Plant growth promoter

Abstract

To provide a novel active ingredient capable of exhibiting a plant growth-promoting effect and capable of being readily and economically produced.SOLUTION: The present invention provides a plant growth promoter containing a nucleic acid such as ribonucleic acid, or a salt thereof, having a molecular weight of 7,000 to 150,000. The nucleic acid or a salt thereof is preferably derived from a microorganism such as Candida genus yeast. The plant growth promoter is preferably a liquid agent, and a content of the nucleic acid or a salt thereof is preferably 0.001 to 10 wt.%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a plant growth promoter. [Background technology]

[0002] Agricultural materials such as pesticides and fertilizers are used to improve crop yields. However, their impact on the environment and human body has become an issue, and development of safe products called "plant growth promoters" (also known as plant growth promoters or plant vitalizers) is underway.

[0003] One of the major factors that hinders improved yields in agricultural crops is poor rooting during the plant's growth process. Plants that have poor rooting during growth slow down their subsequent growth rate, leading to a lower seedling yield. In particular, woody plants are cultivated by cuttings to maintain the characteristics of superior varieties, but the cuttings are often subjected to a variety of stresses during the cutting production process, including damage stress from being separated from the parent branch and drought stress before being cut, which often results in poor rooting. Furthermore, if a superior variety has a trait for poor rooting, the trait will also be inherited when cuttings are taken, making it impossible to fundamentally improve the condition through crossbreeding.

[0004] The main method for dealing with this problem is to use plant hormones to promote rooting (for example, Patent Document 1), but no method has been found that can decisively increase the rooting rate.

[0005] On the other hand, nucleic acids refer to acidic substances contained within the nucleus of cells, and include DNA, RNA, nucleotides, etc. DNA and RNA are polymer chains whose building blocks are nucleotides, and are involved in the storage and transmission of genetic information, as well as functioning as nutrients. Specifically, they are added to powdered milk for infants and infusions for sick people (Non-Patent Document 1), and it has been suggested that they have the effect of promoting the growth of living organisms.

[0006] There have also been reports of administering nucleic acids to plants. For example, Patent Document 2 reports that inosine, a type of nucleic acid, promotes plant rooting. It has also been reported that low-molecular-weight nucleic acids from photosynthetic prokaryotes promote plant growth (Patent Document 3). Patent Document 4 reports that the combined use of an extract containing yeast-derived RNA and proline / uracil, known as a flower bud formation promoter, significantly promotes flowering and fruiting (Patent Document 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3010887 [Patent Document 2] Patent No. 2927269 [Patent Document 3] Japanese Patent Application Publication No. 4-169506 [Patent Document 4] Special Publication No. 5-67121 [Non-patent literature]

[0008] [Non-Patent Document 1] Kato et al., Molecular Nutrition of Nucleic Acids, 2019 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the nucleic acids used in the above examples were all reduced in molecular weight by post-treatment, and it is not known that high-molecular-weight nucleic acids alone can promote plant growth.

[0010] In view of the above problems, an object of the present invention is to provide a novel active ingredient that can exhibit a plant growth-promoting effect and can be produced easily and economically. [Means for solving the problem]

[0011] The present invention provides the following: [1] A plant growth promoter containing a nucleic acid having a molecular weight of 7,000 to 150,000 or a salt thereof. [2] The plant growth promoter according to [1], wherein the nucleic acid comprises ribonucleic acid. [3] The plant growth promoter according to [1] or [2], wherein the nucleic acid or a salt thereof is derived from a microorganism. [4] The plant growth promoter according to [3], wherein the microorganism is a Candida yeast. [5] The plant growth promoter according to any one of [1] to [4], which is a liquid formulation. [6] The plant growth promoter according to any one of [1] to [5], wherein the content of the nucleic acid or a salt thereof is 0.001 to 10% by weight. [7] A method for producing the plant growth promoter according to any one of [1] to [6], comprising carrying out a nucleus removal treatment and a nucleic acid extraction treatment on a microorganism, and extracting nucleic acid or a salt thereof from the microorganism. [Effects of the Invention]

[0012] According to the present invention, there is provided a plant growth promoter that can have a favorable effect on plants, such as improving tolerance to abiotic stress. DETAILED DESCRIPTION OF THE INVENTION

[0013] The plant growth promoter of the present invention contains a nucleic acid or a salt thereof as an active ingredient.

[0014] [1. Nucleic acid or salt thereof] <Definition of Nucleic Acid> As used herein, a nucleic acid is a molecule containing one or more units consisting of a sugar and a nucleotide. When two or more units are contained, the nucleotides are linked by a phosphodiester bond. A nucleic acid in which the sugar is deoxyribose is called deoxyribonucleic acid (DNA), and a nucleic acid in which the sugar is ribose is called ribonucleic acid (RNA), and either can be used. Examples of types of nucleotides include adenosine, guanosine, cytidine, thymidine, and uridine, which are formed by binding a base such as adenine, guanine, thymine, cytosine, or uracil to a phosphate (monophosphate, multiple phosphates, etc.). Nucleic acids may be composed of either one type of nucleotide or two or more types of nucleotides. Furthermore, nucleic acids may be composed of one type alone or a combination of two or more types.

[0015] <Nucleic acid salts> At least a portion of the nucleic acid may be in the form of a salt, such as an alkali metal salt such as sodium or potassium, or an alkaline earth metal salt such as calcium or magnesium.

[0016] <Molecular weight> The molecular weight of the nucleic acid or salt thereof (total amount when two or more nucleic acids are used) is typically 7,000 or more, preferably 8,000 or more, more preferably 9,000 or more, and even more preferably 10,000 or more. This is thought to suppress an increase in osmotic stress, resulting in excellent plant vitality effects. The upper limit is usually 150,000 or less, preferably 130,000 or less, more preferably 100,000 or less, and even more preferably 80,000 or less. This is thought to suppress the formation of chelates of metal components, resulting in excellent plant vitality effects.

[0017] In this specification, the molecular weight refers to the weight average molecular weight (Mw), which can be determined by a method using GPC (gel permeation chromatography) in terms of polyethylene glycol.

[0018] <Origin of nucleic acids> The nucleic acid may be either naturally occurring or artificially synthesized, but naturally occurring nucleic acids are preferred, and nucleic acids derived from microorganisms are more preferred. Examples of nucleic acids derived from microorganisms include extracts or purified products from microorganisms. Examples of microorganisms include yeasts such as asporogenous yeasts and sporogenous yeasts, and are specifically as follows.

[0019] Examples of non-spore-forming yeasts include those of the genus Torulopsis, such as Torulopsis versatilis; those of the genus Candida, such as Candida utilis, Candida tropicalis, and Candida lipolytica; and those of the genus Rhodotorula, such as Rhodotorula glutinis. Candida utilis is sometimes referred to as torula yeast and is sometimes classified as a member of the genus Cyberlindnera (Cyberlindnera jadinii).

[0020] Examples of spore-forming yeasts include yeasts of the genus Shizosaccharomyces, such as Shizosaccharomyces pombe and Shizosaccharomyces octosporus; yeasts of the genus Saccharomyces, such as Saccharomyces cerevisiae, Saccharomyces uvarum, and Saccharomyces rouxii; yeasts of the genus Kluyveromyces, such as Kluyveromyces fragilis and Kluyveromyces lactis; and yeasts of the genus Kluyveromyces, such as Hansenula anomala. Examples of yeasts in the genus Hansenula include yeasts from the genus Hansenula, such as Pichia anomala; yeasts in the genus Pichia, such as Pichia membranaefaciens; yeasts in the genus Debaryomyces, such as Debaryomyces hansenii; and yeasts in the genus Lipomyces, such as Lipomyces starkeyi.

[0021] In addition, yeasts known as brewer's yeast, wine yeast, and baker's yeast can also be used, regardless of whether they overlap with the above-mentioned examples of yeast. More specifically, examples include Saccharomyces yeasts such as Saccharomyces cerevisiae, Saccharomyces uvarum, and Saccharomyces rouxii; Kluyveromyces yeasts such as Kluyveromyces fragilis; Torulopsis yeasts such as Torulopsis versatilis; Candida yeasts such as Candida tropicalis, Candida lipolytica, and Candida utilis; and Rhodotorula yeasts such as Rhodotorula glutinis.

[0022] As the microorganism, non-spore-forming yeast is preferred, Candida yeast is more preferred, and Torula yeast (Candida utilis) is even more preferred.

[0023] <Method of producing nucleic acid or salt thereof> The method for producing nucleic acids or salts thereof is not particularly limited. For example, when nucleic acids are derived from natural products, they can be produced by extracting and purifying them from the natural product (e.g., a microorganism (usually a culture of a microorganism)). The method for culturing the microorganism may be appropriately selected depending on the type of microorganism. For example, in the case of Candida utilis, the cooking extract (the liquid phase of the treated product obtained by the sulfite treatment dissolved in the cooking liquor; typically, the solids content is 10 to 30 wt%) generated during the sulfite cooking of papermaking raw materials (e.g., pulp, chips) can be diluted as needed and used as a culture medium. The dilution can be performed so that the sugar concentration after dilution is 1.0 to 5.0 w / v%. Furthermore, the components of the culture medium may be adjusted as needed; for example, nutrients such as a nitrogen source and a phosphorus source may be added. The amount of nitrogen source (e.g., ammonia) added is preferably 0.05 to 0.3% of the medium. The amount of phosphorus source (e.g., ammonium monophosphate) added is preferably 0.05 to 0.3% of the medium. Like the above-mentioned Candida utilis, the ability to grow (cultivate) using biological resources that are waste materials makes it possible to recycle and reuse waste materials, which is advantageous in that it can contribute to a sustainable, recycling-oriented society.

[0024] Nucleic acid extraction can be performed by microbial enucleation and nucleic acid extraction. Enucleation can be performed by any process capable of separating cell walls from other cellular components (e.g., a process that partially or completely destroys or dissolves the cell walls and releases the contents into the medium). Examples of enucleation methods include alkaline treatment (e.g., using alkaline chemicals such as sodium hydroxide, magnesium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, or sodium carbonate), sodium chloride treatment, cell wall-lytic enzyme treatment, separation treatment (e.g., separation treatment using ion exchange resins or separation gels), filtration (e.g., ultrafiltration), and combinations thereof. Among these, sodium chloride treatment is preferred. In sodium chloride treatment, for example, sodium chloride is added to the culture medium, and then the pH is adjusted to 3 or less (e.g., by adding hydrochloric acid) while stirring and heating as necessary, allowing the nucleic acid-containing phase (usually a precipitate) to be separated and recovered from the yeast residue. The nucleic acid-containing fraction recovered after the denucleation treatment can be purified by redissolving in an alkaline agent (preferably sodium hydroxide or magnesium hydroxide) (pH after redissolution: usually 3 or higher or 4 or higher, with an upper limit of usually 6.5 or lower, or 5 or lower) as a nucleic acid extraction treatment, followed by heating and stirring as necessary, followed by spray drying. The molecular weight of the resulting nucleic acid can be adjusted by the pH at redissolution. For example, the molecular weight of the resulting nucleic acid tends to increase as the pH at redissolution increases, and decreases as the pH at redissolution decreases. The resulting nucleic acid may be in the form of a salt depending on the type of agent used in the nucleic acid extraction treatment. For example, when sodium hydroxide is used as the alkaline agent, the sodium salt of the nucleic acid is obtained, and when magnesium hydroxide is used, the magnesium salt of the nucleic acid is obtained. Furthermore, salts and macromolecules can be removed by further purification treatment (e.g., contact with a peroxide such as hydrogen peroxide or a porous material such as activated carbon) after the nucleic acid extraction treatment, thereby adjusting the molecular weight of the resulting nucleic acid (usually reducing the molecular weight).

[0025] [2. Plant growth promoters] The nucleic acids described above can have a beneficial effect on plants, such as enhancing their resistance to abiotic stress, by utilizing the natural power inherent in plants and their surrounding environment, and can therefore be used as plant growth promoters or so-called plant growth promoters (biostimulants).

[0026] <Plant tolerance to abiotic stress> As used herein, "abiotic stress in plants" refers to stress caused by the plant's environment and is distinct from biotic stress caused by disease or pests. "Abiotic stress" is also referred to as abiotic stress or environmental stress. Examples of abiotic stress include high temperature stress, low temperature stress, osmotic stress, pH stress, oxidative stress, wound stress, and drought stress. The nucleic acids described above can confer tolerance to at least one of the above-mentioned abiotic stresses. Whether or not tolerance to abiotic stress has been conferred can be determined by plant traits. Examples of plant traits include the total plant weight (also referred to as biomass), aboveground part (leaf and stem) length, aboveground part weight, root weight, root weight ratio to total plant weight, presence or absence of leaf burn, presence or absence of leaf wilting, presence or absence of flower malformation, presence or absence of flower drop, fruit sugar content and size, and yield. The aboveground parts and roots of plants can be classified by color (aboveground parts tend to be green, while roots tend to be white) and shape (aboveground parts can be characterized by the presence or absence of plant cell fibers visible under a microscope, etc.).

[0027] When a plant is under abiotic stress, the degree of the plant's traits may be reduced. The term "reduction in the degree of the plant's traits" refers to, for example, a reduction in total weight, above-ground length, above-ground weight, root weight, fruit sugar content and size, and yield, as well as an increase in the occurrence and frequency of leaf scorch, leaf wilting, deformed flowers, and flower drop.

[0028] <Target plants> Target plants for the plant growth promoter include, but are not limited to, angiosperms (monocotyledons and dicotyledons), gymnosperms, ferns, mosses, and algae. The target plants may be either trees or herbs. From the viewpoint of efficient production, it is preferable to target agricultural plants, horticultural plants, and forestry plants. Examples of such plants include Malvaceae (okra, etc.), Brassicaceae (turnip, cauliflower, cabbage, komatsuna, radish, bok choy, Chinese cabbage, broccoli, mizuna, etc.), Gramineae (rice (including paddy rice and upland rice), corn, etc.), Cucurbitaceae (pumpkin, cucumber, watermelon, melon, etc.), Asteraceae (lettuce, etc.), Asparagaceae (asparagus, etc.), Moraceae (fig, etc.), and Araceae (taro, etc.). Lamiaceae plants (perilla, etc.), Zingiberaceae plants (ginger, etc.), Apiaceae plants (celery, carrots, etc.), Polygonaceae plants (buckwheat, etc.), Theaceae plants (tea plant, etc.), Solanaceae plants (tomato, eggplant, bell pepper, paprika, potato, chili pepper, etc.), Alliaceae plants (onion, chive, garlic, leek, etc.), Rosaceae plants (strawberry, apple, etc.), Amaranthaceae plants (sugar beet, spinach, etc.), Convolvulaceae plants (sweet potato, etc.), Vitaceae plants (grapes, etc.), Fabaceae Plants (green beans, edamame, peas, broad beans, peanuts, soybeans, etc.), Rutaceae plants (tangerines, satsuma mandarins, etc.), Oleaceae plants (olive, etc.), Dioscorea plants (yam, etc.), Mangifera plants (mango, etc.), Pyrus plants (avocado, etc.), Pyrus plants (pear, etc.), Cryptomeria plants (cedar, etc.), Chamaecyparis plants (cypress, etc.), Pinaceae plants (pine, such as Japanese black pine), Larch plants (larch, larch, etc.) Examples of suitable plants include Abies (such as Abies sachalinensis), Eucalyptus, Prunus (such as cherry blossom, plum, and tomentosa), Acacia, Myrica, Quercus (such as sawtooth oak), Jacaranda (such as jacaranda), and Santalum (such as sandalwood). Among these, angiosperms (monocotyledons and dicotyledons) with strong vascular systems for transporting high molecular weight components into the body are preferred, and woody plants are more preferred.Among the above examples, woody plants include plants of the family Theaceae, Rosaceae, Vitaceae, Rutaceae, Oleaceae, Mangifera, Crocodile, Pyrus, Cryptomeria, Chamaecyparis, Pinaceae, Larch, Abies, Eucalyptus, Prunus, Acacia, Bayberry, Quercus, Jacaranda, and Sandalwood.

[0029] <How to apply to plants> Examples of methods for using plant growth promoters include (1) adding and mixing the plant growth promoter with soil culture medium (seedbed) or hydroponic culture solution, and (2) directly spraying or applying the plant growth promoter to the target plant and allowing it to absorb water. In the case of (2), the part of the plant to which the plant growth promoter is sprayed or applied is not particularly limited, and it may be, for example, leaves, stems, roots, seeds, flowers, or fruits. Furthermore, the timing of application to the target plant is not particularly limited, and it may be applied for a limited period only, continuously, or intermittently. The plant growth promoter may also be used to prepare cuttings or grafts. For example, a method is available in which the cut surface of the main axis taken from a woody plant (mother tree) is treated with the plant growth promoter (e.g., allowed to absorb a liquid agent), and then the main axis is cut to prepare cuttings. The plant growth promoter may be used in an amount sufficient to exert a plant growth-promoting effect (an effective amount).

[0030] <Optional ingredients> The plant growth promoter may contain components other than nucleic acids and salts thereof, as needed. Examples of optional components include solvents, surfactants, carriers, mineral oils, animal and vegetable oils, water-soluble polymers, thickeners, antifoaming agents, pH adjusters, spreaders, binders, extenders, conventionally known agricultural materials (pesticides and fertilizers; from the viewpoint of reducing the burden on the environment, preferably components derived from bacteria such as actinomycetes and microbial organisms such as yeast, and plant-derived components), and more preferably yeast residues separated when obtaining nucleic acids or salts thereof, and lignin components in the cooking extract.

[0031] <Dosage form> The plant growth promoter may be in any suitable form, including, but not limited to, granular, particulate, or liquid, with liquid being preferred. In the case of a liquid, water is preferred as the solvent. The concentration of the nucleic acid or its salt in water is preferably 0.001 (1 / 100,000) wt% or more, more preferably 0.005 wt% or more, and even more preferably 0.01 (1 / 10,000) wt% or more. This allows the desired effect to be achieved in plants by administering an appropriate amount. The upper limit is preferably 10 wt% or less, more preferably 5 wt% or less, and even more preferably 1 wt%. This allows for an effect commensurate with the amount and prevents the occurrence of undesirable side effects (such as increased osmotic stress in the rhizosphere and chelation of metal ions by components in the composition). Therefore, the concentration is preferably 0.001 (1 / 100,000) to 10% by weight, more preferably 0.005 to 5% by weight, and even more preferably 0.01 (1 / 10,000) to 1% by weight.

[0032] The present invention will now be described by way of examples, which are not intended to limit the invention. [Example]

[0033] Manufacturing Example 1 One liter of the digestion extract (solid content 15% w / v) generated when wood chips mainly composed of domestic broadleaf trees were sulfite cooked (150°C, 9 hours) was diluted with water to a sugar concentration of 3.0%, and a nitrogen source and phosphorus source (ammonia 0.1%, ammonium monophosphate 0.1%) were added to make a culture medium.

[0034] Candida utilis yeast was cultured for 24 hours using the above culture medium. The resulting yeast culture medium was heated and stirred in a 2% by weight aqueous solution of sodium chloride to isolate nucleic acid components. Hydrochloric acid was added to adjust the pH to 1.5, and the mixture was stirred for 2 hours. The resulting precipitate was collected. For redissolution, aqueous sodium hydroxide was added to adjust the pH to 4.8, and the mixture was heated and stirred. The resulting solution was spray-dried to obtain the sodium salt of nucleic acid. The weight-average molecular weight (Mw) of the sodium salt of nucleic acid was 20,000.

[0035] <Measurement of weight average molecular weight> The weight-average molecular weight of the nucleic acid, including the following production examples, was measured by gel permeation chromatography (GPC) (Table 1). The GPC measurement was carried out under the following conditions using a known method in terms of polyethylene glycol. Measuring device: Tosoh Columns used: Shodex Column OH-pak SB-806HQ, SB-804HQ, SB-802.5HQ Eluent: 0.05 mM sodium nitrate / acetonitrile 8 / 2 (v / v) Standard material: polyethylene glycol (Tosoh, GL Science) Detector: Differential refractometer (manufactured by Tosoh) Calibration curve: polyethylene glycol standard

[0036] Manufacturing Example 2 The sodium salt of nucleic acid obtained in Production Example 1 was treated with hydrogen peroxide and activated carbon to remove impurities, yielding a purified nucleic acid. The weight-average molecular weight (Mw) of the nucleic acid was 11,000.

[0037] Manufacturing Example 3 A magnesium salt of ribonucleic acid was obtained in the same manner as in Production Example 1, except that an aqueous magnesium hydroxide solution was used as the redissolving procedure for nucleic acid in Production Example 1. The weight-average molecular weight (Mw) of the magnesium salt of nucleic acid was 20,000.

[0038] Production Example 4 The sodium salt of ribonucleic acid was obtained in the same manner as in Production Example 1, except that the redissolving procedure in Production Example 1 involved adding an aqueous sodium hydroxide solution until the pH reached 5.5, heating and stirring, and spray-drying the resulting solution using a spray dryer. The weight-average molecular weight (Mw) of the sodium salt of nucleic acid was 100,000.

[0039] Manufacturing Example 5 The sodium salt of nucleic acid obtained in Production Example 1 was post-treated for 1 hour in 3% aqueous hydrogen peroxide heated to 60°C to obtain the sodium salt of ribonucleic acid. The weight-average molecular weight (Mw) of the sodium salt of nucleic acid was 5,000.

[0040] Example 1 The sodium salt of the nucleic acid of Production Example 1 was dissolved in ion-exchanged water to a predetermined concentration to prepare an aqueous solution with a concentration of 0.01% by weight.

[0041] Example 2 The sodium salt of the nucleic acid of Production Example 2 was dissolved in ion-exchanged water to a predetermined concentration to prepare an aqueous solution with a concentration of 0.1% by weight.

[0042] Example 3 The sodium salt of the nucleic acid of Production Example 3 was dissolved in ion-exchanged water to a predetermined concentration to prepare an aqueous solution with a concentration of 0.01% by weight.

[0043] Example 4 The sodium salt of the nucleic acid of Production Example 4 was dissolved in ion-exchanged water to a predetermined concentration to prepare an aqueous solution with a concentration of 0.01% by weight.

[0044] Comparative Example 1 The sodium salt of the nucleic acid of Production Example 5 was dissolved in ion-exchanged water to a predetermined concentration to prepare an aqueous solution with a concentration of 0.01% by weight.

[0045] Comparative Example 2 Ion-exchanged water was used as is.

[0046] Comparative Example 3 A commercially available liquid fertilizer containing brewer's yeast cell wall components (Cell Energy, Asahi Biocycle Co., Ltd.) was diluted 1,000 times with ion-exchanged water to prepare an aqueous solution.

[0047] Comparative Example 4 The sodium salt of nucleic acid obtained in Preparation Example 1 was dissolved in ion-exchange water to a concentration of 5.0 wt %, and 0.05 wt % (1 wt % based on the weight of the nucleic acid) of Sumiteam NP (Shin-Nihon Chemical Industry Co., Ltd.) was added as a nuclease. The pH was adjusted to 5.0 with hydrochloric acid or sodium hydroxide, and the mixture was heated at 72°C for 8 hours. The reaction solution was then heated at 95°C for 30 minutes to inactivate the enzyme. The reaction solution was filtered through 5A filter paper, and the resulting solution was diluted with ion-exchange water to a concentration of 0.01 wt % to prepare an aqueous solution. The resulting aqueous solution contained a nucleotide mixture, with molecular weights of each nucleotide being disodium guanylate 369, disodium adenylate 369, disodium cytidylate 367, and disodium uridylate 370, all of which were below 7,000.

[0048] The aqueous solutions prepared in each of the Examples and Comparative Examples were subjected to the following tea seedling growth test and Japanese mustard spinach growth test.

[0049] <Tea seedling growth test (rooting rate, seedling yield rate)> Branches (main axes) were harvested from the mother tree of the target plant (tea variety) "Okuharuka," and the cut surfaces were immersed in the aqueous solutions of each Example and Comparative Example and left to stand for 24 hours. The main axes were cut into sections with one lateral leaf attached to a node (node: approximately 3-10 cm), and the cuttings were immersed in each aqueous solution for several minutes to moisten them, and then cuttings were prepared. "Okuharuka" is known to be difficult to produce high-quality seedlings.

[0050] 10m in a seedling box with a cultivation area of ​​6.7L (1 seedling section 300mm x 600mm x 100mm, capacity 80cc) 2 Fertilized soil was added to the plants to provide 20.7 kg of nitrogen, 6.5 kg of phosphorus, and 13.0 kg of potassium per sample. Two of the above seedling raising boxes were prepared for each sample, and 66 cuttings were planted in each box to form test plots.

[0051] The seedling boxes were placed on outdoor seedling shelves and watered once a day for two months. After that, the cuttings were removed from the cutting beds and counted for those that had roots visible to the naked eye to calculate the rooting rate. After 10 months of seedling raising, the seedling yield rate was calculated as the number of seedlings that were 10 cm or higher in height. The rooting rate and seedling yield rate were evaluated as follows:

[0052] -Evaluation of rooting rate- ○: 80-100% of all individuals have rooted. △: 60-80% of all individuals have rooted. ×: The percentage of rooted individuals among all individuals is less than 60%.

[0053] -Evaluation of seedling yield rate- ○: 70-100% of all individuals reached a seedling height of 10 cm or more. △: 50-70% of all individuals reached a seedling height of 10 cm or more. ×: The percentage of individuals with a seedling height of 10 cm or more out of all individuals was less than 50%.

[0054] <Komatsuna growth test (yield and pH fluctuations)> The nutrient solution tank of a home hydroponic cultivation kit (Aqua Planter Float Mini, Aquaculture Co., Ltd.) was filled with the aqueous solution of each Example and Comparative Example and a basic fertilizer (Hyponica liquid fertilizer added to the aqueous solution so that it was diluted 5,000 times). The pH was adjusted to 6.0 with hydrochloric acid or sodium hydroxide aqueous solution, and Komatsuna seeds were sown on a seedbed sponge and cultivated in a growth chamber (temperature 20°C, 14-hour photoperiod, relative humidity 60%). The weight of the leaves and stems was measured after one month and used as the harvest yield.

[0055] Meanwhile, when rooting of the plant was visually confirmed, the pH of the solution in the nutrient solution tank was adjusted to the specified pH shown in Table 2 using hydrochloric acid or sodium hydroxide solution. After cultivation for three days, the pH was adjusted to 6 using hydrochloric acid or sodium hydroxide solution. After cultivation for one month, the growth status of the leaves, stems, and roots was visually observed. The growth status of the leaves, stems, and roots of individuals cultivated in the same manner, except that the pH of the solution in the nutrient solution tank was kept at 6, was compared and evaluated as follows.

[0056] - pH fluctuation test (evaluation of growth status) - ○: Compared to cultivation at pH 6.0, the size of the stems and roots is almost the same. △: The size of the leaf / stem / root parts is approximately 50% to 90% compared to when cultivated at pH 6.0. ×: Leaf and stem / root area is less than 50% compared to cultivation at pH 6.0.

[0057] The results of the tea seedling growth test are shown in Table 1, and the results of the komatsuna growth test (pH fluctuation) are shown in Table 2.

[0058] [Table 1]

[0059] As shown in Table 1, when no nucleic acid was added (Comparative Example 2) or when nucleic acid with a molecular weight outside the preferred range was used (Comparative Example 1), the growth of the target plants was not improved. However, when nucleic acid with a molecular weight of 10,000 or more was used (Examples 1 to 3), the growth of the target plants was improved, and in particular, an increase in the rooting rate and the resulting improvement in the seedling yield rate were confirmed.

[0060] [Table 2]

[0061] As shown in Table 2, even in growth tests under conditions of varying pH, the growth of the target plants was not improved when the nucleic acid was not added (Comparative Example 2) or when other materials were used (Comparative Example 3), whereas the growth of the target plants was improved when the nucleic acid was added (Example 1).

[0062] <Olive seedling raising test (yield rate)> -Preparation of cuttings- Branches were harvested from the mother tree of the target plant (Olive "Frantoio"), and the cut surfaces were immersed in the aqueous solutions of each Example and Comparative Example and left to stand for 18 hours to prepare cuttings. "Frantoio" is known to have a low rooting rate, and a rooting promoter is usually used during rooting treatment. Cuttings were cut to a shape with two to four lateral leaves attached to the node (node: approximately 5 to 12 cm). The cuttings were then planted in soil either as is or after applying a paste of dried powder of a plant hormone (Luton; Ishihara Biosciences) mixed with an appropriate amount of water to the cut end.

[0063] -Soil preparation- Two seedling boxes with a cultivation area of ​​approximately 11.8 L (each seedling section 326 mm x 477 mm x 76 mm, capacity 525 cc) were prepared for each sample, and 96 cuttings obtained were planted in each seedling box to form test plots.

[0064] -Growth test and evaluation- The seedling boxes were placed on seedling shelves in a greenhouse and raised for two months with watering about once a day. After that, the cuttings were removed from the cutting beds and those that showed visible rooting were potted up, and the rooting rate (%) was measured and evaluated. For olive seedlings, the potted ones were considered the seedling yield rate, so the rooting rate = seedling yield rate.

[0065] [Table 3]

[0066] As shown in Table 3, in the olive seedling raising test, when the case where the nucleic acid was added (Example 1) was compared with the case where the nucleic acid was not added (Comparative Example 2), the rooting rate (seedling yield rate) was high, indicating that the growth of the target plants was improved. Furthermore, compared with the case where nucleotides, which are decomposition products of nucleic acids, were added (Comparative Example 4), Example 1 showed a high rooting rate (seedling yield rate), and in particular, when the plant hormone was added, the rooting rate (seedling yield rate) exceeded 70%, indicating a significant improvement in growth compared to the other addition conditions.

[0067] The results of the above Examples demonstrate that nucleic acids with a molecular weight of 7,000 or more can confer tolerance to abiotic stress to plants and are useful as plant growth promoters.

Claims

1. A plant growth promoter comprising a nucleic acid having a molecular weight of 7,000 to 150,000 or a salt thereof.

2. The plant growth promoter according to claim 1 , wherein the nucleic acid comprises ribonucleic acid.

3. The plant growth promoter according to claim 1 or 2, wherein the nucleic acid or a salt thereof is derived from a microorganism.

4. The plant growth promoter according to claim 3, wherein the microorganism is a yeast of the genus Candida.

5. The plant growth promoter according to claim 1 or 2, which is in the form of a liquid formulation.

6. 3. The plant growth promoter according to claim 1, wherein the content of the nucleic acid or a salt thereof is 0.001 to 10% by weight.

7. A method for producing a plant growth promoter containing nucleic acid or a salt thereof having a molecular weight of 7,000 to 150,000, comprising carrying out a nucleus removal treatment and a nucleic acid extraction treatment on a microorganism, and extracting the nucleic acid or a salt thereof from the microorganism.

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