Method for reducing cadmium content in rice under cadmium stress, rice adjusting method and application

Abstract

The invention provides a method for reducing cadmium content in rice under cadmium stress, a rice adjusting method and application. By adding the exogenous water-soluble organic selenium into the cadmium-polluted farmland soil, the exogenous water-soluble organic selenium is proved to have the effects of promoting the growth of the rice under the cadmium stress and relieving the cadmium stress of the rice; the exogenous water-soluble organic selenium is beneficial for improving the activity of antioxidant enzymes of the rice and reducing oxidative damage, and has a positive effect on relieving cadmium toxicity of the rice; in addition, the exogenous water-soluble organic selenium is beneficial to reducing direct migration of cadmium from rice roots to brown rice and effectively reducing the biological enrichment coefficient of Cd in the brown rice; the exogenous water-soluble organic selenium can promote generation of iron plaque on the root surface of the rice in the mature period and form an effective barrier for Cd absorption of the rice, so that accumulation of cadmium in rice plants is reduced, and toxicity of cadmium to the rice is reduced.

Description

Technical Field

[0001] The invention relates to the regulation of rice, and in particular to a method for reducing the cadmium content in rice under cadmium stress, a rice regulation method and an application thereof. Background Art

[0002] Cadmium (Cd) is one of the harmful elements widely present in heavy metal-contaminated soils. It has a strong migration ability in the soil-crop system. Cadmium pollution in farmland poses a serious threat to arable land quality, food safety and human health. When humans eat rice with excessive cadmium content, it will continue to accumulate in the human body. When cadmium accumulates to a certain level, it will cause arteriosclerosis, kidney atrophy, lung organ damage, and even cancer.

[0003] Selenium (Se) is a trace mineral element beneficial to plants. Exogenous selenium can reduce the uptake of many heavy metals by rice, such as cadmium. However, most studies focus on how exogenous inorganic selenium can alleviate cadmium stress in rice, while there are few reports on the effects of exogenous water-soluble organic selenium on the response of rice to heavy metal cadmium stress. In addition, the physiological indicators of rice have a great influence on the cadmium content in various tissues of rice. How to reduce the cadmium content in rice by regulating the physiological substances of rice is also a technical difficulty that needs to be solved in this field.

[0004] In view of this, it is necessary to provide a method for reducing the cadmium content in rice under cadmium stress, a rice regulation method and application, so as to solve or at least alleviate the technical defects of how to reduce the cadmium content in various tissues of rice through exogenous water-soluble organic selenium, and how to reduce the cadmium content in rice by regulating the physiological substances of rice. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for reducing the cadmium content in rice under cadmium stress, a rice regulation method and application, aiming to solve the above-mentioned technical problems of how to reduce the cadmium content in various tissues of rice through exogenous water-soluble organic selenium, and how to reduce the cadmium content in rice by regulating the physiological substances of rice.

[0006] To achieve the above object, the present invention provides an application of reducing the cadmium content in rice by targeting catalase, peroxidase, superoxide dismutase and malondialdehyde.

[0007] The present invention also provides a rice regulation method based on exogenous water-soluble organic selenium, wherein the regulated substances include catalase, peroxidase, superoxide dismutase and malondialdehyde;

[0008] The rice regulation method comprises: applying exogenous water-soluble organic selenium to the root of the rice to increase the content of the catalase, the peroxidase and the superoxide dismutase in the rice, and reduce the content of the malondialdehyde.

[0009] The invention also provides an application of exogenous water-soluble organic selenium in increasing the concentration of iron film on the root surface of rice.

[0010] The present invention also provides an application of exogenous water-soluble organic selenium in alleviating cadmium stress of rice.

[0011] The present invention also provides a method for reducing the cadmium content in rice under cadmium stress, comprising: increasing the content of catalase, peroxidase and superoxide dismutase in the rice, reducing the content of malondialdehyde, and increasing the concentration of iron film on the root surface of the rice; the rice is planted in cadmium-containing soil.

[0012] The present invention also provides a method for reducing the cadmium content in rice under cadmium stress, comprising: applying exogenous water-soluble organic selenium to the root of the rice, wherein the rice is planted in cadmium-containing soil.

[0013] Furthermore, the cadmium concentration in the cadmium-containing soil is 1-1.5 mg / kg.

[0014] Furthermore, the exogenous water-soluble organic selenium is water-soluble selenomethionine.

[0015] Furthermore, the amount of the exogenous water-soluble organic selenium applied to the soil is 0.1-0.5 mg / kg.

[0016] The present invention also provides an application of any of the above methods for reducing the cadmium content in rice under cadmium stress in rice planting.

[0017] Compared with the prior art, the present invention has at least the following advantages:

[0018] The invention proves that the exogenous water-soluble organic selenium (water-soluble selenomethionine) has the effect of promoting the growth of rice under cadmium stress and alleviating the cadmium stress of rice by adding exogenous water-soluble organic selenium (water-soluble selenomethionine) into cadmium-contaminated farmland soil; the exogenous organic selenium (water-soluble selenomethionine) increases the content of rice antioxidant enzymes, such as catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD), reduces the content of malondialdehyde (MDA), and has a positive effect on alleviating the cadmium poisoning of rice; in addition, the exogenous water-soluble organic selenium (water-soluble selenomethionine) is beneficial to reducing the direct migration of cadmium from rice roots to brown rice, and effectively reduces the bioaccumulation coefficient of Cd in brown rice; the exogenous water-soluble organic selenium (water-soluble selenomethionine) can promote the formation of iron film on the root surface of rice in the mature stage, form an effective barrier for rice to absorb Cd, thereby reducing the accumulation of cadmium in rice plants and alleviating the toxicity of cadmium to rice. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0020] Figure 1 The data comparison diagram of rice yield after harvest of rice in different treatment groups in Example 1 of the present invention; wherein (a) is the number of ears per plant, and (b) is the weight of ears per plant;

[0021] Figure 2 The figures are data comparison diagrams of cadmium concentrations in roots, stems, leaves and brown rice of rice in different treatment groups after harvest in Example 1 of the present invention; wherein (a) is the cadmium concentration in the roots, (b) is the cadmium concentration in the stems, (c) is the cadmium concentration in the leaves, and (d) is the cadmium concentration in the brown rice;

[0022] Figure 3 This is a data comparison diagram of the iron film on the rice root surface after the rice in different treatment groups was harvested in Example 2 of the present invention;

[0023] Figure 4 The figures are data comparison diagrams of the antioxidant enzyme activities and oxidative damage of rice in different treatment groups in Example 3 of the present invention; wherein (a) is a detection data diagram of SOD, (b) is a detection data diagram of POD, (c) is a detection data diagram of CAT, and (d) is a detection data diagram of MDA.

[0024] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0027] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention are in accordance with the prior art mastery of the technicians in the field and the records of the present invention. Any method, equipment and material of the prior art similar or equivalent to the methods, equipment and materials in the embodiments of the present invention can also be used to implement the present invention. In the present invention, CAT refers to catalase, POD refers to peroxidase, SOD refers to superoxide dismutase, and MDA refers to malondialdehyde.

[0028] When rice is planted in cadmium-containing soil, in order to avoid excessive cadmium content in various tissues of rice, the present invention provides an application for reducing the cadmium content in rice by targeting catalase, peroxidase, superoxide dismutase and malondialdehyde; wherein the catalase and the peroxidase are two different enzymes, and the catalytic effects of the two are different.

[0029] That is, the present invention can control the cadmium content in rice by regulating the contents of catalase, peroxidase, superoxide dismutase and malondialdehyde in rice; specifically, in the application, the present invention can reduce the cadmium content in rice by increasing the contents of the catalase, the peroxidase and the superoxide dismutase in rice and reducing the content of the malondialdehyde.

[0030] In order to achieve physiological regulation of rice and regulate related substances in rice that can control cadmium content, the present invention also provides a rice regulation method based on exogenous water-soluble organic selenium, and the regulated substances include catalase, peroxidase, superoxide dismutase and malondialdehyde.

[0031] The rice regulation method comprises: when the rice is planted in cadmium-containing soil, applying exogenous water-soluble organic selenium to the root of the rice to increase the content of the catalase, the peroxidase and the superoxide dismutase in the rice, and reduce the content of the malondialdehyde.

[0032] Since the rice iron film is a physical barrier to heavy metals on the root surface, it can reduce the absorption of cadmium by the rice roots. The present invention also provides an application of exogenous water-soluble organic selenium in increasing the concentration of the rice root surface iron film.

[0033] Based on the effect of exogenous water-soluble organic selenium, the present invention also provides an application of exogenous water-soluble organic selenium in alleviating cadmium stress in rice. In the present invention, the exogenous water-soluble organic selenium alleviates cadmium stress in rice by the following (1)-(5):

[0034] (1) Increase the number of panicles per plant and the weight of panicles per plant in rice under cadmium stress;

[0035] (2) Reduce cadmium concentrations in rice roots, stems, leaves, and brown rice;

[0036] (3) Increase the concentration of iron film on the surface of rice roots;

[0037] (4) Increase the contents of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) in rice under cadmium stress;

[0038] (5) Reduce the content of malondialdehyde (MDA) in rice under cadmium stress.

[0039] Based on the physiological control of rice, the present invention also provides a method for reducing the cadmium content in rice under cadmium stress, comprising: increasing the content of catalase, peroxidase and superoxide dismutase in rice, reducing the content of malondialdehyde, and increasing the concentration of iron film on the root surface of rice; the rice is planted in cadmium-containing soil.

[0040] Based on exogenous water-soluble organic selenium, the present invention also provides a method for reducing the cadmium content in rice under cadmium stress, which belongs to the application of exogenous water-soluble organic selenium in alleviating cadmium stress of rice; the method comprises: applying exogenous water-soluble organic selenium to the roots of rice, and the rice is planted in cadmium-containing soil.

[0041] It should be noted that, in the present invention, the method of applying exogenous water-soluble organic selenium to the roots of rice is: before or after planting rice, the exogenous water-soluble organic selenium is applied to the cadmium-containing soil. In the present invention, the rice can be planted in pots or in the field. In the present invention, reducing the cadmium content in rice includes: reducing the cadmium concentration in rice roots, stems, leaves and brown rice; that is, the present invention can reduce the cadmium content in various tissues of rice and achieve harmlessness of rice.

[0042] In the present invention, the cadmium concentration in the cadmium-containing soil is 1-1.5 mg / kg, forming a soil environment of cadmium stress; if water-soluble organic selenium is not applied, it is easy to cause rice yield reduction and cause a large amount of cadmium in various tissues of rice.

[0043] In the present invention, the exogenous water-soluble organic selenium is preferably water-soluble selenomethionine. It has been confirmed by the present invention that the water-soluble selenomethionine can reduce the cadmium content of various tissues in rice and increase rice yield. In the present invention, the amount of the exogenous water-soluble organic selenium applied to the soil is 0.1-0.5 mg / kg, and can further be 0.125-0.5 mg / kg or 0.250-0.5 mg / kg or 0.375-0.5 mg / kg; the amount of the exogenous water-soluble organic selenium applied to the soil can also be 0.3-0.4 mg / kg. The exogenous water-soluble organic selenium is applied to the soil in the form of a solution.

[0044] In the present invention, before planting rice, base fertilizer and water-soluble organic selenium can be mixed and applied to the soil where rice is planted; before and after applying water-soluble organic selenium, the soil can be plowed; after applying exogenous water-soluble organic selenium, the soil is kept in a flooded condition for 1-3 days.

[0045] The present invention also provides an application of any of the above methods for reducing the cadmium content in rice under cadmium stress in rice planting; the application can be understood as a rice planting method, which adopts any of the above methods for reducing the cadmium content in rice under cadmium stress.

[0046] The invention relates to a new use of exogenous water-soluble organic selenium in alleviating rice cadmium stress and reducing cadmium concentrations in various rice tissues, and provides a solution for improving the current situation of rice cadmium stress and reducing the transport of cadmium from the root to the aboveground part of the rice plant.

[0047] The following are specific examples of the present invention:

[0048] Example 1

[0049] 1. Experimental process:

[0050] In this embodiment, paddy soil taken from Beishan Town, Changsha County, Changsha City, Hunan Province was used for potted plant experiments. 5 kg of naturally dried soil was taken from each pot, and the cadmium content in the soil was 1.2 mg / kg.

[0051] In this embodiment, a total of 5 groups of experiments were conducted, as shown in Table 1, and the numbers of the 5 groups of experiments were CK, S-1, S-2, S-3, and S-4, and 3 repeated experiments were performed in each group. The CK group was the control group, and the amount of organic selenium added was 0 mg / kg; the amounts of organic selenium added to the S-1 group to the S-4 group were 0.125, 0.250, 0.375, and 0.500 mg / kg, respectively; except for the concentration of organic selenium, the other experimental conditions of each group during the planting process remained the same; in this embodiment, the organic selenium was water-soluble organic selenium, which was dissolved in water, and the organic selenium was derived from the water-soluble selenomethionine produced by Xi'an Centennial Kang Biotechnology Co., Ltd., model BNK007.

[0052] When treating the soil of each group, the organic selenium of the corresponding concentration in each group was evenly mixed with the base fertilizer, mixed with the soil and potted, and then flooded with water for 2 days for use.

[0053] Table 1. The setting of organic selenium in each treatment group

[0054]

[0055] Select an appropriate amount of rice seeds with full and uniform grains, use deionized water for flotation to remove the shriveled grains, soak them in 30% H2O2 for 15 minutes for disinfection to prevent microorganisms and other factors from affecting seed germination, and after fully rinsing with deionized water, sprinkle the seeds evenly on the culture dish and soak them in a dark incubator at 30°C for 3 days; then evenly place 10 white seeds per pot in potting soil; take samples for testing at maturity.

[0056] 2. Experimental results:

[0057] 1. Rice yield determination: Exogenous water-soluble organic selenium significantly increases the number and weight of rice panicles.

[0058] All the mature millets were harvested, dried naturally, weighed, and the average number of ears per plant and the average weight of ears per plant (dry weight) were calculated. The results are as follows: Figure 1 As shown; in the present invention, ear weight refers to the grain weight (with husk, dry weight) of mature millet, and single-plant ear weight refers to the grain weight (with husk, dry weight) of mature millet in a single rice plant.

[0059] The average number of ears per plant in the CK group was 9.33, and the average ear weight per plant was 9.52 g; while the ear weight per plant in the organic selenium treatment group increased significantly, and gradually increased with the increase of concentration. The application of 0.5 mg / kg organic selenium in the soil (corresponding to the S-4 group) increased the average number of rice ears by 37.51%, and the average ear weight per plant by 106.93%.

[0060] 2. Determination of cadmium concentration in various organs of rice: Exogenous water-soluble organic selenium significantly reduced the cadmium concentration in various tissues of rice.

[0061] Mature rice roots, stems, leaves and brown rice were collected, dried, crushed and sieved (100 mesh), 0.2000 g of rice sample was weighed into a polytetrafluoroethylene digestion tank, 5 mL of HNO3 and 2 mL of H2O2 were added, and the sample was placed on a microwave digestion instrument. The plant digestion program was selected. After the digestion was completed, the digestion tank was taken out and placed on an acid removal instrument. When the liquid turned into 1 to 2 mL of yellow viscous liquid, the acid removal was stopped, the liquid in the digestion tank was poured into a volumetric flask to make up the volume, and the rinse liquid of the digestion tank was poured into the volumetric flask. A blank group was set up at the same time; and the cadmium concentration was determined in a graphite furnace atomic absorption spectrometer.

[0062] Cadmium content in dry weight of rice roots, stems, leaves and brown rice can be found in Figure 2 shown; from Figure 2 It can be seen that the treatment groups applying organic selenium (water-soluble selenomethionine) significantly reduced the cadmium content in rice roots, stems and leaves, and as the Se concentration increased, the cadmium concentration in the tissue gradually decreased.

[0063] Taking the S-4 group as an example, the cadmium concentrations in the roots, stems and leaves were reduced by 44.65%, 50.46% and 85.98% respectively compared with the CK group (the cadmium concentrations in the roots, stems and leaves were 2.18 mg / kg, 1.55 mg / kg and 0.80 mg / kg respectively).

[0064] In the CK group, the cadmium content of brown rice was 0.369 mg / kg; compared with the CK group, organic selenium significantly inhibited the absorption of cadmium by brown rice, and both did not exceed the limit of 0.20 mg / kg specified in GB2762-2022.

[0065] With the increase of organic selenium application, the cadmium concentration in brown rice gradually decreased. When 0.5 mg / kg of organic selenium was applied to the soil (corresponding to the S-4 group), the cadmium concentration in brown rice was 0.1015 mg / kg, which was 72.5% lower than that in the CK group.

[0066] Example 2

[0067] Detection of iron plaque (IP) on the root surface of rice: Exogenous water-soluble organic selenium significantly increased the content of iron plaque (IP) on the root surface of rice.

[0068] The roots of the mature rice in Example 1 were taken, and the iron film (IP) on the surface of the mature roots was extracted by the DCB (sodium dithionite-ammonium citrate-sodium bicarbonate) method. The fresh roots were soaked in a 0.5mM calcium chloride solution for 30 minutes to remove the cadmium adsorbed on the root surface, and then washed with deionized water; the washed roots were cut into pieces about 1 cm long, soaked in a mixed solution of 0.3mM ammonium citrate and 5mL1mM sodium bicarbonate for 30 minutes, and then 2g of sodium dithionite was added and left at room temperature for 3 hours; finally, the iron concentration in the extract was determined by inductively coupled plasma.

[0069] The iron film of rice is a physical barrier to heavy metals on the root surface, which can reduce the absorption of Cd by rice roots. Figure 3 It can be seen that organic selenium (water-soluble selenomethionine) can significantly increase the iron film content on the surface of rice roots (fresh weight). The iron film content in the CK group was 22.08 mg / kg, and the iron film content in the S-1 group to the S-4 group was 36.77 mg / kg, 38.62 mg / kg, 35.82 mg / kg and 36.30 mg / kg, respectively.

[0070] Example 3

[0071] Determination of antioxidant enzyme activity and membrane lipid peroxidation degree: Exogenous water-soluble organic selenium significantly increased the antioxidant enzyme activity of rice and reduced oxidative damage.

[0072] 1.00 g of rice leaves at the tillering stage (fresh weight) (from Example 1) were quantitatively weighed, and 1 mL of the extract required for the determination of different enzyme contents was added respectively. After freezing and homogenization with an ice bath homogenizer, the mixture was centrifuged and the supernatant was taken for determination. All operations were carried out at 4°C.

[0073] The CAT content was determined by spectrophotometry using a catalase (CAT) kit (Suzhou Keming). 35 μL of sample was mixed with 1 mL of working solution to generate H2O2. CAT can decompose H2O2, causing the absorbance of the reaction solution at 240 nm to decrease with reaction time. The CAT activity was calculated based on the rate of change of absorbance at 240 nm at room temperature within 1 min.

[0074] POD was determined by spectrophotometry using a peroxidase (POD) kit (Suzhou Keming). 50 μL of supernatant sample was mixed with 950 μL of working solution (H2O2 oxidized specific substrate), and the POD activity was calculated based on the characteristic light absorption at 470 nm produced by the substance produced by POD-catalyzed H2O2 oxidation of specific substrate.

[0075] SOD was determined using a superoxide dismutase (SOD) kit (WST-8 method) (Suzhou Keming) with a spectrophotometer. 50 μL of the supernatant sample containing SOD was mixed with the reagent and working solution in turn. The superoxide anion (O 2-. ) can react with WST-8 to produce water-soluble dye formazan, which absorbs at 450nm, while SOD can remove O 2-. , inhibiting the formation of formazan, reducing the absorbance, and then determining the enzyme activity of SOD.

[0076] MDA was determined by spectrophotometry using a malondialdehyde (MDA) assay kit (Suzhou Keming). 0.2 mL of supernatant sample was mixed with 0.6 mL of reagent 1 (thiobarbituric acid) and incubated in a 95°C water bath for 30 min to generate a red product. After centrifugation, the supernatant was measured at 532 nm and 600 nm, and the MDA content was calculated by the absorbance difference.

[0077] from Figure 4 It can be seen that organic selenium (water-soluble selenomethionine) can significantly increase the activity of rice antioxidant enzymes, and there is an upward trend with increasing concentration.

[0078] Taking the S-4 group as an example, compared with the CK treatment group (the CAT, POD and SOD activities in rice leaves were 4211.36 nmol / min / g fresh weight, 942.34 U / g fresh weight and 161.46 U / g fresh weight, respectively), the CAT, POD and SOD activities in rice leaves increased by 17.37%, 26.81% and 17.49%, respectively; at the same time, organic selenium (water-soluble selenomethionine) can significantly reduce the oxidative damage of cadmium to rice, and gradually decreases with increasing concentration; compared with the CK group (MDA content in leaves was 28.48 nmol / g fresh weight), the average MDA content in rice leaves of the S-4 group decreased by 19.56%.

[0079] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An application of reducing the cadmium content in rice by targeting catalase, peroxidase, superoxide dismutase and malondialdehyde.

2. A rice regulation method based on exogenous water-soluble organic selenium, characterized in that: Substances regulated include catalase, peroxidase, superoxide dismutase, and malondialdehyde; The rice regulation method comprises: applying exogenous water-soluble organic selenium to the root of the rice to increase the content of the catalase, the peroxidase and the superoxide dismutase in the rice, and reduce the content of the malondialdehyde.

3. Application of exogenous water-soluble organic selenium in increasing the concentration of iron film on the root surface of rice.

4. Application of exogenous water-soluble organic selenium in alleviating cadmium stress in rice.

5. A method for reducing cadmium content in rice under cadmium stress, characterized in that: include: The content of catalase, peroxidase and superoxide dismutase in rice is increased, the content of malondialdehyde is reduced, and the concentration of iron film on the root surface of rice is increased; the rice is planted in cadmium-containing soil.

6. A method for reducing cadmium content in rice under cadmium stress, characterized in that: include: Exogenous water-soluble organic selenium was applied to the roots of rice grown in cadmium-containing soil.

7. The method for reducing cadmium content in rice under cadmium stress according to claim 6, characterized in that: The cadmium concentration in the cadmium-containing soil is 1-1.5 mg / kg.

8. The method for reducing cadmium content in rice under cadmium stress according to claim 6, characterized in that: The exogenous water-soluble organic selenium is water-soluble selenomethionine.

9. The method for reducing cadmium content in rice under cadmium stress according to claim 6, characterized in that: The amount of the exogenous water-soluble organic selenium applied to the soil is 0.1-0.5 mg / kg.

10. Use of the method for reducing cadmium content in rice under cadmium stress as claimed in any one of claims 6 to 9 in rice planting.

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