A mango alternative to paclobutrazol for shoot control and flowering promotion pgr-multifunctional structured molecule synergistic composition and its application

Abstract

The application discloses a mango shoot control and flower promoting PGRs-multifunctional structured molecular additive synergistic composition and application thereof, and belongs to the technical field of mango growth regulation. The composition is composed of five sub-compositions used in stages, each of the sub-compositions containing a plant growth regulator, a nutrient element and a specific structured molecular additive; the structured molecular additive is combined with the plant growth regulator through physical embedding, electrostatic adsorption or hydrophobic interaction. The application also provides an application method of the composition, including two stages of soil shoot control and leaf surface regulation. Through construction of an intelligent delivery system, the application realizes environment-responsive release, slow release and targeted delivery of active ingredients, effectively solves technical bottlenecks of poor stability, low targeting and high residual risk of traditional plant growth regulators, can accurately regulate the growth cycle of mangoes, significantly improves yield and quality, and greatly reduces pesticide residues and environmental load.

Description

Technical Field

[0001] This invention belongs to the field of mango growth regulation technology. Specifically, it relates to a multifunctional structured molecular adjuvant synergistic composition of PGRs containing paclobutrazol as an alternative to paclobutrazol for controlling shoot growth and promoting flowering in mangoes, and its application. Background Technology

[0002] Mangoes, as an important economic crop in tropical and subtropical regions worldwide, are undergoing increasingly refined and scientific cultivation management. During key growth stages such as shoot control, flowering promotion, and fruit retention, the tree is highly sensitive to endogenous hormones and exogenous regulatory substances. Back in the 1990s, soil application of paclobutrazol was a key technology that effectively solved the problem of difficult mango flowering and promoted off-season production. Currently, in Hainan mango production, in addition to soil application of paclobutrazol, farmers also use foliar spraying of paclobutrazol + potassium dihydrogen phosphate + ethephon to control excessive shoot growth and achieve nutrient accumulation. However, subsequent practice has shown that this technology has serious drawbacks: paclobutrazol treatment leads to a mango seed abortion rate of over 95%, which in turn induces fruit development stagnation, fruit drop, or a sharp drop in single fruit weight to 30-50 grams, severely restricting the final yield. Even more serious is that paclobutrazol has a residual effect in the soil for 0.5 to 1 year (half-life), and it takes as long as 3 years to completely decompose. Its long-term residue not only inhibits the root growth of mangoes and intercrops and interferes with the soil micro-ecology, but also causes continuous pollution to the soil and groundwater. It has been explicitly banned by the green food A-grade and above mango production standards.

[0003] Given the aforementioned limitations of paclobutrazol, research and application in this field have shifted towards other plant growth regulators (PGRs). Through years of trials replacing paclobutrazol with combined applications of various PGRs, including paclobutrazol, mango abortion rates have decreased, and the rate of naturally large fruits has significantly increased. However, current regulatory measures primarily rely on the phased application of PGRs (such as paclobutrazol and mepiquat chloride) with nutrients, using exogenous supplementation to mimic or enhance endogenous hormone signals, thereby guiding tree development. While this strategy reduces the indiscriminate nature of traditional management to some extent, its effectiveness is limited by the inherent defects of PGRs, including low physicochemical stability, poor permeability in plant tissues, and rapid degradation, making it difficult to maintain sufficient target site concentrations of the active ingredients in practical applications. Therefore, multiple high-dose applications are often required to maintain efficacy, increasing production costs and introducing risks of residues and environmental pollution.

[0004] Furthermore, existing PGRs compounding technologies mostly remain at the physical mixing level, lacking molecular-level synergistic design and structural regulation capabilities, thus failing to achieve on-demand release and precise delivery. Especially during critical periods such as mango flower bud differentiation, the tree's physiological state continuously changes, and conventional formulations are unable to respond to internal and external environmental signals (such as pH, light, and osmotic pressure), resulting in a mismatch between the timing of PGR release and the tree's needs, often leading to failure during the critical window period.

[0005] Therefore, the current technical bottleneck in mango cultivation has evolved from a simple issue of efficacy to an urgent need for a highly efficient, precise, and environmentally friendly regulatory system. How to overcome the fundamental limitations of traditional PGRs (propionic acid growers) formulations in their delivery mechanisms and construct a novel synergistic system capable of intelligently responding to mango physiological and environmental signals, achieving efficient utilization and targeted delivery of PGRs, thereby significantly improving cultivation benefits while ensuring fruit safety and ecological sustainability, has become a core technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] This invention provides a multifunctional structured molecular adjuvant synergistic composition of plant growth regulators (PGRs) for controlling shoot growth and promoting flowering in mangoes, which is an alternative to paclobutrazol. It consists of five seed compositions used in stages. Each seed composition contains a plant growth regulator, a nutrient element, and a specific structured molecular adjuvant. The structured molecular adjuvant is a nanoparticle, microcapsule, or nanovesicle formed by molecular self-assembly or chemical cross-linking. It binds to the plant growth regulator through physical encapsulation, electrostatic adsorption, or hydrophobic interaction to achieve environmentally responsive release, sustained release, or targeted delivery of the active ingredient.

[0008] The five-seed composition is as follows:

[0009] (1) The first seed composition used in the early stage of shoot control;

[0010] (2) A second seed composition used in the early stage of shoot control;

[0011] (3) A seed composition for use in the mid-stage of shoot control;

[0012] (4) Substances used in the later stages of shoot control;

[0013] (5) Seed composition for use during flowering.

[0014] Furthermore, the first seed composition for the initial stage of shoot control comprises: 167 ppm of uniconazole, 300 ppm of mepiquat chloride, 3 g / L of potassium dihydrogen phosphate, water, and 200 ppm of polylactic acid-polyethylene glycol self-assembled nanoparticles.

[0015] The mass ratio of uniconazole to mepiquat chloride loaded in the nanoparticles is 1:2.

[0016] Furthermore, the second seed composition for the initial stage of shoot control comprises: 200 ppm of uniconazole, 350 ppm of mepiquat chloride, 3 g / L of potassium dihydrogen phosphate, water, and 200 ppm of polylactic acid-polyethylene glycol self-assembled nanoparticles.

[0017] The nanoparticles contain uniconazole and mepiquat chloride in a mass ratio of 1:2.

[0018] Furthermore, the sub-composition for controlling shoot growth in the mid-term comprises: mepiquat chloride at a total concentration of 350 ppm, chlormequat chloride at a total concentration of 500 ppm, ethephon at a total concentration of 240 ppm, potassium dihydrogen phosphate at a total concentration of 3 g / L, water, and chitosan-sodium alginate composite hydrogel microcapsules at a total concentration of 150 ppm.

[0019] The mass ratio of mepiquat chloride to chlormequat chloride encapsulated in the microcapsules is 3:4.

[0020] Furthermore, the sub-composition for the later stage of shoot control comprises: 300 ppm of mepiquat chloride, 150 ppm of calcium cyclohexane, 5 ppm of inducing agent, 2 g / L of superphosphate and potassium compound fertilizer, water, and 100 ppm of azobenzene-modified polyethylene glycol nanocarrier.

[0021] The mass ratio of calcium cyclohexanoate to inducible agonist loaded on the nanocarrier is 4:1.

[0022] Furthermore, the sub-composition for the flowering period comprises: potassium nitrate at a total concentration of 20 g / L, borax at a total concentration of 10 g / L, ethephon at a total concentration of 200 ppm, 6-benzylaminopurine at a total concentration of 20 ppm, sodium nitrophenolate at a total concentration of 10 ppm, potassium dihydrogen phosphate at a concentration of 10 g / L, water, and phospholipid nanovesicles at a total concentration of 50 ppm.

[0023] The mass ratio of ethephon to 6-benzylaminopurine encapsulated in the nanovesicles is 5:1.

[0024] The present invention also provides an application of the synergistic composition, comprising two stages: soil-based shoot control and foliar regulation.

[0025] (1) During the soil shoot control stage, a ring trench is opened inside the drip line of the tree canopy, and 1 mL of 10% undiluted acetamiprid suspension is applied per meter of tree canopy diameter. After covering with soil, water is poured in.

[0026] (2) During the foliar regulation stage, each seed composition is applied sequentially by spraying: the first and second seed compositions are applied twice each during the initial stage of shoot control; the corresponding seed compositions are applied seven times during the middle stage of shoot control; the corresponding seed compositions are applied three times during the later stage of shoot control; and the corresponding seed compositions are applied three times during the flowering period.

[0027] Furthermore, the interval between each application of foliar regulation in the early stage of shoot control is 5 days; the interval between each application of foliar regulation in the middle stage of shoot control is 7 days; the interval between each application of foliar regulation in the late stage of shoot control is 10 days; and the interval between each application of foliar regulation during the flowering period is 3 days. Beneficial effects

[0028] (1) This invention utilizes four structural molecular auxiliaries with distinct functions (PLA-PEG nanoparticles, chitosan-sodium alginate microcapsules, azobenzene-modified nanocarriers, and phospholipid nanovesicles) to achieve sustained release, pH-responsive release, light-controlled release, and membrane-fused targeted delivery of active ingredients, respectively. This system can intelligently match the physiological needs of mangoes at different phenological stages (early, middle, and late stages of shoot control and flowering induction), enabling plant growth regulators to take effect at the "right time," "right location," and "right concentration," greatly improving the precision and efficiency of regulation. As shown in Example 2, this invention resulted in a shoot growth inhibition rate of up to 85.2%, a flower bud differentiation rate of 93.5%, a fruit setting rate of 87.9%, and a significant increase in yield per acre of 27.8%.

[0029] (2) This invention overcomes the problem of balancing "high yield" and "high quality" in traditional technologies. While achieving high yield (1820 kg per mu), it significantly improves the marketability of the fruit (marketable fruit rate of 92.3%) and internal quality (soluble solids of 19.1%, vitamin C content of 92.3 mg / 100g), and increases the rate of large fruit (single fruit weight ≥500g) to 28.3%. The overall economic benefits are better than those of traditional solutions.

[0030] (3) This invention benefits from the synergistic and reduced-application effects of structured adjuvants, greatly improving the utilization rate of active ingredients and significantly reducing the residue levels of various plant growth regulators in plants while achieving excellent agronomic results. Testing showed that after treatment with this invention, the residue levels of paclobutrazol, mepiquat chloride, chlormequat chloride, and calcium cyclamate in mango fruits, leaves, and branches were all at low levels, and the use of paclobutrazol and its associated long-term soil pollution risks were avoided. This fundamentally improves the residue risks in safe mango production and demonstrates excellent environmental compatibility. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this invention, the present application will be further described in detail below with reference to embodiments. Example 1

[0032] 1. Preparation of PLA-PEG nanoparticles loaded with uniconazole and mepiquat chloride:

[0033] PLA-PEG copolymer, uniconazole, and mepiquat chloride were dissolved in acetone (50 mg / mL) at a ratio of 50:1:2. The solution was then added dropwise to five times its volume of deionized water at a rate of 1 mL / min. The mixture was sonicated for 10 minutes (200 W) with stirring. The acetone was removed under reduced pressure at 40°C, and the resulting powder was freeze-dried to obtain nanoparticles. Analysis revealed nanoparticles with a particle size of 20-80 nm, with encapsulated uniconazole and mepiquat chloride loadings of 2% and 4%, respectively.

[0034] Polylactic acid-polyethylene glycol (PLA-PEG) amphiphilic block copolymers and hydrophobic polyhexane phosphates (PGRs) (uniconazole, mepiquat chloride) self-assemble to form nanoparticles. The hydrophilic segments of PEG enhance leaf spread and penetration, while the PLA core segments provide stable protection for the PGRs and enable sustained release. The nano-size effect significantly improves the penetration efficiency across the cuticle, ensuring sustained and efficient initial shoot control.

[0035] 2. Preparation of chitosan-sodium alginate composite hydrogel microcapsules encapsulating mepiquat chloride and chlormequat chloride:

[0036] Chitosan was dissolved in 1% acetic acid (20 mg / mL), and mepiquat chloride and chlormequat chloride (mepiquat chloride:chlormequat chloride:chitosan-sodium alginate mass ratio 2:3:30) were added as the aqueous phase; Span 80 was dissolved in liquid paraffin (5%) as the oil phase; the aqueous phase was added dropwise to the oil phase at 1000 rpm to form a W / O emulsion, and stirred for 30 minutes; an equal volume of sodium alginate aqueous solution (20 mg / mL) was added, and stirred for 10 minutes; 2% CaCl2 solution was added dropwise for crosslinking for 2 hours, the microcapsules were filtered, washed three times with water, and then freeze-dried to obtain microcapsule powder. Analysis showed that microcapsule powder with a particle size of 100-500 μm was obtained, with encapsulated mepiquat chloride and chlormequat chloride drug loadings of 15.0% and 20.0%, respectively.

[0037] Chitosan and sodium alginate form pH-sensitive composite hydrogel microcapsules through electrostatic interactions, encapsulating polycyclic aromatic hydrocarbon reductases (PGRs) (mepiride and chlormequat chloride). The microcapsules provide sustained release on the leaf surface, and their pH-sensitive properties dynamically regulate PGR release in response to changes in the leaf surface pH microenvironment. Simultaneously, the polysaccharide matrix enhances leaf adhesion, reducing PGR loss.

[0038] 3. Preparation of calcium cyclamate and inducing agent encapsulated on azobenzene-modified polyethylene glycol nanocarriers:

[0039] Azobenzene-PEG copolymer, calcium cyclohexane, and inducing agent were dissolved in dichloromethane (30 mg / mL) at a ratio of 200:4:1. The solution was then added dropwise to a 2% PVA aqueous solution. The mixture was ultrasonically emulsified for 15 minutes (300 W) in an ice bath, stirred at room temperature for 12 hours to evaporate the dichloromethane, and the carrier was collected by centrifugation. The carrier was washed three times with water and then freeze-dried to obtain nanocarrier powder. Analysis showed that the nanocarrier powder had a particle size of 50-150 nm, with encapsulated calcium cyclohexane and inducing agent loadings of 2.0% and 0.5%, respectively.

[0040] Azobenzene-modified polyethylene glycol (PEG) nanocarriers encapsulate polycyclic aromatic hydrocarbons (PGRs) (calcium cyclase and inducing hormones). Azobenzene undergoes cis-trans isomerization under specific wavelength ultraviolet light (365 nm), leading to changes in the hydrophilicity / phobicity or conformation of the carrier, triggering accelerated release of the PGRs. This allows the release of PGRs to dynamically respond to changes in light intensity (during periods of ample light and vigorous flower bud differentiation), achieving precise preparation for flower induction.

[0041] 4. Preparation of phospholipid nanovesicles encapsulating ethephon and 6-benzylaminopurine:

[0042] Lecithin, ethephon, and 6-benzylaminopurine were dissolved in chloroform (10 mg / mL) at a ratio of 100:1:0.2 and evaporated at 40°C to form a film. Ten times the volume of deionized water at 50°C was added for hydration with shaking for 1 hour. The mixture was then sonicated in an ice bath for 20 minutes (400 W) and freeze-dried to obtain nanovesicle powder. Analysis showed that the obtained nanovesicle powder had a particle size of 10-50 nm, with encapsulated ethephon and 6-benzylaminopurine drug loadings of 1.0% and 0.2%, respectively.

[0043] Lecithin self-assembles into nanovesicles, efficiently encapsulating polyurethane (PGRs) (ethephon and 6-benzylaminopurine). The phospholipid structure is similar to that of plant cell membranes, greatly facilitating the transmembrane penetration of PGRs into floral tissues. The nanovesicles provide a stable microenvironment, preventing premature degradation of PGRs and ensuring their efficient flower-promoting and fruit-setting effects during flowering.

[0044] 5. Preparation of the five-seed composition for phased use

[0045] (1) Preparation of the first seed composition in the early stage of shoot control

[0046] Objective: To prepare a 15 L final solution containing 167 ppm uniconazole, 300 ppm mepiquat chloride, 3 g / L potassium dihydrogen phosphate, and 200 ppm PLA-PEG self-assembled nanoparticles.

[0047] The required mass of PLA-PEG self-assembled nanoparticles is 200ppm × 15L = 3.0g.

[0048] The amount of PGRs contained in the 3.0g nanoparticles is: 3.0g × 2% = 0.06g (i.e. 4.0ppm) of uniconazole and 3.0g × 4% = 0.12g (i.e. 8.0ppm) of mepiquat chloride.

[0049] Additional free PGRs need to be added to achieve the target total concentration:

[0050] Additional tebuconazole: (167ppm - 4.0ppm) × 15L = 163.0ppm × 15L = 2.445g.

[0051] Additional mepiquat chloride: (300ppm - 8.0ppm) × 15L = 292.0ppm × 15L = 4.38g.

[0052] Dissolve 3.0g of nanoparticle powder, 2.445g of free tebuconazole, 4.38g of free mepiquat chloride, and 45g of potassium dihydrogen phosphate in an appropriate amount of water, stir well, and finally bring the volume to 15L.

[0053] (2) Preparation of the second seed composition in the early stage of shoot control

[0054] Objective: To prepare a 15 L final solution containing 200 ppm uniconazole, 350 ppm mepiquat chloride, 3 g / L potassium dihydrogen phosphate, and 200 ppm PLA-PEG self-assembled nanoparticles.

[0055] The required mass of PLA-PEG self-assembled nanoparticles is 200ppm × 15L = 3.0g.

[0056] The amount of PGRs contained in the 3.0g nanoparticles is: 3.0g × 2% = 0.06g (i.e. 4.0ppm) of uniconazole and 3.0g × 4% = 0.12g (i.e. 8.0ppm) of mepiquat chloride.

[0057] Additional free PGRs need to be added to achieve the target total concentration:

[0058] Additional tebuconazole: (200ppm - 4.0ppm) × 15L = 196.0ppm × 15L = 2.94g.

[0059] Additional mepiquat chloride: (350ppm - 8.0ppm) × 15L = 342.0ppm × 15L = 5.13g.

[0060] Dissolve 3.0g of nanoparticle powder, 2.94g of free tebuconazole, 5.13g of free mepiquat chloride, and 45g of potassium dihydrogen phosphate in an appropriate amount of water, stir well, and finally bring the volume to 15L.

[0061] (3) Preparation of the mid-term germination composition for shoot control

[0062] Objective: To prepare a 15 L final solution containing 350 ppm mepiquat chloride, 500 ppm chlormequat chloride, 240 ppm ethephon, 3 g / L potassium dihydrogen phosphate, and 150 ppm chitosan-alginate composite hydrogel microcapsules.

[0063] The required mass of composite hydrogel microcapsule powder to be added: 150ppm × 15L = 2.25g.

[0064] The amount of PGRs contained in the 2.25g microcapsule powder is: mepiquat chloride 2.25g × 15.0% = 0.3375g (i.e. 22.5ppm), chlormequat chloride 2.25g × 20.0% = 0.45g (i.e. 30.0ppm).

[0065] Additional free PGRs need to be added to achieve the target total concentration:

[0066] Additional mepiquat chloride: (350ppm - 22.5ppm) × 15L = 327.5ppm × 15L = 4.9125g.

[0067] Additional chlormequat chloride: (500ppm - 30.0ppm) × 15L = 470.0ppm × 15L = 7.05g.

[0068] Dissolve 2.25g of microcapsule powder, 4.9125g of free mepiquat chloride, 7.05g of free chlormequat chloride, and 3.6g (240ppm×15L) of ethephon in an appropriate amount of water, stir well, and finally bring the volume to 15L.

[0069] (4) Preparation of the late-stage shoot control composition

[0070] Objective: To prepare a 15L final solution containing 300ppm of mepiquat chloride, 150ppm of calcium cyclohexane, 5ppm of anaerobic acid, 2g / L of superphosphate-potassium compound fertilizer, and 100ppm of azobenzene-modified PEG nanocarrier.

[0071] The required mass of nanocarrier powder to be added: 100ppm × 15L = 1.5g.

[0072] The amount of PGRs contained in the 1.5g nanocarrier powder is: calcium cyclohexane 1.5g × 2.0% = 0.03g (i.e. 2.0ppm), and inducing hormone 1.5g × 0.5% = 0.0075g (i.e. 0.5ppm).

[0073] To achieve the target total concentration, additional free PGRs and nutrients need to be added:

[0074] Additional mepiquat: 4.5g (300ppm x 15L).

[0075] Additional calcium cyclohexane: (150ppm - 2.0ppm) × 15L = 148.0ppm × 15L = 2.22g.

[0076] Additional inducing agent: (5ppm - 0.5ppm) × 15L = 4.5ppm × 15L = 0.0675g.

[0077] Super phosphorus and potassium compound fertilizer: 30g.

[0078] Dissolve 1.5g of nanocarrier powder, 4.5g of free mepiquat chloride, 2.22g of free calcium cyclohexane, 0.0675g of free inducing agent, and 30g of super phosphorus and potassium compound fertilizer in an appropriate amount of water, stir well, and finally adjust the volume to 15L.

[0079] (5) Preparation of the flower-inducing composition

[0080] Objective: To prepare a 15 L final solution containing 20 g / L potassium nitrate, 10 g / L borax, 200 ppm ethephon, 20 ppm 6-benzylaminopurine, 10 ppm sodium nitrophenolate, 10 g / L potassium dihydrogen phosphate, and 50 ppm phospholipid nanovesicles.

[0081] The required amount of nanovesicle powder to be added is: 50ppm × 15L = 0.75g.

[0082] The amount of PGRs contained in the 0.75g nanovesicle powder is: ethephon 0.75g × 1.0% = 0.0075g (i.e. 0.5ppm), 6-benzylaminopurine 0.75g × 0.2% = 0.0015g (i.e. 0.1ppm).

[0083] To achieve the target total concentration, additional free PGRs and nutrients need to be added:

[0084] Additional ethephon: (200ppm - 0.5ppm) × 15L = 199.5ppm × 15L = 2.9925g.

[0085] Additional 6-benzylaminopurine: (20ppm - 0.1ppm) × 15L = 19.9ppm × 15L = 0.2985g.

[0086] Potassium nitrate: 300g.

[0087] Borax: 150g.

[0088] Sodium nitrophenolate: 0.15g.

[0089] Potassium dihydrogen phosphate: 150g.

[0090] Dissolve 0.75g of nanovesicle powder, 2.9925g of free ethephon, 0.2985g of free 6-benzylaminopurine, 300g of potassium nitrate, 150g of borax, 0.15g of sodium nitrophenolate, and 150g of potassium dihydrogen phosphate in an appropriate amount of water, stir well, and finally bring the volume to 15L. Example 2

[0091] 1. Materials and Methods

[0092] In a 50-mu (approximately 3.3 hectares) orchard of 'Tainong No. 1' mangoes in Sanya City, Hainan Province, the trees were 8 years old, with a spacing of 4 m × 5 m between trees. The orchard was treated with fruit trees of uniform growth.

[0093] Application procedure: Strictly follow the methods described and the time points outlined below.

[0094] (1) Soil-based shoot control: Implemented on May 20, 2023. Dig a circular trench 12 cm deep along the inner side of the tree canopy drip line, apply 8 mL of 10% clopidogrel suspension to each tree (based on a tree canopy diameter of 8 m), cover with soil immediately after application and water thoroughly.

[0095] (2) Leaf control: Use a pressure sprayer (equipped with a fan-shaped nozzle, working pressure 0.3 MPa) to spray the leaves evenly, strictly avoiding high temperature periods and rainy weather.

[0096] a) Initial stage of shoot control: Started on June 10 (when the second clump of leaves begins to turn green).

[0097] June 10 and June 15: Spray the first seed composition for early shoot control prepared in Example 1, 1L per plant, with an interval of 5 days between each spraying.

[0098] June 20 and June 25: Spray the second seed composition for the initial shoot control stage prepared in Example 1, with a spraying amount of 1.2L per plant, and an interval of 5 days between each spraying.

[0099] b) Mid-term shoot control: Started on July 5.

[0100] July 5, 12, 19, 26 and August 2, 9, 16: Spray the shoot-controlling mid-term ferrule composition prepared in Example 1, 1 L per plant, with an interval of 7 days between each application.

[0101] c) Late stage of shoot control: Started on August 25.

[0102] August 25, September 4, and September 14: Spray the late-stage shoot control compound prepared in Example 1, 1L per plant, with an interval of 10 days between each application.

[0103] d) Flowering induction period: Started on September 21 (7 days after the last application of pesticide in the late stage of shoot control).

[0104] September 21, September 24, and September 27: Spray the flowering-inducing seed composition prepared in Example 1 at a rate of 0.8L per plant, with an interval of 3 days between each application.

[0105] Comparative Example 1: Traditional Regulator

[0106] In the same orchard and with the same varieties as in Example 2, the exact same types and concentrations of plant growth regulators were used, but without any structured molecular auxiliaries (i.e., no nanoparticles, microcapsules, nanocarriers, or nanovesicles). The components were simply physically mixed and sprayed. The application time and frequency were exactly the same as in this invention group.

[0107] Comparative Example 2: Soil application of paclobutrazol + foliar application of shoot control

[0108] In the same orchard and variety as in Example 2, after mango harvesting, a 20cm deep circular trench was dug inside the drip line of the tree canopy, and paclobutrazol wettable powder with an active ingredient of 1.5g per meter of canopy diameter was applied. The soil was immediately covered and the soil thoroughly watered after application.

[0109] Foliar shoot control stage: Apply a traditional foliar shoot control agent once each at the initial stage (June 10th), the middle stage (July 5th), and the later stage (August 25th). The foliar shoot control agent is a mixed aqueous solution of paclobutrazol, potassium dihydrogen phosphate, and ethephon. The preparation method is as follows: Add 15% paclobutrazol wettable powder, 99% potassium dihydrogen phosphate, and 40% ethephon aqueous solution to water in the specified proportions to prepare a mixed solution with a final concentration of 500 ppm paclobutrazol, 3 g / L potassium dihydrogen phosphate, and 200 ppm ethephon. Use a pressure sprayer for uniform foliar spraying, applying 1 L per plant.

[0110] Comparative Example 3: Blank Control

[0111] In the same orchard and with the same varieties as in Example 2, the same amount of water was sprayed throughout the process, without any plant growth regulator treatment.

[0112] Effect Comparison and Analysis

[0113] 1. An in vitro sustained-release test was conducted on the PLA-PEG nanoparticles loaded with tebuconazole and mepiquat chloride in Example 1.

[0114] The dialysis bag method was used. A certain amount of drug-loaded nanoparticle suspension (free drug group as control) was placed in a pretreated dialysis bag (MWCO: 3.5 kDa), sealed, and immersed in release medium (pH 5.5 phosphate-buffered saline (PBS) containing 0.1% Tween-80 to maintain leak conditions), and oscillated at 37°C and 100 rpm. At preset time points (0, 2, 4, 8, 12, 24, 48 h), the external release medium was aspirated, and an equal volume of fresh medium was added isothermally. The concentrations of tebuconazole and mepiquat chloride in the samples at each time point were determined by high performance liquid chromatography (HPLC), and the cumulative release rate was calculated. The data are summarized in Table 1.

[0115] 2. A pH-responsive release test was conducted on the chitosan-sodium alginate composite hydrogel microcapsules encapsulated with mepiquat chloride and chlormequat chloride in Example 1.

[0116] A method similar to dialysis bags was used, with two release media of different pH values ​​(pH 5.5 simulating the acidic environment during the active metabolic period of leaves, and pH 7.0 serving as a control). Drug-loaded microcapsules were placed in both media and shaken under the same conditions (37℃, 100 rpm). Samples were taken at equal time intervals, and drug concentrations were determined by HPLC. The data are summarized in Table 2.

[0117] 3. A phototriggered release test was conducted on the polyethylene glycol nanocarrier modified with calcium cyclohexane and inducing agent p-azobenzene in Example 1.

[0118] The drug-loaded nanocarrier solution was placed in a transparent glass bottle and subjected to irradiation with ultraviolet light of a specific wavelength (365 nm) (light intensity fixed at 50 mW / cm²). 2 One group was placed in a dark environment as a control. Both groups of samples were magnetically stirred at the same temperature. Samples were taken at different time points, and after centrifugation to remove the carrier, the concentration of drug released in the supernatant was determined by HPLC. The data are summarized in Table 3.

[0119] 4. Transmembrane permeation test was conducted on the phospholipid nanovesicles coated with ethephon and 6-benzylaminopurine in Example 1.

[0120] The Transwell cell permeation model was used. PBS solution containing drug-loaded nanovesicles was added to the upper chamber (donor chamber) of the Transwell apparatus, while blank PBS was added to the lower chamber (receiver chamber). Free drug solution without vesicles served as a control. The apparatus was incubated at 37°C with constant shaking. The solution in the lower chamber was collected at specific time points, and an equal volume of fresh medium was added. The drug concentration in the receiving chamber was determined by HPLC, and the apparent permeability coefficient (Papp) was calculated. The data are summarized in Table 4.

[0121] 5. The effect data of Example 2 and Comparative Examples 1-3 were all obtained by measuring the corresponding phenological stages using the following methods:

[0122] (1) Shoot growth inhibition rate: 10 days after the last application of the pesticide at the beginning of the shoot control period, 10 trees were randomly selected in each treatment plot. One new shoot was marked in each of the four directions of the tree canopy (east, west, south, north). The length of the shoot was measured regularly with a tape measure, and the average daily growth was calculated. The inhibition rate was obtained by comparing with Comparative Example 3 (blank control).

[0123] (2) Flower bud differentiation rate and flowering index: During the flower bud morphology differentiation period, the outer branches of the upper part of the canopy of each treatment were randomly selected, and the total number of buds and the number of flower buds were counted to calculate the flower bud differentiation rate. During the full bloom period, the average length of 30 inflorescences was randomly measured, and the number of hermaphroditic flowers was counted to calculate the ratio.

[0124] (3) Fruit setting rate and yield: 30 days after flowering (after physiological fruit drop), count the number of fruits set on the marked branches and calculate the fruit setting rate by comparing it with the total number of flowers at flowering time. At harvest, weigh all the fruits of the single plant to be tested, record the yield of the single plant, and convert it into the yield per mu.

[0125] (4) Large fruit rate: At harvest, all fruits of the single tree being tested are graded. The large fruit rate is defined as the percentage of fruits with a single fruit weight ≥ 500 grams to the total number of fruits set on that single tree. No less than 10 trees are randomly selected for each treatment for statistical analysis.

[0126] (5) Fruit quality: Fruits were sorted according to the national first-grade fruit standard (NY / T 492-2002), and the percentage of the total weight of marketable fruit to the total weight of the sample was calculated. 100 marketable fruits were randomly selected and weighed one by one using an electronic balance with an accuracy of 0.1 g, and the average value was calculated. Marketable fruits of uniform size were randomly selected, and the soluble solids (TSS) content of the fruit was determined using a digital display handheld refractometer; the vitamin C content was determined using the 2,6-dichlorophenolindophenol titration method.

[0127] (6) Pesticide residues: On the day of harvest, samples of fruits, mature functional leaves and current year branches of each treatment were randomly collected and analyzed by liquid chromatography-mass spectrometry (LC-MS / MS) according to the method specified in the national standard GB 2763-2021.

[0128] (7) Endogenous hormones: Leaf or bud samples were collected from plants during the key phenological period (flower bud physiological differentiation period), and after being quick-frozen in liquid nitrogen, the contents of gibberellin (GA3) and abscisic acid (ABA) were determined by enzyme-linked immunosorbent assay (ELISA).

[0129] All biological trait data were measured using random sampling, with each treatment repeated at least three times. Data results are expressed as mean ± standard deviation, and significance analysis was performed (*p < 0.05, indicating a significant difference compared to the control group). The test results are summarized in Table 5.

[0130] Table 1

[0131]

[0132] The data in Table 1 show that the cumulative release rates of uniconazole and mepiquat chloride in the drug-loaded nanoparticles were (28.5±1.8)% and (31.2±2.1)% respectively within 24 hours, indicating that more than 65% of the drug remained encapsulated within the particles for sustained release. The cumulative release rate only reached (92.3±3.5)% after 168 hours (7 days), demonstrating significant sustained-release characteristics compared to the free drug group, which released over 95% within 24 hours.

[0133] Table 2

[0134]

[0135] The data in Table 2 show that at pH 5.5, the cumulative release rates of mepiquat chloride and chlormequat chloride reached (65.4±3.2)% and (68.9±3.7)% respectively after 8 hours; while at pH 7.0, the release rates were only (42.1±2.8)% and (45.3±3.1)% respectively. Furthermore, at multiple detection time points (2h, 4h, 12h), the release rate at pH 5.5 was significantly higher than that at neutral pH. These results indicate that the microcapsules can intelligently respond to the physiological signals during the metabolically active period of mango leaves (pH drops to approximately 5.5), achieving rapid and on-demand drug release.

[0136] Table 3

[0137]

[0138] The data in Table 3 show that within 2 hours after the light was turned on, the release rates of calcium cyclohexane and inducing agents reached (45.6±2.5)% and (48.9±2.8)%, respectively; while in the same time period, the release rates of the dark control group were only (21.8±1.9)% and (24.1±2.2)%. Furthermore, the release rate of the light-illuminated group reached over 60% within 4 hours, while the dark group required 8 hours to achieve the same level, demonstrating its excellent light-triggered release performance.

[0139] Table 4

[0140]

[0141] The data in Table 4 show that the Papp values ​​of ethephon and 6-benzylaminopurine encapsulated in phospholipid nanovesicles are (3.28 ± 0.25) × 10⁻⁶. -6 cm / s and (3.45 ± 0.28) × 10 -6cm / s; while the Papp value of the free drug group was only (1.12 ± 0.11) × 10 -6 cm / s and (1.08 ± 0.09) × 10 -6 cm / s. The encapsulation of nanovesicles increased the permeability of both drugs by an average of approximately 3 times, showing a significant difference.

[0142] Table 5

[0143]

[0144] As shown in Table 5, the shoot growth inhibition rate of Example 2 was as high as 85.2%, which was significantly better than the 62.1% of Comparative Example 1 (p<0.001), effectively reducing nutrient consumption from the source and laying a solid foundation for high yield. Regarding key flowering indicators, the flower bud differentiation rate (93.5%), inflorescence length (24.8 cm), and the proportion of hermaphroditic flowers (39.7%) of Example 2 were all significantly higher than those of Comparative Examples 1-3. This indicates that the present invention not only promotes flowering but also cultivates high-quality flowers with high yield potential. The final yield is determined by the fruit set rate, the number of fruits per plant, and the weight of a single fruit. Example 2 showed significant improvements in all three aspects: the fruit set rate increased to 87.9% (significantly higher than Comparative Examples 1-3); the yield per plant reached 54.5 kg; and the final yield was equivalent to 1820 kg per mu (approximately 1820 kg / acre), an increase of 400 kg per mu compared to Comparative Example 1 (1420 kg / acre), representing an increase of approximately 28.2%. Furthermore, the rate of large fruit in Example 2 (28.3%) far exceeded that of Comparative Example 1 (15.5%) and Comparative Example 3 (0.5%), significantly improving the commercial value and economic benefits of the fruit. This is the most direct manifestation of the technical advantages of the present invention, fully demonstrating the high efficiency of its precise control.

[0145] This invention not only pursues high yield but also emphasizes high quality. The internal and external quality of the fruit is simultaneously optimized: the marketable fruit rate reaches 92.3%, meaning that the vast majority of fruits meet market standards, significantly increasing their commercial value; the average single fruit weight is 325g, with a more uniform and larger shape; the internal quality is excellent, with soluble solids (19.1%) and vitamin C content (92.3 mg / 100g) significantly higher than comparative examples 1-3, resulting in better taste, flavor, and nutritional value. This demonstrates that this invention effectively overcomes the technical challenge of often failing to achieve both "high yield" and "high quality" in traditional technologies.

[0146] Most importantly, the residue detection data shows that the present invention (Example 2) can effectively control the residue levels of various plant growth regulators in different parts of the plant. Specifically, the residue levels of the four core plant growth regulators (uniconazole, mepiquat chloride, chlormequat chloride, and calcium cyclamate) in the fruit were all below 0.01 mg / kg; in the leaves, they were all below 0.008 mg / kg; and in the branches, they were all below 0.006 mg / kg. In contrast, in Comparative Example 1, which used a traditional physical mixing method, the residue levels of the above four PGRs in the fruit, leaves, and branches were significantly increased. Although the traditional soil application of paclobutrazol (Comparative Example 2) did not detect paclobutrazol residues in the fruit and mature leaves at harvest time, it still showed a significant residue of up to 0.85 mg / kg in its main site of action—the current year's shoots. This reflects the long-term retention characteristics of paclobutrazol in the xylem tissue of the tree, and its soil residue problem is even more serious. This demonstrates the core advantages of this invention: precise delivery, efficient utilization, and low residue achieved through structured molecular auxiliaries. Simultaneously, this method avoids the use of paclobutrazol, which was not detected in any of the tested sites, thus resolving the long-term environmental pollution and tree health risks associated with traditional technologies and providing a solid technical guarantee for the green and safe production of the mango industry.

[0147] Furthermore, although Comparative Example 2 (soil-applied paclobutrazol + foliar spray) showed significant effects in controlling shoot growth and promoting flowering, it has been phased out by the industry due to its low fruit set rate and serious soil residue pollution. Its yield was 120 kg per mu, significantly lower than that of Example 2 (1820 kg) and Comparative Example 1 (1420 kg).

[0148] In summary, this invention fundamentally changes the action mode of plant growth regulators through an intelligent delivery system of four structural molecular adjuvants with different functions (PLA-PEG nanoparticles, chitosan-sodium alginate microcapsules, azobenzene-modified nanocarriers, and phospholipid nanovesicles), upgrading them from traditional "single application, indiscriminate action" to "on-demand release, precise efficacy." This core mechanism successfully overcomes the application bottlenecks of existing technologies, such as easy degradation of active ingredients, poor targeting, and low utilization rates. Without increasing environmental burden, this invention simultaneously achieves synergistic optimization of "increased yield, improved quality, and ensured safety." Its comprehensive technical effect significantly surpasses traditional physical mixing schemes, providing an effective solution to common industry technical problems in mango cultivation, such as imprecise growth regulation and high risks of chemical pesticide residues. This is of great significance for promoting the industry's transformation towards green, efficient, and sustainable development.

Claims

1. A synergistic composition of a multifunctional structured molecular adjuvant-based shoot-regulating and flower-promoting PGRs (paclobutrazol alternative) for mangoes, characterized in that, It consists of a five-seed composition used in stages; The five-seed composition is as follows: (1) The first seed composition for the initial stage of shoot control comprises: 167 ppm of uniconazole, 300 ppm of mepiquat chloride, 3 g / L of potassium dihydrogen phosphate, water, and 200 ppm of polylactic acid-polyethylene glycol self-assembled nanoparticles; wherein the mass ratio of uniconazole to mepiquat chloride loaded in the nanoparticles is 1:2; (2) A second seed composition for the initial stage of shoot control, comprising: 200 ppm of uniconazole, 350 ppm of mepiquat chloride, 3 g / L of potassium dihydrogen phosphate, water, and 200 ppm of polylactic acid-polyethylene glycol self-assembled nanoparticles; wherein the mass ratio of uniconazole to mepiquat chloride loaded in the nanoparticles is 1:2; The preparation method of polylactic acid-polyethylene glycol self-assembled nanoparticles loaded with uniconazole and mepiquat chloride in the first and second seed compositions used for the initial stage of shoot control is as follows: polylactic acid-polyethylene glycol copolymer, uniconazole, and mepiquat chloride are dissolved in acetone at a mass ratio of 50:1:2 at 50 mg / mL, and dropped into 5 times the volume of deionized water at a rate of 1 mL / min. The mixture is then sonicated at 200 W for 10 minutes with stirring, and the acetone is removed by vacuum evaporation at 40℃. The nanoparticle powder is obtained by freeze-drying. (3) A sub-composition for controlling shoot growth during the mid-term, comprising: mepiquat chloride at a total concentration of 350 ppm, chlormequat chloride at a total concentration of 500 ppm, ethephon at a total concentration of 240 ppm, potassium dihydrogen phosphate at a total concentration of 3 g / L, water, and chitosan-sodium alginate composite hydrogel microcapsules at a total concentration of 150 ppm; wherein the mass ratio of mepiquat chloride to chlormequat chloride encapsulated in the microcapsules is 3:4; The preparation method of chitosan-sodium alginate composite hydrogel microcapsules encapsulating mepiquat chloride and chlormequat chloride in the sub-composition for controlling shoot growth in the middle stage is as follows: Chitosan is dissolved in 1% acetic acid at a concentration of 20 mg / mL, and mepiquat chloride and chlormequat chloride are added, wherein the mass ratio of mepiquat chloride:chlormequat chloride:chitosan-sodium alginate is 2:3:30 to form an aqueous phase; Span 80 is dissolved in 5% liquid paraffin as an oil phase; the aqueous phase is added dropwise to the oil phase at 1000 rpm to form a W / O emulsion, and stirred for 30 minutes; an equal volume of 20 mg / mL sodium alginate aqueous solution is added, and stirred for 10 minutes; 2% CaCl2 solution is added dropwise for crosslinking for 2 hours, the microcapsules are filtered, washed with water 3 times, and then freeze-dried to obtain microcapsule powder; (4) A seed composition for the later stage of shoot control, comprising: 300 ppm of mepiquat chloride, 150 ppm of calcium cyclohexane, 5 ppm of inducing agent, 2 g / L of superphosphate and potassium compound fertilizer, water, and 100 ppm of azobenzene-modified polyethylene glycol nanocarrier; wherein the mass ratio of calcium cyclohexane to inducing agent loaded on the nanocarrier is 4:1; The preparation method of the azobenzene-modified polyethylene glycol nanocarrier carrying calcium cyclic acid and inducing agent in the seed composition used for the later stage of shoot control is as follows: Azobenzene-polyethylene glycol copolymer, calcium cyclic acid, and inducing agent are dissolved in dichloromethane at a mass ratio of 200:4:1 and 30 mg / mL; the solution is added dropwise to a 2% polyvinyl alcohol aqueous solution, ultrasonically emulsified at 300 W for 15 minutes in an ice bath, stirred at room temperature for 12 hours to evaporate all dichloromethane, the carrier is collected by centrifugation, washed with water 3 times, and freeze-dried to obtain nanocarrier powder; (5) A seed composition for use during the flowering period, comprising: potassium nitrate at a total concentration of 20 g / L, borax at a total concentration of 10 g / L, ethephon at a total concentration of 200 ppm, 6-benzylaminopurine at a total concentration of 20 ppm, sodium nitrophenolate at a total concentration of 10 ppm, potassium dihydrogen phosphate at a total concentration of 10 g / L, water, and phospholipid nanovesicles at a total concentration of 50 ppm; wherein the mass ratio of ethephon to 6-benzylaminopurine loaded in the nanovesicles is 5:1; The preparation method of phospholipid nanovesicles encapsulating ethephon and 6-benzylaminopurine in the seed composition used for flower induction is as follows: lecithin, ethephon, and 6-benzylaminopurine are dissolved in chloroform at a mass ratio of 100:1:0.2 at 10 mg / mL, and the mixture is rotary evaporated at 40°C to form a film; 10 times the volume of deionized water at 50°C is added and hydrated by shaking for 1 hour; the mixture is then sonicated at 400 W for 20 minutes under ice bath conditions, and finally freeze-dried to obtain nanovesicle powder.

2. An application of the synergistic composition according to claim 1, characterized in that, It includes two stages: soil-based shoot control and foliar regulation. (1) During the soil shoot control stage, a ring trench is opened inside the drip line of the tree canopy, and 1 mL of 10% undiluted acetamiprid suspension is applied per meter of tree canopy diameter. After covering with soil, water is poured in. (2) During the foliar regulation stage, each seed composition is applied sequentially by spraying: the first and second seed compositions are applied twice each during the initial stage of shoot control; the corresponding seed compositions are applied seven times during the middle stage of shoot control; the corresponding seed compositions are applied three times during the later stage of shoot control; and the corresponding seed compositions are applied three times during the flowering period.

3. The application according to claim 2, characterized in that, The interval between each application of foliar regulation during the initial stage of shoot control is 5 days; the interval between each application of foliar regulation during the middle stage of shoot control is 7 days; the interval between each application of foliar regulation during the late stage of shoot control is 10 days; and the interval between each application of foliar regulation during the flowering period is 3 days.

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