Flower bud induction method for strawberry hydroponic cultivation

Abstract

To provide methods for effectively inducing flower bud formation during hydroponic cultivation of strawberries.SOLUTION: At least strawberry seedlings after cotyledon development are subjected to irradiation with blue light having a peak wavelength in a wavelength range of 400 to 500 nm and near-ultraviolet light with a peak wavelength in a wavelength range of 300 to 400 nm and to the supply of tap water. Active oxygen is generated within the strawberry seedlings by applying oxidative stress. This directs the strawberry seedlings from vegetative growth to reproductive growth to induce flower bud formation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for inducing flower bud formation in hydroponic strawberry cultivation. [Background technology]

[0002] Conventionally, plant cultivation has been carried out by incorporating technology for regulating (controlling or promoting) plant growth using artificial light. For example, the following Patent Document 1 describes a plant cultivation method in which artificial light consisting of blue light having a specific output wavelength and a specific photon flux density is irradiated onto a growing plant, and describes that this method promotes the formation of flower buds in the plant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-258389 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when using the above-mentioned conventional technology on plants that are difficult to grow, such as strawberries and orchids, which are easily affected by temperature, light, nutrients, etc., it was necessary to irradiate the plants with artificial light for a long time. In other words, the time required for the treatment to induce flower bud formation was long, and the amount of electricity required for the artificial light, etc. was also enormous. Furthermore, the resulting flowers and fruits tended to be small and often had low sugar content.

[0005] In the current situation where there is a demand for the cultivation of plants with higher added value, promoting flower bud formation, increasing the number of flowers and fruits, and cultivating high-quality plants not only improves producers' yields and profits, but also has the advantage of providing consumers with high-quality plants (flowers and fruits) regardless of the season.

[0006] The present invention has as its technical object the provision of an improved plant cultivation method based on consideration of the current situation as described above. [Means for solving the problem]

[0007] The method of inducing flower buds in hydroponic strawberry cultivation of the present invention involves irradiating strawberry seedlings, at least after the cotyledons have expanded, with blue light having a peak wavelength in the 400-500 nm wavelength range and near-ultraviolet light having a peak wavelength in the 300-400 nm wavelength range and supplying tap water, thereby generating active oxygen within the strawberry seedlings and applying oxidative stress, thereby shifting the strawberry seedlings from vegetative growth to reproductive growth and inducing flower bud formation.

[0008] In the method for inducing flower buds in hydroponic cultivation of strawberries according to the present invention, the blue light and the near-ultraviolet light may be irradiated onto the strawberry seedlings for 2 to 4 consecutive days. Effect of the Invention

[0009] According to the present invention, it is possible to directly promote the flower bud formation of various plants. That is, when strawberry seedlings after at least the cotyledons have expanded are irradiated with blue light and near-ultraviolet light of a specific wavelength and supplied with tap water, active oxygen is generated in the strawberry seedlings, causing stress due to oxidation. As a result, flower bud formation is induced within several days. This allows the time required for the work of inducing flower bud formation to be significantly reduced. It also makes it possible to grow high-quality plants (flowers and fruits) with large flowers and fruits and high sugar content. [Brief description of the drawings]

[0010] [Figure 1] 1 is a table showing the flower bud induction effect in strawberries depending on the number of days for which an oxidative stress treatment according to the first example is performed (results of Test 1). [Diagram 2] 1 is a table showing the flower bud induction effect in strawberries due to differences in nutrient solution and light source in oxidative stress treatment according to the first embodiment (results of Test 2). [Diagram 3]1 is a table showing the flower bud induction effect of strawberry depending on the light intensity of the oxidative stress treatment according to the first example (results of Test 3). [Figure 4] 13 is a table showing the flower bud induction effect in strawberries depending on the number of days for which an oxidative stress treatment using near-ultraviolet light is performed according to the second example (the results of Test 4). [Diagram 5] 13 is a table showing the flower bud induction effect in strawberries due to differences in nutrient solution and light source in oxidative stress treatment with near-ultraviolet light according to the second embodiment (results of Test 5). [Figure 6] 13 is a table showing the flower bud induction effect of strawberry depending on the light intensity of the oxidative stress treatment in which near-ultraviolet light is added according to the second embodiment (results of Test 6). [Figure 7] 1 is a table showing the flower bud induction effect of Phalaenopsis orchid depending on the number of days for which oxidative stress treatment is applied according to the third embodiment (results of Test 7). [Figure 8] 13 is a table showing the flower bud induction effect of a Phalaenopsis orchid due to differences in nutrient solution and light source in an oxidative stress treatment according to Example 3 (results of Test 8). [Figure 9] 13 is a table showing the flower bud induction effect of Phalaenopsis orchid due to differences in light intensity of oxidative stress treatment according to the third embodiment (results of Test 9). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The plant cultivation method of the present invention is to irradiate a growing plant with a specific blue light and supply a nutrient solution that does not contain nitrogen. By cultivating the plant in this way, after the blue light receptors in the plant receive the blue light, active oxygen is generated and oxidative stress is added. This causes the plant to shift from vegetative growth to reproductive growth, and substances that induce flower bud formation are effectively formed in the leaves of the plant, significantly promoting flower bud formation in the plant.

[0012] Stress due to oxidation (hereinafter referred to as oxidative stress) is a condition that generates active oxygen in the body. Conditions that cause oxidative stress include, for example, strong light, water stress (dryness), carbon dioxide (CO2) deficiency, and low temperature.

[0013] There are two types of blue light receptors in plants: cryptochrome and phototropin. These absorb blue light and near-ultraviolet light, and are involved in promoting, controlling, and regulating flower bud formation in plants. Cryptochrome and phototropin absorb blue light in the wavelength range of 400 to 500 nm and near-ultraviolet light in the wavelength range of 300 to 400 nm. The peak wavelengths of light absorbed by cryptochrome and phototropin are 350 nm and 450 nm. In particular, cryptochrome plays a role in controlling flower bud formation. In addition, substances that induce flower bud formation in plant leaves include, for example, the flowering hormone florigen.

[0014] The present invention is a cultivation method that effectively promotes flower bud formation by applying oxidative stress to growing plants. Cultivation using this method shifts plants from vegetative growth, in which the plants grow larger to maintain the individual, to reproductive growth, in which flower bud formation is promoted to maintain the species. This significantly promotes flower bud formation in plants.

[0015] The blue light having a specific wavelength according to the cultivation method of the present invention will now be described. The light source (blue light) used has an output wavelength peak within the blue region of 400 to 500 nm. In the case of a light source having multiple output peaks or an irregular and broad spectral output pattern, at least 50% of the output energy may be within the wavelength region of 400 to 500 nm.

[0016] From the viewpoint of effective flower bud induction, the spectral width of the peak wavelength of blue light is preferably 100 nm or less at half-width. As light to be irradiated to the plant, in addition to the above-mentioned blue light, light having another peak wavelength (e.g., near-ultraviolet light) may be irradiated as necessary for another purpose such as root elongation or stem differentiation, but since light in the red wavelength range of 600 to 800 nm has a significant inhibitory effect on flower bud induction, the amount of radiation energy contained in this wavelength range is preferably kept to 30% or less of the total radiation energy amount, and more preferably kept to 15% or less.

[0017] A light source for irradiating blue light is required to efficiently emit blue wavelengths and emit little energy other than blue light.Specific examples include blue fluorescent lamps, blue light-emitting diodes, blue laser diodes, and blue filter device lamps.From the viewpoint of monochromaticity and light emission rate, blue light-emitting diodes and blue laser diodes are particularly preferred.

[0018] The light intensity (photon flux density) required in the cultivation method of the present invention varies depending on the target plant species, growth stage, the spectral pattern of the light source used, etc., but is generally 150 to 280 μmol / m 2 / s. In particular, 210 to 250 μmol / m 2 / s is preferable for efficient flower bud formation.

[0019] The nitrogen-free nutrient solution used in the cultivation method of the present invention will now be described. An example of a nutrient solution that does not contain nitrogen is water (H2O). Although a nutrient solution that contains a small amount of nitrogen may be used, the effect of inducing flower bud formation decreases in proportion to the increase in the nitrogen content of the nutrient solution. Therefore, it is preferable to use, for example, tap water that does not contain nitrogen.

[0020] The subject of the cultivation method according to the present invention will be described. The growing plant which is the subject of the cultivation method according to the present invention is preferably a seedling (plant) with leaves formed, and at least the cotyledons are in a state of being expanded. Since the substance which induces flower bud formation is formed in the leaves of the plant, the leaves must be expanded. When an oxidative stress treatment is performed on a seedling with one primary leaf expanded in addition to the cotyledons, flowering is delayed by about 2 to 3 weeks compared to when the stress treatment is performed on a seedling with the cotyledons expanded. Therefore, it is particularly preferable to use a seedling (plant) with at least the cotyledons expanded as the subject of the oxidative stress treatment according to the present invention. It is to be noted that by collecting seedlings with the same number of expanded leaves and performing the oxidative stress treatment, it is possible to align the developmental stage.

[0021] The oxidative stress treatment according to the present invention will now be described. In the present invention, the oxidative stress treatment refers to a treatment in which a growing plant is irradiated with blue light of a specific wavelength or blue light and near-ultraviolet light of a specific wavelength, and a nutrient solution containing no nitrogen is supplied to induce flower bud formation. That is, a series of steps in which a growing plant is irradiated with blue light of a specific wavelength or blue light and near-ultraviolet light of a specific wavelength, and a nutrient solution containing no nitrogen is supplied to cultivate the plant, and active oxygen is generated in the plant body to cause oxidative stress is called oxidative stress treatment. By carrying out the oxidative stress treatment, the plant shifts from vegetative growth to reproductive growth, and flower bud formation is significantly promoted.

[0022] The oxidative stress treatment according to the present invention may be carried out after the cotyledons of a growing plant have expanded. If early flowers are required for purposes such as breeding and crossbreeding, the oxidative stress treatment may be carried out at an early stage after the cotyledons have appeared. In the case of fruit vegetables, fruit trees, grains, and ornamental plants, the oxidative stress treatment may be carried out after the plant has grown to a desired size (for example, after the primary leaves have expanded).

[0023] The oxidative stress treatment according to the present invention is carried out for at least two days on plants whose cotyledons have expanded. In the conventional technology, a long period of time such as 30 days was required for the treatment to induce flower bud formation, but the oxidative stress treatment according to the present invention only requires a few days. The oxidative stress treatment may be carried out for the first few days, and then the plant may be grown in a normal manner and then subjected to the oxidative stress treatment again. The oxidative stress treatment is sufficiently effective in inducing flower bud formation even when it is carried out only once on the plant, but the effect of inducing flower bud formation can be more reliably obtained by periodically carrying out the oxidative stress treatment on the plant multiple times.

[0024] Generally, methods for inducing flower bud formation include irradiating plants with blue light and applying only nitrogen-free (nitrogen-deficient) treatment to plants. However, each method requires long-term treatment of the plants, and short-term treatment (for example, about 3 days) is not effective in inducing flower bud formation. The oxidative stress treatment of the present invention is different from conventional methods in that it applies both conditions of irradiating growing plants with blue light of a specific wavelength or blue light and near-ultraviolet light of a specific wavelength, and supplying a nutrient solution that does not contain nitrogen, and therefore can impart very strong oxidative stress to the plants. Therefore, an excellent flower bud formation effect can be obtained with only a short-term treatment of only about 3 days.

[0025] The irradiation form of the blue light of a specific wavelength may be continuous irradiation or intermittent irradiation (pulse irradiation). In the case of intermittent irradiation, the pulse interval (blinking interval) is not particularly limited, and in either case, it is sufficient that a sufficient amount of irradiation is ensured to obtain the desired effect for each target plant.

[0026] If the plant is grown under normal growing conditions after the oxidative stress treatment, flower buds will form after about one month and can be seen with the naked eye. If flower bud formation is induced by the cultivation method of the present invention, the plant (strain) that has been subjected to the oxidative stress treatment will continue to form flower buds thereafter. Furthermore, if runners (vines) appear, flower buds will also form on the runners.

[0027] If the oxidative stress applied to the plant is too strong, some of the leaves may turn brown after the oxidative stress treatment. In such cases, it is effective to change the irradiation position of the blue light of a specific wavelength or to reduce the light intensity (photon flux density). In other words, by adjusting the irradiation position of the blue light of a specific wavelength depending on the type of plant and the number of expanded leaves, flower bud formation can be promoted more effectively.

[0028] The cultivation method of the present invention can be applied to various plants. For example, many plants have photoperiodism (day length response) that regulates flower bud formation according to the length of daylight (light period), but the cultivation method of the present invention can be applied to any plant, including long-day plants (plants that regulate flower bud formation in response to long days), short-day plants (plants that regulate flower bud formation in response to short days), and neutral plants (plants that do not respond to photoperiods), without any particular limitation.

[0029] Specifically, the present invention can be applied to flowering plants, fruit vegetables, fruit trees, and grains. For example, the present invention can be applied to orchids such as Phalaenopsis, Sympidium, and Dendrogium, cacti, cut flower plants such as roses, carnations, gerberas, gypsophila, lilies, and statice, potted flower plants such as pansies, primulas, begonias, petunias, and cyclamen, fruit vegetables such as tomatoes, cucumbers, melons, strawberries, and peppers, fruit trees such as pears, apples, and grapes, and grains such as corn and wheat. The present invention can also be applied to plants other than those mentioned above.

[0030] The cultivation method according to the present invention is particularly effective for plants that are slow to form flower buds, plants that form few flower buds in the natural state, or plants that are in a state where more seedlings than normal are required. It is also effective when the target plant is cultivated outside of the season suitable for its growth. For example, flower bud formation in strawberries using the commonly used photoperiodism (day length response) takes about two weeks, while it took about 30 days with the conventional technology, but flower bud formation can be induced in about three days with the cultivation method according to the present invention, and the time required for the work of flower bud induction can be significantly reduced.

[0031] The method of cultivating the target plant is not particularly limited. For example, a method of germinating the plant on a sponge cube (germination bed) and then cultivating it hydroponically, a method of germinating and raising the plant in a tray or pot filled with culture soil and then planting and cultivating the plant in a field, a method of aseptically cultivating the tissue on nutrient-containing agar and raising the plant, etc., can be used according to the type of plant and the purpose of cultivation. In particular, hydroponic cultivation has many advantages, such as being able to cultivate the plant without pesticides and regardless of the season. In addition, since it is less likely to be affected by the external environment, the effect of inducing flower bud formation by the oxidative stress treatment according to the present invention can be expected to be greater.

[0032] The near-ultraviolet light of a specific wavelength according to the cultivation method of the present invention will now be described. The light source (near-ultraviolet light) used has an output wavelength peak within the near-ultraviolet region of 300 to 400 nm. In the case of a light source having multiple output peaks or an irregular and broad spectral output pattern, at least 50% of the output energy may be within the wavelength region of 300 to 400 nm. From the viewpoint of effective induction of flower bud formation, the spectral width of the peak wavelength in the near-ultraviolet light is preferably 100 nm or less at half maximum.

[0033] The light source (near-ultraviolet light) used has a peak output wavelength in the wavelength range of 300 to 400 nm. A light source that efficiently emits near-ultraviolet wavelengths and emits little energy other than near-ultraviolet light is required as a light source for irradiating near-ultraviolet light. Specific examples include near-ultraviolet fluorescent lamps, near-ultraviolet light-emitting diodes, near-ultraviolet laser diodes, and near-ultraviolet filter device lamps. From the viewpoint of monochromaticity and light emission rate, near-ultraviolet light-emitting diodes and near-ultraviolet laser diodes are particularly preferred.

[0034] The effect of inducing flower bud formation can be improved by irradiating a growing plant with near-ultraviolet light of a specific wavelength in addition to blue light of a specific wavelength and cultivating the plant by supplying a nutrient solution that does not contain nitrogen. It is also possible to use only near-ultraviolet light of a specific wavelength without using blue light of a specific wavelength. In other words, a growing plant may be irradiated with near-ultraviolet light of a specific wavelength and cultivated by supplying a nutrient solution that does not contain nitrogen. In this case, it is considered that the near-ultraviolet light has little effect on phototropin, which is one of the blue receptors cryptochrome and phototropin.

[0035] The present invention will be specifically described in the following examples. Note that the conditions in the present invention are not limited to the following embodiments, and various changes are possible without departing from the spirit of the present invention.

[0036] <First Example> In the first example, Tests 1 to 3 were carried out on the effect of inducing flower bud formation by oxidative stress treatment according to the cultivation method of the present invention (hereinafter referred to as flower bud induction effect) using strawberry (Fragaria ananassa) seeds.

[0037] (Subject to oxidative stress treatment) The seedlings used in Tests 1 to 3 were grown hydroponically from seeds according to the following procedure. First, the procedure for germinating seeds will be explained. The seeds are placed on a urethane germination bed with sufficient tap water added, and light is shone from above. The light source is preferably white light, which has little growth suppression effect. A temperature of around 25°C is appropriate. While general vegetable seeds germinate in about 2-3 days, strawberry seeds require about 7-10 days to germinate. Seed germination is cultivated using only water until the cotyledons develop leaves.

[0038] Next, the procedure from germination of strawberry seeds to spreading of cotyledons will be explained. After the cotyledons spread, germination stage nutrient solution A (EC value = about 0.6 to 0.8 mS / cm) is circulated under the germination bed. This is because when the cotyledons spread, the stored nutrients in the seeds are used up, and it is necessary for the seeds to absorb various ions from the nutrient solution for further growth. The EC value indicates electrical conductivity (total amount of water-soluble salts).

[0039] Nutrient solution A is circulated for about 5 to 7 days while supplementing with air (oxygen) using an air pump so that the oxygen stored in the solution does not become insufficient. After that, switch to normal growth nutrient solution B (EC value = about 1.8 m S / cm) and circulate nutrient solution A until the cotyledons develop.

[0040] Below, tests 1 to 3 were conducted on flower bud formation by oxidative stress treatment. For each test, seedlings grown by the above-mentioned cultivation method and with expanded cotyledons (hereinafter, "expanded leaves") were used. After the oxidative stress treatment was completed in each test, the seedlings were grown in normal nutrient solution B for about one month, and the flower bud induction effect rate was examined.

[0041] [Test 1: Effect of days on strawberry flower bud induction] We tested the flower bud induction effect of strawberry plants depending on the number of days for which oxidative stress treatment was applied (see Figure 1). Specifically, under the following conditions, oxidative stress treatment was applied to leaf-expanded seedlings for each treatment period (1 to 4 days) continuously.

[0042] (Test 1 conditions) During each treatment period (1 to 4 days), the leaf-expanded plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of a specific wavelength as an oxidative stress treatment. Tap water was used as the nitrogen-free nutrient solution. The light source for blue light was a Raytron LED. The light intensity (photon flux density) was 210 μmol / m on the leaf surface. 2 / s. The peak light wavelength is 450 nm. Twenty leaf-emerged plants were used for each treatment period (1-4 days).

[0043] (Results of Test 1) As shown in Figure 1, the results of Test 1 showed that the flower bud induction rate after one day of treatment was 10%, after two days of treatment was 75%, after three days of treatment was 100%, and after four days of treatment was 100%. Therefore, it was shown that applying oxidative stress to leaf-expanded plants for at least two consecutive days was effective in inducing flower buds, and that applying oxidative stress for three or more days in particular was effective in inducing flower buds.

[0044] [Test 2: Effect of nutrient solution and light source on flower bud induction in strawberries] We tested the flower bud induction effect of strawberry plants using different nutrient solutions and light sources for oxidative stress treatment (see Figure 2). Specifically, under the following conditions, leaf-emerging plants were subjected to oxidative stress treatments with different nutrient solutions and light sources for three consecutive days.

[0045] (Test 2 conditions) The nutrient solution used for the oxidative stress treatment was either normal growth nutrient solution b containing nitrogen (EC value = approximately 1.8 m S / cm) or tap water containing no nitrogen. The light source for the oxidative stress treatment was a Raytron LED, and blue or red light of a specific wavelength was used. The light intensity (photon flux density) of blue or red light was 210 μmol / m on the leaf surface. 2 / s. The peak of each light wavelength is 450 nm for blue light and 650 nm for red light. The conditions for each oxidative stress treatment (combination of nutrient solution and light source used) were: nutrient solution B and blue light of a specific wavelength, tap water and blue light of a specific wavelength, nutrient solution B and red light of a specific wavelength, tap water and red light of a specific wavelength. The oxidative stress treatments for the leaf-expanded plants were carried out under each of the above conditions for three consecutive days. Twenty leaf-expanded plants were used for each oxidative stress treatment.

[0046] (Results of Test 2) As shown in Figure 2, the results of Test 2 showed that the flower bud induction effect rate by oxidative stress treatment under conditions using tap water and blue light of a specific wavelength was 100%. The flower bud induction effect rate by oxidative stress treatment under other conditions (conditions using nutrient solution b and blue light of a specific wavelength, conditions using nutrient solution b and red light of a specific wavelength, conditions using tap water and red light of a specific wavelength) was 0%. Therefore, it was shown that oxidative stress treatment by supplying a nitrogen-free nutrient solution to leaf-expanded plants and irradiating them with blue light of a specific wavelength has an excellent flower bud induction effect. It was also shown that only one of the conditions using blue light of a specific wavelength or tap water has no effect of inducing flower bud formation. In other words, it was shown that only when the leaf-expanded plants are supplied with a nitrogen-free nutrient solution and irradiated with blue light of a specific wavelength, very strong oxidative stress can be applied and a remarkable flower bud induction effect is exhibited.

[0047] [Test 3: Effect of light intensity on flower bud induction in strawberries] We tested the flower bud induction effect of strawberry plants depending on the light intensity (photon flux density) of blue light used for oxidative stress treatment (see Figure 3). Specifically, under the following conditions, we supplied leaf-expanded plants with nitrogen-free nutrient solution for three consecutive days and irradiated them with blue light of specific wavelengths with different light intensities to subject them to oxidative stress treatment.

[0048] (Test 3 conditions) As an oxidative stress treatment, the leaf-expanded plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of different intensities. Tap water was used as the nitrogen-free nutrient solution. The light source for the blue light was a Raytron LED. The peak wavelength of the light was 450 nm. The light intensities (photon flux densities) were 150, 180, 210, and 250 μmol / m 2 It was done at / s. Twenty leaf-emerged plants were used for each light intensity.

[0049] (Results of Test 3) As shown in Figure 3, the test results were: light intensity 150 μmol / m 2 / s flower bud induction rate was 80%, light intensity was 180μmol / m 2 The flower bud induction rate at light intensity 210 was 100%, and at light intensity 250 μmol / m 2 The flower bud induction rate for / s was 100%. Therefore, when a nitrogen-free nutrient solution is supplied to the leaf-expanded plant and blue light of a specific wavelength is irradiated to cause oxidative stress, the light intensity (photon flux density) of the blue light must be at least 150 μmol / m 2 / s or more produced flower bud induction effects. 2 It was shown that when the concentration was 100 / s or higher, a significant flower bud induction effect was observed.

[0050] <Second Example> In the second example, tests 4 to 6 were carried out on the flower bud induction effect of oxidative stress treatment according to the cultivation method of the present invention using strawberry (Fragaria ananassa) seeds. In the second example, the blue light of the specific wavelength used in the first example was replaced with blue light of specific wavelengths and near-ultraviolet light.

[0051] (Subject to oxidative stress treatment) The seedlings used in Tests 4 to 6 were hydroponically grown from seeds in the same manner as in Example 1, and therefore a description thereof will be omitted.

[0052] Below, tests 4 to 6 were conducted on flower bud formation by oxidative stress treatment with near-ultraviolet light. For each test, seedlings grown by the above-mentioned cultivation method and with expanded cotyledons (hereinafter, "expanded leaves") were used. After the oxidative stress treatment in each test, the seedlings were grown in normal nutrient solution B for about one month, and the flower bud induction effect rate was examined.

[0053] [Test 4: Effect of days on flower bud induction in strawberries (addition of near-ultraviolet light)] We tested the flower bud induction effect of strawberry plants depending on the number of days for which oxidative stress treatment using near-ultraviolet light was applied (see Figure 4). Specifically, under the following conditions, oxidative stress treatment was applied to leaf-expanded seedlings for each treatment period (1 to 4 days) continuously.

[0054] (Test 4 conditions) During each treatment period (1 to 4 days), the leaf-expanded plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of a specific wavelength as an oxidative stress treatment. Tap water was used as the nitrogen-free nutrient solution. The light source for blue light and near-ultraviolet light was a Raytron LED. The light intensity (photon flux density) of blue light and near-ultraviolet light was 210 μmol / m on the leaf surface. 2 / s. The peak wavelengths of light are 450 nm for blue light and 350 nm for near-ultraviolet light. Twenty leaf-emerged plants were used for each treatment period (1-4 days).

[0055] (Results of Test 4) As shown in Figure 4, the results of Test 4 showed that the flower bud induction rate after one day of treatment was 15%, after two days of treatment was 80%, after three days of treatment was 100%, and after four days of treatment was 100%. Therefore, it was shown that applying oxidative stress to leaf-expanded plants for at least two consecutive days was effective in inducing flower buds, and that applying oxidative stress for three or more days in particular was effective in inducing flower buds. Compared with the results of Test 1 in the first example, the flower bud induction rate in Test 4 where the treatment days were 1 and 2 was higher than that in Test 1. In other words, a more excellent flower bud induction effect was shown when near-ultraviolet light of a specific wavelength was added (Test 4) than when only blue light of a specific wavelength was irradiated (Test 1).

[0056] [Test 5: Effect of nutrient solution and light source on flower bud induction in strawberries (near-ultraviolet light added)] We tested the flower bud induction effect of strawberry plants using different nutrient solutions and light sources for oxidative stress treatment with near-ultraviolet light (see Figure 5). Specifically, under the following conditions, leaf-emerging plants were subjected to each oxidative stress treatment with different nutrient solutions and light sources for three consecutive days.

[0057] (Test 5 conditions) The nutrient solution used for the oxidative stress treatment was either normal growth nutrient solution b containing nitrogen (EC value = approximately 1.8 m S / cm) or tap water containing no nitrogen. The light source for the oxidative stress treatment was a Raytron LED, and specific wavelengths of blue light, near-ultraviolet light, and red light were used. The light intensity (photon flux density) of blue light and near-ultraviolet light was 210 μmol / m on the leaf surface. 2 / s. The peak wavelengths of light are 450 nm for blue light and 350 nm for near-ultraviolet light. The light intensity (photon flux density) of red light is 210 μmol / m on the leaf surface. 2 / s and the peak light wavelength is 650 nm. The oxidative stress treatment conditions (combinations of nutrient solution and light source used) were: nutrient solution B and blue light and near-ultraviolet light of a specific wavelength, tap water and blue light and near-ultraviolet light of a specific wavelength, nutrient solution B and red light of a specific wavelength, tap water and red light of a specific wavelength. The oxidative stress treatment was carried out under each of the above conditions for three consecutive days on the expanded leaf plants. Twenty leaf-expanded plants were used for each oxidative stress treatment.

[0058] (Results of Test 5) As shown in Figure 5, the results of Test 5 showed that the flower bud induction effect rate by oxidative stress treatment under conditions using tap water and specific wavelengths of blue light and near-ultraviolet light was 100%. The flower bud induction effect rate by oxidative stress treatment under other conditions (conditions using nutrient solution b and specific wavelengths of blue light and near-ultraviolet light, conditions using nutrient solution b and specific wavelengths of red light, conditions using tap water and specific wavelengths of red light) was 0%. Therefore, it was shown that oxidative stress treatment by supplying nitrogen-free nutrient solution to leaf-expanded plants and irradiating them with blue light and near-ultraviolet light of specific wavelengths has a superior flower bud induction effect.

[0059] [Test 6: Effect of light intensity on flower bud induction in strawberries (near-ultraviolet light added)] We tested the flower bud induction effect of strawberry plants depending on the light intensity (photon flux density) of blue light and near-ultraviolet light used in the oxidative stress treatment with the addition of near-ultraviolet light (see Figure 6). Specifically, under the following conditions, we supplied leaf-expanded plants with a nitrogen-free nutrient solution for three consecutive days and irradiated them with blue light and near-ultraviolet light of specific wavelengths with different light intensities (photon flux density) to perform an oxidative stress treatment.

[0060] (Test 6 conditions) As an oxidative stress treatment, the leaf-emerged plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light and near-ultraviolet light of different intensities. Tap water was used as the nitrogen-free nutrient solution. The light source for blue light and near-ultraviolet light was an LED manufactured by Raytron. The peak wavelength of the light was 450 nm for blue light and 350 nm for near-ultraviolet light. The light intensities (photon flux densities) of the blue light and near-ultraviolet light were 150, 180, 210, and 250 μmol / m 2 It was done at / s. Twenty leaf-emerged plants were used for each light intensity.

[0061] (Results of Test 6) As shown in Figure 6, the test results were: light intensity 150 μmol / m 2 / s flower bud induction rate was 85%, light intensity was 180μmol / m 2 The flower bud induction rate at light intensity 210 was 100%, and at light intensity 250 μmol / m 2 The flower bud induction rate for / s was 100%. Therefore, when a nitrogen-free nutrient solution is supplied to the leaf-emerging plants and oxidative stress is caused by irradiating them with blue light and near-ultraviolet light of specific wavelengths, the light intensity should be at least 150 μmol / m 2 / s or more produced flower bud induction effects. 2 It was shown that when the concentration was 100 / s or higher, a significant flower bud induction effect was observed. Compared with the results of Test 3 in the first embodiment, Test 6 was better than Test 3 at a light intensity of 150 μmol / m 2 / s and 180 μmol / m 2 In other words, the flower bud induction rate was higher when the light source for the oxidative stress treatment was a combination of blue light of a specific wavelength and near-ultraviolet light of a specific wavelength (Test 4) than when only blue light of a specific wavelength was used (Test 1).

[0062] <Third Example> In the third example, using seedlings of Phalaenopsis aphrodite, tests 7 to 9 on the flower bud induction effect by oxidative stress treatment were carried out using the same method as in the above-mentioned Example 1. Descriptions of the same contents as those in the above-mentioned Example 1 will be omitted.

[0063] (Subject to oxidative stress treatment) Below, tests 7 to 9 were conducted on flower bud formation by oxidative stress treatment. For each test, leaf-expanded plants (seedlings with expanded cotyledons) of Phalaenopsis orchids grown using cloning technology were used. After the oxidative stress treatment was completed in each test, the plants were grown for about one month in normal growth nutrient solution c (EC value = about 1.8 m S / cm), and the flower bud induction effect rate was examined.

[0064] [Test 7: Effect of days on flower bud induction in Phalaenopsis orchid] A test was conducted to examine the flower bud induction effect of Phalaenopsis orchid depending on the number of days for which oxidative stress treatment was applied (see Figure 7). Specifically, under the following conditions, oxidative stress treatment was applied continuously to leaf-expanded seedlings for each treatment period (1 to 4 days).

[0065] (Test 7 conditions) During each treatment period (1 to 4 days), the leaf-expanded plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of a specific wavelength as an oxidative stress treatment. Tap water was used as the nitrogen-free nutrient solution. The light source for blue light was a Raytron LED. The light intensity was 210 μmol / m on the leaf surface. 2 / s and the peak light wavelength is 450 nm. Twenty leaf-emerged plants were used for each treatment period (1-4 days).

[0066] (Results of Test 7) As shown in Figure 7, the results of Test 7 showed that the flower bud induction rate after one day of treatment was 15%, after two days of treatment was 85%, after three days of treatment was 100%, and after four days of treatment was 100%. Therefore, it was shown that applying oxidative stress to leaf-expanded plants for at least two consecutive days was effective in inducing flower buds, and that applying oxidative stress for three or more days in particular was effective in inducing flower buds.

[0067] [Test 8: Effect of nutrient solution and light source on flower bud induction in Phalaenopsis orchid] We tested the flower bud induction effect of Phalaenopsis orchids depending on the nutrient solution and light source used for oxidative stress treatment (see Figure 8). Specifically, under the following conditions, leaf-expanded plants were subjected to each oxidative stress treatment with different nutrient solutions and light sources for three consecutive days.

[0068] (Test 8 conditions) The nutrient solution used for the oxidative stress treatment was either a normal growth nutrient solution containing nitrogen (EC value = approximately 1.8 m S / cm) or tap water containing no nitrogen. The light source for the oxidative stress treatment was a Raytron LED, and blue or red light of a specific wavelength was used. The light intensity of the blue or red light was 210 μmol / m 2 / s. The peak of each light wavelength is 450 nm for blue light and 650 nm for red light. The conditions for each oxidative stress treatment (combination of nutrient solution and light source used) were: nutrient solution C and blue light of a specific wavelength, tap water and blue light of a specific wavelength, nutrient solution C and red light of a specific wavelength, tap water and red light of a specific wavelength. The oxidative stress treatments for the leaf-expanded plants were carried out under each of the above conditions for three consecutive days. Twenty leaf-expanded plants were used for each oxidative stress treatment.

[0069] (Results of Test 8) As shown in Figure 8, the results of Test 8 showed that the flower bud induction effect rate by oxidative stress treatment under conditions using tap water and blue light of a specific wavelength was 100%. The flower bud induction effect rate by oxidative stress treatment under other conditions (conditions using nutrient solution C and blue light of a specific wavelength, conditions using nutrient solution C and red light of a specific wavelength, conditions using tap water and red light of a specific wavelength) was 0%. Therefore, it was shown that oxidative stress treatment by supplying nitrogen-free nutrient solution to leaf-expanded plants and irradiating them with blue light of a specific wavelength has a superior flower bud induction effect.

[0070] [Test 9: Effect of light intensity on flower bud induction in Phalaenopsis orchid] We tested the flower bud induction effect of Phalaenopsis orchids depending on the light intensity of blue light used for oxidative stress treatment (see Figure 9). Specifically, under the following conditions, we supplied nitrogen-free nutrient solution to leaf-expanded plants for three consecutive days and irradiated them with blue light of specific wavelengths with different light intensities (photon flux densities) to subject them to oxidative stress treatment.

[0071] (Test 9 Conditions) As an oxidative stress treatment, the leaf-expanded plants were supplied with nitrogen-free nutrient solution and continuously irradiated with blue light of different light intensities (photon flux densities). Tap water was used as the nitrogen-free nutrient solution. The light source for the blue light was a Raytron LED. The peak wavelength of the light was 450 nm. The light intensities (photon flux densities) were 150, 180, 210, and 250 μmol / m 2 It was done at / s. Twenty leaf-emerged plants were used for each light intensity.

[0072] (Test 9 results) As shown in Figure 9, the test results were: light intensity 150 μmol / m 2 / s flower bud induction rate was 85%, light intensity was 180μmol / m 2 The flower bud induction rate at light intensity 210 was 100%, and at light intensity 250 μmol / m 2 The flower bud induction rate for / s was 100%. Therefore, when a nitrogen-free nutrient solution is supplied to the leaf-emerging plant and blue light of a specific wavelength is irradiated to cause oxidative stress, the light intensity of the blue light should be at least 150 μmol / m 2 / s or more produced flower bud induction effects. 2 It was shown that when the concentration was 100 / s or higher, a significant flower bud induction effect was observed.

[0073] As is clear from the above, in the plant cultivation method according to the above embodiment, when a growing plant is irradiated with blue light of a specific wavelength and a nitrogen-free nutrient solution is supplied to induce flower bud formation, active oxygen is generated in the plant body, and oxidative stress is added. This causes the plant to shift from vegetative growth to reproductive growth, and substances that induce flower bud formation are effectively formed in the plant's leaves, significantly promoting flower bud formation in the plant, promoting flowering, increasing the number of flowers and fruits, and improving the size of the flowers and fruits and the sugar content of the fruits. It is to be noted that an even better effect of inducing flower bud formation can be obtained by irradiating near-ultraviolet light of a specific wavelength in addition to the blue light.

[0074] Moreover, an excellent flower bud induction effect can be obtained with a shorter treatment time than usual. Thus, the cultivation method according to the embodiment can promote flower bud formation more efficiently and in a shorter time than conventional methods. The cultivation method according to the embodiment can be expected to increase yields by promoting flower bud formation not only in horticultural plants but also in fruit vegetables, fruit trees, and grains, and can be expected to be used in a wide range of agricultural fields.

Claims

1. A method for inducing flower buds in hydroponic strawberry cultivation using strawberry seedlings after at least the cotyledons have expanded, Irradiating the strawberry seedlings with blue light having a peak wavelength in a wavelength range of 400 to 500 nm; and supplying tap water to the strawberry seedlings. By carrying out the process over a 2-4 day period, generating reactive oxygen species within the strawberry seedlings to cause oxidative stress, This shifts the strawberry seedlings from vegetative growth to reproductive growth, thereby inducing flower buds. A method for inducing flower buds in hydroponic strawberry cultivation.

2. A method for inducing flower buds in hydroponic strawberry cultivation using strawberry seedlings after at least the cotyledons have expanded, comprising: Irradiating the strawberry seedlings with blue light having a peak wavelength in the wavelength range of 400 to 500 nm and near-ultraviolet light having a peak wavelength in the wavelength range of 300 to 400 nm; and supplying tap water to the strawberry seedlings. By carrying out the process over a 2-4 day period, generating reactive oxygen species within the strawberry seedlings to cause oxidative stress, This shifts the strawberry seedlings from vegetative growth to reproductive growth, thereby inducing flower buds. A method for inducing flower buds in hydroponic strawberry cultivation.

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