Use of uridine diphosphate glucose in promoting absorption of heavy metal cadmium by hyperaccumulating plants

Abstract

The application discloses application of uridine diphosphate glucose in promoting absorption of heavy metal cadmium by hyperaccumulating plants, and is characterized in that: a water solution of uridine diphosphate glucose is sprayed on leaf surfaces of hyperaccumulating plants in a growth stage, cadmium is enriched by using the growth and heavy metal absorption promoting effect of the uridine diphosphate glucose on the hyperaccumulating plants, and after the hyperaccumulating plants grow, the hyperaccumulating plants are cut or uprooted, and the application is obtained.The application sprays the water solution of the uridine diphosphate glucose on the leaf surfaces of the hyperaccumulating plants, uses the growth and heavy metal absorption promoting effect of the uridine diphosphate glucose on the plants to improve the cadmium accumulation amount of the hyperaccumulating plants, further improves the heavy metal enrichment efficiency, and effectively promotes efficient repair of heavy metal cadmium contaminated soil or water bodies by the hyperaccumulating plants.

Description

Technical Field

[0001] This invention relates to the fields of environmental protection, pollution control and agricultural biotechnology, specifically to the application of uridine diphosphate glucose in promoting the absorption of heavy metal cadmium in hyperaccumulating plants. Background Technology

[0002] Heavy metals originate from both natural and anthropogenic sources. Natural sources primarily include bedrock weathering, while anthropogenic sources mainly include mining, metal smelting, fertilizer application, and wastewater irrigation. Human activities are the main cause of the continuous increase in heavy metals in water bodies and soil. Cadmium is a highly toxic heavy metal that is harmful to aquatic organisms, microorganisms, and crops. Cadmium's greatest threat to agriculture is the production of "cadmium rice" and "cadmium vegetables," and it can cause Itai-itai disease in humans. Furthermore, cadmium can damage renal tubules, leading to diabetes, high blood pressure, cardiovascular disease, and even cancer and birth defects.

[0003] Currently, there are three main methods for remediating heavy metal contaminated soil: physical remediation, chemical remediation, and bioremediation. Phytoremediation, a type of bioremediation, directly utilizes green plants to isolate, remove, and degrade organic and inorganic pollutants in soil and water. Generally, plants can remove heavy metals through phytoextraction, phytostabilization, rhizosphere remediation, or phytofiltration. Phytoremediation technology is recognized as a green and environmentally friendly in-situ remediation technology due to its low cost, high effectiveness, lack of secondary pollution, and high ecological and aesthetic value after reclamation. It can achieve permanent clean remediation of contaminated soil.

[0004] Currently, over 500 hyperaccumulating plant germplasm resources have been identified worldwide for heavy metal contaminated soil remediation. Hyperaccumulating plants can absorb heavy metals from the soil, transporting them from their roots to their above-ground parts without affecting normal life activities. Commonly reported cadmium hyperaccumulating plants include *Sedum aizoon*, *Solanum nigrum*, *Viola baoshanense*, *Aster davidii*, and *Aster subulatus*. *Aster subulatus* Michx., a plant belonging to the genus *Aster* in the Asteraceae family, prefers moist, saline soils and is widely distributed in Guangxi province. As a novel Cd hyperaccumulator, *Aster subulatus* has a large biomass, reaching a height of up to 160 cm, with a taproot length of 30-45 cm. Field and mining area surveys have revealed that *Aster subulatus* has a Cd hyperaccumulation capacity and exhibits strong tolerance. However, current applications of heavy metal hyperaccumulating plants face challenges such as small biomass, long growth cycles, and the tendency for heavy metals to accumulate primarily in the roots with limited transport to the aboveground parts. These limitations restrict the remediation efficiency of plants for heavy metal-contaminated soils. Improving the accumulation capacity of heavy metals in the aboveground parts of plants is crucial for enhancing their application prospects.

[0005] To improve the remediation efficiency of hyperaccumulating plants, those skilled in the art have developed various enhancement technologies, including agronomic enhancement, biotechnology enhancement, and chemical-assisted enhancement. However, phytoremediation technologies for heavy metal contaminated soils have limitations: different ecotypes of plants must be selected for soils with different pollution conditions; the selective action of plants on heavy metals limits the application prospects of phytoremediation technologies in the treatment of soils contaminated with various heavy metals; certain requirements exist regarding soil fertility, climate, water, salinity, pH, drainage, and irrigation systems; hyperaccumulating plants are typically small, have low biomass, slow growth, and long growth cycles, resulting in low remediation efficiency; and plant organs often allow heavy metal pollution to return to the soil through decay and leaf fall.

[0006] Urate diphosphate glucose (UDPG) is a direct precursor in the synthesis of sucrose, hemicellulose, cellulose, gums, glycoproteins, and proteoglycans in plants. It plays a crucial role in plant physiological functions, cell wall synthesis, and growth, and is also important in the glycosylation of a series of secondary metabolites such as steroids, flavonoids, phenylpropane, and terpenes. UDPG is also essential for sucrose formation within cells and the synthesis of cellulose and callose in the ectoplasts. It indirectly participates in the formation of other cell wall polysaccharides, such as hemicellulose and pectin. The plant cell wall is the first point of contact between the plant and soil heavy metals, serving as the first barrier against heavy metal entry into the cell. The main components of the plant cell wall include pectin, hemicellulose, cellulose, and lignin. The cell wall is rich in negatively charged functional groups such as carboxyl, aldehyde, phosphate, and sulfur-containing groups, which can effectively bind heavy metal ions, adsorbing them within the cell wall. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention addresses the limitations of existing phytoremediation technologies, where heavy metal pollution hinders the growth and development of hyperaccumulating plants, resulting in slow growth, small biomass, and low accumulation. It provides an application of uridine diphosphate glucose (UDPG) to promote the absorption of cadmium (Cd) by hyperaccumulating plants. By spraying an aqueous solution of UDPG onto the leaves of hyperaccumulating plants during their growth period, the biomass and Cd content of the hyperaccumulating plants are increased, thereby promoting the absorption of Cd, enhancing the heavy metal accumulation efficiency, and achieving highly efficient remediation of cadmium-contaminated soil or water bodies by hyperaccumulating plants.

[0008] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0009] An application of uridine diphosphate glucose (UDPG) in promoting the absorption of heavy metal cadmium in hyperaccumulators involves spraying an aqueous solution of UDPG onto the leaves of hyperaccumulators during their growth stage. UDPG promotes the growth and heavy metal absorption of hyperaccumulators, thereby enriching cadmium. After the hyperaccumulators have grown, they are harvested or uprooted to obtain the cadmium.

[0010] More specifically, as described above, the hyperaccumulating plants are planted on the soil containing heavy metals that need to be treated and cultivated in a conventional manner. After 13-18 days of cultivation, an aqueous solution of uridine diphosphate glucose (UDPG) is sprayed on the leaves of the hyperaccumulating plants every 2-3 days for a total of 5-7 times. After 40-50 days of cultivation, the hyperaccumulating plants are cut down or uprooted to obtain the product.

[0011] The operation method described above involves spraying a foliar solution of uridine diphosphate glucose at a concentration of 0.1 mg / L to 0.4 mg / L onto the leaves of hyperaccumulating plants during their growth stage. The spraying method is to completely cover the leaves, and the amount of spray is until water drips from the leaf tips.

[0012] Preferably, the 0.1 mg / L to 0.4 mg / L uridine diphosphate glucose aqueous solution is obtained by dissolving uridine diphosphate glucose in deionized water.

[0013] Preferably, an aqueous solution of uridine diphosphate glucose (UDPG) is sprayed onto the leaves of the hyperaccumulating plant, once every 3 days, for a total of 6 sprays.

[0014] Preferably, the concentration of the aqueous solution of uridine diphosphate glucose is 0.1 mg / L or 0.4 mg / L.

[0015] Preferably, the conventional culture involves a 12-hour photocycle, a 25°C photocycle / 20°C darkcycle, a relative humidity of 70%, and a light intensity of 300 μmol / (m²). 2 ·s), maintain 24-hour continuous ventilation, and supplement with Hoglund nutrient solution every 4 days.

[0016] Preferably, the Hoglund nutrient solution is replenished in 100 mL increments each time, continuing until the plant is cut or uprooted.

[0017] Preferably, the hyperaccumulating plant is obtained by culturing hyperaccumulating plant seeds for 15-20 days.

[0018] Preferably, the hyperaccumulating plant is *Aster tataricus*.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention increases the cadmium accumulation of hyperaccumulating plants by spraying UDPG aqueous solution on the leaves of hyperaccumulating plants, thereby enhancing the heavy metal enrichment efficiency and effectively promoting the efficient remediation of cadmium-contaminated soil or water bodies by hyperaccumulating plants. Attached Figure Description

[0021] Figure 1 This study investigated the effects of different exogenous substances on the Cd content in the aboveground and underground parts of *Aster tataricus*.

[0022] Figure 2 The effects of different exogenous substances on Cd accumulation in the aboveground and underground parts of *Aster tataricus*. Detailed Implementation

[0023] The specific embodiments are described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise specified, the raw materials and reagents used in the embodiments are commercially available.

[0024] In this embodiment, the sand-cultured potted plants are grown in plastic resin pots with a diameter of 20cm, a height of 25cm, and a bottom diameter of 16cm.

[0025] In the examples, uridine diphosphate glucose (UDPG) and methyl jasmonate (MeJA) were purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0026] The Hoagland nutrient solution used in the examples consisted of: 5 mM KNO3, 5 mM Ca(NO3)2·4H2O, 2 mM MgSO4·7H2O, 1 mM KH2PO4, 0.045 mM H3BO3, 0.01 mM MnCl2·4H2O, 0.8 μM ZnSO4·7H2O, 0.3 μM CuSO4·5H2O, 0.4 μM Na2MoO4·2H2O, 0.02 μM Na2EDTA, and 0.02 μM FeSO4·5H2O. The pH of the Hoagland nutrient solution was adjusted to 5.6 with 0.1 mmol / L sodium hydroxide or 0.1 mmol / L hydrochloric acid before use.

[0027] Example 1

[0028] To simulate cadmium-contaminated soil, the experiment was conducted using a sand culture pot method. Each pot contained 2.5 kg of quartz sand, and an aqueous solution with a cadmium ion concentration of 30 mg / L was prepared by dissolving CdCl2·2.5H2O in deionized water. The solution was then added until the quartz sand was submerged by more than 1 cm.

[0029] The seeds of *Aster tataricus* were collected from the Guangxi Academy of Agricultural Sciences. After being sterilized with 95% ethanol, the seeds were cultured in cadmium-free seedling trays. After 15-20 days, seedlings with similar growth characteristics (similar plant height, number of leaves, and vigor) were selected as experimental materials. Three seedlings were transplanted into each tray, and the experiment was conducted in five groups, with three replicates per group, for a total of 15 trays.

[0030] The phytoremediation environment (starting from the transplanting of *Aster tataricus* seedlings into pots) was as follows: 12-hour photoperiod, 25°C photoperiod / 20°C darkperiod, 70% relative humidity, and a light intensity of 300 μmol / (m²). 2 •s), maintain continuous ventilation for 24 hours. Replenish with Hoglund nutrient solution every 4 days, each time at a volume of 100mL, until mowing or uprooting.

[0031] This means completing the planting of the hyperaccumulating plant, Aster tataricus.

[0032] Example 2

[0033] Based on the procedures in Example 1, 15 days after planting *Aster tataricus*, foliar sprays of 0.1 mg / L and 0.4 mg / L UDPG aqueous solutions were applied, ensuring the leaves were completely covered, with water dripping from the tips. This was repeated six times, once every three days. After the six sprays, the plants were allowed to grow naturally (no further reagents were applied, only Hoglund nutrient solution was supplemented) for 10 days before harvesting; the *Aster tataricus* plants were then uprooted. This group was designated the UDPG experimental group (UDPG). The biomass and cadmium content of *Aster tataricus* were measured.

[0034] Example 3

[0035] Based on the procedure in Example 1, 15 days after planting *Aster tataricus*, a 0.2 mg / L UDPG aqueous solution was sprayed on the leaves, ensuring the leaves were completely covered, with water dripping from the tips. A total of 7 sprays were performed, once every 2 days. After all treatments were completed, the plants were cultivated for another 23 days before harvesting.

[0036] Comparative Example 1

[0037] Based on the operation in Example 1, 15 days after planting Aster tataricus, 0.1 mg / L and 0.4 mg / L methyl jasmonate solution were sprayed on the leaves to replace the UDPG aqueous solution (methyl jasmonate solution is obtained by dissolving methyl jasmonate in a 50% ethanol solution). Other operations were the same as in Example 2, and this was recorded as the methyl jasmonate control group (MeJA).

[0038] Comparative Example 2

[0039] Based on the operation of Example 1, 15 days after planting Aster tataricus, distilled water was sprayed on the leaves instead of UDPG aqueous solution. Other operations were the same as in Example 2. This was recorded as the control group treated with Cd alone (Cd).

[0040] The types and concentrations of exogenous substances used in Example 2, Comparative Example 1, and Comparative Example 2 are shown in Table 1.

[0041] Table 1.

[0042]

[0043] Biomass and cadmium content of *Aster tataricus* harvested after Example 2, Comparative Example 1, and Comparative Example 2 were determined:

[0044] Biomass determination:

[0045] Remove the quartz sand from the harvested *Aster tataricus* plants, remove the entire plant, rinse the roots with tap water and then ultrapure water, and place the roots in a 20 mmol·L⁻¹ solution. -1 Soak in Na2-EDTA solution (obtained by dissolving Na2-EDTA in deionized water) for 20 minutes to remove residual Cd from the surface. 2+ The plants were then rinsed repeatedly with ultrapure water, dried, and their height was measured. The plants were divided into above-ground and underground sections, and their fresh weight was measured. The samples were then blanched in an oven at 105℃ for 30 minutes and dried at 75℃ until constant weight was achieved, and their dry weight was measured. The dried samples were then pulverized and passed through a 40-mesh sieve (data obtained in Table 2).

[0046] Cd content determination in plants:

[0047] Dry plant samples were digested with H2O2-HNO3 (H2O2 to HNO3 volume ratio 1:10). After the digest was brought to a final volume, the Cd content was determined using a flame-graphite furnace atomic absorption spectrophotometer (PinAAcle 900T, USA). Figure 1 Data). Cd accumulation = tissue Cd content × tissue dry mass (obtained) Figure 2 data).

[0048] result:

[0049] The most direct effect of cadmium (Cd) on plant growth is usually reflected in its growth pattern. As shown in Table 2, compared with Cd treatment alone, exogenous application of UDPG and MeJA both increased the plant height of *Aster tataricus* to some extent. Exogenous application of UDPG and 0.4 mg·L⁻¹... - 1 MeJA significantly increased the biomass of *Aster tataricus*, while spraying with 0.1 mg·L⁻¹... -1 MeJA reduced the biomass of *Aster tataricus*. Among the treatments, low concentrations of UDPG (0.1 mg·L⁻¹) showed the most significant promoting effect on the growth of *Aster tataricus*. -1Compared with Cd treatment alone, UDPG treatment increased the fresh weight of aboveground and belowground parts by 51.2% and 115.7%, respectively, and the dry weight by 72.3% and 83.3%, respectively. Therefore, exogenous spraying of UDPG and 0.4 mg·L⁻¹... -1 MeJA can promote the growth of Aster tataricus under Cd treatment.

[0050] Table 2. Effects of different exogenous substance treatments on the biomass of *Aster tataricus*.

[0051]

[0052] Note: Different lowercase letters in the same column indicate significant differences between treatment groups (P<0.05).

[0053] The effect of exogenous substances on the Cd content of Aster tataricus is shown in the figure. Figure 1 Compared with Cd treatment alone, 0.1 mg·L⁻¹ -1 UDPG treatment increased the Cd content in the aerial parts of *Aster tataricus*, while MeJA treatment decreased the Cd content in the aerial parts of *Aster tataricus*, with 0.4 mg·L⁻¹ decreasing the Cd content. - 1 MeJA treatment reduced Cd content by 65.2% compared to Cd treatment alone. Within the tested concentration range, UDPG significantly increased the Cd content in the underground parts of *Aster tataricus*, with a concentration of 0.1 mg·L⁻¹. -1 UDPG treatment increased the underground Cd content by 45.1% (0.4 mg·L⁻¹) compared to Cd treatment alone. -1 The UDPG treatment increased the Cd content in the underground parts by 13.7% compared to the Cd treatment alone; while the MeJA treatment significantly decreased the Cd content in the underground parts of *Aster tataricus*. This indicates that within the above concentration range, 0.1 mg·L⁻¹ is a suitable treatment. -1 UDPG can increase the Cd content in Aster tataricus and promote the translocation of Cd from the roots to the aboveground parts, while MeJA inhibits the absorption of Cd by Aster tataricus and the translocation of Cd to the aboveground parts.

[0054] The effect of exogenous substances on Cd accumulation in *Aster tataricus* is shown in [reference needed]. Figure 2 The total accumulation of heavy metals is closely related to the plant's ability to absorb heavy metals and its biomass. Compared with Cd treatment alone, UDPG treatment significantly increased Cd accumulation in both aboveground and belowground parts, with an increase of 0.1 mg·L⁻¹. -1 UDPG treatment increased Cd accumulation in the aboveground parts by 87.4%, in the underground parts by 168.9%, and in the whole plant by 138.9%; 0.4 mg·L -1UDPG treatment increased Cd accumulation in the aboveground parts by 87.4%, in the underground parts by 37.9%, and in the whole plant by 70.5%. Both concentrations of MeJA treatment reduced Cd accumulation in both the aboveground and underground parts of *Aster tataricus*, which corresponds to the aforementioned results of MeJA inhibiting the growth of *Aster tataricus* and reducing Cd content.

[0055] In summary, within the aforementioned concentration range, the method of this invention, through exogenous spraying of UDPG, can increase the biomass of *Aster tataricus*, as well as the Cd content and accumulation in the plants, while MeJA treatment has a significant inhibitory effect on Cd accumulation in *Aster tataricus*. In phytoremediation of heavy metal contaminated soil, applying an appropriate concentration of UDPG can improve the remediation efficiency of *Aster tataricus* for Cd-contaminated soil.

[0056] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An application of uridine diphosphate glucose in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: Aqueous solutions of uridine diphosphate glucose are sprayed onto the leaves of hyperaccumulating plants during their growth stage. The uridine diphosphate glucose promotes the growth and heavy metal absorption of hyperaccumulating plants, thereby enriching cadmium. After the hyperaccumulating plants have grown, they are cut down or uprooted to obtain the cadmium.

2. The application of uridine diphosphate glucose according to claim 1 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: More specifically: plant the hyperaccumulating plant on the soil where heavy metals need to be treated, and cultivate it in a conventional manner. After 13-18 days of planting, spray the leaves of the hyperaccumulating plant with an aqueous solution of uridine diphosphate glucose every 2-3 days for a total of 5-7 times. After 40-50 days of planting, cut the plant or uproot it to obtain the product.

3. The application of uridine diphosphate glucose according to claim 1 or 2 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: The hyperaccumulating plant mentioned above is obtained by culturing hyperaccumulating plant seeds for 15-20 days.

4. The application of uridine diphosphate glucose according to claim 1 or 2 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: The hyperaccumulating plant mentioned is *Aster tataricus*.

5. The application of uridine diphosphate glucose according to claim 1 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: The application method involves spraying a foliar solution of uridine diphosphate glucose at a concentration of 0.1 mg / L to 0.4 mg / L onto the leaves of hyperaccumulating plants during their growth stage. The spraying method is to completely cover the leaves, and the amount of spray is until water drips from the leaf tips.

6. The application of uridine diphosphate glucose according to claim 2 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: An aqueous solution of uridine diphosphate glucose was sprayed on the leaves of the hyperaccumulating plant every 3 days for a total of 6 times.

7. The application of uridine diphosphate glucose according to claim 2 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: The standard culture period consisted of a 12-hour photoperiod, a 25°C photoperiod / 20°C darkperiod, a relative humidity of 70%, and a light intensity of 300 μmol / (m²). 2 ·s), maintain 24-hour continuous ventilation, and supplement with Hoglund nutrient solution every 4 days.

8. The application of uridine diphosphate glucose according to claim 7 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: The Hoglund nutrient solution is replenished in 100mL increments each time, continuing until the plant is cut or uprooted.

9. The application of uridine diphosphate glucose according to claim 5 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: The 0.1 mg / L to 0.4 mg / L uridine diphosphate glucose aqueous solution is obtained by dissolving uridine diphosphate glucose in deionized water.

10. The application of uridine diphosphate glucose according to claim 5 in promoting the absorption of heavy metal cadmium in hyperaccumulating plants, characterized in that: The concentration of the aqueous solution of uridine diphosphate glucose is 0.1 mg / L or 0.4 mg / L.

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