Method for promoting coloring of peel and grains of tropical soft-seed pomegranate under high-temperature stress and application

Abstract

The invention belongs to the technical field of fruit tree cultivation, and provides a method for promoting coloring of peels and grains of tropical soft-seed pomegranates under high-temperature stress and application, the method comprises the following steps: carrying out root irrigation treatment on fruit trees by adopting a 5-aminolevulinic acid solution, and the concentration of the 5-aminolevulinic acid solution is 40-80mg. L <-1 >. Through cooperation of a specific exogenous chemical agent and a specific application method and concentration, the anthocyanin content of peel and grains of the tropical soft-seed pomegranate can be effectively increased, coloring is promoted, the sugar-acid ratio of fruits is improved, and therefore the appearance quality and the nutritional quality of the fruits are improved. The method is reasonable in design, easy and convenient to operate, safe, effective, low in equipment requirement and capable of being widely applied to commercialized production of tropical soft-seed pomegranate planting bases.

Description

Technical Field

[0001] This invention belongs to the field of fruit tree cultivation technology, specifically relating to a method and its application for promoting the coloring of the pericarp and seeds of tropical soft-seeded pomegranates under high-temperature stress. Background Technology

[0002] Pomegranate( Punica granatum L.) belongs to the genus *Punica* of the family Lythraceae. Punica The pomegranate is an important economic fruit tree, and its fruit is highly favored by consumers for its bright color, sweet and sour taste, and rich nutrition. The degree of coloring of the peel and seeds is a key indicator for evaluating the commercial value of pomegranates, directly affecting their appearance quality and market competitiveness.

[0003] The 'Danruo No. 1' tropical soft-seeded pomegranate was bred by Hainan Danruo Agricultural Co., Ltd. It is the first tropical soft-seeded pomegranate variety in my country to obtain plant variety rights certification. It can be sold off-season from January to June in Sanya, Ledong, Dongfang and other places in Hainan Province, with high economic benefits. However, the pomegranate fruits harvested in May and June have a phenomenon where the color of the peel and seeds fades from bright red to pink or reddish-yellow due to environmental factors such as high temperature, which greatly reduces the marketability of the fruit. Summary of the Invention

[0004] To address the above technical problems, this invention provides a method and application for promoting coloring of the peel and seeds of tropical soft-seeded pomegranates under high-temperature stress. By using specific exogenous chemical agents in conjunction with specific application methods and concentrations, the anthocyanin content of the peel and seeds of tropical soft-seeded pomegranates can be effectively increased, promoting coloring and improving the sugar-acid ratio of the fruit, thereby enhancing the appearance and nutritional quality of the fruit.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for promoting the coloring of the pericarp and seeds of tropical soft-seeded pomegranates under high-temperature stress, comprising: irrigating the fruit trees with a 5-aminolevulinic acid (5-ALA) solution at a concentration of 40-80 mg·L⁻¹. -1 .

[0007] Preferably, the concentration of the 5-aminolevulinic acid solution is 40 mg·L⁻¹. -1 Or 80 mg·L -1 .

[0008] Preferably, the dosage of the 5-aminolevulinic acid solution for root irrigation is 5 liters per tree per application.

[0009] More preferably, the root irrigation is performed 3 times, once every 10 days.

[0010] Preferably, the 5-aminolevulinic acid solution is prepared by dissolving 5-aminolevulinic acid powder in distilled water and adding 0.2% Tween-20.

[0011] More preferably, the 5-aminolevulinic acid powder is of analytical grade and has an active ingredient content of 99%.

[0012] Preferably, the fruit tree is a 2-year-old layered seedling of 'Danruo No. 1' soft-seeded pomegranate, and the fruit on the layered seedling is 1-2 weeks before the coloring period.

[0013] Preferably, the average daily temperature range during the high-temperature adverse period is 22~34 ℃, with the lowest temperature being 22~30 ℃ and the highest temperature being 27~34 ℃.

[0014] This invention also provides the application of the above method in improving the quality of tropical soft-seeded pomegranate fruits.

[0015] Preferably, improving the quality of tropical soft-seeded pomegranate fruit includes improving the color of the peel and seeds, increasing the anthocyanin content in the peel and seeds, and increasing the sugar-acid ratio of the fruit.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention creatively utilizes 40 mg·L⁻¹ to address the poor coloring of tropical soft-seeded pomegranates under high-temperature stress. -1 80 mg·L -1 Three root irrigations with 5-ALA can simultaneously promote the accumulation of anthocyanins in both the peel and seeds after a period of time, improving poor coloring of pomegranate peel and seeds under high temperatures, promoting coloring, improving the sugar-acid ratio of the fruit, and enhancing the appearance, nutritional quality, and marketability of the pomegranate. This invention is rationally designed, simple to operate, and suitable for large-scale promotion in pomegranate planting bases, effectively solving the problem of poor coloring of pomegranates caused by high temperatures and enhancing their commercial value. Attached Figure Description

[0018] Figure 1 These are photographs of the peel and seed coloring of 'Danruo No. 1' soft-seeded pomegranate layered seedlings after root irrigation with 5-aminolevulinic acid (5-ALA), abscisic acid (ABA), methyl jasmonate (MeJA), top spraying, and treatment with black shade netting. Detailed Implementation

[0019] To more clearly illustrate the present invention, the invention will be further described in detail below with reference to embodiments and accompanying drawings. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0020] Example

[0021] I. Experimental Materials

[0022] 1.1 Root drenching with 5-aminolevulinic acid (5-ALA) and foliar spraying with abscisic acid (ABA) and methyl jasmonate (MeJA)

[0023] 1.1.1 Main Materials

[0024] The soft-seeded pomegranate variety was a two-year-old layered seedling of 'Danruo No. 1'. The fruit of the layered seedling was 1-2 weeks before the coloring stage. It was planted at the Dongfang Base of Hainan Danruo Agricultural Co., Ltd. (located in Dongfang Overseas Chinese Farm, Dongfang City, Hainan Province). 5-ALA and ABA were analytical grade powders produced by Shanghai Yuanye Biotechnology Co., Ltd., and MeJA was an analytical grade oil produced by the same company.

[0025] 1.1.2 Other materials

[0026] Tween-20 (Soleb, 96% purity), distilled water, backpack sprayer, water bucket, watering can (10L capacity), electronic balance (0.001g accuracy), weighing paper, beaker, pipette, graduated cylinder, etc.; temperature and humidity recorder.

[0027] 1.2 Top misting and shade netting treatment

[0028] The soft-seeded pomegranate variety is 'Danruo No. 1', a two-year-old layered seedling. The fruit of the layered seedling is 1-2 weeks before the coloring stage. It is planted at the Ledong base of Hainan Danruo Agricultural Co., Ltd. (located in Jiusuo Town, Ledong County, Hainan Province). The black shade net has 20 needles and a shading rate of about 75%; top misting system is also used.

[0029] II. Test Methods

[0030] The average daily field temperature monitored during the experiment ranged from 22 to 34℃, with the average daily minimum temperature ranging from 22 to 30℃ and the average daily maximum temperature ranging from 27 to 34℃, as shown in Table 1.

[0031] Table 1. Average daily temperature at the base during the test period

[0032]

[0033] 2.1 Root drenching treatment with 5-ALA

[0034] (1) Time and frequency: Select healthy plants with uniform growth and start drenching the roots once every 10 days starting on May 1, 2025, for a total of 3 root drenching treatments.

[0035] (2) Concentration setting

[0036] Treatment 1 (Blank Control): No treatment was performed. Figure 1 The blank control is marked as "Chemistry".

[0037] Treatment 2 (20 mg·L) -1 5-ALA): Dissolve 1.5 g of 5-ALA powder in 75 L of distilled water, add 150 mL of Tween-20, and prepare a solution of 20 mg / L. -1 5-ALA solution. Apply 5 L to the roots of each tree, slowly pouring the solution within a 50 cm radius of the roots. Figure 1 The value is recorded as 20 mg·L. -1 5-ALA root drenching treatment.

[0038] Treatment 3 (40 mg / L) -1 5-ALA): Dissolve 3 g of 5-ALA powder in 75 L of distilled water, add 150 mL of Tween-20, and prepare a 40 mg / L solution. -1 5-ALA solution. Apply 5 L to the roots of each tree, slowly pouring the solution within a 50 cm radius of the roots. Figure 1 The value is recorded as 40 mg / L. -1 5-ALA root drenching treatment.

[0039] Treatment 4 (80 mg·L) -1 5-ALA): Dissolve 6 g of 5-ALA powder in 75 L of distilled water, add 150 mL of Tween-20, and prepare an 80 mg / L solution. -1 5-ALA solution. Apply 5 L to the roots of each tree, slowly pouring the solution within a 50 cm radius of the roots. Figure 1 The value is recorded as 80 mg·L. -1 5-ALA root drenching treatment.

[0040] Treatment 5 (160 mg·L) -1 5-ALA): Dissolve 12 g of 5-ALA powder in 75 L of distilled water, add 150 mL of Tween-20, and prepare a solution of 160 mg / L. -1 5-ALA solution. Apply 5 L to the roots of each tree, slowly pouring the solution within a 50 cm radius of the roots. Figure 1 The value is recorded as 160 mg·L. -1 5-ALA root drenching treatment.

[0041] Each treatment was set up with 3 repetitions, and each treatment had 5 trees. The treatment was carried out in the evening (17:00-18:00).

[0042] 2.2 ABA and MeJA spray treatment

[0043] (1) Time and frequency: Select healthy plants with uniform growth, start on May 11, 2025, and spray again 10 days later, for a total of 2 spray treatments.

[0044] (2) Concentration setting

[0045] Treatment 6 (600 μg·mL) -1 ABA): Dissolve 9 g of ABA powder in a small amount of anhydrous ethanol, add 30 mL of Tween-20, and then add 15 L of distilled water to prepare a solution of 600 μg·mL⁻¹. -1 ABA solution. Use a backpack sprayer to evenly spray the leaves and fruits of pomegranate plants until dripping wet, using 1 L per plant. Figure 1 The value is recorded as 600 μg·mL. -1 ABA spray treatment.

[0046] Treatment 7 (800 μg·mL) -1 ABA): Dissolve 12 g of ABA powder in a small amount of anhydrous ethanol, add 30 mL of Tween-20, and then add distilled water to prepare an 800 μg / mL solution. -1 The ABA solution was applied evenly to the leaves and fruits of the pomegranate plants using a backpack sprayer until dripping wet. The dosage was determined for each plant. Figure 1 The value is recorded as 800 μg·mL. -1 ABA spray treatment.

[0047] Treatment 8 (10 mM MeJA): Dissolve 32.66 mL of MeJA solvent in a small amount of anhydrous ethanol, add 30 mL of Tween-20, and then add distilled water to prepare a 10 mM MeJA solution. Use a backpack sprayer to evenly spray the leaves and fruits of the pomegranate plants until dripping wet, with a dosage of 1 L per plant. Figure 1 The treatment was recorded as 10 mM MeJA spray treatment.

[0048] Treatment Nine (15 mM MeJA): Dissolve 48.99 mL of MeJA solvent in a small amount of anhydrous ethanol, add 30 mL of Tween-20, and then add distilled water to prepare a 15 mM MeJA solution. Use a backpack sprayer to evenly spray the leaves and fruits of the pomegranate plants until dripping wet, with a dosage of 1 L per plant. Figure 1 The treatment was recorded as 15 mM MeJA spray.

[0049] Each treatment was repeated three times, with five trees per treatment, and the treatments were carried out in the evening (18:00-19:00). The bags were briefly removed before spraying and re-bagd 30 minutes after spraying.

[0050] 2.3 Top misting and shading treatment

[0051] Treatment 10 (Blank Control): No treatment was performed. Figure 1 The blank is recorded as a control (physics).

[0052] Treatment 11 (Top misting cooling treatment): On hot, sunny days, spray water mist for 15 minutes using a top misting system at 11:00, 13:00, and 16:00, and hang the fruit on May 1st until harvest after this batch of fruit has matured. Figure 1 The term "spray treatment" is used in this context.

[0053] Treatment 12 (Shade Net Treatment): The shade net was hung at a height of 3.5 m from May 1st until the harvest of this batch of fruit. Figure 1 The middle section indicates that it is a sunshade treatment.

[0054] Treatment Thirteen (Black Shade Net + Top Mist Cooling): Combine the treatments described in Treatments Eleven and Twelve above. Hang the nets from May 1st until the fruit matures and is harvested. Figure 1 The treatment is described as a combination of spraying and sunshade.

[0055] 2.4 Index Measurement

[0056] The color difference of the fruit and peel was measured after the treatment was completed (measured 10 days after the last application of 5-ALA root irrigation, ABA and MeJA spraying, and after fruit ripening for shading net and top spraying treatments). Afterwards, tissue samples were taken from the surface of the pomegranate peel to a depth of 1-2 mm towards the seeds using a peeler, and seed samples were also collected. These samples were quickly placed in liquid nitrogen and brought back to the laboratory for storage at -80 ℃. The anthocyanin content of the peel and seeds was then determined spectrophotometrically. Soluble sugars in the seeds were determined using a kit from Suzhou Greens Biotechnology Co., Ltd. (catalog number: CA-2-W), and citric acid content was determined using a kit from Suzhou Keming Biotechnology Co., Ltd. (catalog number: G0501F).

[0057] III. Results Analysis

[0058] 3.1. Analysis of pericarp and seed color

[0059] 3.1.1 Analysis of fruit peel color

[0060] like Figure 1 As shown, compared with the blank control, pomegranate peel and seeds treated with 5-ALA root irrigation under high temperature stress showed varying degrees of improvement, with the peel and seeds turning redder. The treatment with 40 mg·L⁻¹ resulted in the most significant improvement. -1 5-ALA and 80 mg·L -1 The 5-ALA root drenching treatment showed the best overall performance.

[0061] Table 2 Effects of different treatments on the color parameters of 'Danruo No. 1' pomegranate peel at high temperature

[0062]

[0063] Note: 1. Different lowercase letters after the data in the same column indicate significant differences (α=0.05, HSD test); 2. Peel brightness ( Value); peel Value (higher value indicates reddishness, lower value indicates green); peel Value (the higher the value, the more yellowish; the lower the value, the more bluish).

[0064] As shown in Table 2, different treatments altered the color parameters of the 'Danruo No. 1' pomegranate peel to varying degrees under high temperatures. In the chemical treatments, compared to the blank control (chemical), most treatments significantly reduced... The value of the fruit peel darkened, with 40 mg·L⁻¹ being the most significant. -1 and 80 mg·L -1 The 5-ALA root drenching treatment showed the most significant reduction in severity. The value increased significantly in most treatments, and the redness of the peel was enhanced, especially at 40 mg·L⁻¹. -1 and 80 mg·L -1 The 5-ALA root drenching treatment showed the most significant increase. The values ​​decreased after different treatments, with the highest value at 40 mg·L⁻¹. -1 The effects of spray treatment with 5-ALA and 15 mM MeJA were most pronounced.

[0065] In physical treatments, compared to the blank control (physical), different treatments... All values ​​increased, and the peel gloss also improved. The value also increased significantly in all treatments, indicating that the redness of the peel was enhanced, with the top spraying + shading treatment showing the most significant increase. The overall value decreased, and the yellowing of the peel lessened. Treatment with black shade netting and top spraying + shading resulted in a greater reduction.

[0066] In summary, both chemical and physical treatments improved the color of the fruit peel. Specifically, the chemical treatment group (40 mg·L⁻¹) showed the best results. -1 and 80 mg·L -1 5-ALA root drenching treatment showed the most significant effect in reducing the yellowish tinge of pomegranate peel and enhancing its color intensity, with a better improvement than the optimal treatment (top misting + shading) in the physical treatment group. Therefore, 40 mg·L⁻¹ was used. -1 and 80 mg·L -1 5-ALA root irrigation treatment has the best effect on improving fruit peel color.

[0067] 3.1.2 Grain Color Analysis

[0068] Table 3 Effects of different treatments on the color parameters of 'Danruo No. 1' pomegranate seeds at high temperature

[0069]

[0070] Note: 1. Different lowercase letters after the data in the same column indicate significant differences (α=0.05, HSD test); 2. Grain brightness ( Value); grains Value (higher values ​​indicate reddish hues, lower values ​​indicate green hues); grains Value (the higher the value, the more yellowish; the lower the value, the more bluish).

[0071] Table 3 shows that all treatments altered the color parameters of 'Danruo No. 1' pomegranate seeds to varying degrees under high temperatures. In the chemical treatments, compared to the blank control (chemical), most treatments significantly reduced... The brightness of soft-seeded pomegranate seeds darkened, especially at 40 mg·L⁻¹. -1 and 80 mg·L -1 The 5-ALA root drenching treatment showed the most significant reduction in severity. The value increased significantly in most treatments, and the reddishness of the grains increased, especially at 40 mg·L⁻¹. -1 and 80 mg·L -1 The 5-ALA root drenching treatment showed the most significant increase. The value also increased in most treatments, and the yellowness of the grains increased, especially at 40 mg·L⁻¹. -1 and 80 mg·L -1 The 5-ALA root drenching treatment showed the most significant effect.

[0072] In physical treatments, compared to the blank control (physical), different treatments... The values ​​all decreased, with the black shade net treatment showing the most significant reduction. The value increased significantly in all treatments, indicating an enhanced reddish hue in the kernels, particularly in the black shade net treatment and the top spraying + shading treatment. The value changes most significantly. The overall value increased, and the yellowing of the grains increased. The yellowing was more pronounced when treated with black shade netting and top spraying + shading.

[0073] In summary, both chemical and physical treatments altered the color of the grains. Specifically, the chemical treatment group (40 mg·L⁻¹) showed the most significant change. -1 and 80 mg·L -1The 5-ALA root irrigation treatment was most effective in changing the grain color towards a stronger reddish and yellowish hue, and the degree of improvement was slightly better than the best treatment in the physical treatment group.

[0074] 3.2. Anthocyanin content analysis of pericarp and seeds

[0075] 3.2.1 Analysis of anthocyanin content in pericarp

[0076] Table 4. Effects of different treatments on anthocyanin content in the pericarp of 'Danruo No. 1' pomegranate at high temperature

[0077]

[0078] Note: Different letters after the data in the same column indicate significant differences (α=0.05, HSD test).

[0079] Table 4 shows that the anthocyanin content in the peel of 'Danruo No. 1' pomegranate changed to varying degrees after different treatments at high temperatures. In the chemical treatments, compared with the blank control (chemical), most treatments significantly increased the anthocyanin content, with 40 mg·L⁻¹ being the most significant. -1 and 80 mg·L -1 The 5-ALA root drenching treatment showed the most significant increase, while other treatments such as 600 μg·mL⁻¹ showed the least. - 1 ABA spray treatment and 10 mM MeJA spray treatment also significantly increased [the concentration of the substance]. However, compared to 40 mg·L [the concentration of the substance], [the concentration of the substance was significantly increased]. -1 and 80 mg·L -1 The increase was relatively small with 5-ALA root drenching treatment.

[0080] In the physical treatments, all treatments significantly increased anthocyanin content compared to the blank control (physical). The black shade net treatment and the top misting + shading treatment showed the most significant increases, while the top misting treatment increased anthocyanin content to a lesser extent.

[0081] In summary, both chemical and physical treatments significantly increased the anthocyanin content in the pericarp. Among all treatments, the chemical treatment group (40 mg / L) showed the highest anthocyanin content. -1 and 80 mg·L -1 The 5-ALA root irrigation treatment was the most effective in increasing anthocyanin content, and the degree of improvement was better than that of the optimal treatment in the physical treatment group.

[0082] 3.2.2 Analysis of anthocyanin content in grains

[0083] Table 5. Effects of different treatments on anthocyanin content in 'Danruo No. 1' pomegranate seeds at high temperature.

[0084]

[0085] Note: Different letters after the data in the same column indicate significant differences (α=0.05, HSD test).

[0086] As shown in Table 5, the anthocyanin content of 'Danruo No. 1' pomegranate seeds changed to varying degrees after different treatments at high temperatures. In the chemical treatments, compared with the blank control (chemical), most treatments significantly increased the anthocyanin content of the seeds, with 80 mg·L⁻¹ being the most significant. -1 The 5-ALA root drenching treatment showed the most significant increase, at 40 mg·L⁻¹. -1 5-ALA root drenching is the second best treatment. Other treatments include 20 mg·L⁻¹. -1 5-ALA root drenching treatment and 600 μg·mL -1 ABA spray treatment also significantly increased, but to a lesser extent.

[0087] In the physical treatments, the top spraying treatment did not show a significant change compared to the blank control (physical), but the black shade net treatment and the top spraying + shading treatment significantly increased the anthocyanin content of the grains, with the top spraying + shading treatment showing the most significant increase.

[0088] In summary, both chemical and physical treatments increased the anthocyanin content in the seeds. Specifically, the chemically treated group showed an anthocyanin content of 80 mg / L. -1 and 40 mg·L -1 The 5-ALA root irrigation treatment was the most effective in increasing anthocyanin content, and its promoting effect was superior to that of the physical treatment group.

[0089] 3.3. Analysis of soluble sugars, citric acid, and sugar-acid ratio

[0090] Table 6. Effects of different treatments on soluble sugars, citric acid, and sugar-acid ratio in 'Danruo No. 1' pomegranate at high temperatures.

[0091]

[0092] Note: Different letters after the data in the same column indicate significant differences (α=0.05, HSD test).

[0093] As shown in Table 6, different treatments had varying degrees of effect on the soluble sugar content, citric acid content, and sugar-acid ratio of 'Danruo No. 1' pomegranate at high temperatures. In the chemical treatments, compared to the blank control (chemical), most treatments significantly increased the soluble sugar content, with 40 mg·L⁻¹ being the most significant increase. -1 80 mg·L -1 and 160 mg·L -1 The 5-ALA root drenching treatment showed the most significant effect. The citric acid content in most treatments was lower than that in the control, with the 40 mg·L⁻¹ treatment showing the highest level. -15-ALA showed the most significant effect. The sugar-acid ratio increased significantly in most treatments, indicating improved fruit sweetness, with 40 mg·L⁻¹ being the most prominent. -1 80 mg·L -1 and 160 mg·L -1 The 5-ALA root drenching treatment showed significant results, and the 10 mM MeJA spray treatment also showed outstanding performance.

[0094] In the physical treatments, compared with the blank control (physical), all treatments significantly increased the soluble sugar content, significantly decreased the citric acid content in all treatments, and significantly increased the sugar-acid ratio overall, indicating enhanced fruit sweetness. The top spraying treatment and the black shade net treatment showed the most significant increases.

[0095] In summary, all treatments improved the sugar-acid ratio of the fruit to varying degrees, thereby increasing sweetness. Specifically, the chemical treatment group (40 mg / L) showed the best results. -1 80 mg·L -1 and 160 mg·L -1 5-ALA root irrigation treatment showed a more significant effect in improving the sugar-acid ratio, and the degree of improvement was better than that of the optimal treatment in the physical treatment group.

[0096] Obviously, the above embodiments of the present invention are merely examples to illustrate the present invention more clearly, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all implementation methods here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for promoting coloring of the pericarp and seeds of tropical soft-seeded pomegranates under high-temperature stress, characterized in that, include: The fruit trees were treated with a 5-aminolevulinic acid solution, the concentration of which was 40-80 mg·L⁻¹. -1 The dosage of 5-aminolevulinic acid solution for root irrigation of fruit trees is 5 liters per tree per irrigation, and the number of irrigations is 3 times, once every 10 days.

2. The method according to claim 1, characterized in that, The concentration of the 5-aminolevulinic acid solution is 40 mg·L⁻¹. -1 Or 80 mg·L -1 .

3. The method according to claim 1, characterized in that, The 5-aminolevulinic acid solution is prepared by dissolving 5-aminolevulinic acid powder in distilled water and adding 0.2% Tween-20.

4. The method according to claim 3, characterized in that, The 5-aminolevulinic acid powder is of analytical grade and has an active ingredient content of 99%.

5. The method according to claim 1, characterized in that, The fruit tree in question is a two-year-old layered seedling of the 'Danruo No. 1' soft-seeded pomegranate, and the fruit on the layered seedling is 1-2 weeks before the coloring stage.

6. The method according to claim 1, characterized in that, The average daily temperature range during the high-temperature adverse period is 22~34℃, with the lowest temperature being 22~30℃ and the highest temperature being 27~34℃.

7. The application of the method according to any one of claims 1 to 6 in improving the quality of tropical soft-seeded pomegranate fruit.

8. The application according to claim 7, characterized in that, The improvement of tropical soft-seeded pomegranate fruit quality includes improving the color of the peel and seeds, increasing the anthocyanin content in the peel and seeds, and increasing the sugar-acid ratio of the fruit.

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