Method for inducing flower buds in hydroponic strawberry cultivation

Abstract

This invention provides a method for inducing flower bud formation in hydroponic strawberry cultivation that can effectively induce flower bud formation. [Solution] Strawberry seedlings, after the cotyledons have unfolded, are continuously irradiated for 2 to 4 days with blue light having a peak wavelength in the 400-500 nm range while supplying them with tap water that substantially does not contain a nitrogen source.

Description

[Technical Field]

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

[0002] Conventionally, plant cultivation has incorporated techniques that use artificial light to regulate (control or promote) plant growth. For example, Patent Document 1 below describes a plant cultivation method in which growing plants are irradiated with artificial light consisting of blue light having a specific output wavelength and a specific photosynthetic flux density, and it is stated that this method promotes flower bud formation in plants. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2001-258389 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, when conventional techniques like those described above were used on plants that are easily affected by temperature, light, nutrients, etc., such as strawberries and orchids, which are difficult to grow, it was necessary to irradiate the plants with artificial light for long periods of time. In other words, the time required for the treatment to induce flower bud formation was long, and the amount of electricity required for artificial light, etc., was enormous. Moreover, the resulting flowers and fruits tended to be small, and the sugar content of the fruits was often low.

[0005] In the current climate where there is a demand for cultivating plants with higher added value, promoting flower bud formation to increase the number of flowers and fruits, and growing 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 technical objective of this invention is to provide a plant cultivation method that addresses and improves upon the current situation described above. [Means for solving the problem]

[0007] The present invention relates to a method for inducing flower buds in hydroponic strawberry cultivation, characterized by supplying strawberry seedlings, after the cotyledons have unfolded, with tap water substantially free of nitrogen sources, while continuously irradiating them for 2 to 4 days with blue light having a peak wavelength in the 400-500 nm wavelength range.

[0008] The method for inducing flower buds in hydroponic strawberry cultivation according to the present invention may also involve irradiating the strawberry seedlings with near-ultraviolet light having a peak wavelength in the 300-400 nm wavelength range, in addition to the blue light. [Effects of the Invention]

[0009] According to the present invention, cultivation methods that directly promote flower bud formation in various plants are possible. Specifically, when strawberry seedlings, at least after the cotyledons have unfolded, are irradiated with blue light of a specific wavelength and supplied with tap water, reactive oxygen species are generated within the seedlings, causing oxidative stress. As a result, flower bud formation is induced within a few days. Therefore, the time required for the work necessary to induce flower bud formation can be significantly reduced. Furthermore, it becomes possible to grow high-quality plants (flowers and fruits) with larger flowers and fruits, or fruits with higher sugar content. [Brief explanation of the drawing]

[0010] [Figure 1] This table shows the effect of oxidative stress treatment on strawberry flower bud induction based on the number of days applied according to the first embodiment (results of Test 1). [Figure 2] This table shows the effect of different nutrient solutions and light sources on inducing flower buds in strawberries during oxidative stress treatment according to the first embodiment (results of Test 2). [Figure 3] This table shows the effect of different light intensities on inducing flower buds in strawberries during oxidative stress treatment according to the first embodiment (results of Test 3). [Figure 4]Table showing the flower bud induction effect on strawberries by the number of days of oxidative stress treatment with near-ultraviolet light according to the second embodiment (results of Test 4). [Figure 5] Table showing the flower bud induction effect on strawberries by the differences in nutrient solution and light source of oxidative stress treatment with near-ultraviolet light according to the second embodiment (results of Test 5). [Figure 6] Table showing the flower bud induction effect on strawberries by the differences in light intensity of oxidative stress treatment with near-ultraviolet light according to the second embodiment (results of Test 6). [Figure 7] Table showing the flower bud induction effect on carnations by the number of days of oxidative stress treatment according to the third embodiment (results of Test 7). [Figure 8] Table showing the flower bud induction effect on carnations by the differences in nutrient solution and light source of oxidative stress treatment according to the third embodiment (results of Test 8). [Figure 9] Table showing the flower bud induction effect on carnations by the differences in light intensity of oxidative stress treatment according to the third embodiment (results of Test 9).

Mode for Carrying Out the Invention

[0011] The plant cultivation method of the present invention is to cultivate a growing plant by irradiating it with specific blue light and supplying a nutrient solution containing no nitrogen. By cultivating in this way, after the blue light receptor in the plant receives blue light, reactive oxygen is generated and oxidative stress is applied. As a result, the growth tendency changes from vegetative growth to reproductive growth, and substances that induce flower bud formation are effectively formed in the leaves of the plant, significantly promoting the flower bud formation of the plant.

[0012] Oxidative stress (hereinafter referred to as oxidative stress) is a condition that generates reactive oxygen in vivo. Conditions for applying oxidative stress include, for example, strong light, water stress (drought), carbon dioxide (CO2) deficiency, low temperature, etc.

[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 400-500 nm wavelength range and near-ultraviolet light in the 300-400 nm wavelength range. The peak wavelengths of light absorbed by cryptochrome and phototropin are 350 nm and 450 nm, respectively. Cryptochrome, in particular, plays a role in controlling flower bud formation. Substances that induce flower bud formation in plant leaves include, for example, the flowering hormone florigen.

[0014] This invention relates to a cultivation method that effectively promotes flower bud formation by applying oxidative stress to growing plants. Cultivation using this method shifts the plant's growth from vegetative growth, where the plant grows larger for individual maintenance, to reproductive growth, where flower bud formation is promoted for species maintenance. This significantly accelerates flower bud formation in the plant.

[0015] This invention describes the use of blue light of a specific wavelength in the cultivation method of the present invention. The light source used (blue light) must have its output wavelength peak in the blue region of 400-500 nm. In the case of a light source with multiple output peaks or an irregular and broad spectral output pattern, it is acceptable if at least 50% of the output energy is in the 400-500 nm wavelength range.

[0016] From the viewpoint of effective flower bud induction, the spectral width of the peak wavelength in blue light is preferably 100 nm or less in half width at half maximum. In addition to the blue light mentioned above, other light with peak wavelengths (e.g., near-ultraviolet light) may be irradiated onto plants as needed for other purposes such as root elongation or stem differentiation. However, since light in the red wavelength range of 600 to 800 nm has a significant inhibitory effect on flower bud induction, it is preferable to limit the amount of radiant energy contained in this wavelength range to 30% or less of the total radiant energy, and more preferably to 15% or less.

[0017] For emitting blue light, a light source is required that efficiently emits blue wavelengths and emits little energy other than blue light. Specifically, examples include blue fluorescent lamps, blue light-emitting diodes, blue laser diodes, and blue filter lamps. From the viewpoint of monochromaticity and luminescence, blue light-emitting diodes and blue laser diodes are particularly preferred.

[0018] The required light intensity (photon flux density) in the cultivation method of the present invention varies depending on the target plant species, growth stage, and spectral pattern of the light source used, but is generally between 150 and 280 μmol / m³. 2 It is preferable that the concentration is / s. In particular, 210-250 μmol / m³ 2 Being / s is preferable for efficient flower bud formation.

[0019] The nitrogen-free nutrient solution related to the cultivation method of the present invention will be described. Examples of nitrogen-free nutrient solutions include water (H2O). While it is acceptable to use nutrient solutions containing trace amounts of nitrogen, the effect of inducing flower bud formation decreases in proportion to the increase in nitrogen content of the nutrient solution. Therefore, it is preferable to use, for example, tap water that does not contain nitrogen.

[0020] The target of the cultivation method according to the present invention will be explained. The plants being cultivated according to the present invention are seedlings (plants) with leaves formed, preferably with at least cotyledons unfolded. Since substances that induce flower bud formation are formed in the leaves of the plant, it is necessary for the leaves to be unfolded. When oxidative stress treatment is applied to seedlings with one true leaf unfolded in addition to the cotyledons, flowering is delayed by approximately 2 to 3 weeks compared to when stress treatment is applied to seedlings with unfolded cotyledons. Therefore, it is particularly preferable to use seedlings (plants) with at least unfolded cotyledons as the target of the oxidative stress treatment according to the present invention. Furthermore, by gathering seedlings with the same number of unfolded leaves and applying oxidative stress treatment, the developmental stages can be standardized.

[0021] The oxidative stress treatment according to the present invention will be described below. In this invention, oxidative stress treatment refers to a treatment in which growing plants are irradiated with blue light of a specific wavelength or blue light of a specific wavelength and near-ultraviolet light, and a nitrogen-free nutrient solution is supplied to induce flower bud formation. In other words, oxidative stress treatment refers to a series of processes in which growing plants are cultivated by irradiating them with blue light of a specific wavelength or blue light of a specific wavelength and near-ultraviolet light, and a nitrogen-free nutrient solution is supplied, thereby generating reactive oxygen species within the plant and inducing oxidative stress. By applying this oxidative stress treatment, the growth shifts from vegetative growth to reproductive growth, and flower bud formation is significantly promoted.

[0022] The timing for applying the oxidative stress treatment according to the present invention is anytime after the cotyledons of a growing plant have unfolded. However, if early flowering is required for purposes such as breeding and crossbreeding, the oxidative stress treatment may be performed from an early stage after the cotyledons have emerged. Furthermore, in the case of fruit vegetables, fruit trees, grains, and ornamental plants, the oxidative stress treatment may be applied after the plant has grown to the desired size (for example, after the true leaves have unfolded).

[0023] The oxidative stress treatment according to the present invention is performed on plants whose cotyledons have unfolded for at least two days. While conventional techniques required long periods of 30 days or more to induce flower bud formation, the oxidative stress treatment according to the present invention only requires a few days. Furthermore, after performing the oxidative stress treatment for the first few days and returning to normal growth methods, the oxidative stress treatment may be performed again. Although this oxidative stress treatment is sufficiently effective in inducing flower bud formation even when performed only once on a plant, performing the oxidative stress treatment multiple times periodically on the plant can more reliably induce flower bud formation.

[0024] Generally, methods used to induce flower bud formation include irradiating plants with blue light or applying nitrogen-free (nitrogen-deficient) treatment to plants. However, both methods require long-term treatment of plants, and short-term treatment (e.g., about 3 days) has little effect in inducing flower bud formation. Unlike conventional methods, the oxidative stress treatment according to the present invention applies both conditions to growing plants: irradiation with blue light of a specific wavelength or blue light of a specific wavelength and near-ultraviolet light, and supplying a nitrogen-free nutrient solution. Therefore, it can inflict very strong oxidative stress on plants. As a result, excellent flower bud formation effects can be obtained with only a short-term treatment of about 3 days.

[0025] The irradiation method for blue light of a specific wavelength can be either continuous or intermittent (pulsed) irradiation. In the case of intermittent irradiation, there are no particular restrictions on the pulse interval (flicker interval). In either continuous or intermittent irradiation, it is sufficient to ensure a sufficient amount of irradiation to achieve the desired effect for each target plant.

[0026] After the oxidative stress treatment described above, if the plants are allowed to grow under normal growing conditions, flower buds will form after about one month and can be seen with the naked eye. When flower bud formation is induced by the cultivation method according to the present invention, the plants that have undergone oxidative stress treatment will continue to form flower buds thereafter. Furthermore, if runners (vines) appear, flower buds will also form on those runners.

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

[0028] The cultivation method of the present invention can be applied to a variety of plants. For example, most plants have photoperiodism (photoperiod response) that regulates flower bud formation according to the length of daylight (daytime), but the cultivation method of the present invention can be applied to 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 limitations.

[0029] Specifically, this includes ornamental plants, fruit vegetables, fruit trees, and grains. For example, it can be applied to orchids such as Phalaenopsis, Cymbidium, and Dendrobium, cacti, cut flowers such as roses, carnations, gerberas, baby's breath, lilies, and statice, potted plants such as pansies, primroses, begonias, petunias, and cyclamen, fruit vegetables such as tomatoes, cucumbers, melons, strawberries, and bell peppers, fruit trees such as pears, apples, and grapes, and grains such as corn and wheat. It may also be applied to plants other than those listed above.

[0030] The cultivation method according to the present invention is particularly effective for plants that are slow to form flower buds, plants that naturally produce few flower buds, or plants that require a particularly large number of seedlings compared to normal conditions. It is also effective when cultivating plants outside of the optimal growing season. For example, while strawberry flower bud formation using the commonly employed photoperiodism (day length response) takes about two weeks and about 30 days with conventional techniques, the cultivation method according to the present invention can induce flower bud formation in about three days, significantly reducing the time required for the work necessary to induce flower bud formation.

[0031] The cultivation method for the target plants is not particularly limited. For example, methods such as germinating on sponge cubes (germination beds) and then cultivating them hydroponically, germinating and growing seedlings in trays or pots filled with growing medium before transplanting them to a field for cultivation, or aseptically tissue culturing seedlings on nutrient-rich agar can be used depending on the type of plant and the purpose of cultivation. Hydroponics, in particular, has many advantages, such as being able to cultivate without pesticides and regardless of the season. Furthermore, because it is less susceptible to external environmental influences, the effect of inducing flower bud formation through oxidative stress treatment according to the present invention can be expected to be greater.

[0032] This invention describes near-ultraviolet light of a specific wavelength related to the cultivation method of the present invention. The light source used (near-ultraviolet light) must have its output wavelength peak in the near-ultraviolet region of 300-400 nm. In the case of a light source with multiple output peaks or an irregular and broad spectral output pattern, it is acceptable if at least 50% of the output energy is in the 300-400 nm wavelength range. From the viewpoint of effectively inducing flower bud formation, the spectral width of the peak wavelength in the near-ultraviolet light is preferably 100 nm or less in full width at half maximum.

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

[0034] By irradiating growing plants with near-ultraviolet light of a specific wavelength in addition to blue light of a specific wavelength, and supplying them with a nitrogen-free nutrient solution, the effect of inducing flower bud formation can be improved. Alternatively, the use of near-ultraviolet light of a specific wavelength may be omitted. In other words, growing plants may be irradiated with near-ultraviolet light of a specific wavelength and supplied with a nitrogen-free nutrient solution. In this case, the effect of the near-ultraviolet light on phototropin, one of the blue light receptors (cryptochrome and phototropin), is considered to be minimal.

[0035] The present invention will be described in detail below in each embodiment. However, the conditions in the present invention are not limited to the embodiments described below, and various modifications are possible without departing from the spirit of the invention.

[0036] <First Example> In the first embodiment, strawberry (Fragaria ananassa) seeds were used to conduct three tests (hereinafter referred to as the flower bud induction effect) on the effect of oxidative stress treatment according to the cultivation method of the present invention on inducing flower bud formation.

[0037] (Subjects to be subjected to oxidative stress treatment) The seedlings used in experiments 1-3 were grown hydroponically from seeds using the following procedure. First, let's explain the procedure for germinating the seeds. Place the seeds in a urethane germination bed filled with plenty of tap water and illuminate them from above. White light, which has little growth-inhibiting effect, is preferable as the light source. 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. During seed germination, cultivate the seeds using only water until the cotyledons unfold.

[0038] Next, we will explain the procedure from the germination of strawberry seeds to the unfolding of the cotyledons. After the cotyledons have unfolded, germination nutrient solution a (EC value = approximately 0.6~0.8 mS / cm) is circulated under the germination bed. This is because, during the period when the cotyledons unfold, the stored nutrients in the seed are depleted, and the seed needs to absorb various ions from the nutrient solution for subsequent growth. The EC value indicates the electrical conductivity (total amount of water-soluble salts).

[0039] To prevent a deficiency of dissolved oxygen in nutrient solution a, circulate the solution for approximately 5-7 days while replenishing it with air (oxygen) using an air pump. After that, switch to the normal growth nutrient solution b (EC value = approximately 1.8 mS / cm) and circulate nutrient solution b.

[0040] The following three experiments (1-3) were conducted to investigate flower bud formation through oxidative stress treatment. Each experiment used seedlings grown using the cultivation method described above, with their cotyledons unfolded (hereinafter referred to as "unfolded seedlings"). After the oxidative stress treatment in each experiment, the seedlings were grown in a normal growth nutrient solution b for approximately one month, and the flower bud induction rate was examined.

[0041] [Experiment 1: Effect of number of days on inducing flower bud formation in strawberries] We conducted an experiment to investigate the effect of oxidative stress treatment on inducing flower bud formation in strawberries (see Figure 1). Specifically, under the following conditions, oxidative stress treatment was continuously applied to leaf-developing seedlings for each treatment period (1 to 4 days).

[0042] (Conditions for Test 1) During each treatment period (1 to 4 days), as an oxidative stress treatment, the developing plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of a specific wavelength. Tap water was used for the nitrogen-free nutrient solution. The blue light source used was an LED from Raytron. The light intensity (photon flux density) on the leaf surface was 210 μmol / m². 2 The time interval is / s. The peak wavelength of light is 450 nm. Twenty leaf-developed plants were used for each treatment period (1 to 4 days).

[0043] (Results of Test 1) As shown in Figure 1, the results of Experiment 1 showed that the flower bud induction rate after 1 day of treatment was 10%, after 2 days of treatment was 75%, after 3 days of treatment was 100%, and after 4 days of treatment was 100%. Therefore, it was shown that applying oxidative stress treatment to leaf-developing plants for at least two consecutive days induces flower bud formation. In particular, applying oxidative stress for three days or more resulted in a superior flower bud formation effect.

[0044] [Experiment 2: Effects of different nutrient solutions and light sources on inducing flower bud formation in strawberries] We conducted an experiment to investigate the effect of different nutrient solutions and light sources used in oxidative stress treatment on inducing flower bud formation in strawberries (see Figure 2). Specifically, under the following conditions, leaf-developing plants were subjected to different oxidative stress treatments with varying nutrient solutions and light sources for three consecutive days.

[0045] (Conditions for Exam 2) For oxidative stress treatment, we used either a standard growth nutrient solution b containing nitrogen (EC value = approximately 1.8 mS / cm) or tap water containing nitrogen. For the oxidative stress treatment, a Raytron LED was used as the light source, employing blue or red light of a specific wavelength. The light intensity (photon flux density) of the blue or red light was 210 μmol / m² on the leaf surface. 2 The time interval is / s. The peaks for each wavelength are 450 nm for blue light and 650 nm for red light. The conditions for each oxidative stress treatment (combinations of nutrient solution and light source used) were as follows: using nutrient solution b and blue light of a specific wavelength; using tap water and blue light of a specific wavelength; using nutrient solution b and red light of a specific wavelength; and using tap water and red light of a specific wavelength. Oxidative stress treatment under each of the above conditions was performed on leaf-developing plants for three consecutive days. Twenty leaf-developed plants were used for each oxidative stress treatment.

[0046] (Results of Test 2) As shown in Figure 2, the results of Experiment 2 showed that the flower bud induction rate by oxidative stress treatment under conditions using tap water and blue light of a specific wavelength was 100%. The flower bud induction 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, and 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-developing plants and irradiating them with blue light of a specific wavelength has an excellent flower bud induction effect. It was also shown that using only one of the conditions, either the condition using blue light of a specific wavelength or the condition using tap water, does not induce flower bud formation. In other words, it was shown that only when both the condition of supplying nitrogen-free nutrient solution and the condition of irradiating with blue light of a specific wavelength are applied to leaf-developing plants can a very strong oxidative stress be induced, resulting in a remarkable flower bud induction effect.

[0047] [Experiment 3: Effect of different light intensities on inducing flower bud formation in strawberries] We conducted an experiment to investigate the effect of different light intensities (photon flux density) of blue light used for oxidative stress treatment on inducing flower buds in strawberries (see Figure 3). Specifically, under the following conditions, leaf-developing plants were supplied with a nitrogen-free nutrient solution for three consecutive days, and oxidative stress treatment was applied by irradiating them with blue light of specific wavelengths with different light intensities.

[0048] (Conditions for Exam 3) As an oxidative stress treatment, the plant with developing leaves was supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of varying intensities. Tap water was used for the nitrogen-free nutrient solution. The blue light source used was an LED from Raytron. The peak wavelength of the light was 450 nm. The light intensities (photon flux density) were 150, 180, 210, and 250 μmol / m². 2 I did it with / s. Twenty leaf-developed plants were used for each light intensity level.

[0049] (Results of Test 3) As shown in Fig. 3, as test results, the flower bud induction rate at a light intensity of 150 μmol / m 2 / s was 80%, the flower bud induction rate at a light intensity of 180 μmol / m 2 / s was 90%, the flower bud induction rate at a light intensity of 210 was 100%, and the flower bud induction rate at a light intensity of 250 μmol / m 2 / s was 100%. Therefore, when supplying a nutrient solution without nitrogen to the leaf-expanding plants and irradiating with blue light of a specific wavelength to apply oxidative stress, the light intensity (photon flux density) of the blue light should be at least 150 μmol / m 2 / s or more to show a flower bud induction effect. In particular, when the light intensity is 210 μmol / m 2 / s or more, it has been shown to exhibit a remarkable flower bud induction effect.

[0050] <Second Example> In the second example, Tests 4 to 6 on the flower bud induction effect by the oxidative stress treatment according to the cultivation method of the present invention were conducted using seeds of strawberry (Fragaria ananassa). In the second example, the test was conducted by changing the blue light of the specific wavelength used in the first example to blue light of a specific wavelength and near ultraviolet light.

[0051] (Object to be subjected to oxidative stress treatment) Since the seedlings used in Tests 4 to 6 were hydroponically grown from seeds by the same procedure as in the first example, the description is omitted.

[0052] Hereinafter, Tests 4 to 6 were conducted on flower bud formation by oxidative stress treatment with addition of near ultraviolet light. For each test, seedlings (hereinafter referred to as leaf-expanding plants) in which cotyledons had expanded and grown by the above cultivation method were used. After the oxidative stress treatment in each test, growth was continued for about one month with the normal growth nutrient solution b, and the flower bud induction efficiency was examined.

[0053] [Test 4: Flower bud induction effect of strawberry by number of days (with addition of near ultraviolet light)] We conducted an experiment to investigate the effect of oxidative stress treatment with near-ultraviolet light on inducing flower bud formation in strawberries (see Figure 4). Specifically, under the following conditions, oxidative stress treatment was continuously applied to leaf-developing seedlings for each treatment period (1 to 4 days).

[0054] (Conditions for Exam 4) During each treatment period (1 to 4 days), as an oxidative stress treatment, the developing plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light and near-ultraviolet light of specific wavelengths. Tap water was used for the nitrogen-free nutrient solution. The blue light and near-ultraviolet light sources used were LEDs from Raytron. The light intensity (photon flux density) of the blue light and near-ultraviolet light was 210 μmol / m² on the leaf surface. 2 The time interval is / s. The peak wavelengths are 450 nm for blue light and 350 nm for near-ultraviolet light. Twenty leaf-developed plants were used for each treatment period (1 to 4 days).

[0055] (Results of Test 4) As shown in Figure 4, the results of Experiment 4 showed that the flower bud induction efficacy rate was 15% after 1 day of treatment, 80% after 2 days of treatment, 100% after 3 days of treatment, and 100% after 4 days of treatment. Therefore, it was shown that applying oxidative stress treatment to leaf-developing plants for at least two consecutive days induces flower bud formation. In particular, applying oxidative stress for three days or more resulted in a superior flower bud formation effect. Compared to the results of Test 1 of the first embodiment, Test 4 showed a higher flower bud induction rate for treatment periods of 1 and 2 days than Test 1. In other words, adding near-ultraviolet light of a specific wavelength (Test 4) showed a superior flower bud induction effect compared to irradiating only with blue light of a specific wavelength (Test 1).

[0056] [Experiment 5: Effect of differences in nutrient solution and light source on inducing flower bud formation in strawberries (with the addition of near-ultraviolet light)] We conducted an experiment to investigate the effect of different nutrient solutions and light sources used in oxidative stress treatment with near-ultraviolet light on inducing flower bud formation in strawberries (see Figure 5). Specifically, under the following conditions, leaf-developing plants were subjected to each oxidative stress treatment with different nutrient solutions and light sources for three consecutive days.

[0057] (Conditions for Exam 5) For oxidative stress treatment, we used either a standard growth nutrient solution b containing nitrogen (EC value = approximately 1.8 mS / cm) or tap water containing nitrogen. For oxidative stress treatment, a Raytron LED was used as the light source, employing blue light, near-ultraviolet light, and red light of specific wavelengths. The light intensity (photon flux density) of blue light and near-ultraviolet light was 210 μmol / m² on the leaf surface. 2 The wavelength is / s. The peak wavelengths 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 / m² on the leaf surface. 2 The frequency is / s, and the peak wavelength of light is 650 nm. The oxidative stress treatment conditions (combinations of nutrient solution and light source used) were as follows: conditions using nutrient solution b and blue and near-ultraviolet light of a specific wavelength; conditions using tap water and blue and near-ultraviolet light of a specific wavelength; conditions using nutrient solution b and red light of a specific wavelength; and conditions using tap water and red light of a specific wavelength. Oxidative stress treatment under each of the above conditions was performed on leaf-developing plants for three consecutive days. Twenty leaf-developed plants were used for each oxidative stress treatment.

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

[0059] [Experiment 6: Effect of different light intensities on inducing flower bud formation in strawberries (addition of near-ultraviolet light)] We conducted an experiment to investigate the effect of different light intensities (photon flux density) of blue light and near-ultraviolet light used in oxidative stress treatment with near-ultraviolet light on inducing flower buds in strawberries (see Figure 6). Specifically, under the following conditions, leaf-developing plants were supplied with a nitrogen-free nutrient solution for three consecutive days, and oxidative stress treatment was applied by irradiating them with blue light and near-ultraviolet light of specific wavelengths with different light intensities (photon flux density).

[0060] (Conditions for Exam 6) As an oxidative stress treatment, the plant with developed leaves was supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light and near-ultraviolet light of varying light intensities. Tap water was used for the nitrogen-free nutrient solution. The blue and near-ultraviolet light sources used were LEDs from Raytron. The peak wavelengths were 450 nm for blue light and 350 nm for near-ultraviolet light. The light intensities (photon flux density) of the blue and near-ultraviolet light were 150, 180, 210, and 250 μmol / m², respectively. 2 I did it with / s. Twenty leaf-developed plants were used for each light intensity level.

[0061] (Results of Test 6) As shown in Figure 6, the test results showed a light intensity of 150 μmol / m². 2 The flower bud induction rate at / s was 85%, with a light intensity of 180 μmol / m². 2 The flower bud induction rate at / s was 95%, at a light intensity of 210 it was 100%, and at a light intensity of 250 μmol / m² it was 100%. 2 The flower bud induction rate for / s was 100%. Therefore, when supplying nitrogen-free nutrient solution to a leafing plant and irradiating it with blue light and near-ultraviolet light of specific wavelengths to induce oxidative stress, the light intensity should be at least 150 μmol / m². 2It was shown that a light intensity of 210 μmol / m² or higher produced a flower bud induction effect. In particular, 2 It has been shown that when the value is above / s, it exhibits a significant flower bud induction effect. Compared to the results of Test 3 in the first embodiment, Test 6 showed a light intensity of 150 μmol / m² higher than Test 3. 2 / s and 180 μmol / m 2 The flower bud induction rate was high for / s. In other words, in the oxidative stress treatment, the flower bud induction effect was better when a specific wavelength of near-ultraviolet light was added to a specific wavelength of blue light (Test 4) than when only a specific wavelength of blue light was irradiated (Test 1).

[0062] <Third Example> In the third example, Phalaenopsis aphrodite seedlings were used, and the same method as in Example 1 was employed to conduct tests 7-9 on the effect of oxidative stress treatment on inducing flower buds. The description of the same content as in Example 1 is omitted.

[0063] (Subjects to be subjected to oxidative stress treatment) The following experiments (7-9) were conducted to investigate flower bud formation through oxidative stress treatment. Each experiment used Phalaenopsis orchid plants with unfolded leaves (seedlings with unfolded cotyledons) grown using clonal technology. After the oxidative stress treatment in each experiment, the plants were grown for approximately one month in a normal growing nutrient solution c (EC value = approximately 1.8 mS / cm), and the flower bud induction rate was examined.

[0064] [Experiment 7: Effect of number of days on inducing flower bud formation in Phalaenopsis orchids] We conducted an experiment to investigate the effect of oxidative stress treatment on inducing flower bud formation in Phalaenopsis orchids (see Figure 7). Specifically, under the following conditions, leaf-developing seedlings were continuously subjected to oxidative stress treatment for each treatment period (1 to 4 days).

[0065] (Conditions for Exam 7) During each treatment period (1 to 4 days), as an oxidative stress treatment, the developing plants were supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of a specific wavelength. Tap water was used for the nitrogen-free nutrient solution. The blue light source used was an LED from Raytron. The light intensity was 210 μmol / m² on the leaf surface. 2 The frequency is / s, and the peak wavelength of light is 450 nm. Twenty leaf-developed plants were used for each treatment period (1 to 4 days).

[0066] (Results of Test 7) As shown in Figure 7, the results of Experiment 7 showed that the flower bud induction efficacy rate was 15% after 1 day of treatment, 85% after 2 days of treatment, 100% after 3 days of treatment, and 100% after 4 days of treatment. Therefore, it was shown that applying oxidative stress treatment to leaf-developing plants for at least two consecutive days induces flower bud formation. In particular, applying oxidative stress for three days or more resulted in a superior flower bud formation effect.

[0067] [Experiment 8: Effects of different nutrient solutions and light sources on inducing flower bud formation in Phalaenopsis orchids] We conducted an experiment to investigate the effect of different nutrient solutions and light sources used in oxidative stress treatment on inducing flower bud formation in Phalaenopsis orchids (see Figure 8). Specifically, under the following conditions, leaf-developing plants were subjected to different oxidative stress treatments with varying nutrient solutions and light sources for three consecutive days.

[0068] (Conditions for Test 8) For oxidative stress treatment, we used either a standard growth nutrient solution c containing nitrogen (EC value = approximately 1.8 mS / cm) or tap water containing nitrogen. For the oxidative stress treatment, a Raytron LED was used as the light source, employing blue or red light of a specific wavelength. The light intensity of the blue or red light was 210 μmol / m² on the leaf surface. 2 The time interval is / s. The peaks for each wavelength are 450 nm for blue light and 650 nm for red light. The conditions for each oxidative stress treatment (combinations of nutrient solution and light source used) were as follows: using nutrient solution c and blue light of a specific wavelength; using tap water and blue light of a specific wavelength; using nutrient solution c and red light of a specific wavelength; and using tap water and red light of a specific wavelength. Oxidative stress treatment under each of the above conditions was performed on leaf-developing plants for three consecutive days. Twenty leaf-developed plants were used for each oxidative stress treatment.

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

[0070] [Experiment 9: Effect of different light intensities on inducing flower bud formation in Phalaenopsis orchids] We conducted an experiment to investigate the effect of different light intensities of blue light used for oxidative stress treatment on inducing flower bud formation in Phalaenopsis orchids (see Figure 9). Specifically, under the following conditions, leaf-developing plants were supplied with a nitrogen-free nutrient solution for three consecutive days, and oxidative stress treatment was applied by irradiating them with blue light of specific wavelengths with different light intensities (photon flux density).

[0071] (Conditions for Exam 9) As an oxidative stress treatment, the plant with developing leaves was supplied with a nitrogen-free nutrient solution and continuously irradiated with blue light of different light intensities (photon flux density). Tap water was used for the nitrogen-free nutrient solution. The blue light source used was an LED from Raytron. The peak wavelength of the light was 450 nm. The light intensities (photon flux density) were 150, 180, 210, and 250 μmol / m². 2 I did it with / s. Twenty leaf-developed plants were used for each light intensity level.

[0072] (Results of Test 9) As shown in Figure 9, the test results showed a light intensity of 150 μmol / m². 2 The flower bud induction rate at / s was 85%, with a light intensity of 180 μmol / m². 2 The flower bud induction rate at / s was 90%, at a light intensity of 210 it was 100%, and at a light intensity of 250 μmol / m² it was 100%. 2 The flower bud induction rate for / s was 100%. Therefore, when supplying nitrogen-free nutrient solution to a leafing plant and irradiating it with blue light of a specific wavelength to induce oxidative stress, the light intensity of the blue light should be at least 150 μmol / m². 2 It was shown that a light intensity of 210 μmol / m² or higher produced a flower bud induction effect. In particular, 2 It has been shown that when the value is above / s, it exhibits a significant flower bud induction effect.

[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 supplied with a nitrogen-free nutrient solution to induce flower bud formation, reactive oxygen species are generated within the plant, causing oxidative stress. This shifts the growth from vegetative 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, thereby promoting flowering, increasing the number of flowers and fruits, and improving the size and sugar content of the flowers and fruits. Furthermore, by irradiating with near-ultraviolet light of a specific wavelength in addition to the blue light, an even better effect in inducing flower bud formation can be obtained.

[0074] Furthermore, a superior flower bud induction effect can be obtained with a shorter processing time than usual. Thus, the cultivation method described in the example can promote flower bud formation more quickly and efficiently than conventional methods. The cultivation method described in the example can be used not only for ornamental plants, but also for fruit vegetables, fruit trees, and grains, and is expected to increase yields by promoting flower bud formation, making it applicable to a wide range of agricultural fields.

Claims

1. For strawberry seedlings after the cotyledons have unfolded, This method is characterized by supplying tap water that is substantially free of nitrogen sources, while continuously irradiating it with blue light having a peak wavelength in the 400-500 nm wavelength range for 2 to 4 days. A method for inducing flower buds in hydroponic strawberry cultivation.

2. The method is characterized by irradiating the strawberry seedlings with near-ultraviolet light having a peak wavelength in the 300-400 nm wavelength range, along with the aforementioned blue light. The method for inducing flower buds in hydroponic cultivation of strawberries as described in claim 1.

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