Plant growth-promoting composition

Abstract

This plant growth-promoting composition contains, as an active ingredient, at least one selected from the group consisting of onion extracts and onion powder.

Description

Plant growth promoting composition

[0001] The present invention relates to a plant growth promoting composition and a method for promoting plant growth.

[0002] With the current explosive growth in the human population, producing a sufficient supply of plants for food has become a global challenge. Furthermore, desertification due to the reduction in green space has become a problem, and rising earth temperatures due to global warming have also become a problem, resulting in an increasing number of environmental problems affecting plant growth. In other words, excessive stress on plants caused by global environmental factors often causes problems for plant growth.

[0003] Therefore, there is a need for technologies that promise more efficient harvesting than conventional technologies, and biostimulants are attracting attention as a new technology that reduces damage to plants caused by climate and soil conditions by controlling abiotic stress on plants, thereby providing healthy plants.

[0004] Patent Document 1 discloses a plant stomatal opening promoter containing stevia, and reports that artificially promoting plant stomatal opening with stevia improves heat stress tolerance. Patent Document 2 discloses a composition for activating a gene that activates the ethylene and / or jasmonic acid signaling system, containing a yeast cell wall decomposition product, and reports that applying the yeast cell wall decomposition product to a plant activates the expression of a plant defensin gene involved in the antibacterial properties and disease prevention of the plant. Patent Document 3 discloses a method for increasing grain yields by inoculating a plant for cultivation with a substance containing the cell wall of a methanol-assimilating bacterium.

[0005] Patent No. 6741262 Patent No. 4931388 JP2019-180361

[0006] As mentioned above, studies have been conducted on improving abiotic stress tolerance and increasing yield in plants using various materials, but no reports have been published on the use of onion extract or onion powder.

[0007] As a result of extensive investigations, the present inventors have found, by using an originally developed highly accurate screening method, that, among various materials, one or more selected from the group consisting of onion extract and onion powder act as active ingredients for promoting plant growth, and have thus completed the present invention.

[0008] That is, the present invention is as follows. [1] A plant growth-promoting composition containing as an active ingredient one or more compounds selected from the group consisting of onion extract and onion powder. [2] The plant growth-promoting composition according to above [1], which has one or more plant growth-promoting actions selected from the group consisting of elongation of stems, leaves, or roots, an increase in the number of leaves, promotion of flowering or fruiting, an increase in the number of flowers or fruits, an increase in plant weight or crop yield, greening, and promotion of tillering. [3] The plant growth-promoting composition according to above [1] or [2], which has an action of improving resistance to abiotic stress. [4] The plant growth-promoting composition according to above [3], which has an action of improving resistance to one or more stresses selected from the group consisting of temperature stress, chemical stress, light stress, drought stress, pH stress, salt stress, hypoxic stress, herbicide stress, physical stress, and disease stress. [5] The plant growth-promoting composition according to above [3], which activates a gene in a stress response system. [6] A method for promoting plant growth, comprising applying to a plant, soil or a culture solution in which a plant is grown, a plant growth-promoting composition containing, as an active ingredient, one or more compounds selected from the group consisting of onion extract and onion powder. [7] The method for promoting plant growth according to above-mentioned [6], wherein the plant growth-promoting composition is applied in an amount of 0.001 to 1% by mass relative to the culture solution.

[0009] By applying to plants the composition of the present invention which contains one or more members selected from the group consisting of the onion extract and onion powder, plant growth can be promoted more safely and at lower cost than with conventional materials.

[0010] FIG. 1 shows images showing improvement in root establishment of rice plants in a case where no onion extract or onion powder was added and in a case where 0.36 g (Example 1) of the plant growth-promoting composition containing onion powder was added.

[0011] Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the present embodiment, and various modifications can be made within the scope of the gist of the present invention.

[0012] <Plant Growth-Promoting Composition> The plant growth-promoting composition of the present embodiment contains, as an active ingredient, one or more onion extracts and onion powders. Onions are plants of the genus Allium in the family Amaryllidaceae. Specific examples include Allium cepa. The variety and place of origin of the onion are not particularly limited, and examples thereof include yellow onions, white onions, purple onions (red onions), salad onions, pearl onions, ruby ​​onions, spring onions, and shallots. More specific examples include Kitawase 3, SN-1, SN-3, SN-3A, Okhotsk 222, Okhotsk 1, Okhotsk 333, Kitamomiji 2000, Super Kitamomiji, H235, Kitahayate 2, Bullet Bear, Arrow Bear, Power Wolf, Brown Bear, Kodiak, and Ikol. , Vegas, Hayajiro, Sarari, Caroe One, Ezomaru, Sarasara Gold, Quel Gold, Kurenai, R-5, Red Eye Early, Red Eye II, Red Eye, Red One, Yukigeisha 2, Yukigeisha, White 1, Kitawase 1, Pekoros 22 Super, Pekoros F Okhotsk, Kitami Yellow, Sapporo Yellow, Sorachi Yellow, OPP-5, OMP-3, OSP-3, CS3-12, Toyohira, Shippo Wase 7, Sonic, Tarzan, Turbo, Uzushio, Advance, Answer, Neo Earth, Power, Keru Tama, and Momiji.

[0013] In the present embodiment, the onion extract refers to a concentrated extract of specific components from onions. There are no particular limitations on the parts used for the extraction, and examples include leaf blades, leaf sheaths (petioles), bulbs (scale leaves, storage leaves, edible part), skins (protective leaves), cores, stems (flower stalks and flower bulb bolts), and roots, which may be used alone or in combination. The onion extract can be obtained, for example, by the method described in <Method for preparing plant growth-promoting composition> below. The onion powder is obtained by drying and pulverizing onions or onion extract, and is not particularly limited.

[0014] The plant growth-promoting composition in this embodiment is a composition that has a plant growth-promoting effect, and here, the plant growth-promoting effect includes, for example, growth-promoting effects such as elongation of stems, leaves, or roots, an increase in the number of leaves, promotion of flowering or fruiting, an increase in the number of flowers or fruits, an increase in plant weight or crop yield, greening, or promotion of tillering.

[0015] More specifically, when a plant growth-promoting effect is observed, it refers to, for example, an increase in the actual weight gain (%) or dry weight gain (%) when the plant growth-promoting composition of this embodiment is used compared to when it is not used. When the plant growth-promoting composition is used, the actual weight gain (%) or dry weight gain (%) is preferably increased by 10% or more, more preferably 20%, and even more preferably 30% or more compared to when the plant growth-promoting composition of this embodiment is not used. When a plant growth-promoting effect is observed, it also refers to a case where growth is observed when no growth is observed without the use of the plant growth-promoting composition. Note that the above values ​​are average values ​​for all plants to which the plant growth-promoting composition is applied.

[0016] In addition, the plant growth-promoting effect also includes the effect of improving the activity of plants, such as: 1) Root elongation and improved root survival rate 2) Increased nutrient absorption efficiency 3) Induction of flower buds, promotion of flowering, and increased fruit production 4) Accumulation of sugars and other components 5) Increased water-saving effect 6) Callus induction effect 7) Increase in plant size, particularly elongation or thickening of above-ground and underground parts 8) Repair of wounds That is, the plant growth-promoting composition of this embodiment may have the effects 1) to 8) above in addition to growth-promoting effects such as elongation of stems, leaves, or roots, increased leaf number, promotion of flowering or fruiting, increased number of flowers or fruits, increased plant weight or crop yield, greening, or promotion of tillering.

[0017] The plant growth-promoting composition of this embodiment may have an abiotic stress tolerance-improving effect. That is, it may confer tolerance to a variety of abiotic (environmental) stresses to plants. Examples of abiotic stress include temperature stress such as high temperature stress and low temperature stress, chemical stress, light stress, drought stress, oxidative stress, pH stress, salt stress such as osmotic stress, hypoxic stress, herbivory stress, physical stress, and disease stress. Herbivory stress may be stress resulting from reduced nutrient absorption associated with root suppression due to herbivory, and disease stress may be stress resulting from physiological dysfunction of the plant caused by disease.

[0018] In this embodiment, "abiotic stress tolerance" refers to a trait that allows normal growth even under growth conditions that cause environmental stress, without substantially suffering from undesirable effects such as inability to grow (withering), poor growth (e.g., bleaching or yellowing of the plant, reduced root length or reduced leaf number), reduced growth rate, or reduced plant weight or crop yield. By improving the abiotic stress tolerance of a plant with the plant growth-promoting composition of this embodiment, the plant can grow normally even in external environments that would otherwise have undesirable effects on the growth of a normal plant.

[0019] The plant growth-promoting composition of the present embodiment has the effect of imparting temperature stress tolerance, for example, by promoting normal growth under high-temperature conditions of 35°C to 55°C and low-temperature conditions of 0°C to 10°C. The plant growth-promoting composition of the present embodiment also has the effect of imparting salt stress tolerance, enabling normal growth in the presence of 0.1 to 3.0 mass% sodium chloride. The plant growth-promoting composition of the present embodiment has the effect of imparting drought stress tolerance, enabling normal growth even under relative humidity conditions of 10 to 40%. The plant growth-promoting composition of the present embodiment has the effect of imparting chemical stress tolerance, for example, by promoting normal growth under conditions of deficiency in chemical substances that serve as nutrient sources for plants, such as phosphorus. A chemical deficiency condition may be, for example, a condition in which the amount of a nutrient component is less than that shown in Table 1 below; specifically, a condition in which the amount of a nutrient component is about one-fifth of the amount shown in Table 1.

[0020] In this embodiment, the abiotic stress tolerance of a plant can be evaluated, for example, by the following means. The presence or absence of salt stress tolerance can be confirmed by growing a target plant in a medium or soil to which an appropriate concentration of salt has been added under conditions of a growth temperature and growth period that are suitable for the plant, and evaluating the phenotype. The presence or absence of drought stress tolerance can be confirmed by growing a target plant under conditions of a growth temperature, growth humidity, and growth period that are dry for the plant, and evaluating the phenotype. Furthermore, the presence or absence of low temperature stress tolerance can be confirmed by acclimating a target plant to a low temperature that does not freeze, and then growing the plant under conditions of a growth temperature and growth period that are suitable for the plant, and evaluating the phenotype.

[0021] When the plant growth-promoting composition of the present embodiment has an effect of improving abiotic stress tolerance, it may activate a gene in a stress response system. The gene in the stress response system is not particularly limited, and examples thereof include genes generally known as indicators of response to temperature stress and drought stress.

[0022] The plant growth-promoting composition of this embodiment may contain onion extract or onion powder alone, or may contain both onion extract and onion powder, or may contain onion extract and onion powder in combination with one or more agriculturally acceptable ingredients. Examples of agriculturally acceptable ingredients include, but are not limited to, solvents, carriers, excipients, binders, solubilizers, stabilizers, thickeners, leavening agents, lubricants, surfactants, oily liquids, buffers, disinfectants, antifreeze agents, antifoaming agents, colorants, antioxidants, and additional active ingredients. Preferred agriculturally acceptable carriers are agriculturally acceptable liquid carriers such as water, mineral oil fractions such as kerosene or diesel oil, vegetable or animal oils, cyclic or aromatic hydrocarbons (e.g., paraffin, tetrahydronaphthalene, alkylated naphthalenes or derivatives thereof, or alkylated benzenes or derivatives thereof), alcohols (e.g., methanol, ethanol, propanol, butanol, or cyclohexanol), ketones (e.g., cyclohexanone), amines (e.g., N-methylpyrrolidone), and mixtures thereof.

[0023] When the plant growth-promoting composition of this embodiment contains one or more additional active ingredients, the additional active ingredients can be various compounds known in the art that have the activity of improving environmental stress tolerance. When the plant growth-promoting composition contains such one or more additional active ingredients, the plant's abiotic stress tolerance tends to be further improved.

[0024] The plant growth-promoting composition of this embodiment can be used in combination with conventionally known agricultural materials such as pesticides and fertilizers, and it is preferable to use, as the agricultural materials, components derived from bacteria such as actinomycetes or microorganisms such as yeast.

[0025] The plant growth-promoting composition of this embodiment can be used as an agricultural chemical formulation or pesticide to promote plant growth. The plant growth-promoting composition may be in any form, such as a solid (e.g., powder or granules) or a liquid (e.g., a solution or suspension), and is preferably used in the form of a liquid such as a solution or suspension. When used as a solution, it may be in a liquid state, or may be used as a liquid prepared just before use.

[0026] The formulation of the plant growth-promoting composition of this embodiment is not particularly limited, and can be formulated into formulations commonly used in the art, such as emulsions, wettable powders, liquids, water-soluble powders, dusts, powders, pastes, or granules.

[0027] In this embodiment, the plant to which the plant growth-promoting composition is applied is not particularly limited, and examples thereof include angiosperms and gymnosperms. Examples of target plants include Asteraceae plants such as chrysanthemums and gerberas, Solanaceae plants such as potatoes, tomatoes, and eggplants, Brassicaceae plants such as rapeseed and rapeseed, Poaceae plants such as rice, corn, wheat, sugarcane, and barley, Legumes such as soybeans, Apiaceae plants such as carrots, Lamiaceae plants such as basil, mint, and rosemary, Convolvulaceae plants such as morning glory, Salicaceae plants such as poplars, and Euphorbiaceae plants such as castor beans, cassava, and jatropha. Convolvulaceae plants such as sweet potato, Rutaceae plants such as oranges and lemons, Rosaceae plants such as cherry blossoms and roses, Orchidaceae plants such as moth orchids, Gentianaceae plants such as bellflowers, Primulaces such as cyclamen, Violets such as pansies, Liliaceae plants such as lilies, Amaranthaceae plants such as sugar beets, Vitaceae plants such as grapes, Cupressaceae plants such as cedars and cypresses, Oleaceae plants such as olives and Osmanthus, and Pinaceae plants such as red pine.

[0028] The target plant may be not only the whole plant (i.e., the complete plant body), but also parts of the plant, such as plant tissues or organs (e.g., cut flowers, or vegetative propagation organs such as rhizomes, tubers, corms, or runners), cultured cells, and / or callus.

[0029] The plant growth-promoting composition of this embodiment can be applied to the whole or part of a plant at any stage of growth, including before or after plant emergence (e.g., the whole or part of a seed, seedling, or mature plant).

[0030] <Method for Preparing Plant Growth-Promoting Composition> The plant growth-promoting composition can be prepared, for example, by obtaining an onion extract or onion powder and then mixing it with the agriculturally acceptable ingredients described above, as required. There are no particular restrictions on the method for obtaining the onion extract, and any general method for extracting plant extracts can be used. Specifically, the onion extract can be obtained by a method comprising the steps of crushing onion bulbs and removing impurities to obtain onion juice, concentrating the onion juice obtained in the above step to obtain an onion concentrate, and fractionating the onion concentrate obtained in the above step to obtain an onion extract containing specific components. In the step of obtaining the onion extract, hot water extraction or solvent extraction using various solvents can be used as the method for extracting the extract. An example of hot water extraction is a method in which onions are chopped, water is added to the onions, and the soluble components are extracted at 60 to 100°C. An example of solvent extraction is a method in which onions are treated at a temperature of −15° C. to −25° C. for a time sufficient to disrupt the cell membranes, followed by extraction with water or an alcoholic solvent. There are no particular restrictions on the method for obtaining onion powder, and onion powder can be obtained by drying fresh or frozen onions or onion extract by hot air drying, air drying, dry heat drying, reduced pressure drying or the like and then crushing them into powder.

[0031] (Crushing and Removal Step) Fresh onions or dried onions can be crushed, for example, in a mixer. When crushing onions, an appropriate amount of water may be added to facilitate treatment in the mixer or the like. The crushed onions are filtered using a filter cloth, filter paper or the like to give onion juice from which impurities have been removed. When filtering, an extraction solvent such as water or alcohol may be added beforehand. Instead of filtration, impurities may be removed by collecting a supernatant using a centrifuge.

[0032] (Concentration Step) The onion juice obtained can be concentrated using a rotary evaporator or the like to give an onion concentrate. The concentration may be carried out using a centrifugal evaporator or by freeze-drying. The concentration rate is preferably 3 to 30 times, more preferably 4 to 20 times. A concentration rate of 5 times or more tends to reduce the amount of the plant growth-promoting composition to be added to plants, improving handleability and reducing transportation costs, while a concentration rate of 30 times or less tends to reduce the amount of sediment in the plant growth-promoting composition, making handling easier. In preparing the plant growth-promoting composition, concentration of the onion juice is not essential, and the obtained onion juice may be subjected as it is to the following fractionation step.

[0033] (Fractionation Step) The obtained onion concentrate is fractionated through a column or the like to give an onion extract containing specific components. In the fractionation step, for example, a hydrophilic fraction and a hydrophobic fraction are obtained by passing the onion concentrate through a column, and it is preferable to use the hydrophilic fraction as the onion extract. Before fractionation through a column or the like, the onion concentrate may be heat-treated in an autoclave or the like.

[0034] The onion extract obtained in the fractionation step may, if necessary, be further subjected to purification treatment or treatment to separate highly active fractions. Examples of purification treatments include filtration and adsorption (using an ion-exchange resin column, an activated carbon column, etc.). Examples of treatments to separate highly active fractions include gel filtration, adsorption, silica gel column chromatography, HPLC, etc.

[0035] <Plant Growth-Promoting Method> The plant growth-promoting method of this embodiment is a method for promoting plant growth by applying a composition containing as an active ingredient(s) one or more selected from the group consisting of the above-mentioned onion extract and onion powder to a plant, or to the soil or culture solution in which the plant is growing. In this method, the plant growth-promoting composition can be applied to a plant or a part thereof (for example, a seed, a seedling or a mature plant) at any growth stage including before or after germination. Furthermore, the plant growth-promoting composition can be applied not only to the plant itself but also to the soil, culture medium or culture solution in which the plant is growing. Plant growth can be promoted by applying the plant growth-promoting composition to a plant at any growth stage or to the soil, culture medium or culture solution in which the plant is growing.

[0036] The plant growth-promoting composition may be applied to a plant once or multiple times. Furthermore, when the plant growth-promoting composition is applied at multiple application periods, the plant growth-promoting composition may be applied once or multiple times at each application period.

[0037] The plant growth-promoting composition can be applied to plants by, for example, adding, spraying, coating, immersing, etc. These methods may be used alone or in combination of two or more.

[0038] When the plant growth-promoting composition is applied to a plant in a culture solution in which the plant grows, the amount of the plant growth-promoting composition used relative to the culture solution is preferably 0.001 to 1% by mass. When the amount of the plant growth-promoting composition used is within the above range, a sufficient plant growth-promoting effect tends to be obtained.

[0039] The preferable range of the amount used varies depending on the concentration of onion juice described above, but the above amount is a preferable range when the concentration is 3 to 30 times.

[0040] The present invention will be explained in more detail using examples and comparative examples, but the present invention is not limited to these examples in any way.

[0041] (Method for measuring root weight) The roots of the rice plants were identified based on their color and shape, and the weight of the identified roots was measured in a bottle using a microbalance.

[0042] Example 1 246.5 g of onion bulbs were sliced ​​at intervals of 1 to 10 mm, and 100 g of water was added and the slices were crushed in a mixer. Impurities were removed by filtration using filter cloth and filter paper. The filtrate was concentrated approximately 10 times in a rotary evaporator to give an onion extract. 0.36 g (0.04% by mass) of a solution containing a fraction obtained by fractionating and heat-treating the onion extract obtained above was added to 900 mL of a culture solution for growing rice, and the effect on rice was investigated. The result was that the weight of rice roots increased by 58.5% compared to the case without the addition of onion extract, demonstrating an effect of improving root establishment of rice (see FIG. 1 ). The culture solution before the addition of the onion extract had been adjusted to contain about one-fifth of the amounts of each nutrient listed in Table 1 below.

[0043]

[0044] Example 2 The effect of the onion extract on gene expression in rice was also evaluated.

[0045] (A) Sample preparation Preparation of rice plants (control (CT) and onion-treated group) Rice plants grown under the same experimental cultivation conditions as in Example 1 were prepared in two groups: a CT group and an onion-treated group. RNA was then extracted from the plant tissues. Onion-treated group: Onion extract was added to the culture solution in which the rice was grown, and used to investigate the effect on gene expression in rice. Culture solution in CT group: The same treatment as for the onion extract-treated group was carried out, except that no onion extract was added. RNA extraction RNA samples were obtained using a Maxwell RSC Plant RNA Kit (Promega) and a Maxwell RSC Instrument (Promega) according to the manufacturer's instructions. - RNA quality confirmation Measurement equipment: Agilent 2100 Bioanalyzer <G2939A> (Agilent Technologies), reagent kit: Agilent RNA6000 Nano kit <5067-1511> (Agilent Technologies) and analysis software: 2100 expert software <version B. 02.07> (Agilent Technologies) was used to confirm that there were no problems with the quality of the RNA sample, and then used for library preparation. - Library preparation A library for the next-generation sequencer NextSeq was prepared using the QuantSeq 3'mRNA-Seq Library Prep Kit according to the following steps. 1. Use 100 ng of total RNA. 2. cDNA synthesis using oligo(dT) primer. 3. Removal of template mRNA. 4. Double-stranded cDNA synthesis using random primer. 5. 14-cycle PCR using indexed adapter. 6. Purification using beads.

[0046] (B) Analysis by Next-generation Sequencer - Sequence Analysis Equipment: NextSeq500 (Illumina) Reagent: NextSeq 500 / 550 High Output Kit v2.5 (75 Cycles) <2002490>6> (Illumina) - Sequence (Overview) Sequencing was performed using NextSeq500 according to the following steps. 1. Addition of sequencing reagent 2. Single-base extension reaction 3. Removal of unreacted bases 4. Incorporation of fluorescence signal 5. Removal of protecting group and fluorescence 6. Repeat cycles of 2 Cycles…3 Cycles… and perform up to 75 cycles

[0047] (C) Data Analysis - Primary Data Analysis Analysis program: bcl2fastq ver2.20 (Illumina) Using the program bcl2fastq (Illumina), a fastq file was created from the obtained reads. - Secondary Data Analysis OS of the analysis computer: Ubuntu Desktop 22.04.4 LTS Analysis software: FastQC, hisat2, samtools, HTSeq, DESeq2 Analysis was performed using the above software. 1. Confirmation of read quality Using FastQC, the quality of the bases contained in the obtained fastq file was confirmed. 2. Mapping and sorting Using hisat2, mapping was performed to the Oryza sativa reference genome Oryza sativa Japonica Group (assembly IRGSP-1.0). Subsequently, using samtools, the file was sorted and converted into binary data. 3. Read count Using htseq-count in HTSeq, the number of mapped reads was counted. 4. Statistical analysis Using the DESeq2 package on the statistical package R, the gene expression levels in the CT group and the onion-treated group were compared.

[0048] [Results] Comparison of expression levels between two groups Comparison between two groups was performed using a generalized linear model. The Fold change value (= onion-treated group / CT group) and adjusted p-value of the genes with significantly increased expression levels in the onion-treated group are shown below.

[0049] As shown in Table 2, the gene expression measurement results showed that the use of onion extract increased the expression level of PHO1;2, a gene that contributes to chemical stress tolerance, by 3.27 times in the roots. This enzyme is present on the surface of the roots and directly interacts with external phosphorus. It has been reported that increased gene expression under phosphorus-deficient conditions leads to increased phosphorus absorption (Reference 1). Furthermore, it has been reported that similar genes to this molecule are widely present in plants other than Arabidopsis and rice, such as wheat, chili pepper, lettuce, tomato, and cacao (References 2 and 3). Therefore, onion extract is likely to be effective for many plants other than rice. Reference 1: https: / / bmcplantbiol.biomedcentral. com / articles / 10.1186 / s12870-020-2316-7 Reference 2: https: / / onlinelibrary. wiley. com / doi / 10.1111 / plb. 12668 Reference 3: https: / / www. arabidopsis. org / locus? key=27574

[0050] As shown in Table 2, the gene expression level measurements showed that the use of onion extract increased the expression level of WRKY71, a gene that contributes to salt stress tolerance, by 1.36 times in the aboveground shoots. Generally, salt stress conditions cause delayed flowering, a physiological disorder. However, it has been shown that Arabidopsis plants overexpressing WRKY71 flower even under salt stress conditions (Reference 4). Furthermore, since similar genes to this molecule are widely known to exist in soybeans, oranges, lettuce, tomatoes, grapes, and other plants in addition to Arabidopsis and rice (Reference 5), it is believed that onion extract is effective for many plants other than rice. Reference 4: https: / / academic.oup.com / pcp / article / 59 / 2 / 414 / 4764040#110738917 Reference 5: https: / / www.arabidopsis.org / org / servlets / TairObject? id=28546&type=locus

Claims

1. A plant growth-promoting composition comprising as an active ingredient one or more members selected from the group consisting of onion extract and onion powder.

2. The plant growth-promoting composition described in claim 1, which has one or more plant growth-promoting effects selected from the group consisting of elongation of stems, leaves or roots, increased leaf number, promotion of flowering or fruiting, increased number of flowers or fruits, increased plant weight or crop yield, greening, and promotion of tillering.

3. A plant growth-promoting composition as described in claim 1 or 2, which has the effect of improving abiotic stress resistance.

4. The plant growth-promoting composition described in claim 3, which has the effect of improving stress resistance to one or more stresses selected from the group consisting of temperature stress, chemical stress, light stress, drought stress, pH stress, salt stress, hypoxic stress, herbicide stress, physical stress and disease stress.

5. The plant growth promoting composition according to claim 3, which activates genes in the stress response system.

6. A method for promoting plant growth, which comprises applying to a plant, or to soil or a culture solution in which a plant grows, a plant growth-promoting composition containing as an active ingredient one or more members selected from the group consisting of onion extract and onion powder.

7. The plant growth promoting method according to claim 6, wherein the amount of the plant growth promoting composition used in the culture solution is 0.001 to 1 mass %.

8. The method for promoting plant growth according to claim 6, wherein the onion extract or onion powder is extracted from one or more parts of onions discharged from a farm, a sorting house or a factory.

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