Application of melatonin in improving plant resistance to lead stress

Abstract

The invention relates to the technical field of tea tree planting, and specifically to the application of melatonin in improving plant resistance to lead stress; the plant is a plant of the family Theaceae; the improving plant resistance to lead stress includes: alleviating the wilting, yellowing and falling of plant leaves under lead stress, reducing the lead content of mature plant leaves; increasing the SPAD value of plant leaves under lead stress, and increasing the total phenol, flavonoid and anthocyanin content of plant leaves under lead stress. The invention has the beneficial effects of significantly reducing the lead content in tea trees, reducing the harm of lead to tea trees, ensuring the safe use of tea leaves, and improving the quality index of tea leaves and improving the quality of tea leaves.

Description

Technical Field

[0001] The invention relates to the technical field of tea tree planting, and in particular to application of melatonin in improving plant resistance to lead stress. Background Art

[0002] Heavy metal pollution is one of the most widespread and harmful environmental problems today. In recent years, food pollution caused by excessive heavy metals in cultivated soil has become increasingly serious, causing serious economic losses. Many heavy metals in the soil (such as Cu, Zn, etc.) are essential trace elements for plants and play a very important role in plant growth and development. However, when the heavy metals in plants are excessive and exceed a certain critical value, they will have a stress effect on the plants, causing disorders in their metabolic processes, inhibiting their growth and development, and even causing the plants to wither and die. Some heavy metal elements (such as Hg, Cd, Pb, etc.) are non-essential elements for plants, and trace amounts will be toxic to plants.

[0003] Among the many heavy metal elements, lead has been used by humans for thousands of years due to its low melting point, easy processing, corrosion resistance, and ability to absorb radiation. Mining, metallurgy, electroplating, and the production and use of lead-containing paints, paper, gasoline, explosives, sludge, pesticides, etc., have discharged a large amount of lead into the environment. Therefore, plants that cannot "move autonomously" will inevitably be poisoned by lead pollution, which in turn endangers human health through the food chain. When plants are exposed to lead stress, even at very low concentrations, they can show symptoms of poisoning, such as changes in membrane permeability, disruption of enzyme activity, mitosis blockage, DNA damage, and changes in other physiological processes. However, the toxic effects of lead on plants vary with lead concentration, plant species, plant development stage, etc. Plants absorb lead and transfer and accumulate it to the aboveground parts through a series of physiological and biochemical processes, including activation of metal ions in rhizosphere soil, adsorption and diffusion on the surface of root cells, transport across the plasma membrane of root tissue cells, lateral transport in the cortical cells of root tissue, loading from the pith parenchyma cells of root tissue to the xylem vessels, long-distance transport to the aboveground parts through the xylem, unloading from the xylem to the leaf cells (transport across the leaf cell membrane), distribution and compartmentalization within leaf cells, etc.

[0004] The development of modern molecular biology and biotechnology has made it possible for people to reveal the absorption, transport, accumulation and detoxification mechanisms of lead ions in plants at the molecular level. In the past decade, researchers have always focused on the genes and transport proteins related to plant absorption and accumulation of lead, and have made some progress, but there is still a lack of sufficient understanding of the functions and regulatory molecular mechanisms of these genes and proteins. Therefore, researchers still need to conduct in-depth research on the material basis and molecular mechanism of plant absorption, transport, accumulation, storage, tolerance and detoxification of lead to clarify the key process of lead absorption by crops and control the accumulation of lead in grains, vegetables, etc.; and provide guidance for isolating and cloning genes related to lead hyperaccumulation, cultivating efficient remediation plants, and providing ideal materials for the remediation of lead-contaminated soils.

[0005] Melatonin, chemically known as N-acetyl-5-methoxytryptamine, is a relatively conservative indoleamine compound. Lerner et al. first extracted and detected melatonin from the pineal gland of cattle in 1958, so it is also called pinealogen. Studies have found that melatonin is widely involved in many physiological processes of animals, including regulating the circadian rhythm, hormone secretion, and cell aging and death of animals. In 1995, scientists detected melatonin in plants, thus opening the door to the study of melatonin in plants.

[0006] Melatonin is an indole derivative. Its precursor substance for the synthesis of auxin (IAA) is tryptophan, and both have similar physiological functions. Existing studies have shown that melatonin can promote the germination of plant seeds, root growth, axillary bud differentiation, and the growth and development of reproductive organs (flowers and fruits), and can increase the activity of antioxidant enzymes in plant leaves under low temperature conditions, increase the content of antioxidant substances, reduce the content of H2O2, and improve the resistance of plants to low temperatures. However, there are no reports on the research of melatonin alleviating lead stress in tea plants in the prior art. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art, and proposes the application of melatonin in improving the resistance of plants to lead stress. The application of melatonin to tea trees can significantly reduce the lead content in tea trees, reduce the harm of lead to tea trees, and improve the quality index of tea leaves, which is beneficial to ensuring the nutritional quality of tea leaves and the safe use of tea leaves, and ensuring the health of drinkers; the present invention also provides a method for improving the resistance of plants to lead stress, which can be applicable to the cultivation and management of tea trees in tea gardens under lead stress conditions.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The invention provides application of melatonin in improving the resistance of Theaceae plants to lead stress.

[0010] Theaceae is a family of the dicotyledonous plant class, the subclass Pentacarpus, and most of them are evergreen woody plants. There are about 30 genera and 750 species, mainly distributed in the subtropical and tropical regions of Asia. There are 15 genera and 500 species in China. Theaceae plants have important economic value. Theaceae plants have many uses, such as eating, drinking, viewing, timber utilization, skin care, beauty, and fertilizer production. For example, the young leaves of many teas in the tea group can be processed into tea leaves and used to prepare beverages.

[0011] More preferably, the Theaceae plant is Zijuan and / or Longjing 43.

[0012] Furthermore, the use of melatonin in improving the resistance of Theaceae plants to lead stress includes: alleviating the wilting, yellowing and falling of plant leaves under lead stress, and reducing the lead content of mature leaves of plants.

[0013] Furthermore, the use of melatonin in improving the resistance of Theaceae plants to lead stress includes: reducing the membrane permeability of plant leaves under lead stress.

[0014] Furthermore, the use of melatonin in improving the resistance of Theaceae plants to lead stress also includes: increasing the SPAD value of plant leaves under lead stress, and increasing the total phenol, flavonoid and anthocyanin content of plant leaves under lead stress.

[0015] SPAD value, that is, the leaf chlorophyll content measured by a chlorophyll meter, is an important indicator for measuring the photosynthetic capacity of plant leaves. In tea production, the SPAD value is used to evaluate the nitrogen nutritional status of tea, which indirectly reflects the growth status and potential quality of tea. Existing studies have shown that there is a certain positive correlation between the SPAD value of tea and its yield and quality, which means that tea with a higher SPAD value may have better growth status and higher yield. ‌

[0016] More preferably, during application, a melatonin aqueous solution or a preparation containing melatonin is applied to plants poisoned by lead stress, and the concentration of the applied melatonin is 100-200 µmol / L.

[0017] The present disclosure also provides a method for improving plant resistance to lead stress, comprising: applying a melatonin aqueous solution or a preparation containing melatonin to a plant poisoned by lead stress; in the melatonin aqueous solution or the preparation containing melatonin, the concentration of melatonin is 100-200 µmol / L; and the plant is a plant of the Theaceae family.

[0018] In a preferred embodiment of this scheme, the application method is foliar spraying.

[0019] In a preferred embodiment of the present scheme, the plants are planted hydroponically, the spraying frequency is once a day, the spraying time is after sunset, and the spraying degree is based on water dripping from the leaves.

[0020] Further preferably, when the planting method is hydroponics, the concentration of spraying melatonin is 100 µmol / L.

[0021] In a preferred embodiment of the present scheme, the plants are planted in the field, the spraying frequency is once a week, the spraying time is after sunset, and the spraying degree is based on the dripping of leaves.

[0022] Further preferably, when the planting method is field planting, the concentration of melatonin sprayed is 100-200 µmol / L.

[0023] In a preferred embodiment of the present scheme, the plant is planted in the field; the application method is: pouring a melatonin aqueous solution or a preparation containing melatonin into the soil containing lead ions; adding melatonin to irrigation water and applying it using an irrigation system, which is convenient for application and is convenient for large-scale tea garden cultivation and management;

[0024] Beneficial effects of the present invention: The present invention provides an application of melatonin in improving plant resistance to lead stress; melatonin is applied to the plants of the Theaceae family to alleviate the wilting, yellowing and falling of plant leaves under lead stress, reduce the lead content of mature leaves of plants, increase the SPAD value of plant leaves under lead stress, improve the photosynthesis efficiency of tea plants, and increase the total phenol, flavonoid and anthocyanin content of plant leaves under lead stress;

[0025] Based on the above technical advantages, the present disclosure also provides a method for improving plant resistance to lead stress, wherein a melatonin aqueous solution is applied to plants poisoned by lead stress; experiments have shown that the application of melatonin can significantly reduce the amount of lead accumulation and ensure the healthy growth of tea trees, which is beneficial to ensuring the nutritional quality of tea leaves and the safe use of tea leaves, and ensuring the health of drinkers; the method for improving plant resistance to lead stress disclosed in the present disclosure can be foliar spraying of a melatonin aqueous solution, or can be sprayed with a field watering system, which greatly facilitates its promotion and application in large-scale tea gardens, improves convenience, and can be applicable to the cultivation and management of tea trees in tea gardens under lead stress conditions; the melatonin concentration range for foliar spraying in the field is preferably 100-200 μM, and the melatonin concentration range for field irrigation is preferably 200 μM;

[0026] In addition, the present invention also reduces the permeability of tea cell membranes, making the cell membranes more stable, which can effectively extend the shelf life of tea leaves, making the tea leaves more capable of maintaining integrity and freshness during transportation, and further helping to improve the quality of tea products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a comparison diagram of tea seedling phenotypes before and after the hydroponic Longjing 43 treatment according to Example 1 of the present invention;

[0028] Figure 2 This is a comparison chart of the lead content in the leaves of hydroponic Longjing 43 before and after treatment according to Example 1 of the present invention;

[0029] Figure 3 This is a comparison chart of the SPAD values ​​of the hydroponic Longjing 43 of Example 1 of the present invention;

[0030] Figure 4 This is a comparison chart of the total phenol content of Longjing 43 grown in water in Example 1 of the present invention;

[0031] Figure 5 This is a comparison chart of flavonoid content in hydroponic Longjing 43 of Example 1 of the present invention;

[0032] Figure 6 This is a comparison chart of anthocyanin content in hydroponic Longjing 43 of Example 1 of the present invention;

[0033] Figure 7 This is a comparison diagram of tea seedling phenotypes before and after the hydroponic Zijuan treatment according to Example 1 of the present invention;

[0034] Figure 8 This is a comparison diagram of the lead content in the leaves of the hydroponic purple jasmine before and after treatment according to Example 1 of the present invention;

[0035] Fig. 9 This is a comparison chart of the SPAD value indicators of the hydroponic purple violets in Example 1 of the present invention;

[0036] Fig.10 This is a comparison chart of the total phenol content of the hydroponic purple jujube in Example 1 of the present invention;

[0037] Fig.11 This is a comparison chart of flavonoid contents in hydroponic purple violets of Example 1 of the present invention;

[0038] Fig.12 This is a comparison chart of anthocyanin content in hydroponic purple violets of Example 1 of the present invention;

[0039] Fig.13 This is a comparison chart of lead content in mature leaves of Longjing 43 of treatment groups CK2, M1, M2, and M3 in Example 2 of the present invention;

[0040] Fig.14 This is a comparison chart of lead content in mature leaves of Longjing 43 of treatment groups CK2, M2, M4, and M5 in Example 2 of the present invention;

[0041] Fig.15 This is a comparison chart of lead content in mature leaves of purple jujube in treatment groups CK2, M1, M2, and M3 of Example 2 of the present invention;

[0042] Fig.16 This is a comparison chart of lead content in mature leaves of purple jujube in treatment groups CK2, M2, M4 and M5 of Example 2 of the present invention;

[0043] Fig.17 This is a diagram showing the detection results of superoxide dismutase in tea plants according to Example 1 of the present invention;

[0044] Fig.18 This is a diagram of the tea tree catalase detection result in Example 1 of the present invention;

[0045] Fig.19 This is a diagram of the tea tree catalytic enzyme detection result of Example 1 of the present invention;

[0046] Fig. 20 This is a diagram showing the detection results of the soluble protein content of tea plants in Example 1 of the present invention;

[0047] Fig.21 This is a graph showing the change in dihydroquercetin content in tea plants according to Example 1 of the present invention;

[0048] Fig. 22 This is a graph showing changes in the content of catechins in tea plants according to Example 1 of the present invention;

[0049] Fig.23 This is a graph showing the change in relative conductivity of cell membrane permeability of tea leaves in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description. Example 1

[0051] Indoor hydroponic experiment

[0052] This experiment selected two tea varieties, Zijuan and Longjing 43, with uniform growth, for hydroponic experiment. Melatonin treatment and / or lead stress treatment were carried out during the hydroponic experiment to study the role of melatonin in lead accumulation in tea trees.

[0053] The indoor hydroponic experiment specifically includes the following steps:

[0054] Step 1: Tea seedling cultivation

[0055] Choose two tea seedlings, Longjing 43 (LJ43) and Zijuan (ZJ). First, clean the soil at the roots of the purchased tea seedlings, and rinse the leaves of the tea seedlings until there is no mud. Place the washed tea seedlings in pure water for 1 week.

[0056] Seedling slow-growing method: Use a sponge to fix the tea seedlings to the holes in the black plastic barrel lid. Each hole can hold 1-2 tea seedlings.

[0057] Step 2: Hydroponic treatment

[0058] After one week of tea seedling cultivation, four treatment groups were set up for the two types of tea seedlings, with three biological replicates for each treatment. 5 L of 1 / 4 tea tree nutrient solution (NSP1030, Coolaber, China) was added to the bucket for hydroponics, and the pH was adjusted to 5.0 ± 0.05.

[0059] The hydroponic experiment lasted for 10 days, during which melatonin treatment and / or lead stress treatment were carried out according to the experimental groups.

[0060] 1. Experimental group design

[0061] The 4 treatment groups are:

[0062] CK1: blank control group;

[0063] F1: 100 µmol / L melatonin (100 MT);

[0064] F2: 0.29 mmol / L Pb (0.29 Pb);

[0065] F3: 0.29 mmol / LPb + 100 µmol / L melatonin (0.29 Pb + 100 MT).

[0066] 2. Melatonin treatment:

[0067] (1) Preparation of melatonin stock solution (0.2 M): Accurately weigh 2.3228 g of melatonin powder, dissolve it in anhydrous ethanol, and then dilute it to a 50 mL volumetric flask with distilled water. Preparation of 100 µmol / L melatonin: Take 0.5 mL of the stock solution and dilute it to 1 L.

[0068] (2) Treatment groups F1 and F3 were sprayed with melatonin at a concentration of 100 µmol / L, and CK1 and F2 were sprayed with water. Foliar spraying was adopted, and the spraying time was after sunset every day, and the spraying degree was until water dripped on the leaf surface.

[0069] 3. Lead stress treatment:

[0070] 24 hours after the first foliar spraying of melatonin, the experimental group was subjected to lead stress treatment, in which a portion of the nutrient solution was replaced with a lead acetate treatment solution with a lead acetate concentration of 0.29 mM.

[0071] (1) Preparation of 0.1 mol / L lead acetate stock solution: Weigh 37.933 g of lead acetate trihydrate and dissolve it in nutrient solution to make up to 1 L.

[0072] Preparation of 0.29 mM lead acetate treatment solution: Take out 14.5 ml of nutrient solution from 5 L of nutrient solution and add the same volume of lead acetate stock solution, and adjust the pH to 5±0.05.

[0073] (2) During the lead stress treatment, CK1 and F1 needed to replace 1 / 4 of the nutrient solution every 3 days, while F2 and F3 simultaneously replaced 1 / 4 of the nutrient solution with 0.29 mM lead acetate solution. The lead stress treatment time was 10 days.

[0074] Step 3: Result detection

[0075] After the hydroponic treatment, mature leaves were collected and freeze-dried for the determination of lead content.

[0076] Experimental conclusion:

[0077] The phenotype of Longjing 43 before and after treatment is as follows Figure 1 The lead content of leaves is shown in Figure 2 As shown; SPAD value, total phenol content, flavonoid content, anthocyanin content are shown as Figure 3~Figure 6 Before and after treatment, the phenotype of Zijuan and the lead content of its leaves were as shown in Figure 7 , Figure 8 As shown; SPAD value, total phenol content, flavonoid content, anthocyanin content are shown as Figure 9~Figure 12 The antioxidant enzyme activity and soluble protein of tea tree were analyzed, and the results are shown in Figures 17 to 20 shown.

[0078] Result analysis:

[0079] from Figure 1 and Figure 7 The phenotype diagram shows that under lead stress, the leaves of Zijuan and Longjing 43 tea seedlings wilt, turn yellow and fall off, and a large amount of lead is accumulated on the roots; after spraying melatonin on the leaves, the situation is effectively alleviated, and the number of yellow and wilted leaves is reduced. The mature leaves of Zijuan and Longjing 43 were collected to measure the lead content, and it was found that melatonin can significantly reduce the lead content in the mature leaves of tea trees, alleviating the degree of lead toxicity to tea trees. Figure 3~Figure 6 ,as well as Figure 7 to Figure 12 As shown in the figure, the SPAD value, total phenol, flavonoids and anthocyanin content of tea leaves were analyzed respectively, and it was found that spraying melatonin under lead stress increased its content in tea plants. Flavonoids can regulate the membrane lipid peroxidation reaction and antioxidant enzyme activity in tea plants, thereby eliminating the toxicity of free radicals and antioxidant substances, and improving the antioxidant capacity of cells, thereby enhancing the ability of tea plants to resist lead stress. Figures 17 to 20The antioxidant enzyme activity and soluble protein of tea trees were analyzed respectively. The study showed that the superoxide dismutase (SOD), catalase (POD) and catalytic enzyme (CAT) activities of Longjing 43 and Zijuan were significantly reduced under lead (Pb) stress. However, after foliar spraying of melatonin, the activities of these enzymes were increased to varying degrees, and soluble proteins also had similar patterns, indicating that melatonin can improve the ability of tea trees to remove peroxides and free radicals in the body under lead stress, and enhance the ability of tea trees to resist Pb stress. Fig.21 , Fig. 22 The content changes of catechins and dihydroquercetin in tea trees are shown. As a strong antioxidant, catechins help improve cardiovascular health, promote weight loss and anti-inflammation; while dihydroquercetin performs well in reducing allergic reactions, anti-inflammation and cardioprotection. Under lead stress, the content of samples not sprayed with melatonin was higher than that of the control group (CK). This may be because the tea tree activated its own anti-stress mechanism, resulting in an increase in the content of these two compounds. After spraying melatonin, the catechins and dihydroquercetin content of tea seedlings increased significantly. Therefore, the present disclosure has good application prospects in the field of tea tree cultivation.

[0080] Spraying melatonin can significantly reduce the lead content in tea trees, reduce the harm of lead to tea trees, and improve the quality indicators of tea, thereby improving the quality of tea. It is beneficial to tea growers and consumers.

[0081] In addition, this embodiment also uses relative conductivity (REC) to measure cell membrane permeability; the measurement results are as follows Fig.23 As shown in the figure: Analysis of cell membrane permeability of Longjing 43 and Zijuan showed that there was no significant difference in conductivity between CK and MT treatments, but under lead stress, the relative conductivity decreased significantly, with Zijuan's conductivity slightly lower than Longjing 43. This shows that spraying melatonin can effectively reduce plant cell membrane permeability, protect membrane integrity and enhance stress resistance. In addition, during the transportation of tea, cell membrane permeability directly affects its ability to maintain integrity and freshness. The more stable the cell membrane, the less electrolyte leakage, and the slower the loss of water and nutrients inside the cell, which effectively extends the shelf life of tea. Example 2

[0082] Field trials

[0083] In order to further verify the effectiveness of melatonin in reducing lead stress in tea plants, a field experiment was designed and implemented. In order to be more in line with the actual situation, the frequency of spraying melatonin was reduced, which can also reduce the time and cost of farmers' investment. At the same time, a melatonin concentration was increased to verify the relationship between melatonin concentration and inhibition of lead stress in tea plants.

[0084] This implementation specifically includes the following steps:

[0085] Step 1: Select tea seedlings

[0086] The tea garden in Shaoxing, Zhejiang Province was selected as the test site (the surface lead content of the test site was 30 mg kg-1), and the tea trees were planted and managed in the same way. Two tea varieties, Zijuan and Longjing 43, were selected, which had similar growth.

[0087] Step 2: Field treatment

[0088] Six treatments were set up for Zijuan (ZJ) and Longjing 43 (LJ43) tea trees, respectively, and melatonin treatment and / or lead stress treatment were carried out in the field according to the group design of 6 treatments.

[0089] 1. Group design

[0090] The group design of the 6 treatment groups is:

[0091] CK2: blank control group;

[0092] M1: 100 µmol / L melatonin (100 MT);

[0093] M2: 1.3 mmol / L Pb (1.3 Pb);

[0094] M3: 1.3 mmol / LPb+100 µmol / L melatonin (1.3 Pb+100 MT);

[0095] M4: 200 µmol / L melatonin (200 MT);

[0096] M5: 1.3 mmol / LPb+200 µmol / L melatonin (1.3 Pb+200 MT).

[0097] 2. Melatonin treatment:

[0098] The melatonin concentration applied by M1 and M3 was 100 µmol / L; the melatonin concentration applied by M4 and M5 was 200 µmol / L, and clean water was applied by CK2 and M2. The application method was foliar spraying after sunset, the application frequency was once a week, and the foliar spraying degree was until water dripped on the leaf surface.

[0099] (1) Preparation of melatonin stock solution (0.2 M): Accurately weigh 2.3228 g of melatonin powder and dissolve it in anhydrous ethanol (5 ml). Then make up to volume in a 50 mL volumetric flask with distilled water and store in a sealed container at -4°C.

[0100] (2) Preparation of 100 µmol / L melatonin: aspirate 0.5 ml of the stock solution and dilute to 1 L. Preparation of 200 µmol / L melatonin: aspirate 1 ml of the stock solution and dilute to 1 L.

[0101] 3. Lead stress treatment:

[0102] 24 h after the first foliar spraying of melatonin, the experimental group was treated with lead acetate. M2, M3, and M5 lead stress treatments all used lead acetate treatment solution with a lead acetate concentration of 1.3 mM to irrigate the roots of tea trees to the extent that the soil 20 cm below the root surface of the tea trees was completely wet. The frequency of applying lead solution was once a week, and the treatment time was two weeks (mainly based on the growth of one bud and two leaves).

[0103] Preparation of 1 mol / L lead acetate mother solution: weigh 379.33 g of lead acetate trihydrate and dilute to 1 L of pure water. 1.3 mM lead acetate treatment solution: take 19.3 ml of the mother solution and dilute to 10 L with pure water.

[0104] Step 3: Result detection

[0105] After the field treatment (applying lead twice, waiting for one bud and two leaves to grow), collect the leaves from the top bud to the third and fourth mature leaves, put them in plastic bags, and put them in dry ice. After returning to the laboratory, rinse them with deionized water and freeze-dry them for the determination of relevant lead content.

[0106] Experimental data:

[0107] The field test reduced the frequency of melatonin spraying. Spraying melatonin once a week is more suitable for actual production and application and more feasible. In addition, weather conditions have a great impact on the effect of melatonin in reducing lead content. Try to choose weather without rain or with little rainfall to conduct the test to avoid affecting the experimental results.

[0108] Lead content in mature leaves of Longjing 43 under different melatonin concentrations Fig.13 , Fig.14 As shown in Figure 2, the lead content in mature leaves of Zijuan under different melatonin concentrations is as follows Fig.15 , Fig.16 shown.

[0109] Data Analysis:

[0110] like Figures 13-16 As shown in the figure, after reducing the frequency of melatonin spraying, the lead content in mature leaves of tea trees decreased significantly, and the higher the melatonin concentration, the more obvious the effect of reducing lead content. 200 µmol / L melatonin was better than 100 µmol / L, indicating that this method can be applied in actual production.

[0111] in conclusion:

[0112] The results of the indoor hydroponic experiment showed that daily spraying of melatonin can alleviate the wilting, yellowing and falling of tea seedling leaves, reduce the lead content of mature leaves in hydroponic tea seedlings, and increase their SPAD value, total phenols, flavonoids and anthocyanin content. In order to further verify the feasibility of the experiment, a field test was conducted to reduce the efficiency of melatonin spraying, control input costs, and be more in line with actual production and life, and increase a melatonin concentration of 200 µmol / L. It was found that reducing the spraying frequency can still reduce the lead content of mature leaves in tea trees, and 200 µmol / L melatonin has a better effect.

[0113] The test found that whether from the phenotypic observation of the leaves or the determination of the SPAD value, the application of melatonin not only did not have a negative impact on the cell membrane permeability, but may have promoted the recovery of photosynthesis and cell metabolism to some extent. The reduction of tea cell membrane permeability can also make the cell membrane more stable, which is conducive to extending the shelf life of tea leaves. Therefore, this solution will not affect the cell wall and membrane properties of tea leaves, and has obvious advantages in improving the growth of tea trees and improving the quality of tea leaves.

[0114] Based on the results of indoor and outdoor tests, the present invention provides an effective method for using melatonin, which can be applied to tea garden irrigation systems with high lead content, has a good effect on reducing lead accumulation in tea trees, and can also improve tea quality, increase tea farmers' income, and reduce harm to human health. The application amount of this method is set to spray the melatonin solution to the leaf surface to reach a dripping state, and the melatonin concentration range for field application is selected to be 100-200 µmol / L. It should be noted that after rainfall, the number of spraying should be appropriately increased to ensure the effectiveness of melatonin.

[0115] In addition, it should be noted that melatonin can also be applied to tea gardens through irrigation water, but this method requires a relatively high cost. On the one hand, the adsorption of melatonin in the soil and the complex interactions between other ions in the soil will reduce the effective absorption rate of melatonin by tea trees, affecting its expected physiological regulatory effect. On the other hand, the diffusion rate of melatonin in the soil is slow, which is not conducive to timely alleviating the lead stress effect of tea trees. Therefore, foliar spraying of melatonin can directly act on tea leaves, which not only speeds up the absorption rate, but also avoids soil adsorption and ion interference problems, significantly improving the utilization efficiency of melatonin. In addition, foliar spraying is easy to operate, has controllable dosage, and lower cost, and is suitable for large-scale application in tea gardens.

[0116] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. The use of melatonin in improving the resistance of Theaceae plants to lead stress, characterized in that: The application of melatonin in improving the resistance of Theaceae plants to lead stress includes: alleviating the wilting, yellowing and falling of plant leaves under lead stress, reducing the lead content of mature plant leaves; reducing the membrane permeability of plant leaves under lead stress; increasing the SPAD value of plant leaves under lead stress, and increasing the total phenol, flavonoid and anthocyanin content of plant leaves under lead stress; The Theaceae plant is Zijuan and / or Longjing 43; When applied, a preparation containing melatonin is applied to plants poisoned by lead stress, and the concentration of melatonin applied is 100~200 μmol / L.

2. A method for improving plant resistance to lead stress, characterized in that: include: Applying a melatonin aqueous solution or a preparation containing melatonin to plants poisoned by lead stress; the plants resisting lead stress include: alleviating the wilting, yellowing and falling of plant leaves under lead stress, reducing the lead content of mature plant leaves; reducing the membrane permeability of plant leaves under lead stress; increasing the SPAD value of plant leaves under lead stress, and increasing the total phenol, flavonoid and anthocyanin content of plant leaves under lead stress; In the preparation containing melatonin, the concentration of melatonin is 100-200 μmol / L; The plant is a plant of the family Theaceae; The Theaceae plant is Zijuan and / or Longjing 43.

3. The method according to claim 2, characterized in that The application method is foliar spray.

4. The method according to claim 2, characterized in that: The plants are planted hydroponically, with a spraying frequency of once a day after sunset, and a spraying degree based on water dripping from the leaves.

5. The method according to claim 2, characterized in that: The plants are planted in the field, sprayed once a week after sunset, and sprayed to the extent of dripping on the leaves.

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