Application of 3-hydroxydecanoic acid in promoting growth of watermelon seedlings and enhancing resistance

Abstract

The invention discloses application of 3-hydroxydecanoic acid in promoting growth of watermelon seedlings and enhancing resistance. According to the method, 3-hydroxydecanoic acid solutions with different concentrations are adopted, and watermelon seeds or watermelon seedlings are treated through seed soaking, root application and foliage spraying methods. Practice shows that after the 3-hydroxydecanoic acid biostimulant is applied, the germination performance of watermelon seeds and the growth and development of watermelon seedlings are remarkably improved, and root development, overground part form construction and physiological function improvement of the watermelon seedlings are promoted. Results show that the method provided by the invention not only effectively promotes the growth of the watermelon seedlings, but also enhances the resistance of the watermelon seedlings, and provides a new thought for developing a novel biostimulant capable of promoting the growth, enhancing the stress resistance and improving the quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of plant growth, and particularly relates to the application of 3-hydroxydecanoic acid biostimulant in promoting the growth of watermelon seedlings and enhancing resistance. Background Art

[0002] Watermelon (Citrullus lanatus) is an important horticultural cash crop in the world. China is the largest watermelon producer in the world, with its output accounting for about 60% of the world's watermelon output. The watermelon industry has extremely important economic value and agricultural status in China. During the cultivation process of watermelon, the excessive application of pesticides and chemical fertilizers will seriously affect the ecological environment. Therefore, finding new biostimulants that can improve the yield and quality of watermelon is one of the important ways to achieve green and high-quality development of the watermelon industry in China.

[0003] Biostimulants are a class of chemical substances that are not artificially chemically synthesized and can improve the physiological and biochemical status of plants, enhance the stress resistance of plants, and improve the fertilizer utilization rate of crops. Different from pesticides and traditional fertilizers, they can promote the growth and development of plants through indirect effects within the plants. These substances are derived from nature and do not cause any harmful effects on other animals and the environment, opening up a new path for plant growth, ecological environment protection, and soil improvement. Currently, many types of biostimulants have been widely used in agriculture.

[0004] 3-Hydroxydecanoic acid is a class of natural hydroxy fatty acids, which are more reactive than ordinary fatty acids in chemical properties and can be obtained by extraction from vegetable oils and animal fats. In industrial production, it is mainly obtained by biological conversion of microorganisms. Currently, it has been found to have the functions of inducing plant immune responses, inhibiting colony growth, and inhibiting the mitosis of pollen cells, indicating that it has great application potential in the agricultural field. Therefore, exploring the growth-promoting effect of 3-hydroxydecanoic acid in plants is of great significance for guiding and developing the production of the watermelon industry. Summary of the Invention

[0005] The purpose of the present invention is to provide the application of 3-hydroxydecanoic acid in promoting the growth of watermelon seedlings and enhancing resistance in view of the deficiencies of the prior art, so as to establish a green and environmentally friendly watermelon production technology.

[0006] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0007] In the first aspect, the present invention provides the application of 3-hydroxydecanoic acid in promoting the germination of aged watermelon seeds, and the aged watermelon seeds are subjected to seed soaking treatment.

[0008] The application concentration of the 3-hydroxydecanoic acid is 2 ppm - 20 ppm, and the improved preferred concentration is 5 ppm.

[0009] The specific steps are as follows: After normal disinfection and warm water germination acceleration of the aged watermelon seeds, the 3-hydroxydecanoic acid reagent with a preferred concentration is applied to the aged watermelon seeds by soaking. The soaking duration is 3 hours. After soaking, the residual reagent on the surface needs to be thoroughly washed, and the seeds are placed at 28°C for normal germination.

[0010] The 3-hydroxydecanoic acid with the preferred concentration significantly improves the germination rate, root length and stem diameter of the aged watermelon seeds.

[0011] In the second aspect, the present invention provides an application of 3-hydroxydecanoic acid in promoting the growth of watermelon seedlings, and the watermelon seeds are treated by soaking with 3-hydroxydecanoic acid or the watermelon seedlings are sprayed on the leaf surface.

[0012] Furthermore, if the watermelon seeds are treated by soaking, the application concentration of the 3-hydroxydecanoic acid is 2 ppm - 30 ppm, and the improved preferred concentration is 2 ppm - 10 ppm.

[0013] The specific steps are as follows: After normal disinfection and warm water germination acceleration of the watermelon seeds, the 3-hydroxydecanoic acid reagent with a preferred concentration is applied to the watermelon seeds by soaking. The soaking duration is 3 hours. After soaking, the residual reagent on the surface needs to be thoroughly washed, and the seeds are placed at 28°C for normal germination.

[0014] The growth stimulant with the preferred concentration significantly increases the main root length, fresh weight of the upper and lower parts above and below the ground and root-shoot ratio. The effect of the reagent after soaking fails at 2 - 4 weeks, and it should be supplemented in time at this stage in production. The supplementary application can be carried out by root application or leaf surface spraying, etc.

[0015] Furthermore, if the watermelon seedlings are sprayed on the leaf surface, the application concentration of the 3-hydroxydecanoic acid is 10 ppm - 60 ppm, and the improved preferred concentration is 20 ppm - 30 ppm.

[0016] The specific steps are as follows: In the substrate mode, after the first true leaf of the plant is fully unfolded, the leaf surface is sprayed. Each time, 20 ml of the 3-hydroxydecanoic acid solution is sprayed. Taking the standard that water droplets form on the leaf surface but do not drip off, the spraying treatment is carried out once every 3 days.

[0017] After the preferred concentration of the biostimulant is sprayed on the leaf surface, the dry and fresh weights of the above-ground parts of the watermelon seedlings, plant height, stem diameter, soluble sugar and chlorophyll content are all significantly increased.

[0018] In the third aspect, the present invention provides an application of 3-hydroxydecanoic acid in promoting the root development of watermelon seedlings, and the watermelon seedlings are treated by root application.

[0019] The application concentration of the 3-hydroxydecanoic acid is 5 ppm - 50 ppm, the improved preferred concentration is 10 ppm - 40 ppm, and the further preferred concentration is 10 ppm.

[0020] The specific steps are as follows: After the watermelon seeds are normally disinfected and germinated by warm water soaking, when the watermelon seeds germinate and take root and grow to 3 cm, transfer the seedlings to a seed germination bag, with 3 plants in each bag, and pour about 20 ml of 3-hydroxydecanoic acid solution on the roots of each bag, and apply it to the roots every 2 days.

[0021] After the preferred concentration of the biostimulant is applied to the roots, significant changes occur in the root indexes of the plants, and significant improvements are observed in the total root length, total root surface area, total root volume, and number of root tips, etc., thereby improving the root morphological structure.

[0022] Fourthly, the present invention provides an application of 3-hydroxydecanoic acid in regulating the cold resistance of plants, and spraying 3-hydroxydecanoic acid on the leaf surface to improve the cold resistance of plants.

[0023] The application concentration of the 3-hydroxydecanoic acid biostimulant is 10 ppm - 60 ppm, and the improved preferred concentration is 30 ppm.

[0024] The specific steps are as follows: In the substrate mode, after the first true leaf of the plant is fully unfolded, perform spraying treatment on the leaf surface, spraying 20 ml each time, with the standard that water droplets condense on the leaf surface but do not drip, and perform spraying treatment every 3 days.

[0025] After the preferred concentration of the biostimulant is sprayed on the leaf surface, it can significantly increase the dry and fresh weights of the above-ground parts of the plants, chlorophyll content, Fv / Fm, and antioxidant enzyme activity, while reducing the MDA content and relative conductivity, and enhancing the cold resistance of watermelon seedlings.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) Through precise screening of the biostimulant concentration, the application of 3-hydroxydecanoic acid in soaking seeds, applying to roots, and spraying on the leaf surface was explored, which significantly improved the germination performance of watermelon seeds and the growth and development of watermelon seedlings, and promoted the root development, above-ground morphological construction, and physiological function improvement of watermelon seedlings. It laid a good foundation for the subsequent practical application of biostimulants.

[0028] (2) The enhancement effect of spraying a specific concentration of biostimulant on the leaf surface on the cold resistance of watermelon seedlings was proposed and verified, and this result has good guiding significance for reducing the losses caused by low-temperature disasters and improving the stability and economic benefits of watermelon cultivation in actual production. Description of the Drawings

[0029] Figure 1 It is a comparison diagram of the influence of soaking seeds with 3-hydroxydecanoic acid reagent on the germination of aged watermelon seeds; among them,Figure 1 In (A), it is a comparison chart of the germination of water-soaked seeds (CK) in Example 1 and aged watermelon seeds after soaking with 3-hydroxydecanoic acid at a concentration of 2 - 30 ppm. Figure 1 In (B), it is a statistical chart of the germination rate of aged watermelon seeds after soaking. Figure 1 In (C), it is a statistical chart of the 7-day germination rate of aged watermelon seeds after soaking. Figure 1 In (D), it is a statistical chart of the root length of aged watermelon seeds after soaking. Figure 1 In (E), it is a statistical chart of the stem diameter of aged watermelon seeds after soaking.

[0030] Figure 2 It is a diagram showing the change in the main root length of watermelon plants after soaking with 3-hydroxydecanoic acid.

[0031] Figure 3 It is a comparison chart of the effects of root application of 3-hydroxydecanoic acid on plant root indexes under hydroponic mode.

[0032] Figure 4 It is a comparison chart of the effects of foliar spraying of 3-hydroxydecanoic acid on various indexes of plants under substrate mode; among them, Figure 4 In (A), it is a statistical chart of the stem diameter, plant height, fresh weight of the above-ground part, and dry weight of the above-ground part of plants after foliar spraying with 3-hydroxydecanoic acid at a concentration of 10 - 60 ppm. Figure 4 In (B), it is a statistical chart of the maximum photochemical efficiency of PSII of plants after foliar spraying with 3-hydroxydecanoic acid. Figure 4 In (C), it is a statistical chart of the soluble sugar content of plants after foliar spraying with 3-hydroxydecanoic acid. Figure 4 In (D), it is a statistical chart of the chlorophyll content of plants after foliar spraying with 3-hydroxydecanoic acid.

[0033] Figure 5 It is a phenotypic diagram of plants after foliar spraying with biostimulants under chilling stress treatment.

[0034] Figure 6 It is a comparison chart of the effects of foliar spraying of 3-hydroxydecanoic acid on plant cold resistance indexes. Figure 6 In (A), it is a statistical chart of the soluble sugar content of plants after foliar spraying with 3-hydroxydecanoic acid at a concentration of 10 - 60 ppm. Figure 6 In (B), it is a statistical chart of the MDA content of plants after foliar spraying with 3-hydroxydecanoic acid. Figure 6 In (C), it is a statistical chart of the relative electrical conductivity REC of plants after foliar spraying with 3-hydroxydecanoic acid. Figure 6 In (D), it is a statistical chart of the maximum photochemical efficiency of PSII of plants after foliar spraying with 3-hydroxydecanoic acid. Figure 6 In (E), it is a statistical chart of the chlorophyll content after foliar spraying with 3-hydroxydecanoic acid. Figure 6In (F), it is the statistical chart of the fresh weight and dry weight of the above-ground parts after foliar spraying of 3-hydroxydecanoic acid;

[0035] Figure 7 It is the comparison chart of the influence of foliar spraying of 3-hydroxydecanoic acid on the peroxidase index of plants; among them, Figure 7 In (A), it is the statistical chart of the POD activity of plants after foliar spraying of 3-hydroxydecanoic acid with a concentration of 10 - 60 ppm under low temperature stress, Figure 7 In (B), it is the statistical chart of the CAT activity of plants after foliar spraying of 3-hydroxydecanoic acid under low temperature stress, Figure 7 In (C), it is the statistical chart of the T-SOD activity of plants after foliar spraying of 3-hydroxydecanoic acid under low temperature stress, Figure 7 In (D), it is the statistical chart of the CuZn-SOD activity of plants after foliar spraying of 3-hydroxydecanoic acid under low temperature stress. Detailed implementation mode

[0036] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific implementation cases, but the protection scope of the present invention is not limited to the following specific embodiments. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0037] In the following examples, the watermelon varieties selected are all "Zhemi No. 8", purchased from Zhejiang Wuwangnong Seed Industry Co., Ltd. 3-hydroxydecanoic acid is provided by the School of Chemical Engineering of Zhejiang University.

[0038] Example 1: Promotion of the germination of aged seeds by 3-hydroxydecanoic acid biostimulant

[0039] The following steps are carried out in sequence:

[0040] (1) Disinfect the seeds with 10% (w / w) sodium hypochlorite for 10 min. After thoroughly cleaning, soak the seeds in warm water at 55 °C for 30 min. After taking out, soak them in 20 ml of 3-hydroxydecanoic acid reagents with concentrations of 2 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, and 30 ppm for 3 h, and soak the seeds in equal amount of clear water as the control (CK). Take out, drain, and wash off the residual reagents on the surface with running water, and put them into a petri dish containing moist filter paper. There are 25 seeds in each petri dish, and each treatment has 3 replicates.

[0041] (2) To ensure that the test materials are in a relatively balanced aging state, investigate the effects of 3-hydroxydecanoic acid biostimulant on the germination potential and germination rate of aged seeds. Place the seeds in step (1) in an incubator at 40 °C for 72 h of high-temperature treatment for seed induced aging. Subsequently, transfer them to a dark environment at 28 °C for germination. When the radicle of the seed is exposed by 2 mm, it is the germination state of the seed. Record the number of germinated seeds every 24 h, and measure the root length and stem diameter at 7 d. The calculation formula for the germination rate is: Germination rate / % = Number of germinated seeds / Number of tested seeds × 100.

[0042] As Figure 1 shown, soaking the seeds with 2 - 20 ppm of 3-hydroxydecanoic acid can effectively increase the root length and stem diameter. Only 5 ppm can significantly increase the germination rate, and other concentrations have no significant increase. It shows that soaking the seeds with 3-hydroxydecanoic acid can significantly increase the germination rate, root length and stem diameter of aged watermelon seeds, and 5 ppm of 3-hydroxydecanoic acid has the best effect.

[0043] Example 2: Measurement of growth indicators of soaked seedlings and determination of the duration of the soaking reagent

[0044] Perform the following steps in sequence:

[0045] (1) Disinfect watermelon seeds with 10% (w / w) sodium hypochlorite for 10 min. After washing, soak the seeds in warm water at 55 °C for 30 min. Subsequently, soak them in 20 ml of 3-hydroxydecanoic acid reagents with concentrations of 2 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, and 30 ppm for 3 h, and soak the seeds with equal amounts of clear water as the control (CK). Take them out, drain, and wash off the residual reagents on the surface with running water. Place them in a petri dish containing moist filter paper, with 25 seeds in each petri dish, and 3 replicates for each treatment.

[0046] (2) When the seeds in step (1) germinate and take root about 3 cm, transfer them to a seed germination bag. Select three seeds with uniform and healthy growth in each bag and place them neatly. Observe the root development every 2 days.

[0047] (3) After the true leaves of the plants in step (2) grow, supply them with Hoagland nutrient solution (the formula is shown in Table 1) for the normal growth of the plants. Measure the stem diameter, stem length, main root length, dry and fresh weights of the aboveground and underground parts, root-shoot ratio, and tissue water content at 2 weeks and 4 weeks after soaking to observe the sustainable time of the soaking reagent. Randomly select 3 plants from each group for replication.

[0048] Table 1: Formula table of watermelon Hoagland nutrient solution

[0049]

[0050] As Figure 2As shown, there were significant differences in root length of plants after seed soaking compared with the CK. 3-Hydroxydecanoic acid at 2-10 ppm had the best promoting effect on root length. Moreover, with the increase in concentration, the promoting efficiency of root length decreased slightly, showing an inhibitory effect at high concentrations. As shown in Table 2 and Table 3, when soaked for 2 weeks, 3-hydroxydecanoic acid at 2-15 ppm significantly increased the fresh weight of the aboveground and underground parts and the root-shoot ratio. However, there were almost no significant differences in physiological indexes after soaking for 4 weeks. It is speculated that the reagent for the first seed soaking no longer played a role at 4 weeks, and it should be supplemented and applied in time within 2-4 weeks during production. The above-mentioned supplementary application can be carried out by root application or foliar spraying, etc.

[0051] Table 2: Statistical table of physiological indexes of seedlings soaked with 3-hydroxydecanoic acid for 2 weeks

[0052]

[0053] Table 3: Statistical table of physiological indexes of seedlings soaked with 3-hydroxydecanoic acid for 4 weeks

[0054]

[0055] Example 3: Effects of root application of biostimulants on root morphology construction of plants under hydroponic mode

[0056] (1) Watermelon seeds were disinfected with 10% (w / w) sodium hypochlorite for 10 min, taken out, washed, and soaked in warm water at 55 °C for 30 min. Then they were taken out and placed in a petri dish containing moist filter paper, and germinated in the dark at 28 °C.

[0057] (2) When the seeds in step (1) germinated and took root about 3 cm, they were transferred to a seed germination bag. Three seeds with uniform and healthy growth were neatly placed in each bag. Three bags were taken as replicates for each treatment. Then 20 ml of 3-hydroxydecanoic acid reagent at 5 ppm, 10 ppm, 20 ppm, 30 ppm, 40 ppm, and 50 ppm was added into the bags (the CK group bags were added with an equal amount of clear water as a control). The first irrigation was recorded as 0 d, and then root application was supplemented every 2 days. At the same time, the root development was observed. After 8 d, they were taken out for photographing. Three plants were randomly taken as replicates for each treatment and subjected to root scanning. The WinRhizo root analysis system was used for image scanning to obtain data values such as total root length, average root diameter, total root volume, root surface area, and number of branches.

[0058] As Figure 3 shown, there were significant changes in the root indexes of plants after root application. The total root length, total root surface area, total root volume, and number of root tips were significantly increased. 3-Hydroxydecanoic acid at 10 ppm - 40 ppm had the best promoting effect on the main root and other root indexes. It shows that root application of an appropriate concentration of growth stimulant can effectively increase the total root length and root volume indexes, thereby improving the root morphological structure.

[0059] Example 4: Effects of Foliar Spraying of Biostimulants on Plant Physiological Indexes

[0060] (1) Select watermelon seeds of uniform size, healthy and plump, disinfect them with 10% (w / w) sodium hypochlorite solution for 5 min, rinse them repeatedly with sterile water, and then soak them in warm water at 55 °C for 15 min for germination.

[0061] (2) Place the germinated seeds neatly in a seedling tray for seedling raising. After cultivating strong seedlings, select one healthy seedling from each pot for transplanting, and place it in an incubator for cultivation. The growth conditions are set as 28 °C, 16 h of light, 16 °C, 8 h of darkness, and the humidity is 60%.

[0062] (3) After the first true leaf of the plant is fully expanded, carry out spraying treatment. Spray 20 ml of 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm 3-hydroxydecanoic acid (the CK group sprays an equal amount of clear water as a control). Taking the standard that water droplets form on the leaf surface but do not drip off, carry out foliar spraying treatment once every 3 d. There are 15 plants in each treatment, with 3 replicates. The first spraying is recorded as 0 d.

[0063] (4) Take phenotypic photos 7 d after treatment. For each treatment, randomly select 3 watermelon plants for index measurement. Use an electronic balance to measure the dry and fresh weights of the above-ground parts of the watermelon seedlings, use a ruler to measure the plant height and stem diameter, use the ethanol extraction method to measure the chlorophyll content of the leaves, use a MINI-PAM-II ultra-portable modulated chlorophyll fluorometer to measure Fv / Fm, and use the anthrone colorimetric method for soluble sugar. Each index is measured 3 times repeatedly, and the average value is taken.

[0064] As Figure 4 shown, foliar spraying of 3-hydroxydecanoic acid biostimulant can significantly improve various physiological indexes of plants. Among them, 20 ppm 3-hydroxydecanoic acid performs best in promoting plant height and soluble sugar, and 30 ppm 3-hydroxydecanoic acid significantly promotes the fresh weight of the above-ground part and the total chlorophyll content and has the best effect. Through comprehensive comparison of 7 indexes, it is found that 20 ppm and 30 ppm 3-hydroxydecanoic acid promote the growth and development of watermelon seedlings best.

[0065] Example 5: Effects of Foliar Spraying of Biostimulants on Plant Cold Resistance

[0066] (1) The previous germination, plant transplantation, foliar spraying concentration and method are the same as those in Example 4.

[0067] (2) Spray once again before transferring to a low-temperature incubator after 7 days. After there are no droplets on the leaf surface, transfer them to the low-temperature incubator for cultivation. The growth conditions are set as 10°C, 16 h of light, 7°C, 8 h of darkness, and the humidity is 60%. There are 15 plants in each treatment, with 3 replicates. The low-temperature treatment ends after 72 h. As a control, the group without low-temperature stress is set with growth conditions of 25°C, 16 h of light, 18°C, 8 h of darkness, and other conditions remain unchanged.

[0068] (3) For each treatment, 3 watermelon plants are randomly selected for index determination according to the random sampling method. The measurement methods of leaf chlorophyll, dry and fresh weight, soluble sugar, and chlorophyll fluorescence are the same as in Example 4. The conductivity is measured using a Leici DDSJ-307F conductivity meter; the content of malondialdehyde (MDA) is determined by the thiobarbituric acid (TBA) method; the activity of superoxide dismutase (SOD) is determined by the nitroblue tetrazolium (NBT) reduction method; the activity of peroxidase (POD) is determined by the guaiacol colorimetric method; the activity of catalase (CAT) is determined by the hydrogen peroxide reduction method. Each index is measured 3 times repeatedly.

[0069] As Figure 5 , Figure 6 , Figure 7 shown, under low-temperature stress, treatment with a suitable concentration of the reagent can alleviate the wilting of seedling leaves, increase the dry and fresh weight of the above-ground part, chlorophyll content, Fv / Fm, and antioxidant enzyme activity, and reduce the MDA content and relative conductivity. It can be seen that under low-temperature stress, foliar spraying with a suitable concentration of 3-hydroxydecanoic acid can improve the photosynthetic capacity of watermelon seedlings, reduce the damage of low temperature to cell membranes, improve antioxidant enzyme activity and root activity, and promote the growth of watermelon seedlings. Through comprehensive comparison of each index, it is found that the treatment with 30 ppm of 3-hydroxydecanoic acid has the best effect on alleviating low-temperature stress of watermelon seedlings.

[0070] In summary, the present invention discloses the application of a 3-hydroxydecanoic acid biostimulant in promoting the growth of watermelon seedlings and enhancing resistance. This application uses a suitable concentration of 3-hydroxydecanoic acid solution to treat watermelon seeds or watermelon seedlings by methods of seed soaking, root application, and foliar spraying, explores the growth-promoting effect of 3-hydroxydecanoic acid on watermelon, clarifies the application concentration under different application methods, and at the same time provides a new idea for developing a new type of biostimulant with growth promotion, stress resistance enhancement, and quality improvement.

[0071] Finally, it should also be noted that the above-listed are only several specific embodiments of the present invention. The present invention is not limited to the above embodiments and there can be many variations. All variations that can be directly derived or associated by those of ordinary skill in the art from the disclosed content of the present invention shall be considered as the protection scope of the present invention.

Claims

1. The application of 3-hydroxydecanoic acid in promoting the growth of watermelon seedlings is characterized in that: Use 3-hydroxydecanoic acid to soak watermelon seeds or spray the leaves of watermelon seedlings.

2. The use according to claim 1, characterized in that: The watermelon seeds are soaked, and the 3-hydroxydecanoic acid is applied at a concentration of 2ppm-10ppm; the watermelon seedlings are sprayed on the leaves, and the 3-hydroxydecanoic acid is applied at a concentration of 20ppm-30ppm.

3. The application of 3-hydroxydecanoic acid in promoting the root development of watermelon seedlings is characterized in that: Root fertilizer treatment was applied to watermelon seedlings.

4. The use according to claim 3, characterized in that: The 3-hydroxydecanoic acid is applied at a concentration of 10 ppm to 40 ppm, and is applied to the roots once every 2 days.

5. The application of 3-hydroxydecanoic acid in promoting the germination of aged watermelon seeds is characterized in that: Soak the aged watermelon seeds.

6. The use according to claim 5, characterized in that: The 3-hydroxydecanoic acid is applied at a concentration of 2-20 ppm.

7. The use according to claim 6, characterized in that: The 3-hydroxydecanoic acid was applied at a concentration of 5 ppm.

8. The use of 3-hydroxydecanoic acid in regulating plant cold resistance, characterized in that: Foliar spray of 3-hydroxydecanoic acid can improve plant cold resistance.

9. The use according to claim 8, characterized in that: The plant is watermelon, and the applied concentration of 3-hydroxydecanoic acid is 30 ppm.

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