Application of exogenous compound chemical control measure in reduction of low-temperature early blossoming of tobacco

Abstract

The invention relates to an application of an exogenous compound chemical control measure in reducing low-temperature early blossoming of tobaccos, which comprises the following steps: spraying an exogenous compound measure solution after tobacco transplanting and before low-temperature cold injury comes; the exogenous composite chemical measure solution is a mixed solution of magnesium sulfate and salicylic acid. According to the invention, a low-temperature sensitive tobacco variety Yunyan 87 is adopted as an experimental material, and changes of phenotypes and physiological and biochemical indexes of Yunyan 87 seedling leaves under low-temperature stress and treatment of various allogenic materials are compared and analyzed, so that the effect of the composite measure on resistance to cold stress is proved. The low-temperature adversity resistance of tobacco seedlings is improved by spraying magnesium sulfate with proper concentration on the leaf surfaces of the tobacco seedlings, so that the growth state of the tobacco seedlings encountering low-temperature adversity stress in late spring is promoted to tend to be normal, the phenomena of frostbite and freezing death of the tobacco in the seedling stage after cold stress are reduced, the cold resistance of the tobacco in the seedling stage can be improved, and the yield of the tobacco is increased. In addition, the method has the advantages of being easy to operate, low in cost, obvious in effect and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of tobacco planting, and specifically to the application of exogenous compound chemical control measures in reducing early flowering of tobacco at low temperature. Background Art

[0002] Tobacco (Nicotiana tabacum L.) is a thermophilic crop originating from tropical and subtropical regions, which is relatively sensitive to environmental temperature changes and has poor tolerance to low temperature stress. Since tobacco seedlings are mostly raised in early spring, most southern tobacco-growing areas in China happen to have cold and rainy climates and meteorological conditions of low temperature and few sunshine hours, and tobacco seedlings are often damaged by "late spring cold snap". The "late spring cold snap" causes poor growth of tobacco plants during the "seedling recovery period and root extension period" and induces the occurrence of "early flowering", seriously affecting the yield and quality of tobacco leaves and also restricting the development of high-quality tobacco leaf production.

[0003] Tobacco seedlings experiencing low temperature will cause a series of harms: the temperature being too low may freeze the tobacco seedlings to death; low temperature stress leads to an extended seedling age and a postponed transplanting period, so that the high temperature forcing ripening in the later stage of field growth is serious, and it is easy to induce root and stem diseases such as tobacco bacterial wilt; the leaves of tobacco plants are the harvested organs, and low temperature will cause the reproductive growth of tobacco plants to advance, induce the phenomenon of early flowering, and lead to a decrease in the yield of tobacco leaves. At the same time, production practice has also proved that environmental temperature is the most critical ecological factor affecting the quality and flavor of tobacco leaves in different production areas of China. At present, although the main cultivated varieties such as K326 and Yunyan 87 promoted in production have relatively good comprehensive traits, their tolerance to low temperature environments is poor. To sum up, cold stress encountered by tobacco seedlings during the seedling stage will seriously affect the yield and quality of tobacco leaves, which is an important practical problem existing in flue-cured tobacco production in China.

[0004] In response to this practical problem that frequently occurs in tobacco production, there are currently the following several solutions. First, it can be improved through genetic improvement. By breeding new varieties with strong cold tolerance and utilizing them, the germplasm can be changed to achieve the purpose of increasing cold tolerance. However, at present, the tobacco germplasm with low-temperature tolerance required for genetic improvement is relatively scarce. At the same time, the breeding cycle is long, and to breed varieties with excellent cold tolerance, good agronomic traits, and high yields, a large amount of manpower, material resources, and financial resources are required. And because the existing supporting measures for tobacco planting and baking are already relatively complete, replacing varieties requires replacing a series of corresponding measures. Therefore, the feasibility of breeding and replacing new varieties in production is relatively low. For low temperature at the seedling stage, most crops will adopt some agronomic measures to alleviate it, including increasing the application of base fertilizers and reducing field waterlogging. Some vegetables will adopt measures such as building warm greenhouses. However, these measures generally require a large amount of manpower and material resources input. And due to the uncertainty of low-temperature weather, rashly carrying out such agronomic measures may not achieve good results and may instead cause waste of production materials. Therefore, there is an urgent need for a simple, convenient, low-cost, and effective cold resistance measure for tobacco seedlings in tobacco production. Summary of the Invention

[0005] The purpose of the present invention is to provide a prevention and control measure for reducing the cold damage loss of tobacco and reducing the phenomenon of early flowering to solve the problems raised in the above background technology.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] An exogenous compound chemical control measure,

[0008] After transplanting tobacco and before the advent of low-temperature cold damage, spray the solution of the exogenous compound measure; the solution of the exogenous compound chemical measure is a mixed solution of magnesium sulfate and salicylic acid.

[0009] The spraying amount is 12 - 15 mL per plant for tobacco at the transplanting stage.

[0010] The spraying degree is that the solution forms beads on the tobacco leaves but does not flow down in a stream.

[0011] The spraying frequency is 1 - 3 times before the cold damage comes, once a day.

[0012] The low-temperature range for spraying is 1°C to 15°C.

[0013] In the mixed solution of magnesium sulfate and salicylic acid, the magnesium sulfate is a mixed solution of magnesium sulfate heptahydrate and ultrapure water, and the salicylic acid is a salicylic acid solution in absolute ethanol or 95% ethanol.

[0014] The mixed solution of magnesium sulfate and salicylic acid is a mixed solution of a salicylic acid solution with a concentration of 1 mmol / L and a magnesium sulfate solution with a concentration of 0.5%.

[0015] The preparation method of the spraying solution is to dissolve 0.15 g of salicylic acid solid and 5 g of magnesium sulfate heptahydrate solid in every 1 L of water, and the salicylic acid solid is dissolved with 0.2 mL of absolute ethanol.

[0016] In the prepared exogenous composite chemical measure solution, a surfactant is mixed in. The surfactant is Tween-20 mixed in by volume at 0.1%.

[0017] The spraying time is before 10:00 am or after 4:00 pm every day.

[0018] It is preferably sprayed on cloudy days.

[0019] The preparation time of the mixed solution of magnesium sulfate and salicylic acid is more than 24 hours from the spraying time. This can avoid leaf burning after application caused by insufficient dissolution. Other methods that can make the solution dissolve evenly can also be adopted.

[0020] Beneficial effects:

[0021] When tobacco seedlings encounter continuous low temperature (≤13°C for more than 2 days) from the 6-12 true leaf stage to about 10 days after transplanting, it will accelerate flower bud differentiation and force the tobacco plants to enter reproductive growth prematurely. The combination of low temperature and short sunshine will exacerbate the occurrence of early flowering.

[0022] Based on production practice and combined with laboratory and field test results, the present invention proves that by spraying an appropriate concentration of magnesium sulfate on the leaves of tobacco seedlings, the cold stress resistance of tobacco seedlings can be improved, so as to promote the growth state of tobacco seedlings suffering from "late spring cold" cold stress to tend to be normal, reduce the frostbite and freezing death phenomena of tobacco seedlings after cold stress, and has the characteristics of simple operation, low cost and obvious effect. It has good application prospects and potential in tobacco production and can effectively avoid the occurrence of low temperature and early flowering in tobacco plants.

[0023] Magnesium sulfate enhances the low temperature adaptability of tobacco by stabilizing the chloroplast structure (maintaining the chlorophyll content) and enhancing root activity; salicylic acid induces the expression of stress-resistant proteins and reduces the membrane lipid peroxidation caused by low temperature (the MDA content is reduced by 15%-20%);

[0024] Magnesium sulfate heptahydrate can increase the magnesium ion concentration and relieve magnesium deficiency caused by low temperature. Salicylic acid activates the calcium signaling pathway and synergistically regulates the expression of low temperature response genes. After compound use, it can also reduce the electrolyte leakage rate induced by low temperature.

[0025] The exogenous magnesium sulfate solution significantly reduces the direct damage of low temperature to tobacco leaves and reduces the frostbite area. Its compound application with the salicylic acid solution can further improve the effect. Brief Description of the Drawings

[0026] To more clearly illustrate the solutions in this application, the following provides a brief introduction to the drawings required for the description of the embodiments of this application. Obviously, the drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 Phenotypes of each treatment after 3 days of cold stress treatment with exogenous salicylic acid;

[0028] Figure 2 Statistics of the number of wilted leaves of each treatment after 3 days of cold stress treatment with exogenous salicylic acid;

[0029] Figure 3 Phenotypes of each treatment after 3 days of cold stress treatment with exogenous magnesium sulfate;

[0030] Figure 4 Statistics of the number of wilted leaves of each treatment after 3 days of cold stress treatment with exogenous magnesium sulfate;

[0031] Figure 5 Frostbite phenotypes of each treatment after 3 days of recovery;

[0032] Figure 6 Cold tolerance phenotypes of different treatments after 3 days of cold stress;

[0033] Figure 7 Electrical conductivity of each treatment after 3 days of cold stress;

[0034] Figure 8 Antioxidant enzyme activities of each treatment after 3 days of cold stress. Detailed Description of the Embodiments

[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the description of the embodiments of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the description and claims of this application or the above drawings are used to distinguish different objects and are not used to describe a specific order.

[0037] References to "embodiments" in this document mean that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase may not necessarily refer to the same embodiment at every occurrence in the specification, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0038] To enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0039] An exogenous compound chemical control measure and its application

[0040] After tobacco transplantation and before the advent of low-temperature cold damage, spray the solution of the exogenous compound measure; the solution of the exogenous compound chemical measure is a mixed solution of magnesium sulfate and salicylic acid, and the spraying amount is 12 - 15 mL per transplanted tobacco plant; the spraying degree is that the liquid forms beads on the tobacco leaves but does not flow down in streams; the spraying frequency is 1 - 3 times before the cold damage comes, once a day; the applicable low-temperature range for spraying is 1°C to 15°C.

[0041] For the mixed solution of magnesium sulfate and salicylic acid, the magnesium sulfate is a mixed solution of magnesium sulfate heptahydrate in ultrapure water, and the salicylic acid is a salicylic acid solution in absolute ethanol or 95% ethanol. The mixed solution of magnesium sulfate and salicylic acid is a mixed solution of a salicylic acid solution with a concentration of 1 mmol / L and a magnesium sulfate solution with a concentration of 0.5%.

[0042] In the configured solution of the exogenous compound chemical measure, a surfactant is mixed, and the surfactant is 0.1% Tween-20 mixed by volume. The spraying time is before 10:00 am or after 4:00 pm every day. It is preferably sprayed on cloudy days.

[0043] The preparation time of the mixed solution of magnesium sulfate and salicylic acid is more than 24 hours from the spraying time. This can avoid leaf burning after application caused by insufficient dissolution. Other methods that can make the solution dissolve evenly can also be adopted.

[0044] Explain the effects and principles of the mixed solution of exogenous magnesium sulfate and salicylic acid based on the experimental process.

[0045] Example 1 Improvement of tobacco cold tolerance by exogenous salicylic acid at different concentrations

[0046] Cultivation of tobacco seedlings: Select tobacco seeds of the same size and plumpness harvested at the same time. After sterilizing and disinfecting with 75% alcohol for 1 minute,

[0047] Sterilized tobacco seeds were sown using the water seeding method into 50-well trays filled with nutrient soil that had been sterilized at high temperature. The amount of seeds in each well was controlled at 3 - 4 seeds. After the substrate soil had fully absorbed water, the lid was covered to keep warm and moist, and it was placed in an incubator to germinate.

[0048] When the tobacco seeds germinated until the cotyledons were fully expanded, they were transplanted to seedling pots filled with seedling substrate. The temperature of the incubator was set at 26°C / 24°C, the humidity was set at 40%, the light intensity was 10000 Lx, and the photoperiod was set to 16 h of light and 8 h of darkness for continued cultivation.

[0049] When the tobacco seedlings grew to the three-leaf-one-heart to four-leaf-one-heart stage, that is, the cold-sensitive period of tobacco, tobacco seedlings with consistent growth vigor were selected for standby.

[0050] Application of exogenous magnesium sulfate: Weigh 0.5 g, 1 g, and 2 g of magnesium sulfate heptahydrate, dissolve them in ultrapure water, and transfer them to 100 mL volumetric flasks for volume fixation respectively. After volume fixation, add 100 μL of Tween-20 to each, mix well, and let stand overnight for use.

[0051] Three days before cold treatment, 16 tobacco seedlings with consistent growth vigor of each treatment and each variety were selected, and different concentrations of magnesium sulfate were applied from 8 am to 10 am every day for 3 days, with a total of 3 treatments. The spraying should be uniform and comprehensive to ensure that the spraying solution is evenly distributed on each leaf. Before spraying, each spraying solution needs to be remixed, and the control group was sprayed with ultrapure water.

[0052] Cold stress treatment: After three days of spraying, the temperature of the incubator was adjusted to 4°C / 4°C, the light intensity was 10000 Lx, and the photoperiod was set to 16 h of light and 8 h of darkness for cold stress treatment.

[0053] To explore the actual effect of different concentrations of exogenous salicylic acid on cold stress, the cold-tolerant variety 'NC567' and the cold-sensitive variety 'Taiyan 8' in tobacco germplasm were selected as materials, and 5 exogenous salicylic acid concentrations of water (CK), 0.25 mmol / L, 0.5 mmol / L, 1 mmol / L, and 1.5 mmol / L were set, and cold stress treatment was carried out three days after spraying ( Figure 1 ), and then the number of wilted leaves of each treatment was counted three days after cold stress ( Figure 2 ).

[0054] It can be intuitively found from the phenotypic and number of wilted leaf data that, firstly, the cold tolerance of tobacco variety 'NC567' is significantly better than that of tobacco variety 'Taiyan 8', which can be clearly seen from the number of wilted leaves and phenotypes. Compared with the group sprayed with clear water, exogenous salicylic acid at three concentrations from low to high all improved the cold tolerance of the above two tobacco varieties at the seedling stage, and this improvement in cold tolerance showed an obvious trend with the change of concentration. Whether the concentration is too low or too high, it will affect the improvement effect. At the optimal concentration (1 mmol / L), exogenous salicylic acid significantly reduced the number of wilted leaves of tobacco seedlings at the seedling stage and improved its cold tolerance ability.

[0055] Example 2 Improvement of Tobacco Cold Tolerance by Different Concentrations of Exogenous Magnesium Sulfate

[0056] Cold stress recovery: After seven days of cold treatment, the culture conditions were adjusted to 26°C / 24°C, the humidity was set to 40%, the light intensity was 10000 Lx, and the photoperiod was set to 16 h of light and 8 h of darkness for recovery.

[0057] To explore the actual effect of different concentrations of exogenous magnesium sulfate on cold stress, the cold-tolerant variety 'NC567' and the cold-sensitive variety 'Taiyan 8' in tobacco germplasm were selected as materials, and four exogenous magnesium sulfate concentrations of clear water, 0.5% (CK), 1%, and 2% were set, and cold stress treatment was carried out three days after spraying ( Figure 3 ), and then the number of wilted leaves of each treatment was counted three days after cold stress ( Figure 4 ).

[0058] It can be intuitively found from the phenotypic and number of wilted leaf data that, compared with the group sprayed with clear water, exogenous magnesium sulfate at three concentrations from low to high all improved the cold tolerance of the above two tobacco varieties at the seedling stage. However, this improvement does not increase with the increase of concentration. Instead, spraying exogenous magnesium sulfate at a low concentration (0.5%) has a more obvious and significant improvement ability compared with spraying clear water and other concentration magnesium sulfate groups.

[0059] At the same time, after 7 days of cold treatment and 2 days of recovery, phenotypic observation of cold stress recovery was carried out, and it was obvious that, compared with spraying clear water, exogenous magnesium sulfate could reduce the frost damage area on tobacco leaves after cold stress ( Figure 5 ).

[0060] Example 3 Effects of Different Exogenous Substances on Tobacco Cold Tolerance

[0061] Extraction of crude enzyme solution: Weigh 0.1 g of fully developed functional leaves, quickly grind them into powder in a pre-cooled mortar with liquid nitrogen added, add 1 mL of phosphate buffer solution with a concentration of 150 mM / L and pH = 7.8 pre-cooled at 4°C, transfer the homogenate into a 2 mL centrifuge tube, and centrifuge at 12,000 rpm for 15 minutes at 4°C. The supernatant is the crude enzyme extract. Aliquot the obtained supernatant and store it in a low-temperature refrigerator at 4°C for later use.

[0062] To explore the effects of different types of exogenous chemical measures on the cold tolerance of tobacco seedlings, as well as to explore the actual effects of magnesium sulfate on the cultivated variety 'Yunyan 87' and the interactions between different chemical substances, we selected two other exogenous chemical substances (SA, CaNO3) commonly used to improve cold tolerance besides magnesium sulfate. Four spraying measures other than magnesium sulfate were formulated for comparison.

[0063] Start the experimental treatment. A total of 5 groups are set: namely CK (spraying sterilized water), SA (spraying 1 mmol / L salicylic acid), Mg (spraying 0.5% magnesium sulfate), Ca (spraying 30 mmol / L calcium nitrate), SA+Mg (spraying a mixture of 1 mmol / L salicylic acid and 0.5% magnesium sulfate), SA+Ca (spraying a mixture of 1 mmol / L salicylic acid and 30 mmol / L calcium nitrate). The cultivation method, solution preparation, and cold stress treatment conditions are the same as those in Example 1. The experimental variety is 'Yunyan 87'.

[0064] Perform cold treatment at 4°C three days after spraying, and collect phenotypes three days after cold treatment. It can be clearly found that compared with CK, the four exogenous chemical substance treatments formulated significantly improved the cold tolerance of tobacco ( Figure 6 ). After statistically analyzing the electrical conductivity of each treatment, it was found that compared with CK, after spraying SA+Mg, the electrical conductivity of tobacco seedlings after low-temperature stress was significantly lower than that of CK, and compared with the single spraying measures of SA, Ca, and Mg, SA+Mg had a more significant improvement in cold tolerance ( Figure 7 ).

[0065] At the same time, to better explore and compare the effects of each treatment on cold tolerance, the activities of three antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), of each treatment after 3 days of cold stress were also statistically analyzed ( Figure 8 ). It was found that compared with CK, the SA+Mg treatment significantly improved the activities of antioxidant enzymes, and the high activities of antioxidant enzymes well explained the improvement of tobacco cold tolerance. And compared with the single measures, the combined measures had more obvious effects, which explained from a physiological perspective the reason for the significant improvement of cold tolerance by the combined measures.

[0066] Example 4 Exogenous compound chemical measures can alleviate the damage of tobacco seedlings under freezing injury

[0067] This example was carried out on January 15, 2025, in the tobacco-growing area of Jiaoling County, Meizhou City, Guangdong Province. The tested variety was 'Yunyan 87'. Tobacco seedlings are transplanted at the beginning of each year in Jiaoling County. After transplantation, the tobacco seedlings are often affected by low temperatures, which affects the growth of tobacco. In some cases, extreme low temperatures can cause large areas of tobacco seedlings to be frostbitten and die. On January 15, 2025, Jiaoling County suffered extreme low temperatures after transplantation. The lowest temperatures in the two days after transplantation were 2°C and 3°C respectively. In the experimental setup, six field treatments were set up, namely spraying clear water, SA, MgSO4, CaNO3, SA+MgSO4, and SA+CaNO3 after transplantation. Each treatment had three replicates. The concentration and preparation of the spraying solution were the same as in Example 2, and only one spraying was carried out. And the statistics of frostbite and death of tobacco seedlings were carried out when large-scale replanting was carried out seven days after transplantation (Table 1).

[0068] Table 1 Statistics of frostbite and death rates of different treatments

[0069]

[0070] It can be clearly found from the statistical data that extreme low temperatures have a great impact on tobacco production in the tobacco-growing area, and the subsequent replanting caused by severe low temperatures brings too much manpower and economic damage to production, which is an important factor endangering tobacco production. According to the total statistical table (Table 2), it can be found that compared with CK, each treatment reduced the frostbite rate and death rate of tobacco seedlings under cold stress. Among them, the spraying of exogenous salicylic acid compounded with magnesium sulfate was the most obvious, with the death rate reduced by 8.77% and the frostbite rate reduced by 22.81%. The implementation is simple and the effect is remarkable.

[0071] Table 2 Total statistics of frostbite and death rates of different treatments

[0072] Freezing injury rate Frost injury rate Fresh water 21.05％ 64.04％ SA 17.54％ 44.74％ MgSO4 14.91％ 42.11％ CaNO3 17.54％ 54.39％ SA + MgSO4 12.28％ 41.23％ SA + CaNO3 21.05％ 57.02％

[0073] Meanwhile, taking 1000 seedlings per mu, spraying 14 mL per single plant, and 14 L spraying solution per mu as the standard, the cost of single spraying for each treatment and common antifreeze agents on the market was calculated (Table 3). It can be found that compared with other antifreeze agents sold on the market, although the cost of the exogenous compound chemical measure (SA + MgSO4) is higher than that of single application of magnesium sulfate or salicylic acid, it is still low-cost compared with other measures, and the effect has been verified. The test results are significant, with an obvious alleviating effect on the freezing injury and freezing death rate, and there are actual field data and laboratory data for certification, while there is no clear test data support for the products on the market. Moreover, the configuration of the exogenous compound chemical measure (SA + MgSO4) designed by us is more convenient, easy to calculate, and the chemical substances used as raw materials are not subject to control and are convenient to purchase. It is a new exogenous compound chemical spraying measure that meets the requirements of simple operation, obvious effect, and economic affordability for reducing low-temperature damage to tobacco seedlings at the seedling stage.

[0074] Table 3 Economic cost calculation of different exogenous chemical prevention and control measures

[0075] Note: All the above products are mainly purchased directly from regular channels.

[0076] Example 5 The exogenous compound chemical measure can promote growth and inhibit the early flowering phenomenon after the seedlings are exposed to low temperature.

[0077] This example was transplanted to the tobacco-growing area of Dapu County, Meizhou City, Guangdong Province on January 29, 2024, and the corresponding exogenous chemical measures were sprayed after transplantation. The tested variety was 'Yunyan 87'. The data during the vigorous growth period (before topping) were statistically analyzed on March 19, 2024, and the data after topping (before harvesting) were statistically analyzed on May 6, 2024. The Meizhou tobacco-growing area was also affected by low temperature in 2024. Different from the extreme freeze injury in 2025, the main problem in 2024 was long-term continuous low temperature, which also led to the occurrence of early flowering in some tobacco-growing areas in Meizhou in 2024.

[0078] To further understand the effects of different cold tolerance measures on the growth and development of tobacco and the early flowering phenomenon, in this example, during the approximate vigorous growth period (before topping), the agronomic traits and the number of budding plants of six different exogenous chemical substance treatments (CK, SA, MgSO4, CaNO3, SA + MgSO4, SA + CaNO3) were statistically analyzed (Table 4). It can be clearly seen from the data that the exogenous chemical measures all improved the growth potential of tobacco to a certain extent from the seedling stage to the vigorous growth period. Among them, the promoting effect of the exogenous compound chemical measure (SA + MgSO4) formulated in this patent was the most obvious. And through the budding rate comparison with CK, it was found that the exogenous compound chemical measure significantly delayed the budding period and reduced the budding rate in the same period. The reduction degree was obvious, reaching 33.83% compared with CK.

[0079] Meanwhile, in order to better evaluate the effects of different exogenous measures in reducing early flowering, in this embodiment, the agronomic traits before harvesting after topping were also statistically analyzed (Table 5). From the data of the number of effective leaves, it can be found that compared with the CK, spraying the exogenous composite chemical measure (SA + MgSO4) effectively reduced the occurrence of early flowering, maintained the number of effective leaves at a relatively normal level in production, reduced economic damage, and ensured the safety of tobacco production.

[0080] Table 4 Statistical analysis of agronomic traits of different exogenous chemical measures during the vigorous growth period

[0081]

[0082] Table 5 Statistical analysis of agronomic traits of different exogenous chemical measures during the mature period

[0083] In summary, starting from the actual production requirements, this invention conducts research through laboratory simulation and finally verifies it through actual production, and formulates a new, economical, simple-to-operate, and effective method for reducing low-temperature damage and inhibiting early flowering of tobacco seedlings in the seedling stage by using exogenous composite chemical measures.

[0084] Obviously, the above-described embodiments are only a part of the embodiments of this application, rather than all of them. The preferred embodiments of this application are shown in the drawings, but they do not limit the patent scope of this application. This application can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of this application more thorough and comprehensive. Although this application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing specific embodiments, or perform equivalent replacements on some of the technical features. Any equivalent structure directly or indirectly using the content of this application's specification and drawings in other related technical fields shall be within the scope of the patent protection of this application by the same token.

Claims

1. An exogenous compound chemical control measure, characterized in that: After transplanting tobacco, before the advent of low-temperature cold damage, spray the solution of the exogenous compound measure; the spraying solution of the exogenous compound chemical measure is a mixed solution of magnesium sulfate and salicylic acid. The spraying amount is 12 - 15 mL per transplanted tobacco plant. The spraying degree is that the spraying solution forms beads and aggregates on the tobacco leaves but does not flow down in a stream. The spraying frequency is 1 - 3 times before the cold damage comes, once a day. The applicable temperature range for spraying to enhance cold tolerance is that the ambient temperature is 1℃ - 15℃.

2. The exogenous compound chemical control measure according to claim 1, characterized in that: For the mixed solution of magnesium sulfate and salicylic acid, the magnesium sulfate is a mixed solution of magnesium sulfate heptahydrate in ultrapure water, and the salicylic acid is a salicylic acid solution in anhydrous ethanol or 95% ethanol.

3. The exogenous compound chemical control measure according to claim 2, characterized in that: The mixed solution of magnesium sulfate and salicylic acid is a mixed solution of a salicylic acid solution with a concentration of 1 mmol / L and a magnesium sulfate solution with a concentration of 0.5%.

4. The exogenous compound chemical control measure according to claim 2, characterized in that: The preparation method of the spraying solution is to dissolve 0.15 g of salicylic acid solid and 5 g of magnesium sulfate heptahydrate solid in 1 L of water, and the salicylic acid solid is dissolved with 0.2 mL of anhydrous ethanol.

5. The exogenous compound chemical control measure according to claim 1, wherein: In the prepared exogenous compound chemical measure solution, a surfactant is mixed, and the surfactant is mixed with 0.1% of Tween-20 by volume.

6. The exogenous compound chemical control measure according to claim 1, characterized in that: The spraying time is before 10 am or after 4 pm every day.

7. An exogenous compound chemical control measure according to claim 6, characterized in that: It is preferably sprayed on cloudy days.

8. An exogenous compound chemical control measure according to claim 1, characterized in that: The preparation time of the mixed solution of magnesium sulfate and salicylic acid is 24 hours ahead of the spraying time.

9. Application of the exogenous compound chemical control measure according to any one of claims 1 to 8 in reducing early flowering of tobacco caused by low temperature.

Images