not necessarily drawn precisely. In each drawing, substantially the same configuration is denoted by the same reference numeral, and duplicate descriptions may be omitted or simplified.

[0022] In the following, the XYZ directions are defined as three mutually orthogonal directions, with the upper side being the “+Z side” and the lower side being the “-Z side”.

[0023] In this specification, when explaining the position, posture, orientation, etc. of each configuration, it is assumed to be in the normal use state. For example, the vertical direction of the solid medium in this embodiment corresponds to the vertical direction.

[0024] In addition, hereinafter, terms indicating the relationship between elements such as parallel and perpendicular, terms indicating the shape of elements such as rectangular, and numerical ranges do not represent a strict meaning, but rather mean substantially equivalent ranges, for example, including a difference of about several percent.

[0025] In addition, in this specification, both the microbial cells and the cells represent an individual of one cyanobacterium.

[0026] (Embodiment) [Method for applying plant growth promoter] [1. Overview] First, an overview of the method for applying the plant growth promoter according to this embodiment will be described.

[0027] The method for applying the plant growth promoter according to the embodiment is a method for applying the plant growth promoter in hydroponics, and is carried out in the cultivation process from sowing the seeds 50 of the plant (see (d) in FIG. 1) (hereinafter, also referred to as "after sowing") until at least one transplantation of the plants germinated from the seeds 50.

[0028] The plant to be cultivated may be at least one plant selected from leafy vegetables such as frilly lettuce, leaf lettuce, romaine lettuce, head lettuce, spinach, and mizuna, but is not limited to these leafy vegetables. For example, the plant to be cultivated may be, in addition to leafy vegetables, fruit vegetables, root vegetables, flower plants, fruits, grains, mosses, ferns, foliage plants, or herbs.

[0029] The seeds 50 of the plant to be cultivated may be, for example, those in which various coating materials are coated on the surface with what is called a so-called seed as the core material. In addition, the seeds 5 of the plant to be cultivated are not limited to coated seeds, and may be, for example, seeds immersed in an aqueous solution of a drug and having the drug penetrated into the seeds. The drug may be, for example, a bactericide, a disinfectant, or a growth promoter. The seeds 5 of the plant to be cultivated are not limited to the above examples, and for example, after immersing the seeds in an aqueous solution of a drug, the surface of the seeds may be coated with a coating material.

[0030] The method of applying the plant growth promoter may be carried out in a closed environment such as a plant factory, but is not particularly limited. For example, it may be carried out in an open environment such as open field cultivation. The closed environment includes semi-closed environments such as greenhouses. The environmental conditions such as the driving conditions of the light source, the adjustment conditions of the temperature, humidity and carbon dioxide concentration, and the air conditioning conditions such as air supply in the closed environment may be appropriately set according to the plants to be cultivated.

[0031] The light source for growing plants may be at least one of natural light (so-called sunlight) and artificial light. The artificial light is, for example, light emitted from an artificial light source such as an LED (Light Emitting Diode), a fluorescent lamp, or an organic light emitting diode (OLED). In a plant factory, for example, at least one of a lighting device that takes in natural light (so-called sunlight) and irradiates plants, and a light emitting device equipped with an artificial light source may be used. The light irradiated to plants by these devices affects physiological actions such as photosynthesis and morphogenesis of plants. In this embodiment, an example in which the light source used in a closed environment such as a plant factory is an artificial light source will be described, but it is not limited thereto. For example, the light source may be appropriately selected according to the plants to be cultivated.

[0032] [2. Example of method] FIG. 1 is a diagram schematically showing an example of the method of applying the plant growth promoter according to the embodiment. FIG. 2 is a flowchart showing an example of the method of applying the plant growth promoter according to the embodiment.

[0033] As shown in FIG. 2, the method of applying the plant growth promoter according to the embodiment includes preparing a solid medium 10 (S1), pouring a mixed solution 30 in which a plant growth promoter is added to a hydroponic culture solution into a tray 20 (S2), and placing the solid medium 10 in the tray 20 (S3). Hereinafter, each step of steps S1 to S3 will be specifically described with reference to the drawings.

[0034] [Step S1 (Preparation step of solid medium)] Next, with reference to FIGS. 1(a) and 3, the preparation process of the solid medium 10 in step S1 will be described. FIG. 1(a) is a schematic diagram showing an example of the preparation process of the solid medium. FIG. 3 is a flowchart showing an example of the detailed flow of step S1 in FIG. 2.

[0035] In the preparation process of the solid medium 10 (step S1), a water-retaining carrier 100a is prepared (S11), and the prepared water-retaining carrier 100a is immersed in a hydroponic culture solution (not shown) (S12). Thereby, the solid medium 10 which is the water-retaining carrier 100a impregnated with the hydroponic culture solution is prepared.

[0036] First, to prepare the water-retaining carrier 100a in step S11 means, for example, as shown in FIG. 1(a), cutting the water-retaining carrier 100 into a size corresponding to the size of the tray 20 to prepare the water-retaining carrier 100a.

[0037] The solid medium 10 is used as a germination bed for germinating the seeds 5 of plants (see (d) in FIG. 1) or as a growth bed (so-called seedbed) for growing plant seedlings. The solid medium 10 is a water-retaining carrier 100 impregnated with a hydroponic culture solution containing inorganic substances of nutrient components (such as nitrogen, phosphorus, and potassium, etc.) necessary for plant cultivation, and supplies nutrient components, water, etc. to the plants to be cultivated. The water-retaining carrier 100 is composed of a porous material such as, for example, sponge, foam, or fiber mat. The material of the porous material may be a foamed resin such as polyurethane resin, phenolic resin, polyester resin, polyethylene resin, or polystyrene resin, rock wool, or a fiber material such as coco mat. For example, as shown in FIG. 1(a), in the water-retaining carrier 100, a plurality of cells 1 having cuts 12 in the central portion of the upper surface (+Z side surface) are aligned and connected in a predetermined direction. The plurality of cells 1 may be partially connected to such an extent that they do not separate from the adjacent cells 1. Thereby, the water-retaining carrier 100 can be easily cut into a desired size (for example, the 4×5 cell size in FIG. 1(a)), and further, even when the water-retaining carrier 100 is immersed in a hydroponic culture solution (not shown), the plurality of cells 1 do not separate and maintain a structure that is aligned and connected in a predetermined direction. That is, in step S11, by cutting the water-retaining carrier 100 into a desired size, a water-retaining carrier 100a for the solid medium 10 is prepared. Here, the water-retaining carrier 100a obtained by cutting the water-retaining carrier 100 into a desired size is used for the solid medium 10, but the water-retaining carrier 100 may be used for the solid medium 10 as it is.

[0038] In addition, in FIG. 1, an example in which the water-retaining carrier 100 has a cut 12 on the upper surface is shown, but it is not particularly limited as long as it can accommodate the seeds 5 of plants. For example, it may be a depression. Also, the form of the cut 12 may be appropriately designed according to the type of plant cultivated on the solid medium 10. Further, the size of the solid medium 10 is not particularly limited and may be appropriately designed according to the number of seeds 5 of the plants cultivated on the solid medium 10.

[0039] The shape of the cell 1 of the solid medium 10 is not particularly limited as long as it is a three-dimensional shape. For example, it may be a cube, a rectangular parallelepiped, a columnar body, a hemispherical shape, or a tapered shape. Hereinafter, a solid medium 10 in which a plurality of cube-shaped cells 1 having a cut 12 on the upper surface (the surface on the +Z side) and each side being 30 mm are aligned in a predetermined direction will be described as an example.

[0040] Hereinafter, step S12 will be described in more detail. Although not shown in FIG. 1(a), in step S12, the water-retaining carrier 100a prepared in step S11 is put into the hydroponic culture solution. For example, in step S12, the water-retaining carrier 100a is put into a tank (so-called container) containing the hydroponic culture solution in advance, and the water-retaining carrier 100a is immersed in the hydroponic culture solution. Thereby, the hydroponic culture solution is impregnated into the water-retaining carrier 100a.

[0041] The tank only needs to have a volume in which the water-retaining carrier 100a can be accommodated therein, and its material or shape is not particularly limited. Also, the amount of the hydroponic culture solution in the tank only needs to be at least an amount in which the entire water-retaining carrier 100a can be accommodated in the hydroponic culture solution, and may be appropriately set by the operator.

[0042] The water-retaining carrier 100a may be washed with an aqueous solution using water such as tap water or groundwater as a solvent before being immersed in the hydroponic culture solution, or may be washed with the hydroponic culture solution after being washed with the aqueous solution.

[0043] Note that "the water-retaining carrier 100a is impregnated with the hydroponic culture solution" in this specification means that the water-retaining carrier 100a absorbs the hydroponic culture solution and holds the absorbed hydroponic culture solution inside the water-retaining carrier 100a. In order to efficiently absorb the hydroponic culture solution into the water-retaining carrier 100a, for example, physical compression such as pressing the water-retaining carrier 100a immersed in the hydroponic culture solution in the tank toward the bottom of the tank may be repeated. Thereby, the air contained in the water-retaining carrier 100a is efficiently replaced with the hydroponic culture solution. The physical compression on the water-retaining carrier 100a may be performed by any method that can replace the air in the water-retaining carrier 100a immersed in the hydroponic culture solution with the hydroponic culture solution, and the method is not particularly limited. For example, the physical compression on the water-retaining carrier 100a may be performed manually by an operator, or may be performed by a mechanical method using a jig such as a compressor, and may be appropriately selected according to the design. Note that as a method for replacing the air in the water-retaining carrier 100a with the hydroponic culture solution, for example, the water-retaining carrier 100a immersed in the hydroponic culture solution may be placed in the degassing tower of a vacuum degassing device together with the tank and evacuated.

[0044] The physical compression on the water-retaining carrier 100a is performed until it can be visually confirmed that air (here, bubbles) is no longer emitted from the water-retaining carrier 100a due to the compression. Since the number of compressions varies depending on the size and material of the water-retaining carrier 100a, it may be selected within the range achievable in the operation. For example, the above compression may be repeated until bubbles can no longer be visually confirmed as described above, or may be repeated within the range achievable considering the working time, efficiency, etc.

[0045] By performing the above process, in step S1, the solid medium 10 in which the water-retentive carrier 100a sufficiently absorbs and holds the hydroponic culture solution is prepared. The solid medium 10 prepared in step S1 contains a hydroponic culture solution in an amount such that the hydroponic culture solution drips from the solid medium 10. For example, the solid medium 10 contains a hydroponic culture solution in an amount of about 60% or more and about 80% or less of the volume of the water-retentive carrier 100a. Note that the amount of the hydroponic culture solution contained in the solid medium 10 may vary depending on the material of the water-retentive carrier 100a and the water absorption and retention function (more specifically, the function of absorbing and retaining an aqueous solution such as a hydroponic culture solution) of the material. For example, in the examples described later, the material of the water-retentive carrier 100a is a polyurethane resin. In this case, the solid medium 10 contains a hydroponic culture solution in an amount of 68% of the volume of the water-retentive carrier 100a. Further, for example, the water-retentive carrier 100a shown in FIG. 1(a) is composed of 20 cells 1 each having a size of 2.3 cm in length × 2.3 cm in width × 2.8 cm in height arranged in a plane in 4 rows and 5 columns, and its volume is 296 cm 3 3. In this case, the amount of the hydroponic culture solution contained in the water-retentive carrier 100a may be 200 cm 3 (200 mL), which corresponds to 68% of the volume of the water-retentive carrier 100a. Note that since the specific gravity of the hydroponic culture solution has water as the main component, the amount of the hydroponic culture solution may be calculated with a specific gravity equivalent to that of water (specific gravity = 1).

[0046] Further, the solid medium 10 prepared in step S1 may be stored in the hydroponic culture solution until it is used after immersing the water-retentive carrier 100a in the hydroponic culture solution in step S12. For example, after immersing the water-retentive carrier 100a in the hydroponic culture solution in the tank in step S12, the solid medium 10 may be stored as it is in the tank, or the solid medium 10 may be taken out of the tank and transferred to a storage container or bag filled with the hydroponic culture solution for storage. Note that the storage method of the solid medium 10 may be any method that can prevent the solid medium 10 from drying, and is not limited to the above storage method.

[0047] [Step S2 (Step of Pouring the Mixture into the Tray)] Next, referring to FIGS. 1(b) and 4, the step of introducing the mixed solution 30 into the tray 20 in step S2 will be described. FIG. 1(b) is a schematic diagram showing an example of the step of introducing the mixed solution 30 into a cultivation tray (so-called tray 20). FIG. 4 is a flowchart showing an example of the detailed flow of step S2 in FIG. 2.

[0048] In the step of introducing the mixed solution 30 into the tray 20 (step S2), a mixed solution 30 containing a hydroponic culture solution and a plant growth promoter containing substances involved in promoting plant growth is prepared (step S21), and the prepared mixed solution 30 is introduced into the tray 20 (step S22). Thereby, the tray 20 into which the mixed solution 30 is introduced is prepared. Hereinafter, each step will be specifically described.

[0049] First, step S21 will be described. Step S21 is a step of preparing the mixed solution 30. Note that preparing the mixed solution 30 in step S21 may be, for example, weighing a previously prepared mixed solution 30, or preparing the mixed solution 30 by adding a plant growth promoter to the hydroponic culture solution.

[0050] "Promotion of plant growth" in this specification includes meanings such as promotion of plant growth (specifically, increase in plant height and mass, promotion of germination, or promotion of rooting), and improvement of plant quality (specifically, increase in fruit setting rate, increase in fruit mass, improvement of sugar content), and further includes the meaning of increase in yield as a crop. "Promotion of plant growth" may be achieved by promoting the addition or absorption of nutrient components to promote plant growth, or may be achieved by suppressing the occurrence of algae or diseases that inhibit plant growth.

[0051] The plant growth promoter may be in any dosage form such as a liquid, powder, granule, or tablet, but may be a liquid from the viewpoint of ease of preparation of the mixed solution 30. For example, when the plant growth promoter is a liquid, the mixed solution 30 may be prepared by suspending, dissolving, or dispersing the liquid in a hydroponic culture solution. The liquid plant growth promoter may be, for example, a liquid fertilizer containing aminolevulinic acid or the like, or a liquid in which a plant growth promoting substance such as oxidized glutathione (so-called oxidized glutathione) is suspended, dissolved, or dispersed in water or an aqueous dispersion medium or solvent, or may be a secretion of photosynthetic bacteria (for example, genetically modified cyanobacteria). The modified cyanobacteria and the secretion of the modified cyanobacteria will be described later. Further, the powder plant growth promoter may be a powder fertilizer, may be a powder of a plant growth promoting substance such as oxidized glutathione, or may be a dried powder of a secretion of photosynthetic bacteria (for example, modified cyanobacteria). Further, the granular or tablet plant growth promoter may be a granular or tablet fertilizer, or may be a granule or tablet in which a powder of a plant growth promoting substance or a dried powder of a secretion of photosynthetic bacteria (for example, modified cyanobacteria) is mixed with additives such as a predetermined excipient, binder, and disintegrant. Hereinafter, an example in which the plant growth promoter is a liquid and is a secretion of modified cyanobacteria will be described.

[0052] In step S21, a mixed solution 30 in which the plant growth promoting substance contained in the secretion is suspended, dissolved, or dispersed in the hydroponic culture solution is prepared by adding and mixing the secretion of the modified cyanobacteria to the hydroponic culture solution.

[0053] Note that step S21 and step S22 may be performed simultaneously. For example, after the hydroponic culture solution is poured into the tray 20, the plant growth promoter may be poured into the tray 20 and stirred and mixed in the tray 20.

[0054] The plant growth promoter is, for example, a secretion of a modified cyanobacterium (hereinafter also simply referred to as "secretion") in which the total amount of a protein involved in the binding of the outer membrane and the cell wall in cyanobacteria (also referred to as a binding-related protein) is suppressed to 30% or more and 70% or less of the total amount of the protein in the parent strain (hereinafter also referred to as the parent cyanobacterium). For example, "the total amount of the binding-related protein is suppressed to 30% of the total amount of the protein in the parent strain" means that 70% of the total amount of the protein in the parent strain is lost and it is in a state of being suppressed to 30%. Thus, in the modified cyanobacterium, since the function of the protein involved in the binding of the outer membrane and the cell wall of cyanobacteria is suppressed, the binding of the outer membrane and the cell wall (for example, the binding amount and the binding force) is partially reduced, and the outer membrane is more likely to be partially detached from the cell wall. For example, Non-Patent Document 1 (Hikaru Kibata, Studies on molecular basis of cyanobacterial outer membrane function and its evolutionary relationship with primitive chloroplasts, doctoral thesis, [online], 2018.03.27, Internet: <URL: http: / / hdl.handle.net / 10097 / 00122689>), and Non-Patent Document 2 (Seiji Kojima, Elucidation and application of the bacterial-derived membrane stabilization mechanism and substance permeation mechanism functioning in the chloroplast surface membrane, research expenses, [online], 2018.04.23, Internet: <URL: https: / / kaken.nii.ac.jp / grant / KAKENHI-PROJECT-18H02117>) describe that when the gene slr1841 or the slr0677 gene encoding the binding-related protein is deleted, the cell proliferation ability is lost. On the other hand, in the modified cyanobacterium of the present disclosure, since the expression of the gene encoding the binding-related protein is suppressed, the cell proliferation ability is not impaired.

[0055] Cyanobacteria (also known as blue bacteria or blue-green algae) are a group of eubacteria that decompose water through photosynthesis to produce oxygen and fix CO2 in the air using the obtained energy. Some cyanobacteria can also fix nitrogen (N2) in the air depending on the species. Thus, since cyanobacteria can obtain most of the raw materials (i.e., nutrients) and energy necessary for the growth of the cells from air, water, and light, cyanobacteria can be cultured using inexpensive raw materials and a simple process.

[0056] In addition, cyanobacteria are known to grow rapidly and have high light utilization efficiency. Furthermore, since genetic manipulation is easier compared to other algal species, active research and development have been conducted on substance production using cyanobacteria among photosynthetic microorganisms. However, even if modified to produce a desired substance by genetic manipulation, the substance produced inside the cyanobacterial cells is difficult to be secreted outside the cells (i.e., outside the cell bodies). Therefore, it is necessary to disrupt the cyanobacterial cells to extract the substance produced inside the cells.

[0057] The present inventors have successfully obtained, by genetic modification, cyanobacteria modified with acidic substances inside the cells while maintaining the cell growth ability by partially detaching the outer membrane covering the cell wall of cyanobacteria from the cell wall. And the present inventors have found that desired compounds, proteins, and intracellular metabolites produced inside the cells of the modified cyanobacteria are easily secreted outside the cell bodies. Also, in the above process, the present inventors have also discovered that the secretions of the modified cyanobacteria have the effects of increasing the yields and improving the quality of multiple crop species.

[0058] For example, the protein involved in the binding between the outer membrane and the cell wall may be at least one of the SLH (Surface Layer Homology) domain-containing outer membrane protein and the cell wall-pyruvate modifying enzyme. The modified cyanobacteria are produced by deleting or inactivating the gene encoding at least any one of these proteins (including a gene having a nucleotide sequence 50% or more identical to the gene).

[0059] The modified cyanobacteria produced in this way have a partially reduced binding (e.g., the amount and strength of binding) between the outer membrane and the cell wall without impairing the cell growth function, and the outer membrane is more likely to be partially detached from the cell wall. Therefore, desired compounds, proteins, and metabolites produced inside the cyanobacteria (i.e., inside the cells, hereinafter also referred to as intracellular products) are more likely to leak outside the outer membrane, that is, outside the bacteria. Such modified cyanobacteria do not require extraction operations for intracellular products such as crushing the bacterial cells, so it is less likely that the physiological activity and yield of intracellular products, and thus substances involved in promoting plant growth among intracellular products (so-called plant growth promoters), will decrease. In addition, since the growth function of the modified cyanobacteria is not impaired, the modified cyanobacteria can be repeatedly used even after recovering the intracellular products (i.e., secretions) secreted outside the bacteria. Therefore, by applying the secretions of the modified cyanobacteria to plants as a plant growth promoter, it is possible to effectively increase plant production and improve the quality of the products.

[0060] Here, the ratio of the hydroponic culture solution to the plant growth promoter contained in the mixture 30 will be described with reference to FIG. 5. FIG. 5 is a diagram showing the ratio of the hydroponic culture solution to the plant growth promoter (simply also referred to as the promoter) contained in the mixture 30 and the amount of the plant growth promoter per unit volume of the water-retaining carrier 100 for the solid medium 10 at each ratio. The amount of the hydroponic culture solution contained in the mixture 30 is V C [mL], the amount of the plant growth promoter contained in the mixture 30 is V G [mL], and the volume of the water-retaining carrier 100a for the solid medium 10 (hereinafter, the water-retaining carrier 100a) is V A [cm 3 . Note that the amount of the plant growth promoter per unit volume of the water-retaining carrier 100a will be described in step S22.

[0061] As shown in Fig. 5, a mixed solution of 1 to 6 was prepared, and when the plant growth promoting effect was examined using each mixed solution, the ratio (V C :V G ) of the hydroponic culture solution and the plant growth promoter contained in the mixed solution 30 may be 45:5 or more and 20:30 or less. Thereby, when the mixed solution 30 of the above ratio is applied to plants, for example, a plant growth promoting effect such that the above-ground weight (also referred to as shoot weight) (wet weight) of the plants increases by about 10% is expected. Further, the ratio (V C :V G ) of the hydroponic culture solution and the plant growth promoter contained in the mixed solution 30 may be 40:10 or more and 30:20 or less. Thereby, when the mixed solution 30 of the above ratio is applied to plants, for example, a plant growth promoting effect such that the shoot weight (wet weight) of the plants increases by 20% or more is expected.

[0062] In step S21, for example, in order to evenly cover the bottom surface of the tray 20 with the mixed solution 30, a mixed solution 30 in an amount such that the height from the bottom surface of the tray 20 to the liquid level of the mixed solution 30 poured into the tray 20 is 3 mm or more and 5 mm or less may be prepared. Here, the amount of the mixed solution 30 in the tray 20 is 50 mL, which is 3 mm or more and 5 mm or less. In this case, the mixed solution 30 is the ratio (V C :V G ) of the hydroponic culture solution and the plant growth promoter shown in Fig. 5, and the mixed solution 30 (50 mL) is the sum of the hydroponic culture solution (V C mL) and the plant growth promoter (V G mL). For example, when the mixed solution 30 (50 mL) is the mixed solution 2 described in Fig. 5, the mixed solution 30 is prepared by mixing 45 mL of the hydroponic culture solution and 5 mL of the plant growth promoter.

[0063] Further, the amount of the plant growth promoter per unit volume of the water retention carrier 100a, V G / V A (mL / cm 3 ) is, for example, as shown in Fig. 1(a), assuming that the water retention carrier 100a is composed of 4 × 5 cells 1, when the size of the cell 1 is 2.3 cm in length × 2.3 cm in width × 2.8 cm in height, the volume V of the water retention carrier 100aA =2.3×2.3×2.8×4×5 = 296.24 cm 3 (Hereinafter, let V A =296 cm 3 ). At this time, when 50 mL of the mixed solution 30 (for example, in the mixed solution 30, V C :V G is 0:50) is put into the tray 20, the amount of the plant growth promoter per unit volume of the water-retaining carrier 100a, V G / V A (mL / cm 3 ) is 50 mL÷296 cm 3 = 16.9×10 -2 mL ≈ 17×10 -2 mL / cm 3 . Therefore, the amount of the plant growth promoter per unit volume of the water-retaining carrier 100a, V G / V A (mL / cm 3 ) is, as shown in FIG. 5, when V C :V G in the mixed solution 30 is 45:5, it becomes 1.7×10 -2 mL / cm 3 , when V C :V G is 40:10, it becomes 3.4×10 -2 mL / cm 3 , when V C :V G is 30:20, it becomes 6.8×10 -2 mL / cm 3 , and when V C :V G is 20:30, it becomes 10×10 -2 mL / cm 3 .

[0064] Also, the amount of the plant growth promoter V G is, for example, when V C :V G in the mixed solution 30 is 45:5, the amount of the plant growth promoter per unit volume of the water-retaining carrier 100a (V G / V A ) 1.7×10 -2 mL / cm 3 multiplied by the volume of the water-retaining carrier 100a (VA ) 296 cm 3 is calculated by multiplying.

[0065] Note that, similar to the specific gravity of the hydroponic culture solution described above, since the main component of the plant growth promoter is water, the specific gravity of the plant growth promoter is the same as that of water (specific gravity = 1), and the amount V G (mL) of the plant growth promoter contained in the mixture 30 may be calculated.

[0066] Note that the above amount of the plant growth promoter is merely an example and is not limited thereto, and may be appropriately determined according to the type of the plant growth promoter, the type of the plant, etc.

[0067] Also, in the preparation of the mixture 30, in order to stir and mix the hydroponic culture solution and the plant growth promoter to uniformly adjust the concentration of the plant growth promoter in the mixture 30, a stirrer equipped with a stirring rod, a magnetic stirrer, or a stirring bar may be used, and it may be appropriately selected according to the design.

[0068] Subsequently, step S22 will be described with reference to FIG. 1(b). FIG. 1(b) is a schematic diagram showing an example of the step of introducing the mixture 30 into the cultivation tray (here, the tray 20). In step S22, the mixture 30 prepared in step S21 is introduced into the tray 20. At this time, the mixture 30 is poured into the tray 20 so as to spread uniformly over the tray 20 (in other words, an amount that spreads uniformly over the tray 20). For example, a predetermined amount of the mixture 30 may be directly poured from the container used by the operator to prepare the mixture 30 into the tray 20, or the mixture 30 may be fed from the container by a pump or the like and introduced into the tray 20. The method of introducing the mixture 30 into the tray 20 is not particularly limited to the above example, and may be appropriately selected according to the working environment and working conditions. Note that, as described above, step S21 and step S22 may be performed simultaneously.

[0069] For example, the amount of the mixed solution 30 that evenly (i.e., uniformly) spreads over the bottom surface of the tray 20 may be the minimum amount that completely covers the bottom surface of the tray 20. The amount that becomes uniform is the amount that fills the volume (also referred to as the capacity) of the inner groove of the tray 20 in the range of 3 mm or more and 5 mm or less. Uniformity means a state where the depth of the inner groove of the tray 20 is filled to 3 mm or more and 5 mm or less. For example, the liquid volume of the mixed solution 30 poured into the tray 20 may be an amount such that the height from the bottom surface of the tray 20 to the liquid surface of the mixed solution 30 poured into the tray 20 is 1 / 10 or more and 1 / 6 or less of the height of the solid medium 10. For example, when the height of the solid medium 10 (in other words, the height of the water retention carrier 100a and the cell 1) is about 3 cm, the amount of the mixed solution 30 poured into the tray 20 may be an amount such that the height from the bottom surface of the tray 20 to the liquid surface of the mixed solution 30 poured into the tray is 3 mm or more and 5 mm or less.

[0070] The tray 20 is a container on which the solid medium 10 is placed, and the edge of the flat placement surface (hereinafter also referred to as the bottom surface) is raised. The inner dimensions (length × width × height) of the tray are equivalent to the outer dimensions (length × width × height) of the solid medium 10 (more specifically, about 0 mm to several mm smaller than the outer dimensions of the solid medium 10), and are of a size that can accommodate the solid medium 10 in the tray 20 without gaps. The tray 20 is, for example, a tray with a rectangular bottom surface, and the height of the edge may be appropriately designed according to the size of the solid medium 10 to be placed.

[0071] [Step S3 (Step of placing the solid medium in the tray)] Subsequently, with reference to FIG. 1(c), the step of placing the solid medium 10 on the tray 20 in step S3 will be described. FIG. 1(c) is a schematic diagram showing an example of the step of placing the solid medium 10 in the tray 20.

[0072] In the step of placing the solid medium 10 into the tray 20 (step S3), the solid medium 10 prepared in step S1 is placed into the tray 20 containing the mixed solution 30 prepared in step S2. More specifically, it is placed in the tray 20 by covering the lower surface (-Z side surface) of the solid medium 10 with the liquid surface of the mixed solution 30 placed in the tray 20 (see (c) in Fig. 1).

[0073] The method of placing the solid medium 10 in the tray 20 is not particularly limited as long as the mixed solution 30 in the tray 20 does not overflow. For example, an operator may hold the solid medium 10 by hand and place it in the tray 20, or may use a jig for the operator to grip the solid medium 10 and place it in the tray 20, or a machine such as a robot may perform the above operation instead of the operator.

[0074] Also, as described above, since the inner dimensions of the tray 20 are equal to the outer dimensions of the solid medium 10 and are sized such that the solid medium 10 can be stored in the tray 20 without gaps (in other words, placed), bubbles may be trapped at the boundary between the solid medium 10 and the tray 20 during the process of storing (or placing) the solid medium 10 in the tray 20. In that case, the bubbles may be expelled by pressing the upper surface (+Z side surface) of the solid medium 10 toward the bottom surface of the tray 20. The pressing of the solid medium 10 may be performed by the hand of an operator, a jig, or a machine such as a robot.

[0075] [Seeding process] Next, the seeding process will be described with reference to FIGS. 1(d) and 1(e). FIG. 1(d) is a schematic diagram showing an example of the seeding process. FIG. 1(e) is a cross-sectional view taken along line I-I of the cultivation tank 40 after seeding shown in FIG. 1(d). Although not shown in the flowchart of FIG. 2, the method for applying the plant growth promoter according to the present disclosure may include a seeding process after step S3. In the seeding process, the plant seeds 50 are, for example, placed one by one at equal intervals on the solid medium 10. More specifically, as shown in FIG. 1(d), the whole or a part of the plant seeds 50 are placed so as to be accommodated in the cuts 12 provided in each of the plurality of cells 1. Thereby, as shown in FIG. 1(e), the plant seeds 50 are placed at equal intervals on the solid medium 10. In the seeding process, depending on the type, variety, and shape of the plant seeds, two or more seeds 50 may be placed in the cuts 12, or the seeds 50 may be watered with a hydroponic culture solution or water after being placed.

[0076] [3. Effects, etc.] As described above, the method for applying the plant growth promoter is a method for applying the plant growth promoter in hydroponics, which includes preparing a solid medium 10 that is a water-retentive carrier 100a impregnated with a hydroponic culture solution (step S1), pouring a mixed solution 30 of the hydroponic culture solution and a plant growth promoter containing substances involved in plant growth into a tray 20 (step S2), and placing the solid medium 10 in the tray 20 into which the mixed solution 30 has been poured (step S3).

[0077] Such a method of applying a plant growth promoter can suppress the growth of algae in hydroponics by placing a solid medium 10 that holds a hydroponic culture solution on a tray 20 containing a mixed solution that includes the plant growth promoter. As described above, algae tend to grow on the surface of the solid medium 10 that is exposed to a light source (so-called, exposure surface). Further, when the solid medium 10 contains a plant growth promoter, the growth of algae is promoted. However, in the method of applying the plant growth promoter, at the start of cultivation, the exposure surface of the solid medium 10 does not contain the plant growth promoter, and the plant growth promoter is contained below the exposure surface of the solid medium 10. Therefore, on the exposure surface of the solid medium 10, algae are less likely to be affected by the plant growth promoter, and the growth of algae can be suppressed.

[0078] Also, for example, when the solid medium 10 is placed in the tray 20 into which the mixed solution 30 has been poured (in other words, at the same time as the start of cultivation) and seeds 50 of a plant are sown on the solid medium 10, during the period from sowing to germination, the solid medium 10 in the vicinity of the sown seeds 50 does not contain the plant growth promoter. Then, as time passes after germination, the phenomenon in which the roots of the plant extend in the downward direction (-Z side) of the lower surface of the solid medium 10 and the phenomenon in which the plant growth promoter is diffusively transported in the upward direction (+Z side) of the upper surface of the solid medium 10 proceed simultaneously. And at the time of cotyledon expansion, since the solid medium 10 in the vicinity of the roots of the plant sufficiently contains the plant growth promoter, in hydroponics, it is possible to promote the growth of the cultivated plant while suppressing the generation and growth of algae on the exposure surface.

[0079] From the above, according to the method of applying the plant growth promoter according to the present disclosure, even when the plant growth promoter is applied in hydroponics, the generation and growth of algae on the exposed surface of the solid medium 10 can be suppressed to the same level as when the plant growth promoter is not applied. Further, according to the method of applying the plant growth promoter, as time elapses after germination, the plant growth promoter is diffusely transported to the range that can be absorbed by the roots of the plants in the solid medium 10, so that the growth of the plants can be effectively promoted. Therefore, according to the method of applying the plant growth promoter, in hydroponics, plant production is enhanced and the yield of plants is increased, so that plants can be produced efficiently and stably.

[0080] Further, for example, the method of applying the plant growth promoter is applied in a cultivation process (so-called, initial cultivation process, or germination process) from sowing the seeds 50 of the plant in the solid medium 10 until at least one transplantation of the plants germinated from the seeds 50.

[0081] Thereby, at the start of cultivation, the exposed surface of the solid medium 10 does not contain the plant growth promoter, and the plant growth promoter is contained below the exposed surface of the solid medium 10. More specifically, the liquid mixture 30 gradually penetrates into the solid medium 10 from the portion of the solid medium 10 in contact with the liquid mixture 30 (specifically, as the number of cultivation days elapses), and the plant growth promoter in the liquid mixture 30 diffuses toward the upper surface (+Z side surface) of the solid medium 10. Thereby, in the initial cultivation process, the period in which the exposed surface of the solid medium 10 does not contain the plant growth promoter and the concentration of the plant growth promoter on the exposed surface is lower than the concentration of the plant growth promoter contained in the portion other than the exposed surface is relatively long. Therefore, algae on the exposed surface of the solid medium 10 are less likely to be affected by the plant growth promoter, and the growth of algae can be suppressed. Therefore, in the cultivation process (so-called, initial cultivation process) from sowing the seeds 50 in the solid medium 10 until at least one transplantation of the plants germinated from the seeds 50, the growth of algae can be suppressed.

[0082] Also, for example, in the method of applying the plant growth promoter, in the preparation of the solid medium, a hydroponic culture solution in an amount of 60% or more and 80% or less of the volume of the water-retaining carrier 100a is impregnated into the water-retaining carrier 100a. When the mixture 30 is poured into the tray 20, the height from the bottom surface of the tray 20 to the liquid level of the mixture 30 poured into the tray 20 is 1 / 10 or more and 1 / 6 or less of the height of the solid medium 10, and the mixture 30 in such an amount is poured into the tray 20.

[0083] Thereby, for example, even when the solid medium 10 is placed in the tray 20, the plant growth promoter in the mixture 30 is gradually diffusely transported from the lower part to the upper part of the solid medium 10. Therefore, the generation and growth of algae on the exposed surface of the solid medium 10 can be suppressed, and the growth of plants can be effectively promoted.

[0084] Also, for example, in the method of applying the plant growth promoter, the ratio of the hydroponic culture solution to the plant growth promoter contained in the mixture 30 is 45:5 or more and 20:30 or less.

[0085] Thereby, since the above-ground weight (so-called shoot weight) of the plant is increased, the growth of the plant can be effectively promoted.

[0086] Also, for example, in the method of applying the plant growth promoter, the amount of the plant growth promoter contained in the mixture 30 is 1.7×10 -2 mL / cm 3 or more and 10×10 -2 mL / cm 3 or less per unit volume of the solid medium.

[0087] Thereby, since the above-ground weight (so-called shoot weight) of the plant is increased, the growth of the plant can be effectively promoted.

[0088] Also, for example, in the method of applying the plant growth promoter, the plant growth promoter is a secretion of a modified cyanobacterium in which the total amount of proteins involved in the binding of the outer membrane and the cell wall in cyanobacteria is suppressed to 30% or more and 70% or less of the total amount of such proteins in the parent strain.

[0089] The modified cyanobacteria can be cultured inexpensively and through a simple process by providing only air, water, and light. In addition, since the plant growth promoting substances produced within the cells of the modified cyanobacteria are secreted outside the cells, the secretions containing the plant growth promoting substances can be easily recovered. Further, since the modified cyanobacteria can be repeatedly cultured even after the secretions are recovered, the secretions of the cyanobacteria can be efficiently obtained. Therefore, a plant growth promoter can be obtained inexpensively and efficiently.

[0090] Also, for example, in the method of applying the plant growth promoter, the plant is at least one selected from the group consisting of frilly lettuce, leaf lettuce, romaine lettuce, head lettuce, spinach, and mizuna.

[0091] According to such a method of applying the plant growth promoter, by applying the plant growth promoter during the initial cultivation process from germination to at least the first transplantation, for example, the yield of frilly lettuce after transplantation can be increased, so that the above-mentioned plants can be produced efficiently and stably.

[0092] Also, for example, the method of applying the plant growth promoter is carried out in a plant factory.

[0093] Thereby, since it is carried out in a plant factory where environmental conditions can be controlled, plants can be produced more efficiently and stably.

[0094] (Other embodiments) As described above, the method of applying the plant growth promoter according to one or more aspects of the present disclosure has been described based on the embodiments, but the present disclosure is not limited to this embodiment. Without departing from the spirit of the present disclosure, various modifications conceived by those skilled in the art applied to this embodiment may also be included within the scope of one or more aspects of the present disclosure.

Examples

[0095] Hereinafter, the application method of the plant growth promoter of the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to the following examples in any way.

[0096] In the following examples, the results of a cultivation test of frilly lettuce are shown based on the application method of the plant growth promoter according to the present disclosure. Hereinafter, as the plant growth promoter, the secretion of modified cyanobacteria was used. In the cultivation test, (1) the algal growth inhibitory effect and the growth promoting effect on frilly lettuce in the germination process of the plant growth promoter, (2) the relationship between the addition amount of the plant growth promoter and the weight of frilly lettuce, and (3) the growth promoting effect and the yield increasing effect of the plant growth promoter on frilly lettuce were verified. The germination process refers to the cultivation process from germination to the first transplantation.

[0097] (1) Regarding the algal growth inhibitory effect and the growth promoting effect on cultivated strains of the plant growth promoter in the germination process (Example 1) First, Example 1 will be described. In Example 1, based on the application method of the plant growth promoter according to the present disclosure, the effect of the present disclosure was verified using a mixed solution in which the ratio of the hydroponic culture solution to the plant growth promoter in the mixed solution was 30:20.

[0098] [Preparation process of solid medium] First, a water-retaining carrier is prepared. As the water-retaining carrier, a urethane sponge product made of polyurethane (manufactured by M-type Hydroponics Laboratory Co., Ltd.) in which cells with a size of 2.3 cm in length × 2.3 cm in width × 2.8 cm in height are connected in a planar shape was used. A depression for sowing seeds is formed on the upper surface of each cell. The water-retaining carrier was cut into a size of 4 cells × 5 cells (a total of 20 cells, a total volume of 296 cm 3 ) to prepare a water-retaining carrier (hereinafter, also simply referred to as a carrier).

[0099] Next, the water-retaining carriers sized 4 by 5 were washed. The washing was carried out by putting the above carriers into tap water filled in a 6-L bucket and repeatedly compressing the carriers manually in the water. Compression was repeated until air bubbles escaping from the carriers could no longer be visually confirmed, and then the carriers were taken out of the water. Then, the water was sufficiently wrung out until no tap water dripping from the carriers could be visually confirmed.

[0100] Next, the carriers were immersed in the hydroponic nutrient solution to impregnate the carriers with the hydroponic nutrient solution. The hydroponic nutrient solution was prepared by diluting the stock solution of a commercially available chemical fertilizer for hydroponics with tap water so that the electrical conductivity became 1.0 d / S. Then, a 6-L bucket filled with the hydroponic nutrient solution was prepared.

[0101] Next, the carriers were put into the hydroponic nutrient solution in the bucket, and the carriers were repeatedly compressed manually in the hydroponic nutrient solution. Compression was repeated until air bubbles escaping from the carriers could no longer be visually confirmed. Thus, a solid medium, which is a water-retaining carrier impregnated with the hydroponic nutrient solution, was prepared. The solid medium was stored in the hydroponic nutrient solution until use in the subsequent process.

[0102] [Step of Pouring the Mixture into the Tray] First, a mixture of the hydroponic nutrient solution and the plant growth promoter was prepared. As a result of examining the amount of the mixture that evenly spreads over the bottom surface of the tray, it was found that an appropriate liquid amount is at least about 3 mm to 5 mm from the bottom surface of the tray to the liquid level. In the tray used in this example, since the mixture can be evenly spread over the bottom surface of the tray with a liquid amount of about 40 mL to 60 mL, 50 mL of the mixture was prepared in this example. The amount of the mixture per unit volume of the carrier is obtained by dividing the mixture amount of 50 mL by the volume of the carrier, 296 cm 3 and dividing, resulting in 1.7×10 -2 mL / cm 3This results in. Also, in this example, since the ratio of the hydroponic culture solution to the plant growth promoter in the mixed solution was set to 30:20, the amount of the plant growth promoter contained in 50 mL of the mixed solution was 20 mL. The mixed solution was prepared by adding 20 mL of the plant growth promoter to a container containing 30 mL of the hydroponic culture solution and uniformly mixing it using a stirring rod. The amount of the plant growth promoter per unit volume of the carrier of the solid medium was obtained by dividing the amount of the plant growth promoter in the mixed solution, which was 20 mL, by the volume of the carrier of the solid medium, which was 296 cm 3 to obtain 6.8×10 -2 mL / cm 3 .

[0103] Next, 50 mL of the mixed solution was poured into a tray (inner dimensions: 12 cm in length × 10 cm in width × 3 cm in height, a resin container).

[0104] [Step of placing the solid medium in the tray] Subsequently, the procedure for placing the solid medium in the tray will be described. The solid medium stored in the hydroponic culture solution in the solid medium preparation step was taken out and immediately placed in the tray. At this time, in order to remove the air (in other words, the trapped air bubbles) sandwiched between the solid medium and the tray, the upper surface of the solid medium was gently pressed by hand.

[0105] [Sowing step] Subsequently, the procedure for sowing the seeds of frilly lettuce on the solid medium will be described. One coated seed of frilly ice (manufactured by Snow Brand Seed Co., Ltd.) was placed in each depression of the solid medium, and the seeds of frilly lettuce were sown. Then, the sown solid medium was moved together with the tray to the cultivation device for the germination step, and cultivation was started.

[0106] [Cultivation step] Subsequently, the cultivation step will be described. Here, the cultivation step is the initial cultivation step (so-called germination step) from germination to the first transplantation. The solid medium sown with the seeds of frilly lettuce in the sowing step was irradiated with light using an LED as a light source for 16 hours a day immediately after sowing in the cultivation device for the germination step. The environmental conditions in this step were: the photosynthetic photon flux density on the surface of the solid medium: 330 μmоL / m 2·s, temperature: 22 ± 1 °C, and humidity: 70 ± 10% were maintained and managed. The cultivation period was 7 days.

[0107] [Evaluation] Seven days after cultivation, the tray was taken out from the cultivation device for the germination process, and the weight of the shoot part (so-called, above-ground part) of the cultivated plants and the degree of algal growth were evaluated. Note that the plants that did not germinate were excluded from the evaluation target.

[0108] For the weight of the shoot part, the lowermost part of the stem of the cultivated plants was cut off and discarded, and the remaining part was placed on an electronic balance to measure the weight. The weights of the shoot parts of all the plants to be evaluated were measured, and the average value was taken to calculate the average shoot weight per plant (mg / plant).

[0109] For the degree of algal growth, the number of cells of the solid medium where algae occurred was counted visually, and the ratio of the number of cells where algae occurred to the total number of cells of the solid medium (20 cells) was shown as a percentage (%).

[0110] The evaluation results are shown in Fig. 6. Fig. 6 is a diagram showing the results of Example 1, Comparative Example 1, and Comparative Example 2. In Example 1, the average shoot weight per plant was 82.3 mg / plant. Regarding the degree of algal growth, the occurrence of algae was confirmed in 8 cells out of the solid medium (20 cells), and the ratio of the number of cells where algae occurred to the total number of cells of the solid medium was 40%.

[0111] (Comparative Example 1) Subsequently, Comparative Example 1 will be described. Comparative Example 1 is different from Example 1 in that 50 mL of hydroponic culture solution was put into the tray instead of the mixed solution. That is, in Comparative Example 1, the steps other than the step of putting the mixed solution into the tray were carried out in the same manner as in Example 1.

[0112] [Step of putting the mixed solution into the tray] In Comparative Example 1, a hydroponic culture solution was used instead of the mixed solution. Specifically, 50 mL of hydroponic culture solution was put into the tray.

[0113] [Evaluation] The evaluation results of the weight of the shoot part of the cultivated plants and the degree of algae growth 7 days after cultivation in Comparative Example 1 are shown in FIG. 6. In Comparative Example 1, the average shoot weight per plant was 64.0 mg / plant, which was nearly 20% lower than that in Example 1. Regarding the degree of algae growth, the same results as in Example 1 were obtained. Specifically, algae generation was confirmed in 8 out of 20 cells of the solid medium, and the ratio of the number of cells with algae generation to the total number of cells in the solid medium was 40%.

[0114] (Comparative Example 2) Subsequently, Comparative Example 2 will be described. In Comparative Example 2, in the step of preparing the solid medium, it is different from Example 1 in that the carrier with water retention is impregnated with a mixed solution (hydroponic nutrient solution: plant growth promoter = 30:20). That is, the steps other than the step of preparing the solid medium were carried out in the same manner as in Example 1.

[0115] [Step of preparing solid medium] It was carried out in the same manner as in Example 1 except for (i) immersing the washed carrier in the previously prepared mixed solution to impregnate the carrier with the mixed solution, (ii) putting the carrier into the mixed solution in the bucket and repeatedly compressing the carrier manually in the mixed solution, and (iii) storing the solid medium in the mixed solution until it was used in the subsequent steps.

[0116] Specifically, (i) will be described below. In Comparative Example 2, the hydroponic nutrient solution was prepared in the same manner as in Example 1. Then, 240 mL of the plant growth promoter was added to a 6 L bucket containing 3 L of the hydroponic nutrient solution, and the mixed solution was prepared by uniformly mixing using a stir bar. In (ii) and (iii) above, the mixed solution prepared in the same manner as in (i) was used, respectively.

[0117] [Evaluation] The evaluation results of the weight of the shoot part of the cultivated plants and the degree of algae growth 7 days after cultivation in Comparative Example 2 are shown in FIG. 6. In Comparative Example 2, the average shoot weight per plant was 81.7 mg / plant, and a growth promotion effect almost equivalent to that in Example 1 was observed. Regarding the degree of algae growth, algae generation was confirmed in all 20 cells of the solid medium.

[0118] In Comparative Example 2, not only did algae occur, but the growth of the algae was promoted. For example, from the photograph showing the appearance of the solid medium shown in FIG. 6, it can be seen that the surface (exposed surface) of the solid medium in Comparative Example 2 has changed to a darker green color compared to Example 1 and Comparative Example 1. In Comparative Example 2, it was clearly different from the way the algae grew in Example 1 and Comparative Example 1, and it was confirmed that the growth of the algae was also promoted by the plant growth promoter contained in the solid medium.

[0119] (Discussion) When the plant growth promoter was applied as in Example 1 and Comparative Example 2, the shoot weight increased by about 15 mg or more compared to the case where the plant growth promoter was not applied as in Comparative Example 1. Thereby, it was confirmed that when using the secretion of the modified cyanobacteria as a plant growth promoter, the growth of plants is promoted.

[0120] Also, when comparing the results of Example 1 and Comparative Example 2, in Example 1, the growth of algae was suppressed at the same level as in Comparative Example 2 in terms of both appearance and the proportion of cells in which algae grew. Immediately after the start of cultivation, the solid medium does not contain the plant growth promoter, and as the number of cultivation days elapses, the plant growth promoter in the mixed solution gradually diffuses and is transported upward to the solid medium. Therefore, it is considered that the period during which the concentration of the plant growth promoter is maintained at a high level is short at the exposed surface of the solid medium (more specifically, the part exposed to the light source). In other words, from the results of Example 1 and Comparative Example 2, according to the method of applying the plant growth promoter according to the present disclosure, in the initial cultivation step, the plant growth promoter in the mixed solution placed in the tray gradually diffuses and is transported toward the upper surface of the solid medium, and it was confirmed that the plant growth promoter is contained above the solid medium when the roots of the plants grow. This is considered to be supported by the fact that there is almost no difference in the average shoot weight per plant between Example 1 and Comparative Example 2, and that there is a significant difference in the growth of algae.

[0121] In addition, in Example 1, when the method for applying the plant growth promoter according to the present disclosure was applied to the initial cultivation step in hydroponics, the growth of algae on the solid medium was suppressed to the same level as when the plant growth promoter was not applied, and it was shown that the plant growth promoting effect by the plant growth promoter could be obtained. Therefore, according to the present disclosure, it was confirmed that plants can be efficiently and stably produced in hydroponics.

[0122] (2) Regarding the relationship between the addition amount of the plant growth promoter and the weight of frilly lettuce Subsequently, the relationship between the addition amount of the plant growth promoter and the weight of frilly lettuce cultivated by applying the method for applying the plant growth promoter according to the present disclosure will be described.

[0123] (Experimental Examples 1 to 6) In Experimental Examples 1 to 6, in the step of pouring the mixed solution into the tray, it was carried out in the same manner as in Example 1 except that the mixed solution of Example 1 was replaced with the mixed solutions 1 to 6 shown in FIG. 5.

[0124] Hereinafter, the addition amount of the plant growth promoter is the amount of the plant growth promoter contained in 50 mL of the mixed solutions 1 to 6 shown in FIG. 5. More specifically, in Experimental Example 1, "mixed solution 1" shown in FIG. 5 was used, in Experimental Example 2, "mixed solution 2" shown in FIG. 5 was used, in Experimental Example 3, "mixed solution 3" shown in FIG. 5 was used, in Experimental Example 4, "mixed solution 4" shown in FIG. 5 was used, in Experimental Example 5, "mixed solution 5" shown in FIG. 5 was used, and in Experimental Example 6, "mixed solution 6" shown in FIG. 5 was used. Then, sowing and cultivation were carried out in the same manner as in Example 1, and the average shoot weight (mg / plant) per plant of frilly lettuce cultivated in Experimental Examples 1 to 6 was calculated. The results are shown in FIG. 7. FIG. 7 is a diagram showing the results of Experimental Examples 1 to 6.

[0125] As shown in Fig. 7, the average shoot weight per strain in Experimental Examples 2 to 5 was about 10 mg / strain to 20 mg / strain greater than that in Experimental Examples 1 and 6. In particular, in Experimental Examples 3 and 4, a remarkable growth promoting effect was observed in frilly lettuce. However, from the results of Experimental Examples 4 and 5, it was confirmed that when the ratio of the plant growth promoter to the hydroponic culture solution increased, the plant growth promoting effect decreased.

[0126] Specifically, from the results of Experimental Examples 2 to 4, when the plant growth promoter (here, the secretion of modified cyanobacteria) was added in an amount less than that of the hydroponic culture solution, it was confirmed that the shoot weight of frilly lettuce increased with an increase in the addition amount of the plant growth promoter. In particular, in Experimental Example 4, the shoot weight of frilly lettuce was the largest and the plant growth promoting effect was the highest. On the other hand, in Experimental Example 5, it decreased to the same shoot weight level as in Experimental Example 2. From this, it was confirmed that when a plant growth promoter above a certain level was applied, the plant growth promoting effect decreased. Furthermore, in Experimental Example 6, since the shoot weight decreased to the same level as that of frilly lettuce cultivated only with the hydroponic culture solution without the plant growth promoter (Experimental Example 1), it was confirmed that if the addition amount of the plant growth promoter was too much, conversely, the plant growth promoting effect could not be obtained.

[0127] It should be noted that there are known cases where a compound that promotes plant growth (so-called plant growth promoting substance or plant growth promoter) has an adverse effect when the concentration applied to the plant is too high (that is, the plant growth promoting effect cannot be observed). Although a specific mechanism cannot be shown for such cases, it is quite conceivable that there is an optimal concentration in the application of the plant growth promoter.

[0128] From the results of Experimental Examples 1 to 6, when the secretion of modified cyanobacteria was used as the plant growth promoter, with respect to the volume of the carrier (in other words, the volume of the solid medium), 1.7×10 -2 times to 10×10 -2By adding a double amount of the plant growth promoter, it was confirmed that a plant growth promoting effect of increasing the shoot weight of the cultivated strain (here, frilly lettuce) by 10% or more was expected. In particular, with respect to the volume of the carrier (in other words, the volume of the solid medium), 3.4×10 -2 times to 6.8×10 -2 By adding a double amount of the plant growth promoter, it was confirmed that a plant growth promoting effect of increasing the shoot weight of the cultivated strain by 20% or more can be expected.

[0129] (3) Regarding the growth promoting effect and yield increasing effect of the plant growth promoter on frilly lettuce Subsequently, the growth promoting effect and yield increasing effect on frilly lettuce when cultivating frilly lettuce by applying the application method of the plant growth promoter according to the present disclosure will be described. More specifically, when the application method of the plant growth promoter according to the present disclosure is applied to the initial cultivation step of frilly lettuce, the plant growth promoting effect and yield increasing effect of the present disclosure were verified by measuring the weight of frilly lettuce as the number of cultivation days after transplantation elapsed.

[0130] (Example 2) In Example 2, in the preparation step of the solid medium to the cultivation step (cultivation for 7 days from sowing), except for the number of cells of the solid medium, the inner dimensions of the tray, the amount of hydroponic culture solution used, and the amount of the mixed solution, it was carried out in the same manner as in Example 1. Furthermore, Example 2 is different from Example 1 in that after the cultivation step of Example 1 (cultivation for 7 days from sowing), it was transplanted to a planting plate and cultivated (hereinafter referred to as the cultivation step after transplantation). Hereinafter, the differences from Example 1 will be described.

[0131] In the preparation step of the solid medium, the water-retaining carrier was cut into a size of 25 cells × 12 cells (a total of 300 cells, a total volume of 4444 cm 3 ).

[0132] In the step of pouring the mixed solution into the tray, 750 mL of the mixed solution was poured into a tray (inner dimensions: 28 cm in length × 58 cm in width × 26 cm in height, a container made of expanded polystyrene (manufactured by M-type Hydroponics Research Institute Co., Ltd.). The mixed solution was prepared such that the ratio of the hydroponic culture solution to the plant growth promoter was 30:20, similar to Example 1.

[0133] [Cultivation step after transplantation] Subsequently, the cultivation step after transplantation will be described. In Example 2, after performing the cultivation step of cultivating for 7 days from sowing in the same manner as in Example 1, 47 arbitrary plants out of the plants excluding those with poor germination were transplanted onto a planting plate for hydroponics. Then, the entire planting plate was moved to an artificial weather chamber to start the cultivation after transplantation.

[0134] More specifically, the planting plate is a plate-shaped expanded polystyrene planting plate with dimensions of 60 cm in length × 60 cm in width × 3 cm in thickness. After planting 47 arbitrary plants into each cell of the solid medium in the evenly arranged planting holes on the planting plate, the planting plate was floated on the hydroponic culture solution in the artificial weather chamber to start the cultivation.

[0135] The inside of the artificial weather chamber has its temperature, humidity, and CO2 concentration controlled, and a hydroponic culture solution pool is provided on the bottom surface and an LED light source is provided on the ceiling. By installing the planting plate in a floating manner on the hydroponic culture solution pool, the above-ground part of the cultivated plants is exposed to the light source and the underground part is immersed in the hydroponic culture solution.

[0136] The environmental conditions were managed to maintain a photosynthetic photon flux density of 280 μmol / m 2 ·s, a light irradiation time of 16 hours per day, a temperature of 20 ± 1°C, a humidity of 70 ± 10%, and a CO2 concentration of 1000 ± 100 ppm. The hydroponic culture solution was adjusted to have an electrical conductivity of 2.0 d / S and a pH of 6.0 every few days. The cultivation period was 24 days. Specifically, 16 days after the cultivation, the fresh weight (so-called wet weight) of all plants was measured, and after thinning out by leaving 16 arbitrary plants within the range of the average ± standard deviation, the remaining 16 plants were cultivated for another 8 days, resulting in a total cultivation period of 24 days.

[0137] [Evaluation] The evaluation of the yield of frilly lettuce was carried out by measuring the weight (wet weight) of each plant on the 14th and 24th days after transplantation, and calculating the weight per plant (in other words, the average weight per plant). The evaluation results are shown in Fig. 8. Fig. 8 is a diagram showing the results of Example 2 and Comparative Example 3.

[0138] As described above, in Example 2, a plant growth promoter was applied in the germination process in the same manner as in Example 1. As shown in Fig. 8, in Example 2, the average weight per plant was 19.2 g / plant on the 14th day after transplantation, and 89.2 g / plant on the 24th day after transplantation.

[0139] (Comparative Example 3) Subsequently, Comparative Example 3 will be described. Comparative Example 3 is different from Example 2 in that a hydroponic culture solution is used instead of the mixed solution. That is, in Comparative Example 3, the steps from the preparation of the solid medium to the cultivation process (cultivation for 7 days from sowing) were carried out in the same manner as in Comparative Example 1, and the cultivation process and evaluation after transplantation were carried out in the same manner as in Example 2.

[0140] [Evaluation] The evaluation results of Comparative Example 3 are shown in Fig. 8. As shown in Fig. 8, in Comparative Example 2, the average weight per plant was 17.3 g / plant on the 14th day after transplantation, and 77.6 g / plant on the 24th day after transplantation.

[0141] (Discussion) From the results of Example 2 and Comparative Example 3, the frilly lettuce cultivated in Example 2 had a significantly increased average weight per plant (hereinafter simply referred to as plant weight) compared to the frilly lettuce in Comparative Example 3. Specifically, the plant weight of the frilly lettuce in Example 2 was 11% greater than that of the frilly lettuce in Comparative Example 3 on the 14th day after transplantation, and 15% greater than that of the frilly lettuce in Comparative Example 3 on the 24th day after transplantation. As a result, in Example 2, the plant weight was significantly increased compared to Comparative Example 3 (test by student's t-test), and the yield increased. That is, in Example 2, it was confirmed that by applying the method for applying the plant growth promoter according to the present disclosure in the initial cultivation process (so-called germination process), an effect of increasing the yield of cultivated plants can be obtained.

[0142] This result indicates that during the period from germination to cotyledon expansion and further to true leaf expansion (i.e., the initial cultivation process), strains whose growth was promoted by applying the secretions of modified cyanobacteria as a plant growth promoter will continue to have their growth promoted even without the application of the plant growth promoter during the cultivation process after transplantation. Regarding such a decrease, at the current stage, a specific mechanism cannot be shown, but it was confirmed that applying the secretions of modified cyanobacteria as a plant growth promoter during the germination process can obtain "excellent strains" with a high growth rate.

[0143] From the above, in the method for applying the plant growth promoter according to the present disclosure, by using the secretions of modified cyanobacteria as a plant growth promoter during the initial cultivation process, the growth of frilly lettuce is promoted not only in the initial cultivation process but also in the cultivation process after transplantation, and the yield is increased. Therefore, it was confirmed that according to the method for applying the plant growth promoter according to the present disclosure, plants can be efficiently and stably cultivated in hydroponics.

Industrial Applicability

[0144] According to the method for applying the plant growth promoter according to the present disclosure, even when the plant growth promoter is applied during the germination process of hydroponics, the generation and growth of algae occurring on the surface of the solid medium can be suppressed at the same level as when the plant growth promoter is not applied. Furthermore, even in the processes after the germination process where the plant growth promoter is not used, the growth of plants is promoted, and the production of plants can be effectively enhanced. Therefore, in the agricultural industry (especially in plant factories where environmental conditions are controlled), the yield of plants can be increased.

Explanation of Signs

[0145] 1 cell 10 solid medium 12 cut 20 tray 30 mixture 40 cultivation tank 50 kinds 100, 100a water retention carriers

Claims

1. A method for applying a plant growth promoter in hydroponics, comprising: preparing a solid medium which is a water-retaining carrier impregnated with a hydroponic nutrient solution; putting a mixture of the hydroponic nutrient solution and a plant growth promoter containing a substance involved in promoting plant growth into a tray; placing the solid medium in the tray into which the mixture has been put; sowing the seeds of the plant on the solid medium, and applying the plant growth promoter before germination of the seeds of the plant and until the first transplantation; A method for applying a plant growth promoter.

2. In the preparation of the solid medium, impregnating the water-retaining carrier with 60% or more and 80% or less of the volume of the hydroponic nutrient solution of the volume of the water-retaining carrier; In the putting of the mixture into the tray, putting into the tray a quantity of the mixture such that the height from the bottom surface of the tray to the liquid level of the mixture put into the tray is 1 / 10 or more and 1 / 6 or less of the height of the solid medium; The method for applying a plant growth promoter according to Claim 1.

3. The plant growth promoter is a secretion of a modified cyanobacterium in which the total amount of proteins involved in the binding of the outer membrane and the cell wall in cyanobacteria is suppressed to 30% or more and 70% or less of the total amount of such proteins in the parent strain; The method for applying a plant growth promoter according to Claim 1 or 2.

4. The plant is at least one selected from the group consisting of frilly lettuce, leaf lettuce, romaine lettuce, head lettuce, spinach, and mizuna; The method for applying a plant growth promoter according to any one of Claims 1 to 3.

5. The method for applying the plant growth promoter is carried out in a plant factory; The method for applying a plant growth promoter according to any one of Claims 1 to 4.

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