A lychee cold-resistant agent, its preparation method and application

Abstract

The present invention discloses a litchi cold-resistant agent, which comprises vegetable oil, 1,4-diaminobutane, 2,4-epibrassinolide and inositol. The litchi cold-resistant agent provided by the present invention, its preparation method and application have obvious effects on different varieties of litchi, effectively alleviate the influence of low temperature on the photosynthesis of litchi, and improve the phenomenon of difficult selection of single medicament and inconsistent application effects for a long time.

Description

Technical Field

[0001] The present invention relates to the technical field of litchi cold resistance, and particularly relates to a litchi cold-resistant agent, a preparation method thereof, and an application thereof. Background Art

[0002] Litchi is native to China and is a fruit tree of the genus Litchi in the family Sapindaceae. It prefers a warm climate. Among them, the planting area of litchi in Guangdong is nearly 4 million mu, and the annual output is about 1.2 million tons on average. However, low temperature in winter often causes frost damage to litchi, greatly affecting its annual output of the current year, and is the main factor restricting economic cultivation. Low-temperature cold damage is also a serious natural disaster in agricultural and forestry production. It causes a large reduction in the yield of food crops and has become a widespread problem worldwide. Therefore, it is particularly important to study how to improve the cold resistance of plants.

[0003] Low-temperature stress can make the growth and development of plants abnormal, change their membrane systems, cell osmotic pressure, material metabolism, protoplasmic colloid properties, protective enzyme systems, etc., and even lead to the death of plants. Many studies have shown that spraying plant growth regulator substances on plants can significantly improve the cold resistance of plants. For example, exogenous application of 2,4-epibrassinolide (EBR) can increase the activity of the antioxidant enzyme system, thereby effectively scavenging reactive oxygen species in plants to reduce the damage to plants with different cold resistances during cold stress and the process of returning to normal temperature. Polyamines also have a certain effect on improving the cold resistance of plants, which can relieve the sensitivity of crops to abiotic stress and enhance the cold resistance of plants. Before the low temperature in winter comes, spraying plant growth regulator composite substances on litchi helps to induce a series of physiological and biochemical reactions in litchi, and can effectively improve its own cold resistance, which is very important for the stress resistance and stable yield of litchi.

[0004] In the prior art, most still improve the cold resistance of litchi by applying traditional fertilizers. For litchi with a variety of litchi varieties and different geographical environment conditions, the effect is not ideal. Summary of the Invention

[0005] The present invention aims to solve at least one of the problems in the related art to some extent. For this reason, the purpose of the present invention is to provide a litchi cold-resistant agent, a preparation method thereof, and an application thereof, which have obvious effects on different varieties of litchi, effectively relieve the influence of low temperature on the photosynthesis of litchi, and improve the phenomenon of difficult selection of single agents and inconsistent application effects for a long time.

[0006] To achieve the above object, the present application adopts the following technical solution: A litchi cold-resistant agent includes vegetable oil, 1,4-butanediamine, 2,4-epibrassinolide, and inositol.

[0007] Furthermore, the concentration of 2,4-epibrassinolide in the cold-resistant agent is 1-3 mg / L, the vegetable oil in the cold-resistant agent is diluted 140-160 times, the concentration of 1,4-butanediamine in the cold-resistant agent is 0.05-0.07 mg / L, and the concentration of myo-inositol in the cold-resistant agent is 4-6 mg / L.

[0008] Furthermore, the concentration of 2,4-epibrassinolide in the cold-resistant agent is 2 mg / L, the vegetable oil in the cold-resistant agent is diluted 150 times, the concentration of 1,4-butanediamine in the cold-resistant agent is 0.06 mg / L, and the concentration of myo-inositol in the cold-resistant agent is 5 mg / L.

[0009] Furthermore, it further includes a surfactant; the concentration of the surfactant in the cold-resistant agent is 0.4-0.6 vol%.

[0010] Furthermore, the surfactant is Tween-20.

[0011] Furthermore, the concentration of the surfactant in the cold-resistant agent is 0.5 vol%.

[0012] A preparation method of a litchi cold-resistant agent includes: dissolving 2,4-epibrassinolide in alcohol to obtain an alcohol solution; dissolving vegetable oil, 1,4-butanediamine, and myo-inositol in deionized water respectively to obtain aqueous solutions; mixing the alcohol solution and the aqueous solutions, and adding a surfactant to prepare the litchi cold-resistant agent.

[0013] An application of the litchi cold-resistant agent as described above in litchi cold resistance and frost prevention.

[0014] Furthermore, the cold-resistant agent is sprayed on the leaves and / or branches of litchi.

[0015] Furthermore, the applicable temperature of the cold-resistant agent is -2°C - 4°C.

[0016] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art: In the present application, 2,4-epibrassinolide, vegetable oil, 1,4-butanediamine, and myo-inositol are selected for compounding. The four substances can respectively induce a series of physiological and biochemical reactions in litchi that can effectively improve cold resistance. Among them, 2,4-epibrassinolide improves the cold resistance of litchi by increasing the activity of antioxidant enzymes; vegetable oil improves the cold resistance of litchi by promptly closing the stomata of litchi leaves, reducing the photosynthetic rate, and reducing gas exchange during low temperature; 1,4-butanediamine can promote the generation of low-temperature resistance-related metabolites such as soluble sugars and proline; myo-inositol can regulate ion channels and plasma membrane permeability to maintain the balance of water and nutrients, promote the absorption of nitrogen by plants, quickly supplement phosphorus and potassium, and promote photosynthesis, thereby reducing the impact on plants after the stomata are closed by spraying vegetable oil at the end of low temperature; at the same time, the four substances jointly increase the cold resistance of litchi through multiple action mechanisms such as regulating the antioxidant enzyme system and osmoregulatory substances, making the synergistic effect of the four substances significantly greater than the effect of monomers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present invention and, together with the specification, are used to explain the principles of the present invention.

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for describing the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] In the accompanying drawings:

[0020] Figure 1 It is an observation diagram during the low-temperature period of the Chinese meteorological weather forecast in Example 1;

[0021] Figure 2 It is a picture of litchi leaves after 7 days of spraying the cold-resistant agent and water in the experimental group and the control group in Example 1;

[0022] Figure 3 It is a schematic diagram showing the influence of the experimental group and the control group on the chlorophyll fluorescence parameters of 'Nuomici' litchi in Example 1;

[0023] Figure 4 It is a schematic diagram showing the influence of the experimental group and the control group on the photosynthetic parameters of litchi in Example 2;

[0024] Figure 5 It is a schematic diagram showing the influence of the experimental group and the control group on the inflorescence situation of litchi in Example 2;

[0025] Figure 6Schematic diagram of the influence of the experimental group and the control group on the flowering period of litchi in Example 2;

[0026] Figure 7 Schematic diagram of the influence of the experimental group and the control group on the growth of 'Huaizhi' litchi in Example 2;

[0027] Figure 8 Schematic diagram of the influence of the experimental group and the control group on the chlorophyll fluorescence parameters of 'Huaizhi' litchi in Example 3;

[0028] Figure 9 Schematic diagram of the influence of the experimental group and the control group on the growth indexes of 'Huaizhi' litchi in Example 3. Detailed implementation mode

[0029] The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention. Without departing from the spirit and essence of the present invention, any modification or replacement of the methods, steps or conditions of the present invention belongs to the protection scope of the present invention. If not specifically specified, the experimental materials, reagents, instruments, etc. used in the embodiments of the present invention can be obtained commercially; if not specifically specified, all technical means in the embodiments of the present invention are conventional means well known to those skilled in the art.

[0030] A litchi cold-resistant agent provided by the present application includes vegetable oil, 1,4-butanediamine, 2,4-epibrassinolide and cyclohexanehexol. The preparation method is as follows: dissolve 2,4-epibrassinolide in alcohol to obtain an alcohol solution; dissolve vegetable oil, 1,4-butanediamine and cyclohexanehexol in deionized water respectively to obtain aqueous solutions; mix the alcohol solution and the aqueous solutions, and add a surfactant to prepare a litchi cold-resistant agent.

[0031] Among them, the raw materials of 1,4-butanediamine, 2,4-epibrassinolide and cyclohexanehexol are all solids. In actual preparation, according to the volume of the target cold-resistant agent, weigh the corresponding mass of 1,4-butanediamine, 2,4-epibrassinolide and cyclohexanehexol to ensure that the concentration of 2,4-epibrassinolide in the finally prepared cold-resistant agent is 1-3 mg / L, the concentration of 1,4-butanediamine in the cold-resistant agent is 0.05-0.07 mg / L, and the concentration of cyclohexanehexol in the cold-resistant agent is 4-6 mg / L.

[0032] Among them, the vegetable oil is a liquid. According to the volume of the target cold-resistant agent, measure a specific volume of vegetable oil to ensure that the volume of the vegetable oil in the cold-resistant agent is diluted to 140-160 times. Specific vegetable oil can be selected from any kind of vegetable oil in the prior art. In the present application, the concentration of the vegetable oil should not be too high or too low. When the concentration of the vegetable oil is too high or too low, the use effect of the cold-resistant agent will be affected.

[0033] Further, the cold-resistant agent in this application also includes a surfactant, and the concentration of the surfactant in the cold-resistant agent is 0.4-0.6 vol%, and the specific type of the surfactant can be Tween-20. Measure a specific volume of the surfactant according to the volume of the target cold-resistant agent to ensure that the concentration of the surfactant in the cold-resistant agent is 0.5 vol%.

[0034] The following further explains this application through specific examples:

[0035] Experimental Example 1

[0036] 1-1. Preparation of litchi cold-resistant agent:

[0037] First dissolve 2,4-epibrassinolide in alcohol to form an alcohol solution; mix vegetable oil, 1,4-diaminobutane, and cyclohexanehexol with water to form an aqueous solution; finally mix the alcohol solution and the aqueous solution together and add Tween-20 to prepare a litchi cold-resistant agent. The concentration of 2,4-epibrassinolide in the finally formed cold-resistant agent is 2 mg / L, the vegetable oil in the cold-resistant agent is diluted 150 times, the concentration of 1,4-diaminobutane in the cold-resistant agent is 0.06 mg / L, the concentration of cyclohexanehexol in the cold-resistant agent is 5 mg / L; the concentration of Tween-20 is 3 vol%.

[0038] 1-2. Experimental content:

[0039] This was carried out at the on-campus experimental base of South China Agricultural University in 2022. Eight litchi varieties 'Huaizhi' and 'Nuomici' with the same growth potential and the same size were selected respectively. Four of them were sprayed with the cold-resistant agent as the experimental group, and the remaining four were used as the control group. As Figure 1 shown, according to the Chinese meteorological weather forecast, natural low temperature was observed from February 18 to February 25. The experimental group of litchi was sprayed with the above cold-resistant agent solution within 24 hours before being affected by low-temperature cold damage, that is, sprayed on February 17, 2022.

[0040] The control group of litchi was sprayed with an equal amount of clear water on February 17, 2022. The leaf phenotypes and chlorophyll fluorescence parameters of the litchi varieties 'Huaizhi' and 'Nuomici' in the experimental group and the control group were measured respectively after low temperature (February 25) and three days of recovery (February 28).

[0041] 1-3. Experimental results: The leaf morphology of litchi in the control and treatment groups after experiencing low temperature

[0042] Figure 2 are pictures of litchi leaves seven days after spraying the cold-resistant agent and clear water on the experimental group and the control group. The leaf morphology of the litchi in the experimental group after treatment, compared with the control group, as Figure 2As shown (7 days after spraying), the litchi leaves sprayed with the cold-resistant agent are greener than the control, and the degree of leaf curling is reduced. Among them, after treatment with the cold-resistant agent, more anthocyanins are accumulated in the leaf veins of 'Huaizhi' compared with those treated with clear water, showing a red color. This phenomenon was not observed in 'Feizixiao', but the degree of leaf curling of 'Feizixiao' treated with the cold-resistant agent decreased significantly. This shows that spraying the cold-resistant agent has an obvious tendency to alleviate the degree of curling of litchi leaf morphology under low-temperature stress.

[0043] 1-4. Experimental results: Chlorophyll fluorescence imaging maps of litchi leaves of the control and treatment groups after experiencing low temperature and after low-temperature recovery

[0044] The maximum photochemical quantum yield of PSⅡ (Fv / Fm) represents the potential maximum photosynthetic chemical efficiency of the leaf photosystem II. The Fv / Fm of normal litchi leaves is about 0.75. Under stress environmental conditions, the Fv / Fm value gradually decreases. Therefore, the change in the Fv / Fm value of the leaf reflects the degree of inhibition of the leaf photosystem II. As Figure 3 shown, the chlorophyll fluorescence imaging map of 'Nuomici' litchi shows that after low temperature, the Fv / Fm value of the leaves treated with the cold-resistant agent is significantly stronger than that of the control (the bluer the fluorescence color, the larger the Fv / Fm value). At the same time, both Fo (initial fluorescence) and Fm (maximum fluorescence) are also stronger than those of the control group; after low-temperature recovery, we found that the Fv / Fm fluorescence of the 'Nuomici' leaves sprayed with the cold-resistant agent returned to normal (i.e., about 0.75), showing a significant difference from the control group (about 0.6 for the control group). This shows that the treatment with the cold-resistant agent has a significant enhancing effect on Fv / Fm of litchi leaves under low-temperature stress.

[0045] Experimental Example 2

[0046] 2-1. Preparation of litchi cold-resistant agent:

[0047] First, dissolve 2,4-epibrassinolide in alcohol to form an alcohol solution; mix vegetable oil, 1,4-diaminobutane, and cyclohexanehexol with water to form an aqueous solution; finally, mix the alcohol solution and the aqueous solution together and add Tween-20 to prepare the litchi cold-resistant agent. The concentration of 2,4-epibrassinolide in the finally formed cold-resistant agent is 2 mg / L, the vegetable oil in the cold-resistant agent is diluted 150 times, the concentration of 1,4-diaminobutane in the cold-resistant agent is 0.06 mg / L, the concentration of cyclohexanehexol in the cold-resistant agent is 5 mg / L; the concentration of Tween-20 is 3 vol%.

[0048] 2-2. Experimental content:

[0049] It was conducted at the on-campus experimental base of South China Agricultural University in 2023. Eight litchi varieties 'Huaizhi' and 'Feizixiao' with the same growth trend and size were selected respectively. Among them, 4 were sprayed with the cold-resistant agent as the experimental group; the remaining 4 were used as the control group. Among them, the experimental group was sprayed with the above-mentioned cold-resistant agent solution within 24 hours before the litchi suffered from low-temperature chilling injury, and the control group was sprayed with an equal amount of clear water within 24 hours before the litchi suffered from low-temperature chilling injury.

[0050] During the experiment, the temperature in the controlled greenhouse was set to 4°C to simulate the outdoor low temperature. After 7 days of low-temperature treatment, the low temperature was restored outside the controlled greenhouse. After 3 days of restoration, the photosynthetic indexes were measured, and the flowering period was counted later. Specifically, the photosynthetic parameters of the control group and the experimental group were measured, as well as the flowering situation of litchi in the later stage (flowering rate, main axis length, lateral axis length, number of small nodes).

[0051] 2-3. Experimental results: Photosynthetic parameters of litchi leaves in the control and treatment groups after low temperature and after low temperature recovery

[0052] As Figure 4 shown, from the photosynthetic rate (Pn), it can be seen that compared with the control group, the photosynthetic rates of the litchi varieties 'Huaizhi' and 'Feizixiao' treated with the cold-resistant agent decreased by 97.39% and 78.68% respectively, and still showed a downward trend after low temperature recovery, indicating that spraying the cold-resistant agent caused the stomata of litchi leaves to close and photosynthesis to weaken.

[0053] From the transpiration rate (Tr), it can be seen that compared with the control group, the transpiration rates of all varieties decreased. Thus, it can be known that the cold-resistant agent treatment has a significant inhibitory effect on the transpiration rate of litchi, and the decline is greater after low-temperature treatment than after low-temperature recovery.

[0054] From the intercellular carbon dioxide concentration (Ci), it can be seen that compared with the control group, 'Huaizhi' and 'Feizixiao' increased by 40.37% and 20.25% respectively. The increase amplitude of 'Feizixiao' was smaller, while that of 'Huaizhi' was more obvious, and it still showed an upward trend after low temperature recovery.

[0055] From the stomatal conductance (Gs), it can be seen that compared with the control group, the stomatal conductances of 'Huaizhi' and 'Feizixiao' both decreased significantly. Thus, it can be seen that spraying the cold-resistant agent reduced the stomatal conductance of litchi leaves, and it still showed a decreasing trend after low temperature recovery.

[0056] In summary, spraying the cold-resistant agent treatment has a significant effect on alleviating the low-temperature stress on the photosynthetic characteristics of litchi, and most likely improves the cold resistance of litchi by closing the stomata and reducing the photosynthetic rate to reduce energy consumption.

[0057] 2-4. Experimental results: Inflorescence situations of different litchi varieties in the control and treatment groups after low temperature

[0058] AsFigure 5 As shown in the figure, after the treatment with the cold-resistant agent, the number and length of the main axes of 'Huaizhi' both increased compared with the control group, and the number of leaflets decreased.

[0059] After the treatment with the cold-resistant agent, the lengths of the main axis and lateral axes of the inflorescence axis of 'Feizixiao' were higher than those of the control. Moreover, spraying the cold-resistant agent could more significantly promote the abscission of its primordial leaves and the differentiation of flower buds.

[0060] The results proved that spraying the cold-resistant agent before low temperature could not only effectively reduce the stress of low temperature on the litchi flower spikes, but also effectively promote the differentiation of litchi flower buds.

[0061] 2-5. Experimental results: The flowering situations of different litchi varieties in the control and treatment groups after experiencing low temperature

[0062] As Figure 6 shown, the flowering branch rates of litchi after the treatment with the cold-resistant agent were all higher than those of the control. The increase ranges were different for different varieties. Among them, that of 'Huaizhi' reached 58.67%, with an increase range of 23.33%. In the statistics of the leafy flowering branch rates, we found that there were differences in the changes of different varieties with or without spraying the cold-resistant agent. Both 'Huaizhi' and 'Feizixiao' decreased after the treatment, but the influence on 'Feizixiao' was significantly greater.

[0063] As Figure 7 shown, the lengths of the main axes of the two litchi varieties sprayed with the cold-resistant agent both increased compared with the control group. Moreover, the lengths of the lateral flower axes of the litchi treated with the cold-resistant agent also increased. For 'Feizixiao', the length of the lateral flower axis was 1.4 cm in the control and 15.33 cm after the treatment, an increase of nearly 10 times. However, the number of lateral axes of the litchi sprayed with the cold-resistant agent showed differences among varieties, that is, the number of 'Huaizhi' increased after the treatment, while that of 'Feizixiao' decreased after the treatment. Further statistics on the number of small nodes showed that the number of small nodes of the two litchi varieties sprayed with the cold-resistant agent both increased.

[0064] The results proved that the effect of spraying the cold-resistant agent before low temperature could even last until the flowering period and promote the flowering of litchi. This indicated that the compound agent could, to a certain extent, alleviate the influence of low temperature stress before the flowering period on the flowering of litchi.

[0065] Combined with the experimental results of Example 1 and Example 2, it can be seen that: As mentioned above, within 24 hours before the stress treatment, exogenous spraying of a compound mixed solution containing 2 mg / L 2,4-epibrassinolide, 150-fold diluted vegetable oil, 0.06 mg / L 1,4-diaminobutane, and 5 mg / L cyclohexanehexol (containing 3 vol% Tween-20 at the final concentration) could significantly improve its leaf photosynthetic performance, ensure the normal development of the litchi flower spikes in the later stage, reduce the influence of low temperature on the differentiation of litchi flower buds, reduce the yield loss caused by low temperature stress, and had a significant effect on alleviating the low temperature stress of litchi.

[0066] Experimental Example 3

[0067] 3-1. Preparation of lychee cold resistance agent:

[0068] Experimental group preparation: First dissolve 2,4-epibrassinolide in alcohol to form an alcohol solution; mix vegetable oil, 1,4-butanediamine, and cyclohexanehexol with water to form an aqueous solution; finally mix the alcohol solution and the aqueous solution together and add Tween-20 to prepare the lychee cold resistance agent. In the finally formed cold resistance agent, the concentration of 2,4-epibrassinolide is 2 mg / L, the vegetable oil in the cold resistance agent is diluted 150 times, the concentration of 1,4-butanediamine in the cold resistance agent is 0.06 mg / L, the concentration of cyclohexanehexol in the cold resistance agent is 5 mg / L; the concentration of Tween-20 is 3 vol%.

[0069] Control group 1 preparation: Dilute vegetable oil 150 times with deionized water to obtain Control group 1.

[0070] Control group 2 preparation: Mix vegetable oil and cyclohexanehexol with water to obtain Control group 2. The concentration of cyclohexanehexol in Control group 2 is 5 mg / L, and the vegetable oil is diluted 150 times.

[0071] Control group 3 preparation: First dissolve 2,4-epibrassinolide in alcohol to form an alcohol solution; mix vegetable oil and cyclohexanehexol with water to form an aqueous solution; finally mix the alcohol solution and the aqueous solution together and add Tween-20 to prepare Control group 3. In the finally formed Control group 3, the concentration of 2,4-epibrassinolide is 2 mg / L, the vegetable oil is diluted 150 times, the concentration of cyclohexanehexol in the cold resistance agent is 5 mg / L; the concentration of Tween-20 is 3 vol%.

[0072] Blank control group preparation: Deionized water with the same volume as the experimental example.

[0073] 3-2. Experimental content:

[0074] Conducted at the on-campus experimental base of South China Agricultural University in 2023. Select 16 lychee varieties 'Huaizhi' with the same growth trend and size. Among them, 4 are sprayed with the cold resistance agent in the experimental group; 4 are sprayed with Control group 1; 4 are sprayed with Control group 2; 4 are sprayed with Control group 3; 4 are sprayed with the blank control group.

[0075] During the experiment, the temperature in the controlled greenhouse was set to 4°C to simulate outdoor low temperature. After 7 days of low temperature treatment, the low temperature recovery was carried out outside the controlled greenhouse, and the photosynthetic indexes were measured after 3 days of recovery. Measure the chlorophyll fluorescence value of lychee leaves under low temperature, and measure the relevant indexes of lychee after the recovery temperature.

[0076] 3-3. Experimental results: Chlorophyll fluorescence value of lychee leaves under low temperature

[0077] The maximum photochemical quantum yield of PSⅡ (Fv / Fm) represents the potential maximum photosynthetic chemical efficiency of the leaf photosystem II. The change in the Fv / Fm value of the leaf reflects the degree of inhibition of the leaf photosystem II. As Figure 8 shown, the chlorophyll fluorescence imaging map of litchi shows that after low temperature treatment, the Fv / Fm value of the leaves treated with the cold-resistant agent is significantly stronger than that of the control (the bluer the fluorescence color, the larger the Fv / Fm value). At the same time, both Fo and Fm fluorescence are also stronger than that of the control. We found that there were significant differences between the cold-resistant agent T4 and other treatments. This indicates that the experimental group treatment has a significant enhancing effect on the Fv / Fm of litchi leaves under low temperature stress. At the same time, the effects of the control groups 1-3 are all worse than those of the experimental group.

[0078] 3-4. Experimental results: Effects on related indicators of litchi after low temperature treatment

[0079] As Figure 9 shown, in the figure, T1 represents the control group 1, T2 represents the control group 2, T3 represents the control group 3, T4 represents the experimental group, CK represents the blank control group; Fv / Fm represents the maximum photochemical quantum yield of PSⅡ; Pn represents the photosynthetic rate, Tr represents the transpiration rate; Ci represents the intercellular carbon dioxide concentration; Gs represents the stomatal conductance; REC represents the relative conductivity.

[0080] The cold-resistant agent in the experimental group has a significant effect on alleviating the photosynthetic characteristics of litchi under low temperature stress. The reason may be that by closing the stomata and reducing the photosynthetic rate, the energy consumption is reduced, thereby improving the cold resistance of litchi. The experiment proves that the cold-resistant agent of the present application formula can improve the cold resistance of litchi.

[0081] It can be understood that the above embodiments only represent the preferred embodiments of the present invention. The description is relatively specific and detailed, but it cannot be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. A litchi cold-resistant agent, characterized in that, it comprises vegetable oil, 1,4-butanediamine, 2,4-epibrassinolide and inositol; the concentration of 2,4-epibrassinolide in the cold-resistant agent is 2 mg / L, the vegetable oil in the cold-resistant agent is diluted 150 times, the concentration of 1,4-butanediamine in the cold-resistant agent is 0.06 mg / L, and the concentration of inositol in the cold-resistant agent is 5 mg / L.

2. The litchi cold-resistant agent according to claim 1, characterized in that, it further comprises a surfactant; the concentration of the surfactant in the cold-resistant agent is 0.4 - 0.6 vol%.

3. The litchi cold-resistant agent according to claim 2, characterized in that, the surfactant is Tween-20.

4. The litchi cold-resistant agent according to claim 2, characterized in that, the concentration of the surfactant in the cold-resistant agent is 0.5 vol%.

5. A preparation method of a litchi cold-resistant agent, characterized in that, it includes: dissolving 2,4-epibrassinolide in alcohol to obtain an alcohol solution; dissolving vegetable oil, 1,4-butanediamine and inositol in deionized water respectively to obtain aqueous solutions; mixing the alcohol solution and the aqueous solutions, and adding a surfactant to prepare a litchi cold-resistant agent; the concentration of 2,4-epibrassinolide in the cold-resistant agent is 2 mg / L, the vegetable oil in the cold-resistant agent is diluted 150 times, the concentration of 1,4-butanediamine in the cold-resistant agent is 0.06 mg / L, and the concentration of inositol in the cold-resistant agent is 5 mg / L.

6. An application of the litchi cold-resistant agent according to any one of claims 1 - 4 in litchi cold resistance and frost prevention.

7. The application according to claim 6, characterized in that, the litchi cold-resistant agent is sprayed on the leaves and / or branches of litchi.

8. The application according to claim 6, characterized in that, the applicable temperature of the litchi cold-resistant agent is -2°C - 4°C.

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