JP7639263B2 - Growth activation liquid for growing plant seedlings - Google Patents

Description

The present invention relates to a solution-type plant growth environment improving agent for supplying a concentration of silver ions to cultivated plants and/or soil and/or hydroponic solution for plant cultivation that only partially eliminates soil microorganisms in plant cultivation, nutrient solution microorganisms in plant cultivation, and attached symbiotic microorganisms or endosymbiotic microorganisms of plants.

Silver ions are used as antibacterial agents, disinfectants, and sanitizers for pathogenic microorganisms such as viruses and bacteria, and have been effectively applied to products and methods that have the desired effects. Therefore, silver ions have been used primarily in the fields of health and hygiene, medicine, the food industry, and other fields as a material for preventing and inhibiting the occurrence of microbial diseases.

The applicant and the inventor of the present invention discovered that an aqueous solution containing a low concentration of silver ions, which can only partially eliminate soil microorganisms in plant cultivation, nutrient solution microorganisms in plant cultivation, and attached symbiotic microorganisms and/or endosymbiotic microorganisms of plants, has a remarkable effect on improving the plant cultivation environment, leading to the present invention.

Plants growing in soil or hydroponic culture can only live in a completely sterile environment (free of microorganisms) in extremely special circumstances, and in many cases they grow in symbiosis with microorganisms such as bacteria, archaea, and fungi. In some cases, the symbiosis between these microorganisms and plants is simply a shared habitat, but in many cases, a commensal or mutualistic symbiotic relationship is formed. In commensal relationships, microorganisms may be pathogenic to plants, but while commensal and mutualistic relationships that are not like this are commonly seen, commensal cases in which pathogenicity is observed are very rare. Therefore, many microorganisms that live in soil and water environments are harmless to plant growth, or rather play a role in promoting plant growth.

Antibacterial agents and disinfectants for pathogenic microorganisms such as viruses and bacteria that contain a certain concentration or higher of silver ions are effectively used to prevent the occurrence of microbial infections by eliminating microorganisms, and have become important application technical fields for silver ions in the fields of health and hygiene, medicine, and the food industry. However, in industrial fields where the cultivation of plants is essential, such as agriculture, forestry, and horticulture, it is necessary to maintain the symbiotic relationship between the aforementioned microorganisms and plants, and so the bacteriostatic and disinfectant properties of high concentrations of silver ions above a certain concentration, which eliminate almost all microorganisms, often have the opposite effect.

The product and its application technology of the present invention were discovered through the results of a study conducted to determine the minimum concentration of silver ions effective as an antibacterial and disinfectant agent. When the test bacteria were exposed to an aqueous solution with a silver ion (Ag+) concentration of 0.060 mg/L or more, diluted with dechlorinated water, for 30 minutes and then applied to an NB agar plate medium to measure the number of surviving bacteria, all of the test bacteria of the genus Pseudomonas, Escherichia, and Bacillus lost their proliferation activity, and this concentration of silver ion water demonstrated a complete disinfecting effect. Test bacteria exposed for 30 minutes to a solution with a silver ion (Ag+) concentration of 0.030 mg/L to 0.050 mg/L diluted with dechlorinated water lost proliferation activity in roughly proportion to the range of silver ion concentrations, although this differed depending on the three types of test bacteria used, and the average inactivation rate was 47-69%. Next, the silver ion concentration was reduced to below 0.025 mg/L and the disinfection effect was examined by similar exposure, and the average inactivation rate of all three types of test bacteria was 22% or less (survival rate of 78% or more).

Furthermore, Komatsuna was sown on agar medium for germination prepared using water containing 0.025 mg/L or less of silver ions, and germination and rooting tests were performed on Komatsuna with varying silver ion concentrations. The germination and rooting tests were performed in an artificial weather chamber set at 22°C, with one cycle of 12 hours of 2500 lx white fluorescent light irradiation (light conditions) and 12 hours of no fluorescent light irradiation (dark conditions). When the silver ion concentration added to the agar medium was 0.025 mg/L, the average seedling stalk length 5 days after sowing was 1.18 times and 1.13 times, respectively, compared to when the silver ion concentration was 0.040 mg/L and 0.030 mg/L. On the other hand, when the root length of seedlings in agar culture medium was compared under the same conditions, the average root length of seedlings 5 days after sowing when the silver ion concentration was 0.025 mg/L was 1.52 times and 1.32 times, respectively, compared to when the silver ion concentration was 0.040 mg/L and 0.030 mg/L, and it was found that the growth rate of seedling roots was particularly fast when the silver ion concentration was low at 0.025 mg/L or less. Regarding the germination rate of komatsuna, no significant difference was observed among the three levels of added silver ion concentration.

The growth-promoting effect of the low concentration of silver ions of 0.025 mg/L on the growth of Komatsuna seedlings was observed to be almost the same even when the silver ion concentration of the agar culture medium was further reduced under the same temperature and light irradiation conditions, down to a silver ion concentration of 0.0002 mg/L. However, the average seedling stem length and average seedling root length 5 days after sowing when the silver ion concentration was 0.0001 mg/L were 1.0 times and 1.06 times, respectively, compared to the average seedling stem length and average seedling root length when the silver ion concentration was 0.030 mg/L, and there was no significant difference. Furthermore, when the silver ion concentration was diluted and reduced to 0.00005 mg/L with dechlorinated water, the average seedling stem length and average seedling root length 5 days after sowing were not significantly different from the average seedling stem length and average seedling root length when the silver ion concentration was 0.030 mg/L.

However, it is difficult to store silver ions at a constant concentration of 0.025 mg/L or less for more than four months. Therefore, in this invention, in order to make it possible to store silver ion water at a stable concentration for long periods of time, the silver ion storage stock solution is prepared as a high-concentration aqueous solution with a silver ion concentration of 8 mg/L or more, and this is diluted with dehalogenated water immediately before use as a plant growth environment improvement agent, and low-concentration silver ion water of 0.025 mg/L or less and 0.0002 mg/L or more is used as a growth activation solution for plants with roots, thereby solving this problem.

All the agar culture media used in the germination and rooting tests of Komatsuna were prepared using purified water, but when agar culture media for germination were prepared using tap water disinfected with chlorine containing 5.0 μmol/L of chloramine, which is a residual combined chlorine, or a silver ion aqueous solution containing 5.0 mmol/L of sodium chloride or sodium bromide, and a growth test of Komatsuna was conducted under similar artificial weather conditions, the plant growth promoting effect of silver ions was not observed when the silver ion concentration was 0.010 mg/L, unlike the results when agar culture media containing silver ions was used prepared with purified water. From these results, it was presumed that the free chlorine and residual combined chlorine and halide ions such as chlorine and bromine contained in tap water inhibited the expression of the plant growth promoting effect of low concentrations of silver ions. To eliminate this inhibition, sodium thiosulfate was added to the halogen-containing agar culture medium preparation water, and after dehalogenation treatment, tap water (chloride ion concentration 15 mg/L) was used to prepare the agar culture medium, and a komatsuna germination and rooting test was performed.

This dehalogenation procedure was performed with different concentrations of sodium thiosulfate, and the concentrations of residual halogen ions and halogen compounds were measured each time. An agar culture medium for the germination and rooting test of Komatsuna was then prepared and the germination and rooting test was performed. The test results showed that by performing dehalogenation so that the concentration of residual chloramine was 4.0 μmol/L or less, it was possible to eliminate the halogen inhibition of the low concentration silver ions of 0.010 mg/L or less in promoting Komatsuna growth.

Next, tap water was dehalogenated so that the concentrations of free halogens and combined residual halogen compounds were 1.0 μmol/L or less, and sodium chloride or bromide ions were added so that the chloride ion concentration was 17.7 mg/L to 249 mg/L, to prepare a low-concentration silver ion solution of 0.010 mg/L, which was then used to prepare an agar culture medium for germination and rooting tests of Japanese mustard spinach, and a germination and rooting test was conducted. The test results showed that by using a silver ion solution with a chloride ion or bromide ion concentration of 3.0 mmol/L or less, the halogen inhibition of the low-concentration silver ions of 0.010 mg/L or less in promoting the growth of Japanese mustard spinach can be eliminated.

When silver ions (Ag+) have been used in the environment up until now, it is known that they can no longer maintain their ionic state when they come into contact with reducing compounds or when they form insoluble salts. In the present invention, it is predicted that the silver ions will lose their plant growth-promoting effect when they come into contact with reducing compounds present in the soil or plant culture solution, changing from an ionic state to a non-ionic state. In order to prevent this loss of growth-promoting effect of silver ions, it is considered necessary to re-oxidize silver that has lost its cationic character by reduction and return it to silver ions (Ag+). Therefore, in the present invention, a photooxidation catalyst was added to a low-concentration silver ion solution with a concentration of 0.010 mg/L or less at a concentration 8 times the silver ion concentration by weight, and a test was conducted to see if the growth-promoting effect of silver ions could be restored.

First, the solution was diluted with dechlorinated water that had been deoxidized by aeration with argon gas to a low silver ion concentration of 0.010 mg/L, and dithiothreitol was added to the solution to a concentration of 0.10 mg/L. The solution was then sealed with a butyl rubber stopper and reacted for 30 minutes to reduce the silver ions. The resulting aqueous solution was then used to prepare an agar culture medium for germination. Komatsuna was seeded on the agar culture medium, and a germination and rooting test was carried out in an artificial weather chamber set at 22°C, with one cycle of 13 hours of 2500 lx white fluorescent light irradiation (light condition) and 11 hours of no fluorescent light irradiation (dark condition). As a result, compared to the results of the control test in which dithiothreitol was not added, there was almost no change in the germination rate, but the average seedling stem length on the third and fifth days after sowing was 1.03 times and 0.98 times, respectively. Regarding seedling root length, the average seedling root length on the third and fifth days after sowing was 0.99 and 1.02 times, respectively, compared to the results of the control test in which dithiothreitol was not added, and when 0.10 mg/L dithiothreitol was added, the low concentration of 0.010 mg/L silver ions did not show any effect in promoting root elongation of komatsuna seedlings.

Next, a germination agar culture medium was prepared by adding titanium dioxide nanoparticles with an average primary particle size of 25 nm as a photooxidation catalyst to a solution of 0.20 mg/L to the reaction solution of 0.025 mg/L silver ions and 0.25 mg/L dithiothreitol, which was also prepared using deoxygenated water and dechlorinated water. Using this culture medium, germination and rooting tests of Komatsuna were conducted under conditions of 13 hours of fluorescent light irradiation and 11 hours of non-fluorescent light irradiation in an artificial weather chamber set at 22°C with 2400 lx of white fluorescent light. As a result, compared to the results of the control test in which 0.20 mg/L titanium dioxide was not added, there was almost no change in the germination rate, but the average seedling stem length 5 days after sowing of Komatsuna was 1.39 times. The average seedling root length 5 days after sowing was 1.54 times the results of the control test in which titanium dioxide was not added, confirming the restoration of the high growth promotion effect of 0.025 mg/L silver ions. These results suggest that titanium dioxide nanoparticles function as a photooxidation catalyst that oxidizes metallic silver produced by reduction with dithiothreitol under light irradiation conditions, thereby regenerating silver ions (Ag+) and restoring the growth-promoting effect of low-concentration silver ions on plants.

In the above test, the amount of titanium dioxide nanoparticles added was changed and the germination and rooting test of komatsuna was performed without changing other conditions. When titanium dioxide was added at a concentration below 0.001 mg/L, the growth promotion effect of komatsuna by adding 0.025 mg/L of silver ions was almost not observed. In order to oxidize the reducing compound dithiothreitol and silver to regenerate silver ions (Ag+), it was thought that the amount of titanium dioxide added must be at least 0.001 mg/L. It was thought that the effect of regenerating silver ions by titanium dioxide is such that the amount of titanium dioxide added must be at least 0.001 mg/L. On the other hand, when titanium dioxide exceeding 20 mg/L was added, the growth promotion effect of silver ions on komatsuna was reduced, and it was known that adding titanium dioxide at a concentration exceeding 20 mg/L has a negative effect on the growth of komatsuna seedlings due to excessive progress of photooxidation reactions.

Next, instead of titanium dioxide nanoparticles, tungsten trioxide-palladium alloy nanoparticles and tungsten trioxide-copper alloy nanoparticles with an average primary particle size of 400 nm or less were used to carry out germination and rooting tests of Komatsuna under exactly the same conditions as those for titanium dioxide, with 13 hours of 2500 lx white fluorescent light irradiation (light conditions) and 11 hours of fluorescent light non-irradiation (dark conditions) and at 22°C. Almost the same results were obtained for the growth promotion effect of Komatsuna. Furthermore, the concentration range in which these alloy nanoparticles have a growth promotion effect was the same as that of titanium dioxide. From these findings, it was thought that tungsten trioxide-palladium alloy particles and tungsten trioxide-copper alloy particles act as photooxidation catalysts in the same way as titanium dioxide when added in the same concentration, and can function as oxidation catalysts for the reionization of reduced silver. Therefore, it was believed that tungsten trioxide-palladium alloy nanoparticles or tungsten trioxide-copper alloy nanoparticles with photocatalytic functions could be used as an alternative material to titanium dioxide nanoparticles for promoting plant growth using silver ions according to the present invention.

JP 63-060904 A JP 63-060905 A JP2001-010913 JP2006-141252A

The problem that this invention aims to solve is to make it possible to reduce the amount of disinfectant used, which has been necessary so far to prevent the occurrence of plant diseases in plant cultivation, or to eliminate the use of disinfectants. In addition, it is also intended to make it possible to prevent the emergence of new disinfectant-resistant plant pathogenic microorganisms caused by the continued use of disinfectants. Furthermore, it is also intended to convert industries based on plant cultivation, such as agriculture, forestry, horticulture, and green space development, into more environmentally friendly industries by reducing or eliminating the use of pesticides in plant cultivation.

In order to solve the above problems, the present invention does not rely entirely on the use of pest control agents such as disinfectants and insecticides in plant cultivation, but instead uses a basic means of enhancing the resistance and immunity that plants naturally possess against pathogenic microorganisms and feeding damage by insects, etc., thereby solving the problem of reducing or eliminating the use of disinfectants and insecticides in plant cultivation. In order to realize this basic means, it is considered important to maximize the nutrient intake and growth capabilities of plants. The expression of these capabilities is considered to activate healthy growth in cultivated plants, which in turn gives them immunity and resistance to plant pathogenic microorganisms and resistance to feeding damage by insects, etc.

In order to maximize a plant's inherent ability to take up nutrients and grow, it is necessary to promote vigorous and healthy growth during the seedling stage after germination and root formation, and during the growth stage of the plant's roots (roots and rhizomes) and shoots (stems and leaves, etc.). During the seedling stage, the plant roots in particular need to take in nutrients and absorb water, so vigorous growth of the plant's roots is important for acquiring resistance to plant diseases. The inventors have come up with the invention of a plant growth activation liquid containing a low concentration of silver ions, with an actual use concentration of 0.025 mg/L or less, which is only able to partially eliminate attached symbiotic microorganisms and/or endosymbiotic microorganisms of plants, as described in claim 1 of the invention.

According to the prior art, the effect of silver ions on plant root elongation was not known to be effective at low concentrations of 0.03 mg/L (= 30 ppb) or less. However, in the present invention, it was discovered that the loss of the effect of silver ions on root elongation at such low concentrations is due to the interfering effect of halogen compounds and/or halide ions present in the cultivation soil or cultivation water. As a result, it was discovered that the interference with the effect of silver ions on plant root elongation can be solved by using dehalogenated water used to prepare the silver ion solution so that the concentration of free halogen and combined residual halogen compounds in the water is 4.0 μmol/L or less, and the concentration of halide ions such as chloride ions and bromide ions is 3.0 mmol/L or less.

In conventional methods, it was technically difficult to store a silver ion aqueous solution at a stable concentration for more than a week when the silver ion concentration was 0.03 mg/L or less. However, in the present invention, it is known that by preparing a silver ion preservation solution with a silver ion concentration of 8 mg/L or more, it is possible to maintain the silver ion concentration stably for a long period of time. Therefore, a method is adopted in which the preservation solution is diluted immediately before actual use to make a low-concentration silver ion water of 0.025 mg/L or less, which can be used to stimulate plant growth.

Low concentrations of silver ions of 0.025 mg/L or less promote the growth of plant roots, allowing cultivated plants to absorb more nutrients from the cultivation soil and nutrient solution, which not only results in vigorous growth of the above-ground parts of cultivated plants, but is also thought to have the effect of increasing resistance to infection by pathogenic microorganisms and damage caused by insects, etc. Furthermore, such low concentrations of silver ions do not suppress or eliminate microorganisms that live inside plants (endophytes), and therefore do not disrupt the favorable symbiotic relationship between plants and microorganisms.

As a plant growth activator for cultivating plant seedlings, by dissolving a low concentration of silver ions of 0.0005 mg/L or more and 0.025 mg/L or less in water that does not contain free halogen molecules, halogen acid compounds, hypohalous acid compounds, chloramines, bromoamines, or other halogen compounds at a concentration of more than 4.0 μmol/L, and water that does not contain chlorine ions, bromine ions, or other halide ions at 3.0 mmol/L or more, the effect of promoting the growth of the seedling stem and root after germination and rooting of the plant can be obtained. In particular, since the vigorous growth of the plant root can be induced as an effect of this invention, there is an advantage in that the intake of nutrients and absorption of water by the plant seedling can be vigorous. As a result, the effect of enhancing the immunity to plant diseases and the resistance of the plant itself to feeding damage by insects, etc. is created.

In addition to promoting the growth of plant roots and shoots with low-concentration silver ions of 0.0005 mg/L to 0.025 mg/L, the use of a plant growth activation solution containing added zinc ions at an actual use concentration of 0.0001 mg/L to 2.0 mg/L makes it possible to increase the growth activity of endosymbiotic microorganisms in plants. This is because low-concentration silver ions of 0.0005 mg/L to 0.025 mg/L have almost no effect on the growth activity of soil microorganisms, nutrient solution microorganisms, and endosymbiotic microorganisms in plants, and zinc ions of 0.0001 mg/L to 2.0 mg/L can fully exert their effect of promoting the growth activity of microorganisms, particularly the growth activity of endosymbiotic microorganisms in plants, independent of the presence of silver ions. The increased growth of endosymbiotic microorganisms has the advantage of further activating the growth of plant seedlings.

Similarly, the addition of magnesium ions at an actual use concentration of 0.005 mg/L to 5.0 mg/L to an aqueous solution containing a low concentration of silver ions of 0.0001 mg/L to 2.0 mg/L also has a significant effect on promoting the proliferation activity of plant endosymbiotic microorganisms, just like the addition of zinc ions. The difference with the addition of zinc ions is that magnesium ions at an actual use concentration of 0.005 mg/L to 5.0 mg/L not only promote the proliferation activity of plant endosymbiotic microorganisms, but also promote the root elongation of plant seedlings, although not as much as silver ions. This characteristic gives magnesium ions the advantage of being able to directly exert a synergistic effect on plant growth activation when used in combination with silver ions.

It is known that low concentrations of silver ions between 0.0005 mg/L and 0.025 mg/L are effective in elongating plant roots and shoots, but in environments where there are many reducing substances in the soil and nutrient solution where plants grow, the effect of low concentrations of silver ions gradually disappears. In order to solve this problem, by adding a photooxidation catalyst of fine titanium dioxide, tungsten trioxide-palladium alloy particles, or tungsten trioxide-copper alloy particles with an average primary particle size of 400 nm or less to a low concentration silver ion aqueous solution between 0.0005 mg/L and 0.025 mg/L in an actual use concentration of 0.001 mg/L to 20 mg/L, it becomes possible to continuously obtain the effect of the added silver ions by regenerating the silver ions reduced by reacting with the reducing substances back to silver ions.

As described above, providing plants with low concentrations of silver ions between 0.0005 mg/L and 0.025 mg/L enables the healthy growth of the plants. This brings out the plants' inherent immunity against pathogenic microorganisms and resistance to damage caused by insects, and has the advantage of making plant cultivation safer and more reliable, and even more environmentally friendly, without the use of pesticides such as disinfectants and insecticides that were previously necessary to prevent disease and damage to cultivated plants, or by minimizing the use of such pesticides. As a result, it enables the sustainable development of industries that are based on plant cultivation, such as agriculture, forestry, horticulture, and green space creation.

In the present invention, a solution containing low concentrations of silver ions of 0.0005 mg/L or more and 0.025 mg/L or less and not containing halide ions of 3.0 mmol/L or more is mixed with titanium dioxide particles, tungsten trioxide-palladium alloy particles, or tungsten trioxide-copper alloy particles having an average primary particle size of 400 nm or less as a photooxidation catalyst at an actual use concentration of 0.001 mg/L or more and 20 mg/L or less, as necessary, for practical use. However, storing such a low concentration silver ion solution for practical use after preparation is not only difficult because it is difficult to stably contain low concentration silver ions for a long period of time, but also requires containers for preparing and storing a large amount of solution on the scale of several tons, as shown in the examples, as well as transportation costs to the storage site and the use site.

In order to avoid these needs, in the present invention, the concentration of each of these metal ions and the concentration of the photooxidation catalyst are prepared and stored as a dilution stock solution containing a concentration 100 to 10,000 times higher than the actual use concentration. When using after preparation and storage, it is advantageous to dilute them 100 to 10,000 times with agricultural water such as tap water and/or river water and/or groundwater that can be obtained at the site of use, adjust the concentrations of each ion and the photooxidation catalyst to the actual use concentration, and use it as a plant growth environment improvement agent promptly in farmland, forest land, green space (lawn, etc.), bonsai, etc. without storing it as much as possible. Note that if the dilution water contains free halogen molecules at a concentration exceeding 4.0 μmol/L, it is important to use the dilution water as a dehalogenated solution using a dehalogenating agent such as thiosulfate in order to activate plant growth. Also, if the dilution water contains halide ions such as chloride ions and bromide ions exceeding 3.0 mmol/L, it is important not to use it.

Survival rate of test bacteria (Pseudomonas putida, Escherichia coli, Bacillus subtilis) after 30 minutes of exposure to solutions of various silver ion concentrations The relationship between the silver ion concentration immediately after preparation of the stock solution of silver ion aqueous solution and the residual percentage of silver ions remaining in the stock solution after storing it sealed in a polyethylene bottle at room temperature for 120 days. The relationship between the stalk and root length of Komatsuna seedlings and the chloramine concentration 5 days after sowing, when a germination and rooting test was conducted using an agar culture medium to which 0.010 mg/L of silver ion and 1.0 μmol/L to 7.0 μmol/L of chloramine, a halogen compound, had been added as combined residual chlorine, was The relationship between the stem length and root length of Komatsuna seedlings and the chloride ion concentration 5 days after sowing, when a germination and rooting test was conducted using an agar culture medium to which 0.010 mg/L of silver ion and 0.5 mmol/L to 7.0 mmol/L of chloride ion, a halide ion, had been added. Relationship between the silver ion concentration of water used to prepare agar medium for germination tests and the average stem and root length of Komatsuna seedlings 5 days after sowing When a germination and root growth test was conducted using an agar medium prepared with water containing 0.010 mg/L silver ions and 0.10 mg/L dithiothreitol, the average shoot and root lengths of Komatsuna seedlings 3 and 5 days after sowing were compared with those of agar medium containing no dithiothreitol. Agar culture medium for germination was prepared using a solution in which titanium dioxide nanoparticles with an average diameter of 100 nm were added as a photooxidation catalyst at concentrations of 0.001 mg/L to 30 mg/L in a reaction solution with a silver ion concentration of 0.025 mg/L and a dithiothreitol concentration of 0.25 mg/L. A germination and rooting test for Komatsuna was carried out under conditions of 13 hours of fluorescent light irradiation and 11 hours of non-fluorescent light irradiation in an artificial weather chamber set at 22°C with 2500 lx of white fluorescent light. The relationship between the concentration of added titanium dioxide nanoparticles and the average stem length and root length of Komatsuna seedlings 5 days after sowing was examined.

Below, examples of how to implement the present invention are illustrated in Examples 1 to 7.

Example 1
A growth activation solution was prepared by adding 200 ml of the ion dissolving stock solution with a silver ion concentration of 8 mg/L to 0.016 mg/L using tap water containing 0.40 mmol/L or less of chloride ions and bromide ions, and adding sodium sulfite to the tap water to dehalogenate it so that the concentrations of free halogen compounds and combined residual halogen compounds in the tap water are 4.0 μmol/L or less, and then adding the solution to 0.04 m2 of seedbed material at an even rate of 200 ml. Then, 32 g of rice seeds were sown and raised. (b) The average seedling height (stalk length) and average root length per 30 rice seeds 12 days after sowing were increased by 1.06 times and 1.55 times, respectively, compared to the average seedling height (stalk length) and average root length per 30 rice seeds 12 days after sowing when 32 g of rice seeds were sown in a bed of 1/500 diluted with dehalogenated water without added silver ions, and 200 mL of the solution was evenly added per 0.04 square meter of seedbed material. This means that the growth of the rice seedlings (especially the growth of the seedling roots) was greatly promoted by the silver ion activation solution with a concentration of 0.016 mg/L.

Example 2
Example for growing tomato seedlings: Tap water containing less than 0.40 mmol/L of chloride ions was further dehalogenated by adding sodium sulfite so that the concentrations of free halogens and combined residual halogen compounds were less than 2.0 μmol/L. The silver ion solution was diluted to a silver ion concentration of 0.016 mg/L, and the resulting silver ion solution was added at an even rate of 200 ml per 0.04 square meters of seedbed material. Thereafter, 50 tomato seeds were sown in the seedbed, allowed to germinate and take root, and then grown as seedlings. The average seedling height (stem length) and average root length per 40 plants that had germinated and taken root 16 days after sowing were 1.08 times and 1.64 times greater, respectively, than the average seedling height (stem length) and average root length per 37 plants that had germinated and taken root 16 days after sowing when 50 tomato seeds were sown in a seedbed material containing the same dehalogenated tap water but without the addition of silver ions. This demonstrated that silver ions at a concentration of 0.016 mg/L promote the growth of tomato seedlings (especially the growth of the roots).

Example 3
Example for raising eggplant seedlings: Tap water containing less than 0.40 mmol/L of chloride ions was further dehalogenated by adding sodium sulfite so that the concentrations of free halogens and combined residual halogen compounds were less than 2.0 μmol/L. The silver ion solution was diluted to a silver ion concentration of 0.016 mg/L and added evenly at 200 ml per 0.04 square meters of seedbed material. Thereafter, 50 eggplant seeds were sown in the seedbed, allowed to germinate and take root, and then grown as seedlings. The average seedling height (stem length) and average root length per 41 seedlings that germinated and took root 16 days after sowing were 1.10 times and 1.58 times, respectively, compared to the average seedling height (stem length) and average root length per 39 seedlings that germinated and took root 16 days after sowing when the same dehalogenated tap water but without added silver ions was added to the seedbed material, and 50 tomato seeds were sown. This demonstrated that silver ions at a concentration of 0.016 mg/L promote the growth of eggplant seedlings (especially the growth of the roots).

Example 4
Example for raising cucumber seedlings: Tap water containing less than 0.40 mmol/L of chloride ions was further dehalogenated by adding sodium sulfite so that the concentrations of free halogens and combined residual halogen compounds were less than 2.0 μmol/L. The silver ion aqueous solution was diluted to a silver ion concentration of 0.016 mg/L and added evenly at 200 ml per 0.04 square meters of seedbed material. Thereafter, 50 cucumber seeds were sown in the seedbed, allowed to germinate and take root, and then grown as seedlings. The average seedling height (stem length) and average root length per 44 plants that germinated and took root 14 days after sowing were 1.12 times and 1.60 times larger, respectively, than the average seedling height (stem length) and average root length per 42 plants that germinated and took root 14 days after sowing when 50 cucumber seeds were sown in a seedbed material containing the same dehalogenated tap water but without adding silver ions. This demonstrated that silver ions at a concentration of 0.016 mg/L promote the growth of cucumber seedlings (especially the growth of the roots).

Example 5
Example for raising pea seedlings: Tap water containing less than 0.50 mmol/L of chloride ions was further dehalogenated by adding sodium sulfite so that the concentrations of free halogens and combined residual halogen compounds were less than 2.0 μmol/L. The silver ion solution was diluted to a silver ion concentration of 0.016 mg/L and added evenly at 200 ml per 0.04 square meters of seedbed material. Thereafter, 50 pea seeds were sown in the seedbed, allowed to germinate and take root, and then grown as seedlings. The average seedling height (stem length) and average root length per 47 seedlings that had germinated and taken root 15 days after sowing were 1.30 times and 1.68 times greater than the average seedling height (stem length) and average root length per 48 seedlings that had germinated and taken root 14 days after sowing when 50 pea seeds were sown in a seedbed material containing the same dehalogenated tap water but without the addition of silver ions. This demonstrated that silver ions at a concentration of 0.016 mg/L promote the growth of pea seedlings (especially the growth of the roots).

Example 6
Example for growing pepper seedlings: Tap water containing less than 0.50 mmol/L of chloride ions was further dehalogenated by adding sodium sulfite so that the concentrations of free halogens and combined residual halogen compounds were less than 2.0 μmol/L. The silver ion solution was diluted to a silver ion concentration of 0.016 mg/L and added evenly at 200 ml per 0.04 square meters of seedbed material. Thereafter, 50 bell pepper seeds were sown in the seedbed, allowed to germinate and take root, and then grown as seedlings. The average seedling height (stem length) and average root length per 43 plants that had germinated and taken root 14 days after sowing were 1.12 times and 1.60 times greater than the average seedling height (stem length) and average root length per 41 plants that had germinated and taken root 14 days after sowing when 50 bell pepper seeds were sown in a seedbed material containing the same dehalogenated tap water but without added silver ions. This demonstrated that silver ions at a concentration of 0.016 mg/L promote the growth of bell pepper seedlings (especially the growth of the roots).

Example 7
In addition to the above examples, seedlings of 40 kinds of plants, including corn, radish, Chinese cabbage, cabbage, lettuce, bok choy, lettuce, carrots, burdock, soybeans, green onions, shishito peppers, paprika, okra, melons, watermelons, pumpkins, grapes, blueberries, pears, apples, plums, peaches, persimmons, mandarin oranges, oranges, olives, cedars, cypresses, sumac trees, maples, nandinas, ginkgo trees, white oaks, Japanese sycamore trees, camellias, sasanquas, American dogwoods, mountain laurels, and rose of Sharon, were raised by a nursery company. When seedlings were irrigated with a plant activation solution containing 0.010 mg/L of silver ions, which was prepared by adding sodium sulfite to tap water containing 1.0 mmol/L or less of chloride ions so that the concentrations of free halogens and combined residual halogen compounds were 4.0 μmol/L or less, the cultivation period (number of days) from the sowing date to the time when the seedlings could be shipped could be shortened by 15% or more for all plant seedlings, compared to when the seedlings were irrigated with tap water that did not contain silver ions. For bok choy and Japanese cedar, which showed the shortest cultivation periods, the number of cultivation days until they could be shipped was shortened by 2/3.

Instead of the disinfection that has been required to prevent plant diseases in the cultivation of plant seedlings, a low concentration silver ion solution of 0.0005 mg/L to 0.025 mg/L is applied to plants in the elongation stage, which reduces or eliminates the use of pesticides such as disinfectants and insecticides. This can be used to convert industries based on plant cultivation, such as agriculture, forestry, horticulture, and green space creation, into safer and more secure ones, and can also be used to transform them into environmentally friendly and sustainable industries. Furthermore, reducing or eliminating the use of pesticides in this way can reduce the cost of cultivating plant seedlings, thereby increasing the profitability of industries related to plant cultivation, such as agriculture, forestry, horticulture, and green space creation, and can contribute to reducing the labor force in these industries by reducing the labor required for pesticide spraying, etc. Furthermore, using a liquid containing a low concentration of silver ions of 0.0005 mg/L or more and 0.025 mg/L or less as a growth activation liquid for cultivating plant seedlings is also effective in preventing the emergence of new pesticide-resistant plant pathogenic microorganisms and feeding-damaging insects that have been repeatedly caused by the use of pesticides as described above.

PCR: Abbreviation for polymerase chain reaction. (An enzyme reaction that uses DNA polymerase to amplify all or part of a DNA molecule contained in an organism in vitro.)

16S rRNA: A type of ribosomal RNA found in prokaryotes such as bacteria and archaea, and the 16S rRNA gene that serves as the template is encoded on chromosomal DNA.

Claims (1)

A growth activation liquid for growing plant seedlings having roots , which is a liquid growth activation liquid intended to be used to activate the growth of plant seedlings having roots, containing silver ions at a concentration of 0.0005 mg/L or more and 0.025 mg/L or less, and not containing free residual chlorine and combined residual chlorine with concentrations exceeding 4.0 μmol/L, and not containing chloride ions and bromide ions with concentrations exceeding 3.0 mmol/L.

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