Application of a polysaccharide-based fertilizer in improving the mechanical strength of plant roots and lodging resistance under heavy metal stress

Abstract

The present invention discloses the application of a polysaccharide-based fertilizer in improving the mechanical strength of plant roots and the lodging resistance performance under heavy metal stress conditions, which relates to the agricultural field. The preparation method of the polysaccharide-based fertilizer comprises the following steps: S1: Static culture of the strain capable of producing extracellular polysaccharide to obtain a bacterial liquid; S2: Adding a fermentation medium into a fermentation tank, adjusting the pH value in the tank to 7.5-7.8, heating to 115-121 °C, sterilizing, and cooling; S3: Inoculating the bacterial liquid into the fermentation tank for fermentation, and obtaining a fermentation broth after filtering to remove the bacterial cells, wherein the fermentation broth is the polysaccharide-based fertilizer; S4: Adding trace elements into the fermentation broth according to the type of crops to prepare the polysaccharide-based fertilizer; The polysaccharide-based fertilizer of the present invention can relieve the inhibitory effect of heavy metals on plant roots, improve the root development level, especially it can significantly increase the proportion of structures such as lignin in plant roots, and the mechanical strength of the roots is significantly increased, thereby greatly improving the lodging resistance performance of crops.

Description

Technical Field

[0001] The present invention relates to the field of agriculture, and particularly to a polysaccharide-based fertilizer, a preparation method thereof and an application thereof. Background Art

[0002] Due to the escalation of human activities, global farmland is severely affected by the threat of heavy metal pollution. When growing crops in heavy metal-polluted farmland, their growth and development will be significantly inhibited, reducing the crop yield. At the same time, excessive heavy metals may also be transferred to the above-ground parts of plants and enter the human body through the food chain, leading to serious diseases such as cancer, kidney damage, and osteoporosis.

[0003] The root is the first plant part to come into contact with soil heavy metals. It is a necessary pathway for the transport of heavy metals to the above-ground parts and is also the part with the highest heavy metal accumulation. Therefore, the root is also one of the parts most severely poisoned by heavy metals. The presence of excessive heavy metal elements will not only cause the inhibition of root development and reduce the absorption of nutrient elements by the roots, but also due to the significant decline of indicators such as root length and root weight in the poorly developed roots, the synthesis pathway of root biological macromolecules is blocked, and the underdeveloped root structure will also cause a decline in the lodging resistance of plants, thus seriously affecting the growth of plants.

[0004] In summary, how to reduce the toxic effect of heavy metals on plant roots and improve the root development level and lodging resistance is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a polysaccharide-based fertilizer, a preparation method thereof and an application thereof.

[0006] The technical solution of the present invention is as follows:

[0007] An application of a polysaccharide-based fertilizer in improving the mechanical strength and lodging resistance of plant roots under heavy metal stress conditions, wherein the polysaccharide-based fertilizer comprises microbial polysaccharides obtained by fermenting strains capable of producing extracellular polysaccharides.

[0008] Preferably, the polysaccharide-based fertilizer further comprises trace elements.

[0009] Preferably, the usage method comprises the following steps: treating the crops by root irrigation with the polysaccharide-based fertilizer, spraying 10 - 30 mL / plant each time, applying once every 2 - 4 days, and continuously applying for 3 - 4 weeks; after cultivation, the lignin and mechanical strength of the roots of the crops are significantly improved.

[0010] Preferably, the crops include peppers and / or rapeseed

[0011] Preferably, the preparation method of the polysaccharide-based fertilizer comprises the following steps:

[0012] S1: Static-culturing the strains capable of producing exopolysaccharides to obtain a bacterial liquid;

[0013] S2: Adding a fermentation medium into a fermentation tank, adjusting the pH value in the tank to 7.5 - 7.8, heating to 115 - 121 °C, sterilizing, and cooling;

[0014] S3: Inoculating the bacterial liquid into the fermentation tank for fermentation, filtering to remove the thalli, and obtaining a fermentation broth, thus preparing the polysaccharide-based fertilizer.

[0015] Preferably, in step S1, the strains include Enterococcus faecium and / or Lactobacillus plantarum.

[0016] Preferably, it further comprises the following steps:

[0017] S4: Adding trace elements into the fermentation broth according to the type of crops to prepare the polysaccharide-based fertilizer.

[0018] Preferably, step S1 is specifically: culturing the strains with MRS medium, static-culturing to obtain a bacterial liquid; the OD600 value of the bacterial liquid is 4.0 - 6.0.

[0019] Preferably, in step S2, the fermentation medium comprises: 2 - 3.0 wt% of sucrose, 0.5 - 1.0 wt% of peptone, 0.02 - 0.05 wt% of potassium dihydrogen phosphate, and the balance is water.

[0020] Preferably, in step S3, the fermentation temperature is 28 - 33 °C, the fermentation time is 36 - 40 h, the polysaccharide content in the fermentation broth is 1500 - 2000 mg / L;

[0021] The inoculation amount of the bacterial liquid is 3 - 5% of the volume of the material.

[0022] The beneficial effects of the present invention are as follows: The present invention adopts the polysaccharide-based fertilizer, which can effectively alleviate the inhibitory effect of heavy metals on the roots of plants, improve the root development level. In particular, it can significantly increase the proportion of structures such as lignin in the roots of plants, and the mechanical strength of the roots is significantly increased, thereby greatly improving the lodging resistance of crops. Therefore, the polysaccharide-based fertilizer prepared by the present invention is applied to promoting the root development of plants under cadmium stress, improving the mechanical strength of roots and the lodging resistance. Description of the Drawings

[0023] Figure 1 Shows the effects of the polysaccharide-based fertilizer on the growth performance of peppers under cadmium stress; wherein, CK: control; Cd: cadmium treatment; F(L): low-concentration polysaccharide-based fertilizer; F(H): high-concentration polysaccharide-based fertilizer;

[0024] Figure 2Effect of polysaccharide-based fertilizer on the root development of pepper under cadmium stress; among them, CK: control; Cd: cadmium treatment; F(L): low-concentration polysaccharide-based fertilizer; F(H): high-concentration polysaccharide-based fertilizer;

[0025] In the figure, the letters a, b, c, and d are the results of multiple comparisons. The absence of the same letter between treatments indicates a significant difference at the 0.05 level (p < 0.05). Detailed implementation method

[0026] The purpose of the present invention is to provide an application of a polysaccharide or polysaccharide-based compound fertilizer in the field of alleviating the inhibitory effect of heavy metals on plant root development, which can solve the problems that the root development of plants is inhibited and the lodging resistance trait significantly decreases when under heavy metal stress.

[0027] (1) Preparation method of polysaccharide-based compound fertilizer

[0028] S1: Use MRS medium to culture the strain, which can be Enterococcus faecium or other strains with high extracellular polysaccharide production such as Lactobacillus plantarum, and statically culture to obtain a bacterial liquid; the OD600 value of the bacterial liquid in the present invention is 4.0 - 6.0. When the OD600 of the bacterial liquid is 1.0, the effective viable count of the bacterial suspension is about 3×10 8 CFU / mL.

[0029] S2: Add fermentation medium (sucrose 2 - 3.0 wt%, peptone 0.5 - 1.0 wt%, potassium dihydrogen phosphate 0.02 - 0.05 wt%, the balance is water) to the fermenter, adjust the pH value in the tank to 7.5 - 7.8, heat up to 115 - 121 °C, sterilize, and cool;

[0030] S3: Inoculate the bacterial liquid into the fermenter, the fermentation temperature is 28 - 33 °C, statically culture, intermittently stir the fermentation broth, and the fermentation time is 36 - 40 hours; at this time, the polysaccharide content in the fermentation broth is about 1500 - 2000 mg / L.

[0031] S4: After the fermentation is completed, collect the fermentation broth, filter to remove the bacteria to obtain the fermentation broth, which contains a large amount of microbial polysaccharides. This polysaccharide substance can be directly applied to plants or trace elements can be added to it to prepare a polysaccharide-based fertilizer.

[0032] S5: According to the type of crop, add different amounts of trace elements (such as zinc sulfate, magnesium sulfate, etc.) to the fermentation broth to prepare a polysaccharide-based fertilizer.

[0033] As a preferred embodiment of the present invention, in step S3, the inoculation amount of the bacterial liquid is 3 - 5% of the volume of the material.

[0034] As a preferred embodiment of the present invention, in step S5, the addition amount of zinc sulfate in the trace elements is 0.5-1.0 wt%, and the addition amount of magnesium sulfate is 0.5-1.0 wt%.

[0035] (2) Use of the polysaccharide-based compound fertilizer

[0036] Plants were treated by root irrigation with polysaccharide or polysaccharide-based compound fertilizer solutions at different concentrations (concentrations of 0, 20, 40 mg / mL). Each plant seedling was sprayed with 20 mL of the polysaccharide-based compound fertilizer solution, applied once every 2-4 days, and continuously applied for 3-4 weeks.

[0037] In the present invention, the plants include chili peppers and / or rapeseed.

[0038] The application of the polysaccharide-based compound fertilizer of the present invention in alleviating the inhibitory effect of cadmium stress on the root development of chili peppers is a pioneering invention. When the polysaccharide-based compound fertilizer is used to alleviate cadmium stress in crops such as chili peppers, it can increase the plant height of chili peppers under cadmium stress, increase the fresh weight of chili peppers under cadmium stress, increase the root length of chili peppers under cadmium stress, and reduce the mass of cadmium elements transferred from the roots of chili peppers to the parts above the roots of chili peppers, thereby avoiding a decrease in yield or plant death when chili peppers are under cadmium stress. In particular, it can increase the level of root development of chili peppers under cadmium stress and at the same time increase the mechanical strength of the roots, thereby improving the lodging resistance of chili peppers.

[0039] The following is a specific study as an example of the present invention. The examples described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention. For those not specified in the examples, the techniques or conditions described in the literature in the art or according to the product instructions are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0040] The preparation method of the polysaccharide-based fertilizer used in the following examples is as follows:

[0041] S1: Enterococcus faecium was cultured using MRS medium, and static culture was carried out to obtain an Enterococcus faecium bacterial solution; the OD600 value of the bacterial suspension in the present invention is about 5.0. When the OD600 of the bacterial suspension is 1.0, the effective viable count of the bacterial suspension is about 3×10 8 CFU / mL.

[0042] S2: Fermentation medium (sucrose 2 wt%, peptone 1 wt%, potassium dihydrogen phosphate 0.05 wt%) was added to the fermentation tank, the pH value in the tank was adjusted to 7.5-7.8, the temperature was raised to 115-121 °C, sterilized, and cooled;

[0043] S3: Inoculate the Enterococcus faecium bacterial solution into the fermentation tank. The fermentation temperature is 28 - 33°C. Cultivate it statically and intermittently stir the fermentation broth. The fermentation time is 40 hours. At this time, the polysaccharide content in the fermentation broth is about 2000 mg / L. The inoculation amount of the Enterococcus faecium bacterial solution is 3% of the material volume.

[0044] S4: After the fermentation ends, collect the fermentation broth. After filtering to remove the bacteria, the obtained fermentation broth contains a large amount of microbial polysaccharides.

[0045] S5: Add zinc sulfate and magnesium sulfate to the fermentation broth to prepare a polysaccharide-based fertilizer. The addition amount of zinc sulfate is 0.5 wt%, and the addition amount of magnesium sulfate is 1.0 wt%.

[0046] Example 1

[0047] 1. Test materials

[0048] Chili pepper variety: Xiangyan Seed Industry Soft Skin 1728.

[0049] 2. Test design and treatment method

[0050] Select plump chili pepper seeds and place them in hot water at 50°C for 10 min, stirring constantly. Then, soak the scalded seeds in warm water at 30°C for 6 - 8 h. During this process, remove the shriveled seeds floating on the water surface, and thoroughly wash the pulp, pericarp, and mucus on the seed surface with warm water. Then, soak the seeds in a 0.1% (g / mL) potassium permanganate solution for 15 - 20 min to remove potential viruses. After cleaning, place the seeds evenly on a moist gauze and cover with the other half of the gauze. Subsequently, place the seeds in an incubator at 28°C for germination until the seeds show white tips. After germination, transplant them into a plug tray and cultivate them in a culture room. The cultivation conditions are set as follows: day-night temperature / photoperiod is 26°C, 12 h / 22°C, 12 h, the light intensity is 216 μmol / (m 2 ·s), and the humidity is maintained at 60%. After 7 days, transfer the chili peppers into pots filled with 1 kg of nutrient soil. The Cd content in the soil of the Cd treatment group is 50 mg / mL.

[0051] Start the test treatment after transplanting into the cadmium-containing soil. Treat the chili pepper seedlings with different concentrations of polysaccharide-based compound fertilizer solutions (concentrations of 0, 20, 40 mg / mL, containing 0.5 wt% zinc sulfate and 1.0 wt% magnesium sulfate) by root irrigation. Spray 20 mL of the polysaccharide-based compound fertilizer solution on each chili pepper seedling, apply it once every three days, and apply it continuously for three weeks. Then, place all the chili pepper seedlings in the culture room to continue growing. After one month, observe the phenotypes and take samples.

[0052] 3. Sample determination

[0053] (1) Phenotype determination

[0054] Measure the plant height and root length with a ruler, and weigh the fresh weight of the whole plant with an electronic balance.

[0055] (2) Root development determination

[0056] Use the WinRHIZO PRO 2007 root analysis system to perform a whole-root scan of each seedling's roots, and collect and analyze data on root morphology, root architecture (including taproot length, number of first-order lateral roots, lateral root length, number of root tips, average root diameter, root surface area, root volume), root length, root volume, and root area of fine roots (L ≤ 2 mm) and thick roots (L > 2 mm).

[0057] (3) Cadmium content determination

[0058] Take 0.05 g of pepper roots and leaves as samples respectively, digest and precipitate them with HNO3 and HClO4 in a ratio of 4:1 (v / v), adjust the volume of the dissolved sample to 10 mL with deionized water, and then determine the Cd concentration by flame atomic absorption spectrometry (FAAS).

[0059] 4. Test results

[0060] From the test results Figure 1 and Figure 2 it can be seen that cadmium (Cd) treatment will severely inhibit the plant height and biomass per plant of peppers, while after adding low-concentration (F(L): 20 mg / L) and high-concentration (F(H): 40 mg / L) polysaccharide-based fertilizers, the above indicators of peppers can be improved, and in the high-concentration dose group, its growth situation is even higher than that of the control group.

[0061] The above results indicate that the polysaccharide-based fertilizer can well improve the growth performance of peppers under cadmium stress.

[0062] From Figure 1 and 2 it can also be seen that excessive cadmium will severely inhibit the root development of plants. After adding the polysaccharide-based fertilizer, not only the growth indicators of the roots are enhanced, the cadmium content in the above-ground part decreases, but also the lignin content in the roots is significantly increased, indicating that the mechanical strength of the pepper roots is improved. The above research results show that the polysaccharide-based fertilizer can significantly improve the root development of peppers under cadmium stress, while increasing the lignin content in their roots, significantly improving the mechanical strength of the roots, and enhancing the lodging resistance of plants.

[0063] Example 2

[0064] 1. Test materials

[0065] Rapeseed variety: Huayouza 62.

[0066] 2. Test design and treatment method

[0067] The test materials were planted by soil culture method, with a row spacing of 20 cm and a plant spacing of 15 cm. The management was the same as that of general fields. The Cd content in the soil of the Cd treatment group was 60 mg / mL.

[0068] When the cultivation reached 2 months, the rape was treated by root irrigation. 40 mL of polysaccharide-based compound fertilizer solution was sprayed on each seedling once a week for three consecutive weeks. 10 days before the silique maturation stage, 6 plants with strong growth and consistent growth trends were randomly selected from each treatment to measure the traits per plant.

[0069] 3. Sample determination

[0070] The determination of each index was carried out with reference to the literature (Liu Xingbei, Research on the Effects and Mechanisms of Seed Soaking with Uniconazole and Gibberellin on the Lodging Resistance of Fagopyrum esculentum Moench [D], Southwest University; Wei Dingyi, Functional Analysis of Gibberellin in the Lodging Resistance and Heterosis of Brassica napus L. [D], Yangtze University).

[0071] 3. Test results

[0072] It can be seen from Table 1-2 of the test results that cadmium stress inhibited the growth of rape and severely inhibited its root development. Many indexes, including the main root length and root surface area, showed a serious decline, and the lodging resistance of rape was severely damaged. After adding the polysaccharide-based compound fertilizer, not only the growth and root development indexes of rape were improved, but also its lodging resistance was significantly enhanced.

[0073] Table 1 Effects of different treatments on the growth and lodging resistance of rape

[0074]

[0075] Note: CK: control; Cd: cadmium treatment; F(L): low-concentration polysaccharide-based fertilizer; F(H): high-concentration polysaccharide-based fertilizer

[0076] Table 2 Effects of different treatments on the root growth of rape

[0077]

[0078]

[0079] Note: CK: control; Cd: cadmium treatment; F(L): low-concentration polysaccharide-based fertilizer; F(H): high-concentration polysaccharide-based fertilizer.

[0080] In summary, the use of polysaccharides or polysaccharide-based compound fertilizers alone can alleviate the inhibition of heavy metals such as cadmium on the root development of plants. The content of substances such as lignin in the plant roots increases significantly, thereby improving the root development level and mechanical strength of plants. When polysaccharides or polysaccharide-based compound fertilizers are used to alleviate heavy metal stress in plants, they have the advantages of simple operation, low cost, health and environmental protection, and good effects, and can be applied to the cultivation and production of different types of crops.

[0081] The above-described embodiments merely represent the preferred embodiments of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, various corresponding changes and deformations can be made based on the technical solutions and concepts described above, and all such changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. Use of a polysaccharide-based fertilizer in enhancing the mechanical strength of plant roots and lodging resistance under heavy metal stress conditions, characterized in that, The polysaccharide-based fertilizer includes microbial polysaccharides obtained by fermenting strains capable of producing extracellular polysaccharides; The heavy metal is cadmium; The preparation method of the polysaccharide-based fertilizer includes the following steps: S1: Static culture of the strains capable of producing extracellular polysaccharides to obtain a bacterial solution; S2: Add a fermentation medium to the fermenter, adjust the pH value in the tank to 7.5 - 7.8, heat up to 115 - 121 °C, sterilize, and cool; S3: Inoculate the bacterial solution into the fermenter for fermentation, filter to remove the bacteria to obtain a fermentation broth, and thus prepare it; In step S1, the strains include Enterococcus faecium; S4: According to the type of crop, add zinc sulfate and magnesium sulfate to the fermentation broth to prepare the polysaccharide-based fertilizer.

2. The application according to claim 1, wherein The usage method includes the following steps: Treat the crop by root irrigation with the polysaccharide-based fertilizer, spray 10 - 30 mL / strain each time, apply once every 2 - 4 days, and apply continuously for 3 - 4 weeks; After cultivation, the lignin and root mechanical strength of the crop are significantly improved.

3. The application according to claim 2, wherein The crops include peppers and / or rapeseed.

4. The application according to claim 1, wherein Step S1 is specifically: Cultivate the strains with MRS medium, perform static culture to obtain a bacterial solution; The OD600 value of the bacterial solution is 4.0 - 6.

0.

5. The application according to claim 1, characterized in that, In step S2, the fermentation medium includes: 2 - 3.0 wt% of sucrose, 0.5 - 1.0 wt% of peptone, 0.02 - 0.05 wt% of potassium dihydrogen phosphate, and the balance is water.

6. The application according to claim 1, characterized in that, In step S3, the fermentation temperature is 28 - 33 °C, the fermentation time is 36 - 40 h, and the polysaccharide content in the fermentation broth is 1500 - 2000 mg / L; The inoculation amount of the bacterial solution is 3 - 5% of the volume of the material.

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