Dicotyledonous plant cultivation method and dicotyledonous plant cultivation device

Abstract

Provided is a method for growing a plant, capable of guiding the growth direction of upper leaves with a simple device configuration.　In this invention, a plant is grown by irradiating a dicotyledonous plant with light emitted from a blue laser light source. The blue laser light source includes a phototropin absorption peak; the wavelength band of the laser light is 430 nm-485 nm inclusive; and the laser light is emitted from above the dicotyledonous plant with an intensity equal to or higher than a predetermined photon flux density (PPFD). Thus, the growth direction of the upper leaves is guided upward in the vertical direction.

Description

Method for growing dicotyledonous plants and device for growing dicotyledonous plants

[0001] The present invention relates to a plant cultivation method.

[0002] In cultivation methods that irradiate plants with artificial light, it is known that irradiating plants with high-intensity light allows for more rapid cultivation than irradiating plants with low-intensity light. However, when irradiated with high-intensity light, the leaves spread horizontally, causing the upper leaves (upper leaves) and lower leaves (lower leaves) of leafy vegetables to overlap, resulting in poor light delivery to the lower leaves, which causes the lower leaves to age. This requires the effort of trimming the lower leaves.

[0003] Therefore, Patent Document 1 discloses that by irradiating a plant with light in the wavelength range required for photosynthesis and far-red light (for example, light with a wavelength of 700 to 800 nm) at a light intensity range of 10:1 to 3:1, it is possible to promote the growth of plant leaves so that they stand upright even under high light intensity with a photosynthetic photon flux density of 200 μmol / m2 / s or more.

[0004] Furthermore, Patent Document 2 discloses a plant cultivation device that includes upper lighting that irradiates the plants with light from above and lower lighting that irradiates the plants with light from below, so that light reaches not only the upper leaves but also the lower leaves.

[0005] On the other hand, in order to operate a plant factory at low cost, a light source that diffuses laser light using a light diffusing element and irradiates the plants with a laser light that is approximately uniform and irradiated onto the crop cultivation area with an inexpensive and simple configuration has been described. The laser light has center wavelengths of 405 nm, 660 nm, and 780 nm. In particular, an example of cultivating Bunashimeji mushrooms with a 405 nm laser light has been disclosed.

[0006] JP 2014-023473 A JP 2022-124073 A Patent No. 6106853 A

[0007] As described above, the technology of Patent Document 1 requires light in the wavelength range required for photosynthesis and far-red light (for example, light with a wavelength of 700 to 800 nm), so in addition to the visible light source currently used in general light sources for plant cultivation, it is necessary to attach a far-infrared light source to the plant cultivation device and prepare a control circuit, which requires additional installation space and increases costs.

[0008] Furthermore, the technology in Patent Document 2 is configured to irradiate the lower leaves with light from below, but the structure of plant leaves makes it difficult for light irradiated from the underside to enter the leaves, making it difficult for light to reach the chlorophyll that is effective in photosynthesis.

[0009] The technology of Patent Document 3 involves irradiating diffused laser light, but since the object of cultivation is Bunashimeji mushrooms, there is no mention of guiding the growth direction of the upper leaves.

[0010] An object of the present invention is to provide a plant growing method that can guide the growth direction of upper leaves while using a simple device configuration.

[0011] To achieve the above object, the present invention provides a plant cultivation method for irradiating a dicotyledonous plant with light emitted from a blue laser light source, the blue laser light source including the absorption peak of phototropin, the laser light having a wavelength band of 430 nm to 485 nm, and the laser light having an intensity equal to or greater than a predetermined photon flux density (PPFD), from above the dicotyledonous plant, thereby guiding the growth direction of upper leaves vertically upward.

[0012] According to the present invention, it is possible to provide a plant growing method that can guide the growth direction of upper leaves while using a simple device configuration.

[0013] FIG. 1 is a diagram illustrating the configuration of a dicotyledonous plant growing apparatus 100 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the configuration of a dicotyledonous plant growing apparatus 100 according to an embodiment of the present invention, which irradiates red light in addition to blue laser light. FIG. 3 is a diagram illustrating a specific configuration example 3 of the dicotyledonous plant growing apparatus 100 according to an embodiment. FIG. 4 is a graph showing the spectra of a laser light source according to an example and an LED according to a comparative example. FIG. 5 is a diagram showing the growing conditions for tobacco, lettuce, and Arabidopsis according to an example. Photographs of the appearance of tobacco grown according to an example and tobacco grown according to a comparative example. Photographs of the appearance of lettuce grown according to an example and lettuce grown according to a comparative example. Photographs of the appearance of Arabidopsis grown according to an example and Arabidopsis grown according to a comparative example. (a) and (b) are graphs showing the plant height and upper leaf unfolding angle of tobacco (LASER) grown according to the example and tobacco (LED) grown according to the comparative example; (c) and (d) are graphs showing the plant height and upper leaf unfolding angle of lettuce (LASER) grown according to the example and lettuce (LED) grown according to the comparative example; (e) and (f) are graphs showing the plant height and upper leaf unfolding angle of Arabidopsis (LASER) grown according to the example and lettuce (LED) created according to the comparative example.

[0014] An embodiment of the present invention will be described below.

[0015] In this embodiment, light having a wavelength at the absorption peak of phototropin and not containing blue light of other wavelengths is irradiated onto the dicotyledonous plant from above, thereby inducing the growth direction of the upper leaves of the dicotyledonous plant to grow vertically upward.

[0016] For example, as shown in Figure 1, a dicotyledonous plant cultivation device 100 is used that combines a blue laser light source 1 and an optical element 2 that irradiates the entire dicotyledonous plant 10 with laser light 3 emitted from the blue laser light source 1 from above the dicotyledonous plant 10.

[0017] The laser light 3 emitted from the blue laser light source 1 is laser light having a wavelength corresponding to the absorption peak of phototropin and does not contain blue light of other wavelengths. In particular, the laser light 3 is preferably light having a wavelength of either 450 nm or 480 nm±3 nm, which is the absorption peak of phototropin D450 in the ground state, and is particularly preferably light having a wavelength of 450 nm, which is the maximum absorption peak.

[0018] More specifically, the wavelength band of the laser beam 3 is preferably included in the wavelength band of 430 nm to 485 nm, which is the absorption peak wavelength band of Phototropin D450, and more preferably in the band of 445 nm to 455 nm. Note that the laser beam 3 may be configured not to include wavelengths shorter than 430 nm or longer than 485 nm.

[0019] It should be noted that the laser light 3 does not need to be in phase when it is irradiated onto the dicotyledonous plant 10 .

[0020] In this way, by irradiating the dicotyledonous plant 10 with narrow-band laser light 3 having a wavelength corresponding to the absorption peak of phototropin, the blue light sensor protein phototropin absorbs the laser light 3, and the dicotyledonous plant 10 effectively exhibits phototropism (a phenomenon in which stems and other parts bend toward light). Therefore, by irradiating the dicotyledonous plant 10 from above with laser light 3 having a wavelength corresponding to the absorption peak of phototropin, the growth direction of the upper leaves 11 of the dicotyledonous plant 10 can be guided vertically upward. In other words, the growth direction of the upper leaves 11 of the dicotyledonous plant 10 is guided toward the irradiation position of the light source of the laser light 3.

[0021] As will be shown in the examples below, the phenomenon of the growth direction of the upper leaves 11 of a dicotyledonous plant 10 being induced vertically upward by irradiating the plant from above with laser light 3 having a wavelength at the absorption peak of phototropin is more pronounced when the wavelength band of the irradiated light is narrower, such as with laser light 3, than when using an LED. This is presumably because the change from ground state phototropin D450 to activated state phototropin S390 due to light absorption is reversed by irradiation with light of a different wavelength band (especially light with a shorter wavelength). Therefore, it is desirable that the wavelength band be narrow, as described above.

[0022] The light intensity of the laser light 3 when it reaches the dicotyledonous plant 10 is set to a predetermined photosynthetic photon flux density (PPFD) or higher, specifically, for example, 150 μmol m s or higher.

[0023] The optical element 2 may be any element capable of irradiating the entire dicotyledonous plant 10 with a wide-spread laser beam. For example, an optical fiber, a diffuser, a light guide plate, a polygon mirror for scanning the laser beam, or other elements may be used. The optical element 2 may be built into the blue laser light source 1.

[0024] In this embodiment, the upper leaves 11 grow vertically upward, and as a result, the distance between the upper leaves 11 and the lower leaves 12 increases in the vertical direction, as shown in Fig. 1. This prevents the laser light 3 irradiated from above from being cast in the shadow of the upper leaves 11, making it difficult for the laser light 3 to irradiate the lower leaves 12 that have grown earlier.

[0025] This allows the lower leaves 12 to be irradiated with sufficient light to grow and prevent deterioration of the lower leaves 12. Therefore, there is no need to trim the lower leaves 12 when shipping the dicotyledonous plant 10. In the past, the lower leaves aged and required labor to trim them before shipping, but in this embodiment, aging of the lower leaves can be suppressed, thereby reducing labor (labor costs).

[0026] In this embodiment, the above-described effects can be achieved with a simple configuration in which the light source 1 is simply changed to a laser light source.

[0027] In addition to the blue laser light 3, it is also possible to further irradiate the dicotyledonous plant 10 with light 6 of a wavelength other than blue. For example, as shown in FIG. 2, red light 6 from a red light source 4 can be further irradiated onto the dicotyledonous plant 10 from an oblique or lateral direction to promote growth. The red light source 4 can be, for example, a 660 nm red LED light source or a laser light source. Here, it is preferable to use a light source including a wavelength band that promotes photosynthesis, and it is preferable to use laser light with a narrow band that does not cause physiological disorders. An optical element 5 can also be used to widen the irradiation angle of the light 6.

[0028] Furthermore, in this embodiment, since the distance between the upper leaves 11 and the lower leaves 12 is wide in the vertical direction, irradiating the light 6 from an oblique direction allows the light to be irradiated from an angle close to perpendicular to both the upper leaves 11 and the lower leaves 12. Therefore, the light necessary for growth can be easily irradiated to both the upper leaves 11 and the lower leaves 12, thereby improving the growth rate.

[0029] When laser light 3 having the wavelength of the absorption peak of phototropin is irradiated from above, the growth direction of the upper leaves 11 of the dicotyledonous plant 10 is induced vertically upward, and the upper leaves 11 are induced to grow at an angle between 40° and 60° with respect to the vertical. Therefore, when irradiating light 6 from an oblique direction, it is desirable to set the irradiation direction (θ) of light 6 with respect to the vertical within an angle range between 40° and 60°, as shown in Figure 2.

[0030] <Device Configuration Example 1> An example of the device configuration of the dicotyledonous plant growing device 100 will be described with reference to FIG.

[0031] 3 uses an optical fiber and its end face as the optical element 2 that widens the irradiation angle of the laser light 6 from the blue laser light source 1. Also, an optical fiber with a three-branched tip and its end face is used as the optical element 5 that widens the irradiation angle of the light 6 emitted via the red light source 4. A diffuser plate may be provided on the optical path beyond the end face of the optical fiber. The output end face 2a of the optical fiber used as the optical element 2 and the three output end faces 5a of the optical fiber used as the optical element 5 are all positioned directly above the dicotyledonous plant 10.

[0032] The end face of the fiber 2a that emits the blue laser light 3 is arranged so that the optical axis of the emitted light faces vertically downward.

[0033] Of the three exit end faces 5a of the optical fiber that emits the red light 6, one is positioned so that the optical axis of the emitted light faces vertically downward, that is, it is positioned at a position extended in the growth direction of the dicotyledonous plant 10. On the other hand, the optical axes of the remaining two exit end faces 5a are positioned so that they are inclined 40 to 60 degrees to the left and right, respectively, with respect to the vertical axis.

[0034] This allows blue laser light 3 and red light 6 to be irradiated vertically downward at a predetermined aperture angle from the upper exit end faces 2a, 5a of the dicotyledonous plants 10 arranged at intervals in a matrix.

[0035] Furthermore, red light 6 can be emitted obliquely downward at a predetermined aperture angle from the exit end face 5a of the optical fiber above the dicotyledonous plant 10 in the adjacent row toward the upper leaves 11 and the lower leaves 12.

[0036] Instead of using the aperture angle of the end faces 2a and 5a of the optical fibers, the irradiation angle of the light may be widened by using a swinging mirror to scan the light.

[0037] Moreover, the optical elements 2 and 5 may be diffusion plates.

[0038] <Device Configuration Example 2> Another device configuration example of the dicotyledonous plant growing device 100 will be described with reference to FIG.

[0039] The example of the device configuration in Figure 4 is similar to the example of the device configuration in Figure 3, but in this configuration, the output end faces 2a of the optical fibers are arranged in a row directly above the row of dicotyledonous plants 10, and two optical fibers with output end faces 5a inclined by 40 to 60 degrees in the left and right directions are arranged in a row above the rows of dicotyledonous plants 10.

[0040] This allows blue laser light 3 to be emitted vertically downward at a predetermined aperture angle from emission end face 2a directly above dicotyledonous plants 10 arranged at intervals in a matrix. Also, red light 6 can be emitted obliquely downward from emission end face 5a of the upper optical fiber between the rows toward upper leaves 11 and lower leaves 12.

[0041] Alternatively, a mixed light of blue laser light and red light may be irradiated from the end face 2 a of the optical fiber directly above the dicotyledonous plant 10 .

[0042] <Device Configuration Example 3> Another device configuration example of the dicotyledonous plant growing device 100 will be described with reference to FIG.

[0043] A blue laser light source 1 and an optical element 2 are placed directly above dicotyledonous plants 10 arranged at intervals in a matrix.

[0044] The light source 4 is arranged between the rows of dicotyledonous plants 10 at least in the left-right direction, emitting light 6 at a height from the cultivation surface of the dicotyledonous plants 10 to near the top of the upper leaves 11.

[0045] This allows blue laser light 3 to be emitted from directly above dicotyledonous plants 10 arranged at intervals in a matrix. Also, red light 6 can be emitted from light sources 4 between the rows toward upper leaves 11 and lower leaves 12 on the sides of dicotyledonous plants 10.

[0046] Of course, instead of the light source 1 and the optical element 2 directly above the dicotyledonous plant 10, the end face 2a of the optical fiber in FIG. 3 can also be disposed.

[0047] An example of the present invention will be described. In the example, as shown in Fig. 6, a laser diode (LD) with a peak wavelength of 450±3 nm and a half-width of 2.5 nm was used as the blue laser light source 1, and a diffuser plate capable of expanding the irradiation range of the laser light was used as the optical element 2. As shown in Fig. 7, the dicotyledonous plant 10 was grown under irradiation with laser light 3 from above for 12 days, 24 hours a day. The temperature and humidity were set to 25°C and 45%, respectively.

[0048] The grown dicotyledonous plants 10 were tobacco, lettuce (Red Fire), and Arabidopsis thaliana, as shown in Figure 7. The photon flux density (PPFD) of the laser light 3 when it reached the dicotyledonous plant 10 was 150 μmol m s.

[0049] As a comparative example, a dicotyledonous plant 10 was grown using an LED with a wavelength peak of 464 nm and a half-width of 22 nm as a light source, with the other conditions being the same as those in the example.

[0050] Photographs of the appearance of the dicotyledonous plants grown in the examples and comparative examples are shown in Figures 8 and 9, and the results of measuring the plant height and the spreading angle of the upper leaves from the horizontal direction are shown in Figures 11(a) to (f).

[0051] As is clear from the photograph of appearance in Figure 8, the tobacco of the Example had a longer plant height than the tobacco of the Comparative Example. Furthermore, the upper leaves of the tobacco of the Example unfolded to an angle close to vertical, and the unfolded angle from the horizontal direction was greater than that of the tobacco of the Comparative Example (see Figures 11(a) and (b)).

[0052] As is clear from the external appearance photograph in Figure 9, the lettuce (Red Fire) of the Example was longer than the lettuce of the Comparative Example. Furthermore, the upper leaves of the Example lettuce expanded to an angle close to vertical, and the expansion angle from the horizontal direction was greater than that of the Comparative Example lettuce (see Figures 11(c) and (d)).

[0053] As is clear from the photograph of appearance in Figure 10, the Arabidopsis thaliana of the Example was longer in height than the Arabidopsis thaliana of the Comparative Example. Furthermore, the upper leaves of the Arabidopsis thaliana of the Example unfolded to an angle close to vertical, and the unfolding angle from the horizontal direction was greater than that of the lettuce of the Comparative Example (see Figures 11(e) and (f)).

[0054] These results confirmed that the embodiment in which the blue laser was irradiated from above the plant was able to guide the growth direction of the later-emerging upper leaves 11 in a vertical direction. This is thought to be because, as described above, the phenomenon of guiding the growth direction of the upper leaves 11 of the dicotyledonous plant 10 in a vertically upward direction was more pronounced with narrow-band light such as laser light 3 than with LED. Therefore, by using the blue laser light source 1, the change from D450 to S390 occurred more preferentially than with LED, and the degree of leaf erection was greater. Therefore, the present invention can provide a plant cultivation method and a dicotyledonous plant cultivation device that are capable of guiding the growth direction of the upper leaves 11 despite having a simple device configuration.

[0055] The techniques of the present embodiment and examples can be used for growing plants used in horticulture and vegetable cultivation, for example, in a plant growth light source device (for use in a plant factory, etc.) or a light source device for greenhouse horticulture (including a light source for supplemental lighting).

[0056] REFERENCE SIGNS LIST 1 Blue laser light source 2 Optical element 2a Emission end face of optical fiber 3 Blue laser light 4 Red light source 5 Optical element 5a Emission end face of optical fiber 6 Red light 10 Dicotyledonous plant 11 Upper leaf 12 Lower leaf 100 Dicotyledonous plant cultivation device

Claims

1. A method for cultivating a dicotyledonous plant, comprising irradiating a dicotyledonous plant with light emitted from a blue laser light source, the blue laser light source including the absorption peak of phototropin, the wavelength band of the laser light being 430 nm or more and 485 nm or less, and irradiating the dicotyledonous plant from above with an intensity equal to or greater than a predetermined photon flux density (PPFD), thereby guiding the growth direction of the upper leaves vertically upward.

2. A method for growing dicotyledonous plants according to claim 1, characterized in that the wavelength of the absorption peak of said phototropin is the wavelength of the absorption peak of phototropin D450.

3. A method for growing dicotyledonous plants as described in claim 2, characterized in that the wavelength band of the laser light is 450±3 nm or 480±3 nm, which is the absorption peak of phototropin D450.

4. A method for growing dicotyledonous plants according to claim 3, characterized in that the wavelength band of the laser light is within the range of 445 nm to 455 nm.

5. A method for growing dicotyledonous plants according to claim 1, wherein the predetermined photon flux density (PPFD) is 150 μmol m-2 s-1 or more.

6. A method for growing a dicotyledonous plant as described in claim 1, characterized in that red light is further irradiated onto the upper and lower leaves of the dicotyledonous plant from diagonally above or from the side of the dicotyledonous plant.

7. A method for growing a dicotyledonous plant according to claim 1, wherein the dicotyledonous plant is tobacco, lettuce, or Arabidopsis thaliana.

8. A dicotyledonous plant cultivation device comprising: a blue laser light source; and an optical element that irradiates the entire dicotyledonous plant with laser light from the blue laser light source from above the plant, wherein the blue laser light source includes the absorption peak of phototropin, the wavelength band of the laser light is 430 nm or more and 485 nm or less, and the dicotyledonous plant is irradiated from above with an intensity equal to or greater than a predetermined photon flux density (PPFD), thereby guiding the growth direction of upper leaves vertically upward.

9. The dicotyledonous plant growing device according to claim 8, further comprising a red light source, wherein the red light source irradiates light onto the upper and lower leaves of the dicotyledonous plant from diagonally above or from the side.

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