Method for prolonging fresh-keeping period of fresh cut Chinese rose flowers by adding nano-silver and application

Abstract

The invention discloses a method for prolonging the fresh-keeping period of fresh cut Chinese rose flowers by adding nano-silver (AgNPs) and application demonstration. According to the method, AgNPs is added into the water solution for arranging the fresh cut Chinese rose flowers, so that the final concentration of the water solution is 2.5 mu g / mL, the water balance capability, the oxidation resistance and the antibacterial property of the fresh cut Chinese rose flowers can be remarkably improved, and the fresh-keeping period (vase life) of the fresh cut Chinese rose flowers is effectively prolonged. The invention provides a new method for prolonging the refreshing time of the fresh cut Chinese rose flowers, and the method has obvious practical application value.

Description

[0001] The invention is supported by the National Natural Science Foundation of China (31901184), Tianjin Natural Science Foundation (17JCYBJC22500) and Tianjin Key Experiment Open Fund for Animal and Plant Resistance. Technical Field

[0002] The invention belongs to the field of biotechnology, and in particular relates to a method for prolonging the shelf life of fresh cut roses and an application thereof. Background Art

[0003] At present, people's demand for plant preservation technology is increasing. However, many industry practitioners lack good post-harvest preservation methods, which leads to a certain degree of economic losses. Therefore, the field of plant preservation shows broad application research prospects. As an important part of plant preservation, fresh cut flower preservation also plays an important role in the industry.

[0004] The main reasons for the aging and wilting of fresh cut flowers include: (1) The water balance is destroyed: After the cut flowers are harvested, due to transpiration, water is consumed rapidly. If the water absorption rate is lower than the water loss rate, the cell turgor pressure decreases and the tissue wilts. (2) Cell aging: After shearing, a large amount of ethylene is produced, which produces a large number of reactive oxygen free radicals, causing the cut flowers to wilt. (3) Tracheal blockage: After the cut flowers are harvested, the incision at the end of the flower stem is easily blocked by bacteria and their secretions, metabolic products, etc., resulting in reduced water absorption of the xylem trachea, which eventually causes the water balance to be destroyed and wilted. (4) Respiratory consumption and lack of energy: After the cut flowers are separated from the body, photosynthesis weakens and the sugar content decreases, which affects normal metabolism and shortens the lifespan. To delay the aging of fresh cut flowers, corresponding measures should be taken, such as low-temperature storage, gas-controlled storage, keeping the trachea unobstructed, adding preservatives, etc.

[0005] There are many types of fresh cut flower preservatives on the market, mainly including the following categories: (1) Bactericidal preservatives: such as potassium permanganate, sodium bisulfite, etc., are mainly used for sterilization and preservation, inhibiting bacterial infection and extending the shelf life of flowers. (2) Inhibition of ethylene production: such as silver nitrate, silver thiosulfate, etc., by inhibiting ethylene production, delaying flower aging. (3) pH regulators: such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, etc., used to adjust the pH value of preservatives to ensure that cut flowers get enough nutrition and water. (4) Nutrients: such as sucrose, glucose, etc., provide nutrition for cut flowers, ensure their normal physiological functions, and make the flowers more colorful.

[0006] In recent years, with the widespread application of nanomaterials, nanomaterials have also shown broad prospects in the field of fresh cut flowers, which not only improves the preservation effect and quality of fresh cut flowers, but also promotes the innovation and development of cut flower preservation technology. Nanoparticles are tiny particles with a size between 1 and 100 nanometers. They can be composed of different types of materials such as metals, oxides, semiconductors, etc. They have unique physical, chemical and optical properties, and show obvious size effects and interface effects. Scientists have manufactured nanomaterials through microorganisms and plants, and have found that they can effectively extend the shelf life of plants without changing their chemical composition. For example, ion-chelated porous chitosan nanocrystals (Cu 2+ -ChNC) is used for efficient post-harvest preservation, which can effectively remove pesticide and herbicide residues on fruits and vegetables and significantly extend their shelf life. In addition, graphene oxide treatment of fresh cut roses extends their vase life.

[0007] Nanosilver (AgNPs) has strong antioxidant and antibacterial properties and is an environmentally friendly material. Studies have shown that the bioreduction properties of sage in the synthesis of sage and AgNPs particles enhance the antioxidant properties of environmentally friendly silver plant nanostructures. A large number of studies have also shown that AgNPs have antibacterial activity against Gram-positive and Gram-negative bacteria (such as Bacillus cereus, Bacillus subtilis, Escherichia coli and Staphylococcus aureus), so they are widely used in medical disinfection and sterilization. AgNPs are currently mainly used in the medical field, and there are few studies on AgNPs in the field of fresh cut flower preservation.

[0008] This study selected the fresh cut flowers of the rose variety 'Corolla' (Rosa chinensis 'Corolla') as experimental materials, and used morphological observation, cell activity determination, antioxidant and antibacterial index evaluation and other research methods to screen out the appropriate concentration of AgNPs that can effectively extend the shelf life of rose fresh cut flowers, and explore its preservation mechanism. Therefore, the present invention provides a method and application demonstration for extending the shelf life of rose fresh cut flowers using AgNPs. Summary of the invention

[0009] The purpose of the present invention is to disclose a method for extending the shelf life of fresh cut roses by adding nanosilver (AgNPs) of appropriate concentration.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0011] Observation and comparison experiments were carried out on fresh cut rose flowers with and without added AgNPs or with different concentrations of AgNPs. The survival, external morphology, cell activity, antioxidant enzyme activity and colony number of fresh cut rose flowers under different treatments were compared, and the optimal concentration of AgNPs that can effectively extend the shelf life of fresh cut rose flowers was screened out. At the same time, the vase life, relative water content, antibacterial and antioxidant effects of fresh cut rose flowers after AgNPs treatment were explored.

[0012] To this end, the present invention discloses the following technical contents:

[0013] A method for extending the shelf life of fresh cut roses by adding nanosilver (AgNPs) at an appropriate concentration, characterized by providing a suitable method for adding AgNPs and an optimal concentration. Method: Adding AgNPs to a water solution for culturing fresh cut roses. Optimum concentration: 2.5 μg / mL.

[0014] The present invention further discloses an application demonstration of extending the shelf life of fresh cut roses by adding an appropriate concentration of AgNPs. The application refers to adding AgNPs to the water solution of fresh cut roses to a final concentration of 2.5 μg / mL, thereby improving the water balance ability, antioxidant and antibacterial properties of the fresh cut roses, thereby effectively extending the shelf life (vase life) of the fresh cut roses.

[0015] The present invention provides a method and application for extending the shelf life of fresh cut roses by adding AgNPs. Compared with the prior art, the method has the following beneficial effects: by adding a certain concentration of AgNPs to cultivate fresh cut roses, the water balance ability, antioxidant and antibacterial properties of the fresh cut roses can be significantly improved, thereby extending the shelf life (vase life) of the fresh cut roses. The present invention provides a new method for extending the shelf life of fresh cut roses.

[0016] The present invention further discloses an application demonstration of extending the shelf life of fresh cut roses by adding AgNPs.

[0017] The experimental results show that: Figure 1 The morphological observation results of fresh cut roses treated with different concentrations of AgNPs. As can be seen from the figure, 2.5μg / mL AgNPs treatment can effectively extend the shelf life of fresh cut roses. The roses in the control group showed crooked heads at 7 days, the roses treated with 0.05-10μg / mL AgNPs had a shelf life of about 9 days, and the roses treated with 2.5μg / mL AgNPs were still very firm at 11 days, and their shelf life was 15 days. Therefore, compared with the control group, 2.5μg / mL AgNPs treatment effectively extended the shelf life of fresh cut roses by 8 days.

[0018] Figure 2The relative water content (WBV) of fresh cut rose flowers treated with different concentrations of AgNPs. When the water absorption is greater than the water loss, the relative water content is positive; when the water absorption is lower than the water loss, the relative water content is negative. Figure 2 It can be seen that as the number of days of cultivation of fresh cut flowers increases, the relative water content in the fresh cut flowers shows a decreasing trend. By comparing the 2.5μg / mL AgNPs treatment group and the control group, it can be seen that the relative water content of rose cut flowers in the 2.5μg / mL AgNPs treatment group is always higher than that in the control group, that is, the water balance ability of rose cut flowers treated with 2.5μg / mL AgNPs is higher than that of the control group.

[0019] Figure 3 The antioxidant enzyme activities of fresh cut roses treated with different concentrations of AgNPs. Compared with the control group, except for the high concentration (10-80 μg / mL) of AgNPs, the other concentrations of AgNPs treatment increased the activities of three antioxidant enzymes in fresh cut roses (P < 0.05), including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Among them, the three antioxidant enzyme activities of the 2.5 μg / mL AgNPs treatment group were the highest, significantly higher than those of the control group, indicating that the 2.5 μg / mL AgNPs treatment significantly enhanced the antioxidant capacity of fresh cut roses.

[0020] Figure 4 The results of Evans blue staining of rose fresh cut flower petals after being treated with different concentrations of AgNPs. Evans blue staining is a commonly used cell activity dye, which can reflect cell activity through staining. The darker the staining, the lower the cell activity, and the lighter the staining, the higher the cell activity. Figure 4 It can be seen that the blue color of the cut flower petals in the 2.5 μg / mL AgNPs treatment group was lower than that in the control group and the other concentrations of AgNPs treatment groups.

[0021] Figure 5 The results of bacterial solid-liquid culture at the end of the cut stem of fresh cut rose flowers treated with different concentrations of AgNPs. Figure 5 The results of 24 h of expanded culture on solid culture medium showed that with the increase of AgNPs concentration, the number of bacterial colonies at the base of the rose fresh-cut flower stems decreased. Figure 5 The culture in liquid culture medium also proved that the amount of bacteria in the control group was much greater than that in the AgNPs treatment group, and as the concentration of AgNPs increased, the number of bacteria decreased significantly (P<0.05). Therefore, AgNPs can effectively inhibit the reproduction of bacteria at the end of the cut stem of fresh cut roses and have obvious antibacterial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The morphology of fresh cut rose flowers treated with different concentrations of AgNPs.

[0023] Figure 2 Relative water content (WBV) of fresh cut rose flowers treated with different concentrations of AgNPs.

[0024] Figure 3 Antioxidant enzyme activities of fresh cut rose flowers treated with different concentrations of AgNPs.

[0025] Figure 4 These are the Evans blue staining results of fresh cut rose petals treated with different concentrations of AgNPs.

[0026] Figure 5 These are the results of bacterial solid-liquid culture at the end of the cut stem of fresh cut rose flowers treated with different concentrations of AgNPs.

[0027] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with specific embodiments.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0030] The various raw materials and equipment used in the present invention are all conventional commercially available products and can be directly purchased from the market.

[0031] The sources of the biomaterials used in the examples are as follows: Chinese roses were purchased from Caozhuang Flower Market in Tianjin, and AgNPs stock solution was purchased.

[0032] Embodiment 1:

[0033] Rose cut flower preparation

[0034] The flowers used in the experiment were purchased from Caozhuang Flower Market in Xiqing District, Tianjin. Cut flowers of Rosa chinensis′Corolla′ with uniform thickness, uniform bud size, lush and healthy growth were selected. After cutting, the flower stem length was retained to 0.25m, the leaves were removed, and the flowers were inserted into vases for cultivation at room temperature.

[0035] Embodiment 2:

[0036] Treatment of fresh cut roses with different concentrations of nanosilver

[0037] Fresh cut roses were cultured in tap water without any reagents as the control group, and fresh cut roses were treated with different concentrations of AgNPs solution (prepared by diluting 1000mg / / L AgNPs stock solution) as the experimental group. A total of 11 groups (control group + 10 AgNPs treatment groups) were set up, namely control group, 0.01μg / mL treatment group, 0.05μg / mL group, 0.25μg / mL treatment group, 1μg / mL treatment group, 2.5μg / mL treatment group, 5μg / mL treatment group, 10μg / mL treatment group, 20μg / mL treatment group, 40μg / mL treatment group, 80μg / mL treatment group. After waking up, the fresh cut roses were vase-inserted into each treatment group, with 5 replicates in each group, and the liquid volume in each vase was 0.5L. The liquid was changed every three days.

[0038] Embodiment 3:

[0039] Index determination

[0040] (1) Relative water content of fresh cut roses

[0041] After culturing for 1, 3, 5, 7, 9, and 11 days, the weight of each rose fresh cut flower was weighed and recorded as fresh weight (FW). Five replicates were set for each group.

[0042] The calculation formula of relative water content (WBV) of fresh cut roses is: subtract the fresh weight of the previous days from the fresh weight of the latter days, for example: WBV after 1 day of treatment = FW after 3 days of treatment - FW after 1 day of treatment. Use the same formula to calculate the WBV values ​​of other treatment times and calculate the average value.

[0043] (2) Antioxidant enzyme activity assay

[0044] After 1, 4, and 7 days of culture, 1 g of fresh and clean petals were taken from each group, washed with distilled water, dried with filter paper, and homogenized on ice with 9 mL of phosphate buffered saline (PBS, pH = 7.2) solution in a mortar. After grinding, the mixture was placed in a centrifuge tube. Centrifuge at 13,000 r for 20 min at 4°C, and the supernatant (enzyme solution) was taken for enzyme activity testing. The activity of superoxide dismutase (SOD) was determined by the nitroblue tetrazolium method. The activity of peroxidase (POD) was determined by the guaiacol method. The activity of catalase (CAT) was determined by the hydrogen peroxide decomposition method. The determination of the activities of these three antioxidant enzymes are all common plant physiology methods.

[0045] (3) Cell activity detection

[0046] On the 2nd and 7th day of culture, petals were taken from each experimental group and placed in Evans blue dye solution (v:v=1:3) prepared with distilled water for 24 h. Decolorization was performed by adding decolorization solution. Then, decolorization was performed again with a mixture of glacial acetic acid: glycerol: strong decolorization solution: anhydrous ethanol in a volume ratio of 1:1:2:6. The decolorization was promoted by heating in a 100°C water bath. After the petals were decolorized, they were photographed.

[0047] (4) Antibacterial activity determination

[0048] ① Solid culture medium: After 6 days of culture of fresh cut roses, use a sterilized inoculation loop to collect bacteria from the base of the cut flower stems, and then inoculate the bacteria on MS solid culture medium, with three replicates for each group. Take photos after 24 hours of expansion culture.

[0049] ②Liquid culture medium: After culturing the fresh cut roses for 7 days, use a sterilized inoculation loop to take bacteria from the base of the cut flower stems, put the bacteria into MS liquid culture medium, stir and inoculate, then put it into a constant temperature shaker at 37°C, 200r / min, and expand the culture for 24 hours. After 24 hours, take the culture solution and drop it into a bacterial counting plate (0.5%). Counting plate (0.1mm, 1 / 400mm 2 ) and counted under a microscope.

[0050] The total number of bacteria in 1 mL of bacterial solution = (the total number of bacteria in 5 squares / 5) × 25 × 10000 × dilution factor

[0051] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for extending the shelf life of fresh cut roses by adding nanosilver (AgNPs), characterized in that Provides a suitable method and optimal concentration for adding AgNPs. Method: Add AgNPs to the water solution for rose fresh cut flower arrangement. Optimal concentration: 2.5μg / mL.

2. Application of the method and concentration of adding AgNPs as described in claim 1 in extending the shelf life of fresh cut roses.

3. The application described in claim 2 refers to adding AgNPs to the rose fresh cut flower arrangement aqueous solution in the manner and concentration described in claim 1 to improve the water balance ability, antioxidant and antibacterial properties of the rose fresh cut flowers, thereby effectively extending the shelf life (vase life) of the rose fresh cut flowers.

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