Method for relieving stress of cadmium on duckweed by luteolin

Abstract

The invention discloses a method for relieving stress of cadmium on duckweed by luteolin. Aiming at the problem that the growth of the duckweed is inhibited due to cadmium pollution in a water body, a concentration gradient experiment determines that the highest Cdconcentration which can be borne by the duckweed is 10 [mu] mol, and the optimal concentration of luteolin for relieving cadmium stress is 200 [mu] mol. In a cadmium-containing polluted water body, 200 micromoles of luteolin is added into each 100ml of the cadmium-containing polluted water body, so that the growth of the duckweed can be remarkably promoted, the number of leaves, fresh weight and root length can be increased, the activity of antioxidant enzymes (CAT, POD and SOD) can be improved, the content of malonaldehyde (MDA) and the accumulation of active oxygen can be reduced, and the content of chlorophyll can be improved to enhance photosynthesis. Meanwhile, the method can reduce cadmium accumulation in the duckweed, and efficient bioremediation is achieved. The method is simple and convenient to operate, low in cost and environment-friendly, provides a new technical path for water body cadmium pollution treatment, and has a wide application prospect in the field of ecological restoration.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental biotechnology and ecological restoration technology, and particularly relates to a method for relieving stress of cadmium on lemna by using luteolin. BACKGROUND

[0002] With the acceleration of global industrialization and urbanization, heavy metal pollution has become a key problem threatening the safety of water environment. Among them, cadmium (Cd) has become one of the most concerned heavy metals in water pollution due to its high toxicity, strong migration and bioaccumulation. Cadmium mainly enters the water ecosystem through industrial wastewater discharge (such as electroplating, smelting, battery production), mine runoff, agricultural fertilizer and pesticide abuse, and urban sewage leakage, etc., which poses a serious threat to aquatic biodiversity and human health. According to the data of the World Health Organization (WHO), more than 15% of the global surface water is at risk of exceeding the standard of cadmium concentration. The cadmium pollution of water bodies around some mining and industrial areas in China is particularly serious. The cadmium concentration in some areas is far higher than the national surface water Class III standard (0.005 mg / L), and the over-standard rate is as high as more than 30%, which urgently needs efficient and sustainable treatment technology.

[0003] The harm of cadmium to aquatic ecosystems has multidimensionality: low concentration of cadmium can inhibit the photosynthesis, respiration and material metabolism of aquatic plants, leading to plant growth retardation, leaf yellowing, root shrinkage and even death, and destroying the primary productivity of water bodies. For fish and other aquatic animals, cadmium can enter the body through gill respiration and feeding, accumulate in organs such as liver and kidney, cause cell damage, immune function decline and reproduction disorders, and then be transmitted through the food chain, ultimately threatening human health. Long-term exposure to cadmium-polluted environment can lead to kidney failure, bone disease (such as "Itai-Itai disease"), increased risk of cardiovascular disease, and even induce malignant tumors. Its toxicity has been listed as a Class I carcinogen by the International Agency for Research on Cancer (IARC).

[0004] At present, the remediation technologies for cadmium-polluted water bodies mainly include physical, chemical and biological methods. Physical remediation technologies such as activated carbon adsorption and clay mineral adsorption can quickly reduce the cadmium concentration in water bodies, but they have problems such as high cost of adsorption materials, difficulty in regeneration after saturation, and easy secondary pollution. Chemical remediation technologies such as chemical precipitation and redox method can make cadmium form precipitates or transform into other forms by adding chemical reagents, but the dosage of reagents needs to be accurately controlled, and excessive dosage can lead to imbalance of water pH or introduction of new pollutants, which is difficult to apply to large-area and low-concentration cadmium-polluted water bodies. Membrane separation technology has high separation efficiency, but the cost of membrane components is high, and it is easy to be contaminated and blocked, which leads to high operation and maintenance cost, limiting its application in large-scale water remediation.

[0005] Bioremediation technology has become a research hotspot for low-concentration cadmium pollution treatment in water bodies due to its low cost, environmental friendliness, and no secondary pollution. Duckweed (e.g., Lemna minor, Spirodela polyrrhiza) is a small floating aquatic plant widely distributed in water bodies. It has the characteristics of fast growth (daily biomass increase of 20%-30%), large surface area, strong heavy metal adsorption capacity, and easy artificial harvesting, and is considered as a potential biological model for cadmium pollution remediation in water bodies. Studies have shown that duckweed can reduce the concentration of cadmium in water through root adsorption, surface precipitation, and intracellular enrichment. However, its remediation efficiency is severely limited by cadmium stress. High concentrations of cadmium can damage the cell structure of duckweed, inhibit chlorophyll synthesis and photosynthesis efficiency, and reduce photosynthetic rate by 30%-50%. At the same time, it can cause a large accumulation of reactive oxygen species (ROS) in the cell, leading to membrane lipid peroxidation damage, a significant increase in malondialdehyde (MDA) content, and inhibition of antioxidant enzyme (e.g., SOD, POD, CAT) activity. Ultimately, it leads to the inhibition of duckweed growth and biomass reduction, greatly limiting its application in cadmium-contaminated water bodies.

[0006] Natural plant-derived compounds have shown great potential in enhancing plant stress resistance due to their low toxicity, good environmental compatibility, and functional diversity. Luteolin (3', 4', 5, 7-tetrahydroxyflavone) is a flavonoid compound widely found in natural plants such as celery, honeysuckle, and chrysanthemum. It has a unique chemical structure and biological activity, and has been proven to have strong antioxidant, anti-inflammatory, plant hormone signal regulation, and metabolic promotion functions. Existing studies have shown that luteolin can effectively alleviate the damage of abiotic stress (e.g., drought, salt, and low temperature) to terrestrial plants (e.g., wheat, corn, and Arabidopsis) by removing excess free radicals in the plant body, activating the antioxidant enzyme system, and regulating the synthesis of osmotic substances. However, its application in aquatic plants under heavy metal stress has not been reported.

[0007] Our team's previous research has found that the content of flavonoid metabolites in duckweed changes significantly under cadmium stress, suggesting that flavonoids may be involved in the cadmium stress response process of duckweed. Through screening experiments on dozens of natural compounds, it was confirmed that luteolin has a specific alleviating effect on the growth inhibition and oxidative damage of duckweed under cadmium stress. Compared with other polyphenolic compounds (e.g., coffee acid ethyl ester), luteolin has the advantages of more extensive sources, lower cost, and better water solubility, making it more suitable for large-scale water remediation applications. However, the optimal concentration, mechanism, and practical application parameters of luteolin in alleviating duckweed cadmium stress are not yet clear, which limits its promotion in water cadmium pollution bioremediation.

[0008] Therefore, the development of duckweed cadmium stress resistance technology based on luteolin and the clarification of its application conditions and efficiency are of great theoretical and practical significance for improving the efficiency of water cadmium pollution bioremediation. SUMMARY

[0009] The technical problem to be solved by the present application is that in the existing remediation of cadmium pollution in water bodies, physical and chemical methods have the defects of high cost, complex operation, easy secondary pollution and difficulty in being applicable to large-area low-concentration polluted water bodies, while duckweed as a potential biological remediation material is inhibited in growth (such as leaf yellowing, root shortening, and increased mortality) and physiological function (such as decreased antioxidant enzyme activity and chlorophyll content and accumulated active oxygen) under high-concentration cadmium stress, and the remediation efficiency is low; meanwhile, the application of luteolin in relieving the stress of heavy metals on aquatic plants, the optimal concentration and the mechanism have not been clear, and it is urgent to provide a method based on luteolin to improve the survival ability and remediation efficiency of duckweed in cadmium-polluted environment.

[0010] The technical scheme adopted by the present application is: a method for relieving the stress of cadmium on duckweed by using luteolin, comprising: determining the highest Cd²⁺ concentration that can be tolerated by duckweed; determining the optimal concentration of luteolin for relieving the cadmium stress of duckweed; and adding the optimal concentration of luteolin to the cadmium-containing polluted water body to relieve the stress.

[0011] As a further scheme of the present application: the method for determining the highest Cd²⁺ concentration is: setting 0 μmol, 10 μmol, 20 μmol, 40 μmol, 80 μmol, and 160 μmol of Cd²⁺ solution, and culturing duckweed in MS culture solution under the conditions of temperature (25±3) ℃ and natural light for 7 days, and observing to determine that the highest tolerance concentration is 10 μmol; the duckweed includes Spirodela polyrrhiza and Azolla.

[0012] As a further scheme of the present application: the method for determining the optimal concentration of luteolin is: adding 0 μmol, 100 μmol, 200 μmol, 400 μmol, 800 μmol, and 1600 μmol of luteolin to 10 μmol of Cd²⁺ solution, taking blank control (0 μmol of Cd²⁺) and cadmium stress control (10 μmol of Cd²⁺) as references, and screening out the optimal concentration of 200 μmol.

[0013] As a further scheme of the present application: the proportion of adding luteolin is: adding 200 μmol of luteolin to every 100 ml of cadmium-containing water body.

[0014] As a further scheme of the present application: the duckweed is local duckweed in Ji'an, Jiangxi.

[0015] The use of luteolin in preparing a preparation for relieving the stress of cadmium on duckweed, and the concentration of luteolin in the preparation is 200 μmol.

[0016] A water body cadmium pollution remediation composition comprises luteolin and duckweed growth culture solution, the concentration of the luteolin is 200 micromoles, and the duckweed growth culture solution is MS culture solution; the composition is used for promoting growth of duckweed and enhancing cadmium absorption capacity of the duckweed.

[0017] As a further scheme of the present application, the preparation method of the luteolin solution is as follows: luteolin is dissolved in DMSO to prepare a mother liquor, the concentration of the mother liquor is 0.1 M, and different concentrations of solutions used in experiments are obtained by diluting the mother liquor.

[0018] The present application has the following beneficial effects: 1. Significantly improving survival ability of duckweed under cadmium stress, and guaranteeing remediation sustainability. By optimizing the concentration of luteolin to 200 micromoles, the present application can effectively alleviate the growth inhibition of duckweed caused by 10 micromoles of Cd²⁺, so that the number of duckweed leaves is increased by 60% and the fresh weight is increased by 55% compared with the cadmium stress control, the root length is restored to 85% of the blank control, and the stress symptoms such as leaf yellowing and root atrophy are significantly improved, thereby ensuring stable growth and reproduction of duckweed in the cadmium-polluted environment and providing a guarantee for the biomass of the continuous water body remediation.

[0019] 2. Strengthening stress resistance metabolism through multiple physiological regulation, and improving remediation efficiency. Luteolin can activate the antioxidant enzyme system in duckweed, significantly improve the activities of SOD, CAT and POD, reduce the accumulation of reactive oxygen species (ROS) and the content of malondialdehyde (MDA), and reduce the damage of membrane lipid peroxidation; meanwhile, the contents of chlorophyll a, chlorophyll b and total chlorophyll are increased, the photosynthesis efficiency is maintained, the normal physiological metabolism of duckweed is ensured, the comprehensive resistance of duckweed to cadmium stress is enhanced from the physiological aspect, and the continuous absorption and enrichment efficiency of duckweed to water cadmium is indirectly improved.

[0020] 3. Reducing the accumulation of cadmium in duckweed, and reducing the risk of secondary pollution. The present method can significantly reduce the accumulation of cadmium in duckweed while promoting the growth of duckweed. Experimental data show that, after adding 200 micromoles of luteolin, the cadmium content in duckweed is significantly reduced compared with the cadmium stress group alone, which makes the subsequent treatment of the harvested duckweed biomass more simple and safe, reduces the potential risk of secondary pollution caused by cadmium transfer through duckweed residues or biological transfer, and improves the environmental safety of biological remediation.

[0021] 4. The natural compound is adapted to the green remediation demand, and has excellent environmental compatibility. Luteolin, as a natural flavonoid compound, widely exists in plants such as celery and honeysuckle, has low toxicity and easy degradation, has no risk of chemical residue, and avoids the secondary pollution of water body caused by traditional physical / chemical remediation methods; the water solubility of luteolin is slightly higher than that of other polyphenols (such as coffee acid ethyl ester), the dispersibility in water is better, the efficiency is higher, and the green and environmental protection concept of ecological remediation is more suitable.

[0022] 5. The technical parameters are clear and the operation is simple and easy to scale up and apply. The application specifies the highest tolerance Cd²+ concentration (10 micromoles) of duckweed and the optimal addition concentration (200 micromoles) of luteolin through concentration gradient experiments, and specifies the addition ratio of each 100ml cadmium-containing water body and the solution preparation method (DMSO dissolving mother liquor dilution), the operation process does not require complex equipment or professional technology, and the cost is significantly lower than that of traditional methods such as physical adsorption and chemical precipitation, which is suitable for the remediation of different sizes, low concentration cadmium contaminated water bodies such as mine wastewater, rivers and lakes, and has low application threshold. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The growth of duckweed under different concentrations of cadmium in the method for relieving the stress of cadmium on duckweed by luteolin.

[0024] Figure 2 The statistical results of the number of leaves, fresh weight and root length of duckweed under different concentrations of cadmium in the method for relieving the stress of cadmium on duckweed by luteolin; A in the figure is the number of leaves of duckweed; B in the figure is the fresh weight of duckweed; C in the figure is the root length of duckweed; D in the figure is the statistical result of the root length of duckweed.

[0025] Figure 3 The growth of duckweed under different concentrations of cadmium in the method for relieving the stress of cadmium on duckweed by luteolin.

[0026] Figure 4 The statistical results of the number of leaves and fresh weight of duckweed under different concentrations of cadmium in the method for relieving the stress of cadmium on duckweed by luteolin; A in the figure is the number of leaves of duckweed; B in the figure is the fresh weight of duckweed.

[0027] Figure 5 The growth of duckweed under different concentrations of cadmium + luteolin in the method for relieving the stress of cadmium on duckweed by luteolin.

[0028] Figure 6 The statistical results of the number of leaves, fresh weight and root length of duckweed under different concentrations of cadmium + luteolin in the method for relieving the stress of cadmium on duckweed by luteolin; A in the figure is the number of leaves of duckweed; B in the figure is the root length of duckweed; C in the figure is the fresh weight of duckweed; D in the figure is the statistical result of the root length of duckweed.

[0029] Figure 7This invention relates to a method for alleviating cadmium stress on duckweed using luteolin, and the detection of enzyme activities (CAT, POD, MDA, SOD) in duckweed under different treatments. Figure A shows the detection results of CAT enzyme in duckweed; Figure B shows the detection results of POD enzyme in duckweed; Figure C shows the detection results of MDA enzyme in duckweed; and Figure D shows the detection results of SOD enzyme in duckweed.

[0030] Figure 8 The figures show the detection results of chlorophyll content in duckweed under different treatments according to a method for alleviating cadmium stress on duckweed using luteolin according to the present invention; A in the figure shows the detection result of chlorophyll a content in duckweed; B in the figure shows the detection result of chlorophyll b content in duckweed; and C in the figure shows the detection result of total chlorophyll content in duckweed.

[0031] Figure 9 The figures show the detection results of cadmium content in water and cadmium content in duckweed under different treatments according to a method for alleviating cadmium stress on duckweed using luteolin. A and B in the figure represent the detection results of cadmium content in water, while C and D in the figure represent the detection results of cadmium content in duckweed. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way.

[0033] All data in this invention embodiment were analyzed using Excel to evaluate the significant differences in leaf number, fresh weight, root length, enzyme activity (CAT, POD, MDA, SOD), and other physiological and morphological parameters among different treatments; the values ​​are presented as mean ± standard deviation.

[0034] Example 1: Effects of different Cd2+ concentrations on the growth characteristics of duckweed Concentration gradient screening To screen for the optimal cadmium concentration that duckweed can tolerate, a cadmium concentration gradient screening was conducted. 100 ml of prepared MS medium was poured into disposable plastic cups, and different cadmium concentrations were set sequentially: 0, 10 μmol, 20 μmol, 40 μmol, 80 μmol, and 160 μmol. Two replicates were set for each gradient, and 20 healthy duckweed plants were placed in each cup. The plants were cultured at (25±3) ℃ under natural light for 7 days, and their growth in solutions with different cadmium concentrations was observed. The same cadmium concentration gradient was set for *Lemna minor* (also known as *Lemna minor*) as a control. The results showed that the highest cadmium concentration that duckweed could tolerate was 10 μmol.

[0035] Statistically analyze the number of leaves, fresh weight, and root length of *Lemna minor*, as well as the number of leaves and fresh weight of *Lemna minor*. To better analyze the growth of duckweed, after 7 days, the number of leaves, fresh weight, and root length of duckweed in solutions with different cadmium concentrations were counted. The results showed that as the cadmium concentration increased, the number of leaves and fresh weight of duckweed gradually decreased, and the root length also gradually shortened, indicating that duckweed was under cadmium stress. Since the roots of duckweed are relatively short, only the number of leaves and fresh weight of duckweed were counted, and the results were the same as those of duckweed.

[0036] The growth of duckweed in solutions with different cadmium concentrations is as follows: Figure 1 As shown, by Figure 1 It can be seen that, compared with the control group CK, the growth of duckweed was significantly inhibited as the cadmium concentration continued to increase. The leaves of duckweed gradually dispersed, withered and even died. Finally, it was determined that the most suitable cadmium concentration that duckweed could withstand was 10 μmol.

[0037] The growth of *Lysimachia christinae* in cadmium solutions of different concentrations is as follows: Figure 3 As shown, by Figure 3 It can be seen that compared with the control group CK and duckweed, duckweed is more resistant to cadmium stress, but the growth of duckweed is also inhibited when the cadmium concentration is too high.

[0038] The statistical results of leaf number, fresh weight, and root length of *Peperomia tinctoria* in cadmium solutions of different concentrations are as follows: Figure 2 As shown, Figure 2 The figures A and D in the table represent, in order, the number of leaves, fresh weight, and root length of *Duckweed*, photographs, and statistical results of root length. Compared with the control group (CK), the number of leaves, fresh weight, and root length of *Duckweed* all decreased with increasing cadmium concentration.

[0039] The statistical results of the number of leaves and fresh weight of *Lysimachia christinae* in cadmium solutions of different concentrations are as follows: Figure 4 As shown, Figure 4 In the table, A represents the number of leaves of *Lemna minor*, and B represents its fresh weight. Compared with the control group (CK), both the number of leaves and the fresh weight of *Lemna minor* decreased significantly with increasing cadmium concentration.

[0040] Example 2: Effects of different luteolin concentrations on duckweed growth Concentration gradient screening of cadmium + luteolin Adding luteolin solution to a Cd2+ solution of 10 μmol showed that it could alleviate the stress of cadmium on duckweed. To find the optimal concentration of luteolin, a concentration gradient experiment was set up, with concentrations of 0, 100 μmol, 200 μmol, 400 μmol, 800 μmol, and 1600 μmol. The results showed that a certain concentration of luteolin solution could effectively alleviate the stress of cadmium on duckweed, but if the concentration was too high, it would have a certain inhibitory effect. Therefore, the optimal concentration of luteolin was determined to be 200 μmol.

[0041] Count the number of leaves, fresh weight, and root length of duckweed. In order to better observe the growth of duckweed, the number of leaves, fresh weight and root length were used as growth indicators. The results showed that when luteolin was 100-200 umol, the number of leaves and fresh weight of duckweed showed a significant upward trend. When luteolin was 400-1600 umol, the number of leaves and fresh weight of duckweed decreased significantly, indicating that luteolin could alleviate the stress of cadmium on duckweed, but too high a concentration would not have a mitigating effect.

[0042] In the CK, Cd2+ 10 umol, Cd2++ luteolin 200 umol cups, two duckweeds were selected and laid on the agar plate, and the root length was observed and photographed. The results showed that compared with the control CK, the root length of duckweed in Cd2+ 10 umol was significantly shortened, and the root length of duckweed in Cd2++ luteolin 200 umol was significantly lengthened, further indicating that luteolin 200 umol could effectively alleviate the stress of cadmium.

[0043] The growth of duckweed in different concentrations of cadmium+luteolin solution is shown in Figure 5 As can be seen from Figure 5 Compared with the control group CK and Cd2+ 10 umol, luteolin can alleviate the stress of cadmium on duckweed, and the effect is best at 200 umol, and too high a concentration will have an inhibitory effect.

[0044] The number of leaves, fresh weight and root length of duckweed in different concentrations of cadmium+luteolin solution are shown in Figure 6 As can be seen from Figure 6 A-D in Figure 6 As can be seen from

[0045] Example 3 Effect of different treatments on enzyme content and chlorophyll content in duckweed Detection of enzyme activity (CAT, POD, MDA, SOD) The content of various antioxidant enzymes in duckweed was determined when Cd2+ was 0, Cd2+ 25 umol, and Cd2++ luteolin 200 umol, respectively. Cd2+ was used as a control. The results showed that the content of various antioxidant enzymes in duckweed decreased sharply when treated with Cd2+ 25 umol, but increased when treated with Cd2++ luteolin 200 umol, indicating that luteolin 200 umol helped duckweed to remove active oxygen in the body.

[0046] Determination of chlorophyll content (chlorophyll a, chlorophyll b, total chlorophyll content) The contents of chlorophyll a, chlorophyll b and total chlorophyll in the duckweed under the conditions of Cd2+ 0, Cd2+ 10 umol and Cd2++ luteolin 200 umol were measured respectively, and Cd2+ 0 was used as a control. The results showed that the contents of chlorophyll a, chlorophyll b and total chlorophyll in the duckweed decreased significantly under the condition of Cd2+ 10 umol, but increased significantly under the condition of Cd2++ luteolin 200 umol, which further indicated that luteolin could affect the content of chlorophyll in duckweed.

[0047] The enzyme contents of duckweed under the conditions of Cd2+ 0, Cd2+ 25 umol and Cd2++ luteolin 200 umol are shown in Table A-D, wherein A-D are the statistical results of CAT, POD, MDA and SOD respectively. Figure 7 Figure 7 When the enzyme contents were measured, each enzyme kit was used for detection, and the sample was treated for 1 hour before detection. Then, 0.2 g of the sample was weighed, 1 ml of the extraction solution in the kit was used for grinding, the grinding solution was transferred to a test tube for centrifugation, and the supernatant was detected by a spectrophotometer according to the instructions in the kit.

[0048] The chlorophyll contents of duckweed under the conditions of Cd2+ 0, Cd2+ 10 umol and Cd2++ luteolin 200 umol are shown in Table A-C, wherein A-C are the detection results of chlorophyll a, chlorophyll b and total chlorophyll content respectively. Figure 8 Figure 8 When the chlorophyll content was measured, the duckweed leaves were allowed to turn yellow before detection. First, 0.3 g of the sample was weighed, then the extraction solution was prepared by mixing ethanol and propanol (1:2), 1 ml of the extraction solution was used for grinding, the mortar was washed with the extraction solution, all the liquid was transferred to a test tube, the volume was made to 10 ml, and the solution was dark treated for 3 hours. The supernatant was detected by a spectrophotometer according to the instructions in the kit.

[0049] Example 4: Effect of different treatments on cadmium accumulation in duckweed Determination of cadmium content in water body and duckweed ​​The content of cadmium in the water body with Cd2+ 0umol, Cd2+ 5umol, Cd2+ 10umol, Cd2+ 5+ luteolin 200umol, Cd2+ 10+ luteolin 200umol was determined by atomic absorption method, and the results showed that the content of cadmium in the water body with cadmium solution alone increased obviously, and the content of cadmium in the water body with cadmium + luteolin solution increased more obviously, which indicated that luteolin inhibited the absorption of cadmium by duckweed, so the content of cadmium in the water body was high. Then the content of cadmium in duckweed was determined, first the cadmium in duckweed was extracted by digestion method, and then atomic absorption method was used for determination, and the results showed that the content of cadmium in duckweed with cadmium solution alone decreased obviously, and the content of cadmium in duckweed with cadmium + luteolin solution decreased more obviously.

[0050] The content of cadmium in the water body and the content of cadmium in duckweed under the treatment of Cd2+ 0, Cd2+ 5umol, Cd2+ 10umol, Cd2+ 5umol + luteolin 200umol, Cd2+ 10umol + luteolin 200umol are shown in Figure 9 Figure 9 A and B in the above table are the statistical results of the content of cadmium in the water body under different treatments, and C and D are the statistical results of the content of cadmium in duckweed under different treatments. When determining the content of cadmium in the water body, first prepare 5 standard solution with cadmium solution, then filter 10ml water sample from the sample cultured for 7 days with a syringe and a filter head, and determine by atomic absorption method; when determining the content of cadmium in duckweed, first extract cadmium in duckweed by digestion method, and then determine by atomic absorption method.

[0051] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​

Claims

1. A method for alleviating cadmium stress on duckweed using luteolin, characterized in that, include: Determine the maximum Cd that duckweed can withstand. 2+ Concentration; Determining the optimal concentration of luteolin to alleviate cadmium stress in duckweed; Add the optimal concentration of luteolin to cadmium-contaminated water to alleviate stress.

2. The method for alleviating cadmium stress on duckweed using luteolin according to claim 1, characterized in that, Determine the highest Cd 2+ The concentration method is as follows: set Cd concentrations of 0 μmol, 10 μmol, 20 μmol, 40 μmol, 80 μmol, and 160 μmol. 2+ The solution was prepared by culturing duckweed in MS medium at 25±3℃ under natural light for 7 days, and the maximum tolerated concentration was determined to be 10 μmol. The duckweed included duckweed and purple duckweed.

3. A method for alleviating cadmium stress on duckweed using luteolin according to claim 2, characterized in that, The method for determining the optimal concentration of luteolin is as follows: in 10 μmol Cd 2+ Luteolin was added to the solution at concentrations of 0 μmol, 100 μmol, 200 μmol, 400 μmol, 800 μmol, and 1600 μmol, with a blank control of 0 μmol Cd. 2+ Compared with cadmium stress control 10 μmol Cd 2+ For reference, the optimal concentration was determined to be 200 μmol.

4. A method for alleviating cadmium stress on duckweed using luteolin according to claim 3, characterized in that, The ratio of luteolin added is: 200 μmol of luteolin per 100 ml of cadmium-containing water.

5. A method for alleviating cadmium stress on duckweed using luteolin according to claim 4, characterized in that, The duckweed in question is a local variety from Ji'an, Jiangxi Province.

6. The use of luteolin in the preparation of formulations to alleviate cadmium stress on duckweed, characterized in that, The concentration of luteolin in the formulation is 200 μmol.

7. A composition for remediating cadmium pollution in water bodies, characterized in that, The composition comprises luteolin and duckweed growth culture medium, wherein the concentration of luteolin is 200 μmol and the duckweed growth culture medium is MS culture medium; this composition is used to promote duckweed growth and enhance its cadmium absorption capacity.

8. The water cadmium pollution remediation composition according to claim 1, characterized in that, The luteolin solution was prepared by dissolving luteolin in DMSO to prepare a stock solution with a concentration of 0.1 M. Solutions of different concentrations used in the experiment were obtained by diluting the stock solution.

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