Ethyl caffeate as a method to alleviate cadmium stress in duckweed

Abstract

This invention discloses a method for alleviating cadmium stress on duckweed using ethyl caffeate. With industrial development, cadmium pollution in water bodies seriously threatens the ecosystem and human health, and traditional remediation methods have shortcomings. Although duckweed has the potential for water body remediation, cadmium stress inhibits its growth. This invention, through concentration gradient experiments, determines the maximum Cd concentration that duckweed can withstand. 2+ The optimal concentration of ethyl caffeate for alleviating cadmium stress is 200 μmol, with a concentration of 10 μmol. Adding 200 μmol of ethyl caffeate per 100 ml of cadmium-contaminated water significantly promotes duckweed growth, increases leaf number, fresh weight, and root length, enhances antioxidant enzyme content, reduces MDA content, increases chlorophyll content, and strengthens photosynthesis. It also significantly reduces cadmium accumulation in duckweed, achieving efficient bioremediation of cadmium pollution in water bodies. This method is simple to operate, low in cost, and environmentally friendly, showing broad application prospects in the field of water pollution control.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of environmental science and biotechnology, specifically to a method and application of using ethyl caffeate to alleviate cadmium stress on duckweed in order to achieve bioremediation of cadmium pollution in water bodies. Background Technology

[0002] Duckweed, a small, floating aquatic plant belonging to the Araceae family, includes the common green duckweed and purple duckweed. It is widely distributed in freshwater environments worldwide, such as ponds, lakes, and ditches. Duckweed plants are tiny and reproduce rapidly, quickly covering the water surface under suitable conditions, making them excellent experimental materials. Duckweed has a long history in traditional Chinese medicine and is considered to have various medicinal values. Its main medicinal part is the whole plant, which is pungent and cold in nature, and enters the lung and bladder meridians. Duckweed has diaphoretic and exterior-releasing effects, as well as heat-clearing, detoxifying, anti-inflammatory, analgesic, and antioxidant properties.

[0003] With rapid industrialization and urbanization, as well as large-scale mining, massive amounts of metals and heavy metal ions are released into the environment, causing severe water pollution and becoming one of the world's most significant environmental problems. Metals such as copper (Cu) and zinc (Zn), and heavy metals such as lead (Pb), cadmium (Cd), and chromium (Cr), due to their high toxicity and non-degradability, pose a serious threat to aquatic ecosystems and even human health. While traditional physical and chemical treatment methods are effective, they are costly and may cause secondary pollution. In contrast, using aquatic plants to remediate heavy metal-polluted waters has advantages such as low cost, ease of operation, and environmental friendliness, and has become a research hotspot in recent years. Cadmium (Cd), as a toxic heavy metal, can cause numerous problems such as liver and kidney damage, nervous system abnormalities, and weakened immunity with long-term exposure to cadmium-contaminated water or food.

[0004] To address this serious problem, through extensive literature review and field investigation, we discovered that duckweed can still thrive even in polluted wastewater and effectively improve eutrophication. Therefore, we selected duckweed as a model organism for our experiments, using only duckweed from Ji'an, Jiangxi Province, to avoid interference from geographical location and species. Our preliminary results showed that cadmium pollution in water significantly reduced the growth rate of duckweed, causing rapid leaf dispersion and yellowing, and premature death at excessively high concentrations. To further investigate the inhibitory mechanism of cadmium stress on duckweed growth and develop new methods to alleviate cadmium stress, we screened dozens of drugs through in vitro additive experiments and analyzed the secondary metabolomics of duckweed under cadmium stress, finding a significant change in the abundance of the polyphenol caffeic acid. In vitro additive experiments showed that caffeic acid had a significant effect in alleviating cadmium stress, with ethyl caffeate showing the best mitigating effect. Caffeic acid is a widely distributed phenolic acid compound in the plant kingdom, found not only in coffee beans, common fruits and vegetables, but also abundantly in traditional Chinese medicinal plants. In recent years, scholars have discovered that caffeic acid and its derivatives, such as phenethyl caffeate, methyl caffeate, and ferulic acid, can not only improve hyperglycemia but also alleviate the progression of diabetic complications through multiple mechanisms. However, research on the mitigation of cadmium stress in plants by caffeic acid derivatives has not been reported, and the relevant mechanisms of action remain a blank. We used biochemical, molecular biological, and cell biological methods to conduct an in-depth study on the mechanisms by which caffeic acid derivatives alleviate cadmium stress. This research is expected to reveal the mechanism of action of caffeic acid in plant resistance to cadmium stress and provide new insights for research on the stress resistance of duckweed. Summary of the Invention

[0005] This invention aims to provide a method for alleviating cadmium stress in duckweed using ethyl caffeate, analyze the effects of cadmium stress on the growth and development of duckweed, reveal the mechanism by which ethyl caffeate alleviates cadmium stress, provide a new approach for research on duckweed stress resistance, and provide theoretical support and practical guidance for the bioremediation of cadmium pollution in water bodies, thereby improving the stability and efficiency of aquatic plant remediation technology for heavy metal polluted water bodies.

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

[0007] This invention, using duckweed as the test plant, found that adding a certain amount of prepared ethyl caffeate solution to the culture medium when duckweed is under cadmium stress can effectively alleviate cadmium stress and reduce cadmium accumulation in the duckweed. Therefore, this invention provides a method for alleviating cadmium stress in plants and reducing cadmium accumulation in plants.

[0008] Specifically, by setting different concentrations of Cd 2+ The solution was screened to determine the highest Cd that duckweed could withstand. 2+Concentration; at a given Cd concentration 2+ Based on the existing concentration, different concentrations of ethyl caffeate were added to screen for the most suitable mitigating concentration. Experiments verified that the highest Cd concentration that duckweed could tolerate was determined. 2+ The optimal concentration for ethyl caffeate to alleviate symptoms is 200 μmol, with a concentration of 10 μmol.

[0009] Furthermore, in cadmium-contaminated water bodies, 200 μmol of ethyl caffeate was added per 100 ml of water. At the same time, the quantity and growth environment of duckweed in the water body were ensured to alleviate cadmium stress on duckweed, promote duckweed growth, and thus improve the duckweed's ability to remediate cadmium in the water body.

[0010] More specifically, the duckweed culture medium was prepared using MS, and Cd 2+ The solution was prepared by adding DMSO to CdCl2, and Cd... 2+ The mother liquor concentration was 0.1M, and the Cd used in the experiment... 2+ All solutions were obtained by diluting their mother liquor; the ethyl caffeate solution was obtained by dissolving DMSO, with a mother liquor concentration of 0.1M. The different concentrations of ethyl caffeate used in the experiment were all obtained by diluting their mother liquor.

[0011] The beneficial effects achieved by the present invention using the above technical solution are as follows:

[0012] 1. Growth promotion: Experiments show that adding 200 μmol of ethyl caffeate can significantly alleviate the inhibition of duckweed growth by cadmium stress, increase the number of duckweed leaves, increase fresh weight, and lengthen roots, thereby improving the survival and reproduction capacity of duckweed in cadmium-polluted water.

[0013] 2. Physiological improvement: Ethyl caffeate can increase the content of antioxidant enzymes (CAT, POD, SOD) in duckweed, reduce the content of MDA, and reduce the damage of reactive oxygen species to duckweed cells; at the same time, it can increase the chlorophyll content, improve the photosynthetic efficiency of duckweed, and ensure its normal physiological functions.

[0014] 3. Enhanced Cadmium Removal: It can reduce the cadmium content in water, promote the absorption of cadmium by duckweed, improve the remediation effect of duckweed on cadmium pollution in water, and provide a more effective biological remediation method for the treatment of cadmium pollution in water.

[0015] 4. Wide range of applications: This method is simple to operate, low in cost, and environmentally friendly. It is not only suitable for laboratory research, but can also be extended to actual water cadmium pollution remediation projects, and has broad application prospects. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0017] Figure 1 This shows the growth of *Aquilaria sinensis* under different concentrations of cadmium treatment using this method.

[0018] Figure 2 These are the statistical results of the number of leaves, fresh weight, and root length of *Lycoperdon perlatum* under different concentrations of cadmium treatment using this method.

[0019] Figure 3 This shows the growth of *Lemna minor* under different concentrations of cadmium treatment using this method.

[0020] Figure 4 These are the statistical results of the number of leaves and fresh weight of *Lemna minor* under different concentrations of cadmium treatment using this method;

[0021] Figure 5 This shows the growth of duckweed under different concentrations of cadmium + ethyl caffeate treatment using this method;

[0022] Figure 6 These are the statistical results of the number of leaves, fresh weight, and root length of duckweed under different concentrations of cadmium + ethyl caffeate treatment using this method.

[0023] Figure 7 This method is used to detect enzyme activity (CAT, POD, SOD, MDA) in duckweed under different treatments.

[0024] Figure 8 These are the detection results of chlorophyll content in duckweed under different treatments using this method;

[0025] Figure 9 The staining of duckweed with NBT under different treatments according to this method;

[0026] Figure 10 These are the detection results of cadmium content in water bodies and cadmium content in duckweed under different treatments using this method. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] 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. Example 1: Effects of different Cd2+ concentrations on the growth characteristics of duckweed

[0029] 1. Cd 2+ Concentration gradient screening

[0030] Add 100 ml of prepared MS culture medium to each disposable plastic cup, and then add prepared Cd22-dioxanone solution. 2+ Solutions were prepared with concentration gradients of 0, 10 μmol, 20 μmol, 40 μmol, 80 μmol, and 160 μmol, with two replicates for each concentration. A solution with a metal concentration of 0 μmol served as a control. Twenty healthy *Dendrobium nobile* plants were placed in each plastic cup and cultured at (25±3)℃ under natural light for 7 days. Growth was observed. *Dendrobium chrysanthum* was also cultured with the same concentration gradient as a control. The results showed that *Dendrobium nobile* could tolerate a maximum Cd concentration of [missing information - likely a specific concentration]. 2+ The concentration is 10 μmol.

[0031] 2. Count the number of leaves, fresh weight, and root length of *Lemna minor* and the number of leaves and fresh weight of *Lemna minor*.

[0032] For a more comprehensive analysis, the number of duckweed leaves and their fresh weight were counted. The results showed that as Cd... 2+ As the concentration of [agent] increases, the inhibitory effect of duckweed gradually strengthens, leading to a gradual decrease in the number of duckweed leaves and a gradual reduction in fresh weight.

[0033] Duckweed at different concentrations of Cd 2+ Growth in solution as follows Figure 1 As shown, by Figure 1 It can be seen that, compared with the control (CK), as the cadmium concentration increases, the leaves of duckweed gradually disperse, turn yellow, and even die, and the growth of duckweed is significantly inhibited. The optimal cadmium concentration that duckweed can accept is 10 μmol.

[0034] Zi Ping at different concentrations of Cd 2+ Growth in solution as follows Figure 3 As shown, by Figure 3 It can be seen that, compared with the control (CK) and Figure 1 Compared with the growth of duckweed, purple duckweed was found to be more resistant to cadmium stress, but the growth of purple duckweed was also inhibited as the cadmium concentration increased.

[0035] Duckweed at different concentrations of Cd 2+ The statistical results of leaf number, fresh weight, and root length in the solution are as follows: Figure 2 As shown; Figure 2 The middle AD values ​​represent different concentrations of Cd in *Aquilegia oleracea*. 2+ The number of leaves, fresh weight, and root length of *Duckweed* in solution were photographed, and the root length of *Duckweed* was statistically analyzed. Compared with the control, the number of leaves, fresh weight, and root length of *Duckweed* all decreased significantly with increasing cadmium concentration.

[0036] Because the roots of *Lemna minor* are relatively short, only the number of leaves and fresh weight were counted. *Lemna minor* was tested at different concentrations of Cd. 2+ The statistical results of the number of leaves and fresh weight in the solution 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, both the number of leaves and the fresh weight of *Lemna minor* decreased significantly with increasing cadmium concentration.

[0037] Example 2: Effects of different ethyl caffeate concentrations on duckweed growth

[0038] 1. Cd 2+ +Concentration gradient screening of ethyl caffeate

[0039] To alleviate Cd 2+ To investigate the stress on duckweed, ethyl caffeate was selected from numerous substances through screening, and this was confirmed through repeated experiments. Therefore, a gradient experiment was designed based on this finding. (The last sentence appears to be incomplete and possibly refers to a different topic.) 2+ Based on a concentration of 10 μmol, we added ethyl caffeate at concentrations of 0, 50 μmol, 100 μmol, 200 μmol, 400 μmol, and 800 μmol, respectively, to Cd... 2+ Concentrations of 0 and Cd 2+ A concentration of 10 μmol was used as a control, and it was found that ethyl caffeate could significantly alleviate Cd. 2+ While caffeic acid ethyl ester (CET) exerts a stress-relieving effect on duckweed, its effect disappears with increasing concentration, exhibiting significant inhibition. Therefore, the optimal concentration of CET was determined to be 200 μmol.

[0040] 2. Count the number of leaves, fresh weight, and root length of duckweed.

[0041] At concentrations of ethyl caffeate (50-200 μmol), the number of duckweed leaves gradually increased, and the fresh weight significantly rose. However, with increasing ethyl caffeate concentration, both the number of duckweed leaves and the fresh weight showed a significant decreasing trend, indicating that a certain concentration of ethyl caffeate helps alleviate Cd. 2+ It can stress duckweed, but if the concentration is too high, it can have a certain inhibitory effect.

[0042] In Cd 2+ Cd is 0 2+ 10 μmol, Cd2+ Two duckweed plants with the same root length were selected from each of the 200 μmol / L caffeic acid ester beakers and laid flat on a plate containing agar. Photos were taken with a mobile phone for comparison. The results showed that Cd... 2+ At 10 μmol, the root length of duckweed was significantly shortened, but at Cd... 2+ When ethyl caffeate was added at 200 μmol, the root length of duckweed significantly increased, even reaching levels comparable to Cd. 2+ Compared to the root length of duckweed at 0, this further confirms that 200 μmol of ethyl caffeate can effectively alleviate Cd. 2+ The coercion of duckweed.

[0043] Duckweed in different Cd 2+ Growth under +caffeic acid ethyl ester concentration treatment is as follows: Figure 5 As shown, compared with the control group CK and Cd 2 + Compared to +10 μmol, ethyl caffeate can alleviate the stress of cadmium on duckweed, with the best mitigation effect at 200 μmol. Conversely, excessively high concentrations of ethyl caffeate can also inhibit duckweed growth.

[0044] Duckweed in different Cd 2+ Leaf number, fresh weight, and root length under caffeic acid ethyl ester concentration treatment are as follows: Figure 6 As shown; Figure 6 In the figures, AD represents the number of leaves, root length, fresh weight, and root length of duckweed, respectively. As the concentration of ethyl caffeate increases, the number of leaves and fresh weight of duckweed first increase and then decrease, reaching their optimal values ​​at 200 μmol of ethyl caffeate.

[0045] Example 3: Effects of different treatments on enzyme and chlorophyll content in duckweed

[0046] 1. Enzyme activity detection (CAT, POD, SOD, MDA)

[0047] Cd was measured separately 2+ Cd is 0 2+ 25 μmol, Cd 2+ The content of various antioxidant enzymes in duckweed was determined by adding 200 μmol of ethyl caffeate, with a metal content of 0 as a control. The results showed that Cd 2+ At 25 μmol, the content of various antioxidant enzymes in duckweed decreased sharply, but in Cd 2+ When 200 μmol of ethyl caffeate was added, the content of various antioxidant enzymes in duckweed increased, indicating that a certain amount of ethyl caffeate helps to remove reactive oxygen species generated in duckweed.

[0048] 2. Determination of chlorophyll content (chlorophyll a, chlorophyll b, total chlorophyll content)

[0049] Cd was measured separately 2+ Cd is 0 2+ 10 μmol, Cd 2+ The chlorophyll content of duckweed was measured at 200 μmol of caffeic acid ethyl ester, with a metal content of 0 as a control. The results showed that Cd 2+ At 10 μmol, the contents of chlorophyll a, chlorophyll b, and total chlorophyll in duckweed all decreased significantly. Chloroplasts are one of the main organelles in plants that produce reactive oxygen species and are also important organs for photosynthesis. Cd 2+ It can stimulate the production of large amounts of reactive oxygen species, and excessive reactive oxygen species can induce membrane lipid peroxidation. (Cd-dependent) 2+ If excessive reactive oxygen species are produced in plant chloroplasts after stress and cannot be cleared in time, the structure and function of chloroplasts will be damaged, leading to a decrease in chlorophyll content. At 200 μmol of Cd²⁺ + ethyl caffeate, the chlorophyll content in duckweed increased significantly, indicating that a certain concentration of ethyl caffeate can affect chlorophyll content.

[0050] duckweed in Cd 2+ Cd is 0 2+ 25 μmol, Cd 2+ Enzyme content under treatment with 200 μmol of ethyl caffeate is as follows: Figure 7 As shown, Figure 7 The results of CAT enzyme, POD enzyme, SOD enzyme, and MDA enzyme detection are presented in the table below, in descending order. For each enzyme, a dedicated kit was used. Before measuring enzyme activity, duckweed was briefly treated for 1 hour. Then, 0.2g of each sample was weighed, added to 1ml of the respective extraction buffer, ground, and centrifuged. After centrifugation, the samples were analyzed using a spectrophotometer according to the kit instructions.

[0051] duckweed in Cd 2+ Cd is 0 2+ 10 μmol, Cd 2+ Chlorophyll content after treatment with 200 μmol of ethyl caffeate is as follows: Figure 8 As shown, in Figure 8 In the figures, AC represent the statistical results of chlorophyll a, chlorophyll b, and total chlorophyll content of duckweed, respectively. To determine the chlorophyll content, 0.3g of duckweed under different treatments was weighed, and under light-protected conditions, extraction buffer (ethanol:acetone 1:2) was added and the mixture was ground. The mortar was then rinsed with the extraction buffer, and all liquid was transferred to test tubes, brought to a final volume of 10ml, and incubated in the dark for 3 hours. The chlorophyll content was then measured using a spectrophotometer according to the kit instructions. Example 4: Effects of different treatments on duckweed cytology

[0052] NBT staining

[0053] From Cd respectively 2+ Cd is 0 2+ 10 μmol, Cd 2+ A small amount of duckweed was picked from a 200 μmol / L cup of ethyl caffeate and its roots were stained with NBT. After 30 minutes, it was observed under an optical microscope. The results showed that the roots of the duckweed treated with NBT were purple, and the color changed from light to dark and then from dark to light again, indicating that the duckweed was under cadmium stress, and ethyl caffeate could help the duckweed alleviate this stress.

[0054] duckweed in Cd 2+ Cd is 0 2+ 10 μmol, Cd 2+ Cellular observation under treatment with 200 μmol of ethyl caffeate, as follows: Figure 9 As shown, Figure 9 The image shows the staining of duckweed with NBT. Duckweed under different treatments was placed in test tubes, and NBT staining solution was added according to the instructions in the kit. The staining time was more than half an hour. After destaining, the condition of the middle part of the duckweed root was observed under an optical microscope and photographed for preservation. Example 5: Effects of different treatments on cadmium accumulation in duckweed

[0055] Determination of cadmium content in water bodies and duckweed

[0056] Cd was determined by atomic absorption spectrometry. 2+ 0 μmol, Cd 2+ 5 μmol, Cd 2+ 10 μmol, Cd 2+ 5+ caffeic acid ethyl ester 200 μmol, Cd 2+ The cadmium content in water at 200 μmol / L of ethyl caffeate (Cd) 2+ With 0 as the control, the results showed that Cd 2+ 5 μmol, Cd 2+ The cadmium content in water increased significantly at a concentration of 10 μmol / L. 2+ + ethyl caffeate 200 μmol and Cd 2+ The increase in cadmium content in water was more pronounced with the addition of luteolin (200 μmol), indicating that ethyl caffeate can inhibit the absorption of cadmium by duckweed. Subsequent determination of cadmium content in duckweed using digestion and atomic absorption spectrometry revealed that Cd... 2+ 5 μmol, Cd 2+ The cadmium content in 10 μmol of duckweed decreased, Cd 2 + + 200 μmol of ethyl caffeate, Cd2+ The cadmium content in duckweed also decreased with 200 μmol of luteolin, indicating that ethyl caffeate can help duckweed absorb a certain amount of cadmium and alleviate cadmium stress.

[0057] duckweed in Cd 2+ Cd is 0 2+ 5 μmol, Cd 2+ 10 μmol, Cd 2+ 5 μmol + 200 μmol of ethyl caffeate, Cd 2+ The cadmium content in water and duckweed after treatment with 10 μmol + 200 μmol of ethyl caffeate are as follows: Figure 10 As shown, in Figure 10 Tables A and B show the statistical results of cadmium content in water bodies, while C and D show the statistical results of cadmium content in duckweed. When determining the cadmium content in water bodies, a standard curve was first prepared using a cadmium solution. Then, 10 ml of water sample was filtered from the 7-day cultured sample using a syringe and a filter head, and the sample was measured using atomic absorption spectrometry. When determining the cadmium content in duckweed, the cadmium was first extracted from the duckweed using a digestion method, and then measured using atomic absorption spectrometry.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, material, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, material, or apparatus.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

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

2. The method for alleviating cadmium stress on duckweed using ethyl caffeate according to claim 1, characterized in that: The maximum Cd that duckweed can withstand is determined. 2+ The concentration method is as follows: Cd was set at different concentration gradients 2+ The solution, wherein the concentration gradient includes 0 μmol, 10 μmol, 20 μmol, 40 μmol, 80 μmol, and 160 μmol; Healthy duckweed and purple duckweed were placed in containers containing different concentrations of Cd. 2+ The solution was cultured in MS medium under the following conditions: temperature (25±3)℃, natural light, and culture period of 7 days. Observe the growth of duckweed to determine the maximum Cd that duckweed can withstand. 2+ The concentration is 10 μmol.

3. The method for alleviating cadmium stress on duckweed using ethyl caffeate according to claim 1, characterized in that: The method for determining the optimal concentration of ethyl caffeate to alleviate cadmium stress on duckweed is as follows: In Cd 2+ Based on a concentration of 10 μmol, ethyl caffeate solutions with different concentration gradients were prepared, including 0 μmol, 50 μmol, 100 μmol, 200 μmol, 400 μmol, and 800 μmol. Duckweed was placed in a solution containing different concentrations of ethyl caffeate and 10 μmol Cd. 2+ Cultured in MS medium with Cd 2+ Concentrations of 0 and Cd 2+ A concentration of 10 μmol was used as a control. By observing the growth of duckweed, the optimal concentration of ethyl caffeate to alleviate cadmium stress on duckweed was determined to be 200 μmol.

4. The method for alleviating cadmium stress on duckweed using ethyl caffeate according to claim 1, characterized in that: The addition of the optimal concentration of ethyl caffeate to cadmium-contaminated water means adding it at a ratio of 200 μmol of ethyl caffeate per 100 ml of water.

5. The method for alleviating cadmium stress on duckweed using ethyl caffeate according to any one of claims 1-4, characterized in that: The duckweed mentioned is a local variety from Ji'an, Jiangxi Province.

6. The use of ethyl caffeate in the preparation of formulations for alleviating cadmium-induced stress on duckweed, characterized in that: The concentration of ethyl caffeate in the formulation is 200 μmol, which is determined by reacting 10 μmol of Cd. 2+ The effective concentration that can significantly alleviate cadmium stress in duckweed was obtained by adding different concentrations of ethyl caffeate to the culture medium.

7. A composition for the remediation of cadmium pollution in water bodies, characterized in that: The composition contains ethyl caffeate at a concentration of 200 μmol, and is used to promote the growth of duckweed in cadmium-contaminated water and enhance the duckweed's ability to remediate cadmium in the water. The composition also includes a culture medium suitable for duckweed growth, which is selected from culture medium, solid culture medium or water remediation carrier.

8. The composition for remediation of cadmium pollution in water bodies according to claim 7, characterized in that, It also includes a culture medium suitable for the growth of duckweed, wherein the culture medium is MS culture medium.

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