Treatment method for enhancing coloring and sugar increasing of citrus fruits based on 5-aminolevulinic acid

Abstract

The invention relates to the technical field of plant cultivation and nutrition, and discloses a treatment method for enhancing coloring and sugar increasing of citrus fruits based on 5-aminolevulinic acid. And phosphite serving as a carbon immobilization catalyst and polyhydric alcohol serving as a product transfer accelerant are creatively compounded. The preparation method comprises the key step of accurately regulating and controlling the pH value of the system so as to ensure the stability and efficient absorption of the preparation. According to the application method, foliage spraying is carried out in specific time windows of the young fruit stage and the expansion stage of citrus, so that the effect of the preparation is matched with the key physiological rhythm of fruit development. Through the synergistic effect of the composition and the method, the photosynthetic whole chain of light harvesting-carbon sequestration-transportation is systematically optimized, the soluble solid content and the sucrose content of the citrus fruits can be remarkably increased, the color turning of the peel is effectively promoted, and the method is safe, stable and outstanding in effect.

Description

Technical Field

[0001] The present invention relates to the technical field of plant cultivation and nutrition, and in particular to a method for enhancing the coloring and sugar content of citrus fruits based on 5-aminolevulinic acid. Background Art

[0002] Citrus is one of the most important fruit varieties in my country and globally. Its quality, particularly its sweetness, flavor, and appearance, is a key factor in determining its commercial value and market competitiveness. Therefore, in the cultivation and management of citrus, effectively improving fruit quality—increasing sugar, reducing acid, and promoting color—has always been a key goal pursued by fruit growers and agricultural technicians.

[0003] To achieve this goal, various methods have been developed and applied in the prior art. These methods primarily include applying macronutrient or trace element fertilizers to meet basic nutritional needs, and using various plant growth regulators and biostimulants to regulate plant growth and development. For example, supplementing elements such as potassium, boron, and magnesium can promote sugar accumulation and transport, while the use of biostimulants such as amino acids and seaweed extracts can improve plant stress resistance and photosynthetic efficiency to a certain extent. These technologies have achieved certain results in practice.

[0004] However, existing technologies for improving citrus quality still have significant limitations. Current approaches often focus on a single step in plant physiological processes, such as simply supplementing a specific nutrient or stimulating a specific metabolic pathway, lacking a holistic consideration of the complex, systematic process that shapes fruit quality. Sugar production through photosynthesis, sugar transport to the fruit, and sugar conversion and accumulation within the fruit are interconnected, dynamic processes known as "source-stream-sink." Shortcomings in any one step can become a bottleneck limiting final quality. Due to their limited focus, existing technologies often result in a "severely patchy" approach, making it difficult to break through the quality barrier. Furthermore, many products are simply a simple physical blend of multiple ingredients, failing to truly achieve synergistic effects based on plant physiological mechanisms. This results in inconsistent and limited improvements, making it difficult to meet the growing market demand for high-quality citrus. Therefore, developing a new technology that can systematically address the entire photosynthetic chain and leverage the synergistic effects of various components to stably and efficiently improve the overall quality of citrus has significant practical significance and application value. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a method for enhancing the color and sugar content of citrus fruits based on 5-aminolevulinic acid, which solves the technical problems of the existing citrus quality improvement technology, which lacks systematic regulation of the entire photosynthesis chain and poor synergistic effects between components, resulting in limited and unstable sugar content and coloring effects.

[0006] To achieve the above-mentioned purpose, the application provides a treatment method for enhancing color and sugar of citrus fruits based on 5-amino levulinic acid.

[0007] The method comprises the following steps: a. Constructing a synergistic core system: mixing 5-amino levulinic acid or its salt, phosphite and polyol in an aqueous medium to obtain a synergistic core system; b. Preparing a complete functional preparation: further adding free amino acid, reducing sugar and vitamin C to the synergistic core system prepared in step a, and adjusting the pH value to obtain a functional preparation stock solution; c. First key period application: diluting the functional preparation stock solution prepared in step b, and then spraying the citrus plants by foliar spraying; d. Second key period application: spraying the citrus plants again by foliar spraying within 25-35 days after the first application.

[0008] In some preferred embodiments of the application, the technical features in step a can be further refined. Specifically, the phosphite can be preferably potassium phosphite, which is a high-efficiency source of phosphorus and potassium, and also has the function of a biological stimulant; the polyol can be preferably sorbitol, which is a high-efficiency form of photosynthetic product transport in plants.

[0009] In other preferred embodiments of the application, the concentrations of the effective components in the functional preparation stock solution prepared in step b are optimized to achieve better synergistic effects. Specifically, the final concentrations of the components can be: 5-amino levulinic acid or its salt: 5-50 g / L, phosphite: 50-200 g / L, polyol: 50-150 g / L, free amino acid: 50-100 g / L, reducing sugar: 10-50 g / L, and vitamin C: 10-100 mg / L.

[0010] To ensure the stability of the preparation and the effectiveness during application, it is necessary to adjust the pH value of the functional preparation stock solution to the range of 4.0-7.0 in step b.

[0011] To ensure the expected synergistic effects between the functional components, the execution order of steps a and b has technical implications. Preferably, the specific operation of step a is to first add phosphite and polyol in an aqueous medium and stir until dissolved to construct a basic framework for carbon assimilation and transport, and then add 5-amino levulinic acid or its salt. Correspondingly, the preferred operation of step b is to sequentially add free amino acid, reducing sugar and vitamin C as basic nutrients and stress protection modules to the system prepared in step a, and then stir uniformly before finally adjusting the pH value.

[0012] In field application, the dilution operation in step c and step d is to dilute the functional preparation stock solution with water by 200-1000 times to obtain a working solution concentration suitable for spraying. In order to achieve the ideal coverage effect, the operation of foliar spraying is to uniformly spray the front and back of the citrus plant leaves, and the leaves are fully wetted but no dripping is generated. In order to achieve the target effect, the recommended application amount of functional preparation stock solution per mu is 50-500 ml.

[0013] Further, in order to make the components better absorbed and utilized by plants, the free amino acid can be at least one of glycine, glutamic acid, alanine or a combination thereof, and the reducing sugar can be glucose or fructose.

[0014] The application provides a 5-amino levulinic acid-based method for enhancing coloration and sugar content of citrus fruits. 1. The application constructs a synergistic technical system by scientifically compounding multiple functional components, which significantly improves the internal quality of citrus fruits. The specific components in the composition act on multiple core physiological links such as light energy capture, carbon fixation and product transport, and work together to make the generation and accumulation efficiency of photosynthetic products far exceed the level that can be achieved by single component or simple mixture, thereby effectively increasing the sucrose content and soluble solids content of citrus.

[0015] 2. The application can significantly improve the appearance quality of citrus fruits and promote uniform and rapid coloration of fruit peels. This is due to the fact that the synergistic system provides sufficient energy and nutrients for the fruits, accelerates the degradation of chlorophyll and the synthesis of pigments such as carotenoids, making the fruit peels more bright and beautiful. At the same time, healthy tree bodies and excellent fruit development state also make the final fruit shape more regular and the commercial value higher.

[0016] 3. The application adopts a specific preparation method, especially precise control of the pH of the preparation system, which effectively ensures the high stability and high bioavailability of the product. This method ensures that the active components can remain dissolved and stable in the preparation for a long time, avoiding the decrease in potency or precipitation during storage. At the same time, the appropriate pH also greatly promotes the absorption efficiency of the leaves to the components, ensuring the maximization of application effect.

[0017] 4. The application realizes the perfect balance between synergistic effect and safety by limiting the use of components within a specific concentration range. The concentration range adopted by this method is the best window that ensures the maximum synergistic effect between components and does not cause stress or physiological damage to plants. This avoids the negative effects that may be caused by improper concentration of certain biological stimulants, ensuring the high efficiency and high safety of the application method in improving fruit quality.

[0018] 5、The present application realizes the maximization of technical effects by innovatively proposing to apply at a specific critical period in the growth cycle of citrus. The application precisely matches the action time of the high-efficiency preparation with the physiological peak period of fruit development and sugar accumulation, so that the enhanced photosynthetic capacity can be maximally guided to the target organ of fruit, thereby fully exerting the potential of the preparation and achieving a breakthrough in the quality of fruit. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0020] Embodiment 1 The present embodiment provides a preparation method of a synergistic citrus quality improver.

[0021] 1. Preparation components: 5-amino levulinic acid hydrochloride: 25 g, potassium phosphite: 120 g, sorbitol: 100 g, complex free amino acid: 80 g, glucose: 30 g, vitamin C: 50 mg, citric acid-sodium citrate buffer solution: appropriate amount, deionized water: add to 1000 mL.

[0022] 2. Preparation steps: (1) In a 1000 mL preparation tank, add about 700 mL of deionized water, start the stirring device, adjust the rotation speed to 200 rpm, and maintain the solution temperature at 25°C.

[0023] (2) Under stirring, weigh 120 g of potassium phosphite and 100 g of sorbitol and add them into the preparation tank, and continue stirring until they are completely dissolved.

[0024] (3) Weigh 25 g of 5-amino levulinic acid hydrochloride and dissolve it in 50 mL of deionized water to prepare a mother liquor, and slowly pump the mother liquor into the preparation tank under stirring, and mix uniformly.

[0025] (4) Continue stirring, and continue to add 80 g of complex free amino acid, 30 g of glucose, and 50 mg of vitamin C into the tank, and continue stirring for 10 minutes to ensure that all components are uniformly dispersed.

[0026] (5) Monitor the solution using a pH meter, and add the previously prepared citric acid-sodium citrate buffer solution dropwise to accurately adjust the pH value of the preparation to 5.5.

[0027] (6) Stop stirring, transfer the solution to a 1000 mL volumetric flask, rinse the preparation tank with deionized water and add the rinse to the volumetric flask, and finally dilute to the calibration line with deionized water.

[0028] (7) Pour the solution after dilution back into the preparation tank, stir again for 15 minutes for homogenization treatment, then filter through a filter membrane with a pore size of 3 μm, and divide the filtrate into clean, light-proof HDPE bottles, seal to obtain the finished product.

[0029] Example 2 The present example provides a preparation method of a synergistic citrus quality improver.

[0030] 1. Formulation components: 5-amino levulinic acid: 5 g, potassium phosphite: 50 g, sorbitol: 50 g, complex free amino acid: 50 g, fructose: 10 g, vitamin C: 10 mg, potassium dihydrogen phosphate-potassium hydrogen phosphate buffer pair: appropriate amount, deionized water: add to 1000 mL.

[0031] 2. Preparation steps: (1) In a 1000 mL preparation tank, add about 600 mL of deionized water, start the stirring device, adjust the speed to 100 rpm, and maintain the solution temperature at 15°C.

[0032] (2) Slowly add 50 g of potassium phosphite and 50 g of sorbitol to the water under stirring, and stir until completely dissolved.

[0033] (3) Weigh 5 g of 5-amino levulinic acid and directly slowly sprinkle it into the above solution under stirring to dissolve and mix.

[0034] (4) Maintain stirring, and sequentially add 50 g of complex free amino acid, 10 g of fructose, and 10 mg of vitamin C, and continue stirring for 15 minutes.

[0035] (5) Monitor with a pH meter, and accurately adjust the pH of the preparation to 4.0 by adding phosphate buffer solution dropwise.

[0036] (6) Dilute the solution to 1000 mL with deionized water.

[0037] (7) Continue stirring the solution after dilution for 10 minutes, then filter through a filter membrane with a pore size of 5 μm, divide the filtrate, seal to obtain the finished product.

[0038] Example 3 The present example provides a preparation method of a synergistic citrus quality improver.

[0039] 1. Formulation components: 5-Aminolevulinic acid phosphate: 50g, potassium phosphite: 200g, sorbitol: 150g, complex free amino acids: 100g, mixture of glucose and fructose (mass ratio 1:1): 50g, vitamin C: 100mg, citric acid-sodium hydroxide buffer: appropriate amount, deionized water: add to 1000mL.

[0040] 2. Preparation steps: (1) Add about 800 mL of deionized water to a 2000 mL preparation tank, turn on the stirring device, adjust the speed to 300 rpm, and maintain the solution temperature at 30 °C.

[0041] (2) Under strong stirring, slowly add 200g potassium phosphite and 150g sorbitol, stirring until completely dissolved to form a high concentration base liquid.

[0042] (3) Dissolve 50 g of 5-aminolevulinic acid phosphate in 100 mL of deionized water to prepare a concentrated mother liquor, and slowly inject the mother liquor into the preparation tank while stirring.

[0043] (4) Maintain stirring and continue to add 100 g of complex free amino acids, 50 g of carbohydrate mixture and 100 mg of vitamin C to the tank and stir for 20 minutes to ensure that the components can still be evenly dispersed at high concentrations.

[0044] (5) Use a pH meter to monitor the solution, add sodium hydroxide solution for coarse adjustment, and then use citric acid solution for fine adjustment to accurately adjust the final pH value of the preparation to 7.0.

[0045] (6) Carefully dilute the high concentration solution to 1000 mL with deionized water.

[0046] (7) The solution after volume adjustment is homogenized and stirred for the final 20 minutes, and then filtered through a precision filter with a pore size of 1 μm. The clear filtrate is divided into clean, light-proof containers and sealed to obtain the finished product.

[0047] Comparative Example 1: Compared with Example 1, the difference is that the preparation components do not contain potassium phosphite, and the remaining components, preparation steps and application methods are the same.

[0048] Comparative Example 2: Compared with Example 1, the difference is that the preparation components do not contain sorbitol, and the other components, preparation steps and application methods are the same Comparative Example 3: Compared with Example 1, the difference is that the amount of 5-aminolevulinic acid hydrochloride in the preparation components is increased to 60 g, and the other components, preparation steps and application methods are the same.

[0049] Comparative Example 4: Compared with Example 1, the difference is that the amount of potassium phosphite in the preparation components is reduced to 40g, and the other components, preparation steps and application methods are the same.

[0050] Comparative Example 5: Compared with Example 1, the difference is that step 5 is omitted in the preparation process, that is, the final pH value of the preparation is not precisely adjusted, and the remaining components, preparation steps and application methods are the same.

[0051] Comparative Example 6: Compared with the application method of Example 1, the difference is that the application period is changed: the first application is during the peak flowering period of citrus, and the second application is 10 days after the first application. The preparation method of the preparation is exactly the same as that of Example 1.

[0052] Test Example 1: Verification of the effect of synergistic components 1. Description of experimental steps 1. Experimental Materials and Grouping: Twenty healthy citrus trees, approximately six years old, with similar growth and fruit yield, were selected from the same orchard. Using a randomized block design, they were divided into two groups of 10 trees each: the experimental group and the control group. Each tree served as a replicate.

[0053] 2. Preparation processing: Experimental group: The preparation solution prepared in Example 1 was used.

[0054] Control group: The original solution of the preparation prepared in Comparative Example 1 was used. Both preparations were diluted 800 times with clean water before use, stirred evenly and then used.

[0055] 3. Application Method: The first spraying should be carried out when the citrus flowers are about 2 / 3 of their blooms withered, and the second spraying should be carried out 30 days after the first spraying. Use an electric sprayer to evenly spray the foliage of the citrus trees in each group, ensuring that both sides of the leaves are fully wetted, with no dripping as the standard. To prevent drift contamination, set up protective rows between treatments, and spray in the early morning or evening when there is no wind.

[0056] 4. Sample collection and processing: When the fruit reached commercial maturity, five uniformly sized, pest-free fruits were randomly picked from the upper middle of each tree in the east, south, west, and north directions, for a total of 50 fruits per group. Fruits from the same group were mixed, and 20 were randomly selected for subsequent index measurement.

[0057] Index determination: Soluble solids content: After squeezing the juice from the pulp, filter it with gauze and measure the filtrate with a handheld saccharimeter (refractometer).

[0058] Sucrose content and total acid content: The juice samples were determined by high performance liquid chromatography, and the sucrose content (g / 100g) and the total acid content (g / 100mL) calculated as citric acid were calculated.

[0059] Solid-acid ratio: Calculate the ratio based on the measured soluble solid content and total acid content.

[0060] Experimental data Table 1 Comparative test data of treatment effects of Example 1 and Comparative Example 1

[0061] Summary of experimental results As shown in the test data in Table 1, the experimental group treated with the method of Example 1 of the present invention had significantly better soluble solids content, sucrose content, a core quality indicator, and solid-acid ratio, a comprehensive evaluation of taste, than the control group treated with the method of Comparative Example 1. Due to the lack of potassium phosphite in its preparation, the fruit quality indicators of the control group were poor, which intuitively demonstrates the importance of the synergistic effect of the various components in the specific composition of the present invention.

[0062] The above results profoundly reveal the technical mechanism of the method of the present invention. The present invention does not simply enhance the "light energy capture" ability of photosynthesis through 5-aminolevulinic acid, but rather constructs an interlocking "photosynthetic full-chain synergistic system." In the formula of the experimental group, 5-aminolevulinic acid and phosphite work together. The former enhances the chlorophyll content, while the latter, as a key biostimulant, effectively catalyzes the "carbon fixation" link, so that the captured light can be efficiently converted into carbohydrates. In the control group lacking phosphite, although the light energy capture ability may be improved to a certain extent, the subsequent carbon fixation link becomes a "bottleneck", resulting in the inability to simultaneously improve the photosynthetic efficiency, which ultimately manifests as a significant reduction in the accumulation of products such as sucrose.

[0063] Therefore, this test confirms a core inventive point of the present invention: its superior technical effect stems from the clear synergistic effects between the components, based on plant physiological processes, rather than the simple addition of the effects of the individual components. It is the presence of phosphite, a key component, that opens the pathway from light capture to carbon fixation, maximizing the effectiveness of the entire sugar-enhancing and coloring method. This fully demonstrates that the specific functional component combination proposed in this invention is essential for achieving the intended technical objectives and has significant advanced features.

[0064] Test Example 2: Verification of the effect of synergistic components Description of experimental steps 1. Experimental Materials and Grouping: Twenty healthy citrus trees with uniform growth, age, and fruit yield were selected from a separate area of ​​the same orchard as in Test Example 1. Using a randomized block design, these trees were divided into two groups of 10 trees each: the experimental group and the control group.

[0065] Preparation processing: 2. Experimental group: The preparation solution prepared in Example 1 was used.

[0066] Control group: The original solution of the preparation prepared in Comparative Example 2 was used. Both preparations were diluted 800 times with clean water before use, stirred evenly and then used.

[0067] 3. Application method: The application period and method are the same as those in Test Example 1. That is, spray the leaves twice, at the 2 / 3 stage of citrus flower withering and 30 days thereafter, to ensure standardized operation and prevent cross contamination.

[0068] 4. Sample collection and processing: The operating procedures are the same as those in Test Example 1. At the commercial maturity of the fruit, sufficient and representative fruit samples were collected according to the specifications for subsequent index determination.

[0069] 5. Determination of Indicators: Soluble solids content: Same as in Test Example 1, using a handheld sugar meter. Sucrose content: Same as in Test Example 1, using high performance liquid chromatography. Vitamin C content: Determine the vitamin C content of the juice sample using the 2,6-dichloroindophenol titration method.

[0070] Experimental data Table 2 Comparative test data of treatment effects of Example 1 and Comparative Example 2

[0071] Summary of experimental results The test data in Table 2 clearly demonstrate that the experimental group treated using the method of Example 1 of the present invention significantly outperformed the control group treated using the method of Comparative Example 2 in terms of three key quality indicators: soluble solids content, sucrose content, and vitamin C content. The lack of sorbitol alone in the formulation of Comparative Example 2 led to a significant decline in fruit quality, strongly demonstrating the critical importance and indispensability of the polyol component in the formulation of the present invention.

[0072] This result is highly consistent with the "synergistic enhancement of the entire photosynthetic chain" mechanism described in the present invention. The method of the present invention efficiently produces a large amount of photosynthetic products in the "production workshop" of the leaves through the synergistic effect of 5-aminolevulinic acid and phosphite. However, these products need to be efficiently transported from the leaves to the fruits for accumulation before they can ultimately be converted into fruit quality. The polyols such as sorbitol in the formula of the present invention play the role of this "logistics accelerator", which can significantly improve the loading and transportation efficiency of the phloem. Due to the lack of this key "transport" link promoter in the control group, the sugars efficiently produced by the leaves could not be smoothly transported to the fruit, forming a bottleneck of "high yield at the source end and insufficient storage end", which ultimately manifested as insufficient accumulation of sugar and soluble solids in the fruit. At the same time, the reduction in the supply of energy substances also affected the synthesis of other metabolites in the fruit.

[0073] Therefore, this test validates the integrity and innovative nature of the present invention from another perspective. It demonstrates that the success of this method doesn't rely solely on improving a single step in photosynthesis, but rather systematically optimizes the entire chain of "light capture-carbon fixation-transport." The addition of polyols solves the problem of efficient distribution of photosynthetic products, a key step in ensuring that the high energy production at the leaf tip is ultimately reflected in fruit quality, fully demonstrating the scientific nature and synergistic effects of the present composition design.

[0074] Test Example 3: Verification of the rationality of the core component concentration range Description of experimental steps 1. Experimental materials and grouping: Twenty healthy citrus trees were selected from locations and conditions similar to those described above and randomly divided into two groups, 10 trees in each group, namely the experimental group and the control group.

[0075] 2. Preparation processing: Experimental group: The preparation solution prepared in Example 1 was used.

[0076] Control group: The original solution of the preparation prepared in Comparative Example 3 was used. Both preparations were diluted 800 times with clean water before use, stirred evenly and then used.

[0077] 3. Application method: The application period and method are the same as those in Test Example 1. During the entire experimental period, regularly observe and record the growth status of the leaves of trees in each treatment group, paying special attention to any adverse physiological phenomena such as yellowing, burnt edges, and deformities.

[0078] 4. Sample collection and processing: The operating procedures are the same as those in Test Example 1. During the commercial maturity of the fruit, sufficient and representative fruit samples were collected according to the specifications.

[0079] 6. Determination of Indicators: Soluble Solids Content and Solid-Acid Ratio: Same method as Test Example 1. Citrus Chromaticity Index: Using a portable colorimeter, measure three evenly spaced points around the equator of each fruit. The average value is the CCI value for that fruit. A higher CCI value indicates a more mature orange-red peel color. Leaf Physiological Status: 15 days after the second application, visually assess each tree and record the percentage of plants showing slight yellowing or leaf edge scorch.

[0080] Experimental data Table 3 Comparative test data of treatment effects of Example 1 and Comparative Example 3

[0081] Summary of experimental results The experimental data in Table 3 clearly show that the experimental group using the method of Example 1 of the present invention significantly outperformed the control group using the method of Comparative Example 3 in terms of fruit soluble solids content, solid-to-acid ratio, and citrus chromaticity index, which characterizes the color of the peel. More notably, due to the use of an ultra-high concentration of 5-aminolevulinic acid in the control group, some leaves of the plants showed adverse physiological reactions. This result strongly demonstrates that simply increasing the concentration of the core component does not necessarily lead to better results; exceeding the specific optimization range can actually have negative effects.

[0082] This phenomenon profoundly reveals the complexity of plant physiological regulation and the scientific nature of the concentration range defined by the method of the present invention. There is an optimal concentration window for the action of any biologically active substance. In the method of the present invention, 5-aminolevulinic acid within a specific range can serve as a precursor for chlorophyll synthesis, safely and effectively improving photosynthetic efficiency. However, once its concentration is too high, it may cause stress to plant cells, disrupt normal metabolic balance, and even produce cytotoxicity, directly damaging the leaves that serve as photosynthesis factories. The leaf scorch phenomenon that occurred in the control group is a manifestation of this negative effect. The photosynthetic capacity of the damaged leaves will inevitably decrease, resulting in a reduction in the production and output of sugars, which ultimately makes the sugar accumulation and color development of the fruit inferior to those of the experimental group.

[0083] Therefore, this testing fully demonstrates a key innovation of the present invention: the achievement of its technical effectiveness hinges not only on the selection of functional components, but also on the discovery of the specific concentration range within which these components are safe and highly effective. This demonstrates that the success of the present invention is based on a deep understanding of plant physiology and extensive experimental optimization, and that the concentration parameters provided are essential technical features for achieving the intended technical objectives and balancing synergy and safety. It also demonstrates that the present invention is a meticulously designed, complete technical solution, not a simple summation of components, and that the defined parameter ranges themselves constitute an essential component of the invention.

[0084] Test Example 4: Verification of the rationality of the concentration range of synergistic components Description of experimental steps 1. Experimental materials and grouping: Twenty healthy citrus trees were selected from locations and conditions similar to those described above and randomly divided into two groups, 10 trees in each group, namely the experimental group and the control group.

[0085] 2. Preparation processing: Experimental group: The preparation solution prepared in Example 1 was used.

[0086] Control group: The original solution of the preparation prepared in Comparative Example 4 was used. Both preparations were diluted 800 times with clean water before use, stirred evenly and then used.

[0087] 3. Application method: The application period and method are the same as those in Test Example 1. Two standardized foliar sprays were applied to the crowns of the citrus trees in each group.

[0088] 4. Sample collection and processing: The operating procedures are the same as those in Test Example 1. During the commercial maturity of the fruit, sufficient and representative fruit samples were collected according to the specifications.

[0089] 5. Index determination: Soluble solids content: Same method as Test Example 1. Sucrose content: Same method as Test Example 1, measured by high performance liquid chromatography. Citrus color index: Same method as Test Example 3, measured by a portable colorimeter.

[0090] Experimental data Table 4 Comparative test data of treatment effects of Example 1 and Comparative Example 4

[0091] Summary of experimental results As shown in the test data in Table 4, the experimental group treated with the method of Example 1 of the present invention achieved significantly higher fruit soluble solids content, sucrose content, and citrus chromaticity index than the control group treated with the method of Comparative Example 4. The potassium phosphite concentration in the control group preparation fell below the effective range defined by the present method, significantly reducing its effect on improving fruit quality. This result clearly demonstrates the necessity of the component concentration ranges proposed by the present invention, and in particular, the establishment of its lower limit has important technical significance.

[0092] The experimental results profoundly confirm the synergistic mechanism on which the present invention relies. In the technical system of the present invention, sufficient phosphite is a key catalyst as a carbon fixation link, and its role is to undertake and convert the energy brought by the light-harvesting link enhanced by 5-aminolevulinic acid. In the control group, due to insufficient concentration of phosphite, its catalytic ability cannot match the enhanced light energy capture ability, causing the "carbon fixation" link of the entire photosynthetic chain to once again become an efficiency bottleneck. This is like a production line. Even if the supply of front-end raw materials is increased, if the processing capacity of the mid-end processing equipment is insufficient, the final output will still be limited. Therefore, the sugar accumulation of the fruits in the control group and the color conversion process that depends on energy supply are both inhibited.

[0093] This test strongly supports a core inventive point of the present invention: its outstanding effect does not come from the simple existence of individual ingredients, but from a synergistic system in which each component can only be fully activated within a specific concentration range. The lower concentration limit determined by the present invention is the critical threshold to ensure that each link can match each other and improve synchronously. Below this threshold, the system synergistic effect will collapse and the expected technical level will not be achieved. This fully demonstrates that the formula parameters of the present invention have been scientifically designed and optimized, and its limitation on the concentration range is an indispensable part of the complete technical solution, reflecting the rigor and advancement of the invention.

[0094] Test Example 5: Verification of the Necessity of Preparation Steps Description of experimental steps 1. Experimental materials and grouping: Twenty healthy citrus trees were selected from locations and conditions similar to those described above and randomly divided into two groups, 10 trees in each group, namely the experimental group and the control group.

[0095] 2. Preparation processing: Experimental group: The preparation solution prepared in Example 1 was used.

[0096] Control group: The preparation solution prepared in Comparative Example 5 was used. Samples of both preparation solutions were taken and allowed to stand at room temperature in the dark for 7 days. Changes in appearance were observed and recorded. Subsequently, both preparation solutions were diluted 800-fold with water before use, stirred thoroughly, and then set aside.

[0097] 3. Application method: The application period and method are the same as those in Test Example 1. Two standardized foliar sprays were applied to the crowns of the citrus trees in each group.

[0098] 4. Sample collection and processing: The operating procedures are the same as those in Test Example 1. During the commercial maturity of the fruit, sufficient and representative fruit samples were collected according to the specifications.

[0099] 5. Index determination: Soluble solids content and solid acid ratio: the method is the same as that of Test Example 1.

[0100] Preparation stability observation: Samples of the two preparation stock solutions were sealed and allowed to stand at room temperature for 7 days. The clarity of the solution and the presence of stratification or precipitation were observed and recorded with the naked eye.

[0101] Experimental data Table 5 Comparative test data of treatment effect and formulation stability of Example 1 and Comparative Example 5

[0102] Summary of experimental results The experimental data in Table 5 clearly show that the experimental group using the method of Example 1 of the present invention significantly outperformed the control group using the method of Comparative Example 5 in terms of both the physical stability of the preparation itself and the ultimate effect on improving fruit quality. Since the control group omitted the precise pH control step during the preparation process, not only did the preparation become physically unstable, but its biological effect was also greatly weakened, which directly demonstrates the necessity of the specific steps in the preparation process of the present invention.

[0103] This result profoundly reveals the innovative connotation of the method of the present invention in the preparation process. First, from a physicochemical point of view, the preparation of the present invention is a complex system containing a variety of acids, bases, salts and organic matter, and its pH value directly determines the solubility and ionic state of each component. The pH value of the control group preparation that was not pH-controlled deviated from the stable range, resulting in a decrease in the solubility of some components and the formation of precipitation over time. This instability not only affects the shelf life and commercial value of the product, but also means that the concentration of the active ingredient in the spray solution is no longer accurate during actual use. Secondly, from the perspective of plant physiology, the absorption efficiency of foliar spraying is closely related to the pH value of the spray solution. An optimized solution in a specific pH range can better match the charge characteristics of the leaf epidermis and promote the transmembrane transport of nutrients and active ingredients. Due to the inappropriate pH, the preparation of the control group greatly reduced the absorption efficiency of the leaves for the active ingredients, and even if the ingredients existed, they could not be efficiently utilized.

[0104] Therefore, this test strongly demonstrates a core inventive point of the present invention: its success lies not only in the innovative formulation, but also in the innovative preparation method. Precise pH control is a key technical step in ensuring the effectiveness of the present invention's formulation throughout its entire process, from production and storage to final field application. It ensures the product's physical stability and bioavailability, a prerequisite for activating the synergistic effects of the entire formulation. This fully demonstrates that the preparation method disclosed herein, including the specific process steps, is an indivisible whole, and that these specific steps are crucial for achieving the ultimate technical purpose of the present invention.

[0105] Test Case 6: Innovative Verification of Application Methods Description of experimental steps 1. Experimental materials and grouping: Twenty healthy citrus trees were selected from locations and conditions similar to those described above and randomly divided into two groups, 10 trees in each group, namely the experimental group and the control group.

[0106] 2. Formulation Treatment: Both the experimental and control groups used the same batch of formulation solution prepared in Example 1. It was diluted 800-fold with water before use, stirred evenly, and then used. In this test, the formulation used in both groups was identical.

[0107] 3. Application method: Experimental group: The application method described in Example 1 of the present invention was used, that is, the first spraying was performed when the citrus flowers were 2 / 3 withered, and the second spraying was performed 30 days after the first spraying.

[0108] Control group: The application method described in Comparative Example 6 was used. The first spraying was performed during the peak flowering period of the citrus fruits, and the second spraying was performed 10 days after the first application. Except for the different application times, the remaining spraying procedures remained the same.

[0109] 4. Sample collection and processing: The operating procedures are the same as those in Test Example 1. During the commercial maturity of the fruit, sufficient and representative fruit samples were collected according to the specifications.

[0110] 5. Index determination: Soluble solids content: Same method as Test Example 1. Sucrose content: Same method as Test Example 1, measured by high performance liquid chromatography. Citrus color index: Same method as Test Example 3, measured by a portable colorimeter.

[0111] Experimental data Table 6 Comparative test data of treatment effects of application methods of Example 1 and Comparative Example 6

[0112] Summary of experimental results The experimental data in Table 6 demonstrates a striking conclusion: even with the exact same formulation, differing solely in the timing of application can lead to significant differences in the final fruit quality. The experimental group, using the specific timing specified in Example 1, exhibited significantly higher soluble solids content, sucrose content, and citrus chromaticity index than the control group, which used the method of Comparative Example 6. This irrefutable evidence demonstrates that the specific timing of application proposed by the present invention is a key component in achieving its superior technical results.

[0113] This result profoundly reveals the scientific connotation of the method of the present invention being highly compatible with the growth and development rhythm of plants. During the growth cycle of citrus, the focus of nutrient distribution changes dynamically. The 2 / 3 period of flowering and withering selected by the present invention is a strong reservoir establishment period when young fruits have just formed and begin to develop rapidly. Application at this time can direct the enhanced photosynthetic production capacity to the fruit to the greatest extent, laying a solid foundation for subsequent sugar accumulation and quality formation. The second application precisely acts on the critical stage of fruit enlargement and rapid sugar accumulation, further strengthening this process. In contrast, during the peak flowering period selected by the control group, the physiological focus of the plant is on flowering and pollination, not fruit development. Premature application results in a large amount of photosynthetic products being consumed in nutritional growth rather than target organs; and its premature second application also misses the peak of sugar accumulation in the later period. This mismatch in time results in the same high-quality fertilizer not being used to the best effect, and the effect is greatly reduced.

[0114] Therefore, from the perspective of the application method, this test strongly highlights a core inventive point of the present invention: it not only provides a novel composition, but more importantly, it provides a complete set of efficient technical solutions that include a specific time-sequential application strategy. By discovering and defining this optimal time window, the present invention precisely couples the highly effective biological agent with the intrinsic physiological rhythm of the plant, thereby fully stimulating the potential of the composition. This fully demonstrates that the method steps of the present invention are not conventional operations in the field, but are the result of in-depth research and ingenious design. This specific application method itself is an indispensable technical feature for achieving the purpose of the present invention, reflecting the integrity and innovativeness of the invention.

[0115] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for enhancing the coloring and sugar content of citrus fruits based on 5-aminolevulinic acid, characterized in that: a. Constructing a synergistic core system: 5-aminolevulinic acid or a salt thereof, a phosphite and a polyol are mixed in an aqueous medium to obtain a synergistic core system; b. Preparation of a complete functional preparation: In the synergistic core system obtained in step a, free amino acids, reducing sugars and vitamin C are further added, and the pH value is adjusted to obtain a functional preparation solution; c. The first critical period of application: In the citrus flowers 2 / 3 period, the functional preparation solution obtained in step b was diluted and sprayed on the citrus plants; d. Second critical period application: within 25 to 35 days after the first application, the citrus plants are sprayed on the leaves again.

2. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 1, characterized in that: The phosphite described in step a is potassium phosphite; and the polyol is sorbitol.

3. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 1, characterized in that: The final concentration of each component in the functional preparation stock solution described in step b is: 5-aminolevulinic acid or its salt: 5-50 g / L; Phosphite: 50-200 g / L; Polyol: 50-150g / L; Free amino acids: 50-100 g / L; Reducing sugar: 10-50 g / L; Vitamin C: 10-100 mg / L.

4. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 1, characterized in that: The pH adjustment described in step b is to adjust the pH value of the functional preparation stock solution to a range of 4.0 to 7.

0.

5. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 1, characterized in that: The specific operation of step a is to first add phosphite and polyol into an aqueous medium and stir until dissolved, and then add 5-aminolevulinic acid or a salt thereof.

6. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 1, characterized in that: The specific operation of step b is to add free amino acids, reducing sugars and vitamin C in sequence to the system prepared in step a, stir evenly and then adjust the pH value.

7. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 3, characterized in that: The dilution in step c and step d is to dilute the functional preparation stock solution with water by 200 to 1000 times.

8. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 7, characterized in that: For the foliage spraying in step c and step d, the amount of functional preparation stock solution used per mu is 50 to 500 ml.

9. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 3, characterized in that: The free amino acid is at least one of glycine, glutamic acid, and alanine, or a combination thereof, and the reducing sugar is glucose or fructose.

10. The method for enhancing color and increasing sugar content of citrus fruits based on 5-aminolevulinic acid according to claim 1, characterized in that: The foliar spraying described in step c and step d is specifically to spray the front and back of the leaves of the citrus plants evenly, so that the leaves are fully moistened but no dripping occurs.

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