Resistance and control agent for preventing rice from absorbing cadmium and application thereof

Abstract

The invention relates to a method for improving cadmium stress resistance of rice by using carbon quantum dots (CDs), which solves the technical problem that rice growth is affected due to the fact that rice is deeply poisoned by cadmium in the prior art by spraying the carbon quantum dots on leaf surfaces of the rice or irrigating the carbon quantum dots into root soil of the rice. CDs are used as a leaf surface resistance and control agent to treat cadmium-stressed rice, and it is found that on the premise that growth and development of the rice are not affected, CDs can improve the stress resistance of the rice by promoting photosynthesis of the rice and can stimulate a rice defense system to generate more antioxidant enzymes to cope with oxidative damage caused by Cd stress. Besides, CDs can also reduce the concentration of DTPA-Cd in soil and reduce accumulation of Cd on the overground part so as to further reduce the toxicity of Cd to rice, and meanwhile, the Cd content of the overground part of the rice is reduced so as to be beneficial to reducing accumulation of Cd in grains, so that CDs can be used as a leaf surface resistance and control agent to effectively relieve cadmium toxic rice, thereby promoting growth and development of the rice and improving the yield.

Description

Technical Field

[0001] The invention belongs to the technical field of crops, and particularly relates to an inhibitor for blocking rice from absorbing cadmium and application thereof. Background Art

[0002] Cadmium (Cd) is a highly mobile toxic heavy metal. Long-term intake of cadmium through diet will damage the respiratory system and bones. Rice is an important food crop in my country and has been shown to easily absorb Cd from Cd-contaminated soil and accumulate in its grains. Therefore, reducing the Cd content in rice is of great significance.

[0003] The new technology currently is to use foliar barrier agents. Foliar barrier agents usually contain a variety of elements required for plant growth and development, and these nutrients can be transported to other parts of the crop through the apoplast pathway. Foliar barrier agents can also change the transport and accumulation of heavy metals in plants and the absorption of trace elements. Currently, most of the application of lime, phosphate and calcium silicate reduces the activity of cadmium in the soil. The application of these amendments is to reduce the bioavailability of cadmium in the soil, thereby reducing the absorption of cadmium by rice, but it will affect the acid-base balance and nutrient supply of the soil. Some amendments will also reduce the efficiency of photosynthesis, thereby affecting the growth and yield of rice. Summary of the invention

[0004] The invention provides a control agent for preventing rice from absorbing cadmium and application thereof, aiming to solve the technical problem in the prior art that rice is deeply poisoned by cadmium and the growth of rice is affected.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present invention provides an inhibitor for preventing rice from absorbing cadmium, wherein the inhibitor comprises carbon quantum dots.

[0007] In a second aspect, the application of the inhibitor for preventing rice from absorbing cadmium as described in the first aspect in rice cultivation.

[0008] In a third aspect, the present invention provides a method for preventing crops from absorbing cadmium, comprising spraying the inhibitor described in the first aspect onto rice leaves or irrigating the inhibitor described in the first aspect into the soil at the roots of rice.

[0009] In a preferred embodiment, the rice is hydroponic rice or soil-grown rice.

[0010] In a preferred embodiment, when the rice is hydroponic rice, the frequency of spraying the inhibitor on the leaves of the hydroponic rice is once every 6-8 days, 8-12 ml each time, and the spraying is continued for 18-23 days.

[0011] Based on the above scheme, spraying once every 6-8 days can ensure that the inhibitor continues to play a role during the growth of rice, avoiding the weakening of the effect due to long intervals. 8-12ml each time can ensure that enough inhibitor covers the surface of rice leaves and improve the inhibitor effect. Continuous spraying for 18-23 days can cover the key growth stages of rice, such as tillering, booting and filling, so as to effectively block the absorption and transport of cadmium throughout the growth cycle.

[0012] In a preferred embodiment, when the rice is hydroponic rice, the ratio of the cadmium concentration in the water to the carbon quantum dots in the added inhibitor is 1:4-6.

[0013] Based on the above scheme, the bioavailability of cadmium in the hydroponic environment is higher because cadmium ions move freely in water and are easily absorbed by the roots. Therefore, a higher concentration of carbon quantum dots is required to reduce the bioavailability of cadmium. This can ensure that the carbon quantum dots form an effective adsorption layer in the water, thereby more effectively adsorbing and fixing cadmium ions, reducing the free state of cadmium in the water, reducing its bioavailability, and thereby reducing the absorption of cadmium by rice.

[0014] In a preferred embodiment, when the rice is soil-grown rice, the inhibitor is irrigated into the soil at the root of the rice, and the ratio of the cadmium content in the soil to the carbon quantum dots in the inhibitor added and mixed into the soil is 95-105:1.

[0015] Based on the above scheme, the roots of soil-grown rice grow in the soil, and the cadmium concentration in the soil is relatively low and unevenly distributed. The soil itself has a certain adsorption and buffering capacity, which can partially fix cadmium ions. Moreover, the absorption of cadmium is not only affected by soil adsorption and fixation, but also by the combined effects of microorganisms and organic matter around the roots. These factors can reduce the bioavailability of cadmium, so relatively low concentrations of carbon quantum dots can effectively block the absorption of cadmium.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention provides a control agent for blocking rice from absorbing cadmium and its application. The rice seed germination was tested by using carbon quantum dot (CDs) solution of different concentrations. The test proved that CDs would not have a negative impact on the germination of rice seeds. Moreover, after being treated with 100 μg / L CDs solution, the germination rate, root length and embryo length of rice were significantly improved, indicating that CDs has a positive effect on promoting seed germination and early growth. On this basis, by spraying CDs solution on the leaves, the growth inhibition of rice under cadmium stress was significantly alleviated. Spraying CDs under cadmium stress increased the rice plant height by 17.2%, the aboveground dry weight of rice by 27.7%, the underground dry weight by 27.6% and the root length by 7.2%. This shows that CDs can effectively alleviate cadmium toxicity and promote rice growth without damaging the germination of rice seeds.

[0018] 2. The present invention has been proved through experiments that: under cadmium stress, the chlorophyll content of rice is reduced by 20%, while spraying CDs can restore its chlorophyll content to a normal level. Compared with the cadmium stress treatment, spraying CDs increases the electron transfer efficiency by 19.5%, spraying CDs under cadmium stress increases Y(II) by 6.8%, and spraying CDs under cadmium stress increases qP by 20% and 29%, respectively. The improvements in electron transfer efficiency, actual light conversion efficiency and photochemical quenching parameters indicate that spraying CDs can improve the photosynthesis efficiency of rice.

[0019] 3. The present invention has been proved through experiments that after applying carbon quantum dots (CDs) to rice, the activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) of rice are all improved, especially the activity of POD enzyme is increased by 82% compared with the control. MDA is the final product of lipid peroxides in plants, which can reflect the degree of oxidative damage of plants. Among them, the MDA content under cadmium stress is increased by 41% compared with the control group, while spraying CDs can reduce the MDA content by 16.2% compared with the cadmium stress treatment; after spraying CDs under cadmium stress, not only the H in rice is reduced, but also the MDA content under cadmium stress is reduced. 2 O 2 The content of O in rice was reduced by 10%. 2 - The content decreased by 23.5%, which shows that the application of CDs can effectively enhance the antioxidant capacity of rice.

[0020] 4. DTPA-Cd is considered to be the most mobile form of cadmium in the soil and is most easily absorbed by plants to cause toxicity to plants. The present invention has been proven through experiments that spraying CDs solution on the leaves and mixing CDs into the soil can reduce the DTPA-Cd content in the soil. Under cadmium stress, the DTPA-Cd content is reduced by 17.6% after foliar spraying of CDs, and by 14% after applying CDs to the soil.

[0021] 5. The present invention has been proved by experiments that both foliar spraying and soil application of CDs can reduce the cadmium content in rice tissues. Among them, under the stress of cadmium, foliar spraying of CDs can reduce the Cd content in rice leaves and leaf sheaths by 10.1% and 9.3%, respectively, and soil application of CDs can significantly reduce the Cd content in leaves and leaf sheaths by 22% and 17%, respectively.

[0022] The present invention relates to a method for improving the resistance of rice to cadmium stress by using carbon quantum dots (CDs). Through experiment one, rice seeds were treated with CDs solutions of different concentrations (0, 10, 100, 500, 1000 μg / L), and it was found that 100 μg / L CDs solution significantly increased the germination rate, root length and embryo length, indicating that CDs has a positive effect on promoting seed germination and early growth. In experiment two, foliar spraying of 5 mg / L CDs solution significantly alleviated the growth inhibition of rice under cadmium stress, increasing plant height by 17.2%, aboveground dry weight by 27.7%, underground dry weight by 27.6%, and root length by 7.2%. Experiment three showed that foliar spraying and soil application of CDs can reduce the DTPA-Cd content in the soil by 17.6% and 14%, respectively, and significantly reduce the Cd content in rice tissues, especially the Cd content in leaves and leaf sheaths by 22% and 17%, respectively. CDs improve rice's resistance to cadmium stress by promoting photosynthesis and enhancing antioxidant capacity, while reducing the content of available cadmium in the soil and the cadmium content in rice tissues, ultimately improving rice yield and quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 Characterization of CDs of the present invention: (a) transmission electron microscopy (TEM); (b) particle size distribution diagram; (c) excitation and emission spectra.

[0025] Figure 2 Effects of carbon quantum dots CDs on rice seed germination: (a) hypocotyl length; (b) root length; (c) germination rate.

[0026] Figure 3 The growth status of rice seedlings under different treatments: (a) rice plant height; (b) rice root length; (c) rice seedling photos; (d) dry weight of aboveground and underground rice parts.

[0027] Figure 4Effects of CDs on rice photosynthesis: (ac) chlorophyll, chlorophyll a, and chlorophyll b contents; (d) electron transfer efficiency (ETR); (e) actual light conversion efficiency (Y II); (f) photochemical quenching coefficient (qP).

[0028] Figure 5 Effects of CDs on rice antioxidant system: (a) POD; (b) CAT; (c) SOD; (d) MDA content; (e) H 2 O 2 Content; (f)O 2 - content.

[0029] Figure 6 Effects of CDs on available cadmium in soil and Cd content in rice: (a) DTPA-Cd concentration; (b) Cd concentration in leaves; (c) Cd concentration in stems; (d) Cd concentration in roots. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present invention.

[0031] Embodiment 1:

[0032] This embodiment provides an inhibitor for preventing rice from absorbing cadmium, and the inhibitor includes carbon quantum dots.

[0033] Embodiment 2:

[0034] This embodiment provides the use of the inhibitor for preventing rice from absorbing cadmium as described in Example 1 in rice cultivation.

[0035] Embodiment three:

[0036] This embodiment provides a method for preventing crops from absorbing cadmium, which comprises spraying the inhibitor described in Example 1 onto the leaves of rice or irrigating the inhibitor described in Example 1 into the soil at the roots of rice.

[0037] Wherein, the rice is hydroponic rice or soil-cultured rice.

[0038] When the rice is hydroponic rice, the frequency of spraying the inhibitor on the leaves of the hydroponic rice is once every 6-8 days, 8-12 ml each time, and the spraying is continuous for 18-23 days. The ratio of cadmium concentration in water to carbon quantum dots in the added inhibitor is 1:4-6.

[0039] When the rice is soil-grown rice, the inhibitor is irrigated into the soil at the root of the rice, and the ratio of the cadmium content in the soil to the carbon quantum dots in the inhibitor added and mixed into the soil is 95-105:1.

[0040] The present invention will be further explained below in conjunction with experiments:

[0041] 1. Test methods

[0042] 1.1 Synthesis and characterization of CDs

[0043] The synthesis method of CDs was based on (Zhou et al., 2013). The morphology and size of CDs were analyzed using a transmission electron microscope (JEOL JEM-2100F, Japan), and the excitation and emission peaks of CDs were confirmed using a fluorescence spectrophotometer (RF-6000).

[0044] 1.2. Effect of CDs on rice seed germination

[0045] After disinfection and rinsing, the seeds (Jinzao 645) were placed in culture dishes, with 20 seeds in each dish. 15 ml of CDs solution of different concentrations (0, 10, 100, 500, 1000 μg / L) was added to the culture dishes, with 3 replicates for each concentration. After germination for 3 days in the dark, the germination rate was calculated, and the root length and embryo length were measured.

[0046] 1.3. Effect of CDs on rice growth and development under Cd toxicity

[0047] In the hydroponic test, after germination, rice seeds were transferred to half of the culture solution and cultured in a light incubator (temperature 25°C, relative humidity 70%, light intensity 400μmolm-2s-1, light 16h / 8h) for 7 days. After 7 days, the rice seedlings grew to about 15cm and were transferred to beakers containing nutrient solution, 6 plants per beaker.

[0048] The experiment set up 4 treatment groups:

[0049] CK: Cd concentration 0 mg / L, sprayed CDs concentration 0 mg / L;

[0050] CDs (CDs-5): Cd concentration 0 mg / L, spraying CDs concentration 5 mg / L (screened by concentration gradient test);

[0051] Cd: Cd concentration 1 mg / L, sprayed CDs concentration 0 mg / L;

[0052] Cd+CDs: Cd concentration is 1 mg / L, and sprayed CDs concentration is 5 mg / L.

[0053] Foliar spraying was performed every two days, 5 ml each time, and three replicates were set for each treatment group. Two weeks later, rice physiological indicators were harvested and measured, and chlorophyll fluorescence parameters were measured using a chlorophyll fluorescence meter (LI-6800).

[0054] 1.4. Effect of CDs on cadmium content in rice tissues

[0055] In a soil culture experiment, two weeks after rice seedlings were raised, seedlings of uniform size were selected and transplanted into pots filled with 3 kg of soil. The soil was taken from a rice field and the cadmium concentration was about 10 mg / kg. The cadmium stress group was recorded as Cd.

[0056] Treatment group 1 (CDs-5): foliar spraying of CDs, foliar spraying of 5 mg / L CDs solution, once a week, 10 ml each time, for 3 consecutive weeks;

[0057] Treatment group 2 (CDs-0.1): CDs were mixed into the soil, and the concentration of CDs mixed into the soil was 0.1 mg / kg.

[0058] The rice plants were harvested after 50 days, and the concentration of available cadmium (DTPA-Cd) in the soil and the concentration of Cd in various parts of the rice were determined.

[0059] 2. Test results

[0060] Data were analyzed using IBM SPSS Statistics 27. Each treatment was repeated three times. One-way ANOVA and Duncan's multiple comparisons were used to analyze the significance of the mean values ​​of each data (P<0.05).

[0061] 2.1 CDs characterization

[0062] from Figure 1 From a and b, we can see that the average size of CDs is about 3 nm, with the best excitation wavelength around 340 nm and the best emission wavelength around 430 nm. Figure 1 c) Their tiny size allows them to enter the leaves through stomata and exert their effects. The unique optical properties of CDs can help the pigments on the thylakoid membrane capture more sunlight and increase the rate of light conversion.

[0063] 2.2 Effects of CDs on rice seed germination

[0064] CDs have the characteristics of good water solubility and low biological toxicity. In order to explore whether its biological toxicity will have a negative impact on rice, a germination test was conducted. Figure 2 It can be seen from ac that at appropriate concentrations, CDs will not affect the germination of rice seeds. Furthermore, the application of CDs during the maturity and development stage of rice will not be toxic to rice.

[0065] 2.3 Effects of CDs on rice growth under Cd toxicity

[0066] like Figure 3 As shown in ad, single application of CDs can significantly increase the plant height and aboveground dry weight of rice, which increased by 22.2% and 54.4% compared with the control group; spraying CDs under cadmium stress can alleviate the cadmium toxicity of rice. Compared with the treatment group without CDs spraying, spraying CDs increased the aboveground dry weight of rice by 27.7%, the underground dry weight by 27.6%, the plant height by 17.2%, and the root length by 7.2% under cadmium stress. In summary, foliar spraying of CDs can promote rice growth and root development, which is helpful to improve the resistance of rice to cadmium stress.

[0067] 2.4 Effects of CDs on Rice Photosynthesis under Cd Poisoning

[0068] like Figure 4 As shown in Figure ac, the chlorophyll content of rice decreased by 20% under cadmium stress, while spraying CDs can restore its chlorophyll content to normal levels. This is because CDs can promote the synthesis of chlorophyll, and CDs have strong conjugation on the surface of chloroplasts, can transfer electrons to chloroplasts by absorbing light, and CDs are excellent electron donors and acceptors, which can participate in the electron transfer process of photosynthesis and improve the efficiency of electron transfer ( Figure 4 d), spraying CDs increased the electron transfer efficiency by 19.5% compared with cadmium stress treatment. Cadmium stress significantly reduces the actual light conversion efficiency (Y(II)). CDs can improve the chloroplast light capture capacity and light conversion efficiency. After CDs treatment of cadmium stress rice, its Y(II) increased by 6.8% ( Figure 4 e). qP is the photochemical quenching parameter of chlorophyll fluorescence, which can reflect the ability of PS II to carry out photochemical reactions. Spraying CDs can improve the photochemical reaction ability of rice. For the control group and cadmium stress, qP increased by 20% and 29%, respectively ( Figure 4 f). Therefore, CDs can promote rice photosynthesis and convert carbon dioxide (CO 2 ) is converted into carbohydrates and stored, which is more conducive to the accumulation of carbohydrates. Therefore, compared with the increase in plant height and root length, the increase in rice dry weight is more significant ( Figure 3 d).

[0069] Effects of CDs on rice viability enzyme activities and oxidative damage under 2.5Cd toxicity

[0070] like Figure 5As shown in ac, cadmium stress stimulates the antioxidant stress of rice, and the activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) are all increased. Therefore, a certain degree of cadmium stress can be tolerated through its own defense system. After the application of CDs, the activities of these antioxidant enzymes are further increased, especially the POD enzyme activity, which is increased by 82% compared with the control.

[0071] MDA is the final product of lipid peroxides in plants and can reflect the degree of oxidative damage in plants. Figure 5 As shown in d, the MDA content under cadmium stress increased by 41% compared with the control group, while spraying CDs could reduce the MDA content by 16.2% compared with the cadmium stress treatment, thereby alleviating the oxidative damage of rice. 2 O 2 and O 2 - Respectively reduced by 10% and 23.5% ( Figure 5 e and f), this is because CDs have a high antioxidant capacity and can act as a reactive oxygen scavenger in plant tissues. After spraying CDs under cadmium stress, it was found that ( Figure 5 e) H in rice 2 O 2 This is because CDs are oxidized by horseradish peroxidase (HRP) and H 2 O 2 Degradation to H 2 O 2 The content of H 2 O 2 Regulate some physiological and biochemical processes of rice.

[0072] In summary, CDs can stimulate the defense system of rice, enhance the activity of rice antioxidant enzymes, and can also act as reactive oxygen scavengers to alleviate oxidative damage in rice, thereby reducing the toxicity of cadmium to rice.

[0073] 2.6 Effects of CDs on soil available cadmium (DTPA-Cd) and rice Cd content under Cd poisoning

[0074] DTPA-Cd is considered to be the most mobile form of cadmium in soil and is most easily absorbed by plants, causing toxicity to them. Figure 6 As shown in a, both foliar spraying and soil application of CDs can reduce the DTPA-Cd content in the soil, which was reduced by 17.6% and 14% respectively compared with the cadmium stress group.

[0075] Regarding the Cd content in rice tissues, CDs as foliar barrier agents can reduce the Cd content in rice leaves, leaf sheaths, and roots ( Figure 6b, c, d), can reduce 10.1%, 9.3%, 5.8% respectively, so it mainly reduces the Cd content in the aboveground tissues, which is beneficial to reduce the final Cd content in the grains. After CDs were added to the soil, it was found that the accumulation of Cd in the root system increased by 5.4% ( Figure 6 d), while the Cd content in leaves and sheaths decreased more significantly, by 22% and 17%, respectively. This is because CDs can change the transport and accumulation of Cd in rice, similar to the role of soil passivators, so that more Cd is fixed in the roots, thereby reducing its transfer to the aboveground part.

[0076] Summary: The present invention uses CDs as a foliar barrier to treat cadmium-stressed rice, and finds that CDs can improve rice's own stress resistance by promoting rice photosynthesis, and can also stimulate the rice defense system to produce more antioxidant enzymes to cope with the oxidative damage caused by Cd stress. CDs can also reduce the concentration of DTPA-Cd in the soil and reduce the accumulation of Cd in the aboveground part, further reducing the toxicity of Cd to rice. At the same time, reducing the Cd content in the aboveground part of rice is conducive to reducing the accumulation of Cd in the grain. Therefore, using CDs as a foliar barrier can effectively alleviate cadmium poisoning of rice, thereby promoting the growth and development of rice and increasing yield.

[0077] The present invention is not limited to the above-mentioned optional implementation modes. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A control agent for preventing rice from absorbing cadmium, characterized in that: The barrier control agent includes carbon quantum dots.

2. Use of the inhibitor for preventing rice from absorbing cadmium as claimed in claim 1 in rice planting.

3. A method for preventing crops from absorbing cadmium, characterized in that: The inhibitor according to claim 1 is sprayed on the leaves of rice or irrigated into the soil at the root of rice.

4. A method for preventing crops from absorbing cadmium according to claim 3, characterized in that: The rice is hydroponic rice or soil-cultured rice.

5. A method for preventing crops from absorbing cadmium according to claim 4, characterized in that: When the rice is hydroponic rice, the frequency of spraying the inhibitor on the leaves of the hydroponic rice is once every 6-8 days, 8-12 ml each time, and the spraying is continued for 18-23 days.

6. A method for preventing crops from absorbing cadmium according to claim 5, characterized in that: When the rice is hydroponic rice, the ratio of the cadmium concentration in the water to the carbon quantum dots in the added inhibitor is 1:4-6.

7. A method for preventing crops from absorbing cadmium according to claim 4, characterized in that: When the rice is soil-grown rice, the inhibitor is irrigated into the soil at the root of the rice, and the ratio of the cadmium content in the soil to the carbon quantum dots in the inhibitor added and mixed into the soil is 95-105:1.

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