Application of exogenous glutamic acid in promoting cadmium accumulation in draba alpine

Abstract

This invention belongs to the field of heavy metal pollution remediation technology, specifically involving the application of exogenous glutamic acid in promoting cadmium accumulation in *Aster tataricus*. The invention specifically investigates the effect of foliar spraying of an aqueous glutamic acid solution on the growth and accumulation of cadmium in *Aster tataricus* under cadmium stress. Results showed that spraying *Aster tataricus* with glutamic acid solution significantly increased its fresh weight, dry weight, chlorophyll a content, and carotenoid content, and also significantly increased its cadmium accumulation, providing technical support for enhancing phytoremediation.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal pollution remediation technology, specifically involving the application of exogenous glutamic acid in promoting cadmium accumulation in Aster tataricus. Background Technology

[0002] According to the 2022 China Ecological Environment Status Bulletin, the overall soil environmental condition of agricultural land in my country is stable. The main pollutants affecting the quality of agricultural land soil are heavy metals, with cadmium (Cd) being the primary pollutant. Existing research shows that excessively high Cd levels in soil not only slow plant growth and reduce biomass, but also alter plant cell membrane permeability, genetic material, enzyme activity, respiratory metabolism, and photosynthesis. Furthermore, Cd is not biodegradable in the environmental medium, and its pollution is characterized by long-term, cumulative, hidden, and irreversible nature, making Cd pollution remediation difficult. How to effectively and economically remediate Cd pollution in the soil environment is currently a hot topic and a challenge in the research field. Therefore, there is an urgent need for effective and economical remediation technologies for Cd-contaminated soil.

[0003] Currently, the remediation of heavy metal contaminated soil can be mainly carried out through physical, chemical, and biological methods. 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 currently a hot research topic in academia. Compared with other technologies, it has advantages such as low cost, no secondary pollution, and broad application prospects. Furthermore, it offers high ecological benefits and aesthetic value after reclamation, achieving permanent clean remediation of contaminated soil. It is a recognized environmentally friendly in-situ green remediation technology.

[0004] *Aster subulatus* Michx., also known as scissor-leaved aster, white chrysanthemum, wild aster, nine-dragon arrow, and awl-shaped aster, is a plant belonging to the genus *Aster* in the family Asteraceae. It grows in moist, saline soils and is distributed in Guangxi, Jiangsu, Zhejiang, Jiangxi, Hunan, and Fujian provinces. *Aster subulatus* is a fast-growing plant with high biomass, strong stress resistance, and the potential to accumulate or hyperaccumulate one or more heavy metals. Although phytoremediation has shown great advantages in the remediation of heavy metal-contaminated environments, it still has some limitations in practical applications, such as long remediation cycles, relatively singular accumulation capabilities, susceptibility to extreme environmental factors, and the disposal of residual heavy metal-containing biomass after remediation. Therefore, how to enhance the advantages of phytoremediation and improve its efficiency has become an important topic of concern for scholars both domestically and internationally. To improve the efficiency of hyperaccumulating phytoremediation, scientists have developed various enhancement technologies, including agronomic enhancement, biotechnology enhancement, and chemical-assisted enhancement.

[0005] Glutamate plays a crucial role in plant growth, stress resistance, photosynthesis, and immune defense. For example, it participates in auxin synthesis and metabolism, promoting auxin biosynthesis and transport, regulating nutrient allocation, and improving nutrient utilization efficiency. As a response signaling molecule, glutamate levels increase under abiotic stress, participating in the antioxidant defense system, regulating osmotic regulation, and enhancing tolerance to abiotic stress. Glutamate regulates the expression of photosynthesis-related genes and enzyme activity, affecting photosynthetic efficiency and regulating chlorophyll and photosynthetic pigment synthesis. Glutamate also plays a vital role in plant immune defense.

[0006] There are currently no reports on using exogenous glutamic acid to promote the remediation of heavy metal pollution by hyperaccumulating plants.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide the application of exogenous glutamic acid in promoting the enrichment of cadmium in Aster tataricus.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] The first objective of this invention is to provide the application of exogenous glutamic acid in promoting the accumulation of heavy metals in hyperaccumulating plants.

[0011] A second objective of this invention is to provide a heavy metal remediation agent, wherein the heavy metal remediation agent comprises the aforementioned glutamic acid.

[0012] More specifically, the heavy metal remediation agent is composed of glutamic acid and deionized water.

[0013] More specifically, the concentration of glutamic acid in the heavy metal remediation agent is 0.5-20 mg / L.

[0014] A third objective of this invention is to provide the application of the aforementioned heavy metal remediation agent in promoting the accumulation of heavy metals in hyperaccumulating plants.

[0015] More specifically, the hyperaccumulating plant includes *Aster tataricus*; the heavy metal includes cadmium.

[0016] The fourth objective of this invention is to provide the application of the exogenous glutamic acid or the heavy metal remediation agent in improving the stress resistance and promoting the growth of Aster tataricus in areas contaminated with heavy metals.

[0017] The fifth objective of this invention is to provide the application of the exogenous glutamic acid or the heavy metal remediation agent in increasing the chlorophyll and carotenoid content of Aster tataricus in areas contaminated with heavy metals.

[0018] The sixth objective of this invention is to provide a method for promoting the remediation of heavy metal pollution by using exogenous glutamic acid in Aster tataricus. Specifically, during the growth period of Aster tataricus, a glutamic acid solution is sprayed on the leaves every 3 days for a total of 6 times; and Aster tataricus is harvested 10 days after the end of the foliar spraying.

[0019] More specifically, the glutamic acid solution has a concentration of 0.5-20 mg / L.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention investigates the effects of foliar spraying with an aqueous glutamic acid solution on the growth and accumulation of cadmium in the hyperaccumulating plant *Aster tataricus* during its growth period. The results showed that when *Aster tataricus* under cadmium stress was sprayed with 0.5, 5, and 20 mg / L glutamic acid solutions, the fresh weight increased by 47.8%, 25.1%, and 42.6%, respectively; the dry weight increased by 41.7%, 25.7%, and 49.2%, respectively; the chlorophyll a content increased by 25.5%, 18.4%, and 32.7%, respectively; and the carotenoid content increased significantly by 281.1%, 259.5%, and 302.8%, respectively. The accumulation of cadmium also significantly increased by 89.7%, 69.3%, and 118.0%, respectively, providing technical support for strengthening the remediation of hyperaccumulating plants. Attached Figure Description

[0022] Figure 1 Biomass (plant height, fresh weight, dry weight) of Aster tataricus under different treatments;

[0023] Figure 2 Chlorophyll content of Aster tataricus under different treatments;

[0024] Figure 3 The cadmium content in the roots of *Aster tataricus* under different treatments;

[0025] Figure 4 The accumulation of cadmium in *Aster tataricus* under different treatments. Detailed Implementation

[0026] The technical solution of this invention patent will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0027] 1. Materials and Methods

[0028] 1.1 Test Materials

[0029] L-Glutamic acid (99%, CAS: 56-86-0, Shanghai Aladdin Biochemical Technology Co., Ltd.);

[0030] Seeds of Aster tataricus were collected from a lead-zinc mining area about 120km from Yulin City, Guangxi Province.

[0031] 1.2 Pot Experiment

[0032] To simulate cadmium-contaminated soil, the experiment was conducted using sand culture in pots, with 1.5 kg of quartz sand in each pot. *Aster tataricus* was collected from a lead-zinc mining area approximately 120 km from Yulin City, Guangxi Province. The seeds were sterilized with 95% ethanol and then cultured in cadmium-free seedling trays. After a period of time, seedlings with similar growth characteristics (similar plant height, number of leaves, and vigor) were selected as experimental materials, and three seedlings were transplanted into each pot, for a total of 15 pots.

[0033] The experimental environment was as follows: 12-hour light cycle, 25℃ light cycle / 20℃ dark cycle, relative humidity 70%, and light intensity 300 μmol / (m²). 2 •s), maintain continuous ventilation for 24 hours. Replenish with Hoglund's nutrient solution every 4 days, adjusting the pH to approximately 5.6 with 0.1 mmol / L sodium hydroxide or 0.1 mmol / L hydrochloric acid. One week after planting *Aster tataricus*, add 500 mL of 100 mmol / L Cd solution to 12 pots, and set up one group (3 pots) of sand culture pots without Cd solution as a blank control (CK).

[0034] 1.3 Experimental Design of Foliar Spraying

[0035] Glutamic acid experimental group: Based on the above operations, after 3 days, different concentrations of glutamic acid aqueous solution were sprayed, resulting in 5 treatment groups (Table 1). The spraying was limited to dripping from the leaf tips and completely covered the leaves. A total of 6 sprays were applied, once every 3 days. After all treatments were completed, the plants were cultivated for another 10 days before harvesting. The biomass and cadmium content of *Aster tataricus* were measured. Cadmium treatment control group: Deionized water was used instead of glutamic acid aqueous solution for foliar spraying.

[0036] Table 1 Experimental Design

[0037]

[0038] 1.4 Sample Processing and Analysis

[0039] After the experiment, the entire *Aster tataricus* plant was removed from the pot, washed with tap water, and rinsed thoroughly to remove the fine fibers from the roots. The roots were then soaked in a 20 mmol / L Na2-EDTA solution for 20 minutes to remove adsorbed cadmium ions. After repeated rinsing with deionized water and air-drying, the fresh weight and height of the entire plant were measured. The *Aster tataricus* was divided into above-ground and underground parts, placed in an oven at 105℃ for 30 minutes to kill the enzymes, and then dried at 70℃ until constant weight. The dry weight was then measured, and the sample was ground in stainless steel and passed through a 40-mesh sieve. The sample was digested using a mixed solvent of H2O2-HNO3 in an intelligent electrothermal digester. The heavy metal content of the digest was determined using a flame-graphite furnace atomic absorption spectrometer.

[0040] 1.5 Experimental Results

[0041] 1.5.1 Effects on biomass

[0042] See results Figure 1 .

[0043] Depend on Figure 1 It can be seen that, compared with the control group, the plant length, fresh weight, and dry weight of the Cd treatment group were significantly reduced by 28.4%, 37.3%, and 38.3%, respectively.

[0044] like Figure 1 As shown in -A, compared with Cd, the plant height of Aster tataricus in the 0.5Glu, 5Glu, and 20Glu treatment groups did not change significantly;

[0045] like Figure 1 As shown in Figure B, compared with Cd, the fresh weight of *Aster tataricus* increased by 47.8%, 25.1%, and 42.6% in the 0.5Glu, 5Glu, and 20Glu treatment groups, respectively.

[0046] like Figure 1 As shown in -C, the dry weight increased by 41.7%, 25.7%, and 49.2%, respectively.

[0047] This indicates that spraying glutamic acid can increase the biomass of Aster tataricus to a certain extent and has a certain promoting effect on the growth of Aster tataricus under cadmium stress.

[0048] 1.5.2 Effect on chlorophyll content

[0049] See results Figure 2 .

[0050] Depend on Figure 2 It can be seen that, compared with the control group, the contents of chlorophyll a, b and carotenoids in the Cd-treated control group decreased by 51.7%, 19.5% and 67.3% respectively, that is, Cd treatment inhibits the photosynthesis of Aster tataricus.

[0051] The chlorophyll a content of Aster subulatus under each treatment follows the order of Cd<5Glu<0.5Glu<20Glu<CK, wherein the chlorophyll a content of 20Glu, 0.5Glu and 5Glu is increased by 25.5%, 18.4% and 32.7% respectively compared with that of Cd;

[0052] The chlorophyll b content of Aster subulatus under each treatment follows the order of Cd<5Glu<0.5Glu<20Glu<CK. Compared with that of Cd, the chlorophyll b content of 20Glu is increased by 12.6%, while that of 0.5Glu and 5Glu has no significant change;

[0053] The carotenoid content of Aster subulatus under each treatment follows the order of Cd<CK<5Glu<0.5Glu<20Glu. Compared with that of CK, the carotenoid content of 0.5Glu, 5Glu and 20Glu is increased by 24.4%, 17.3% and 31.5% respectively; compared with that of Cd, the carotenoid content of 0.5Glu, 5Glu and 20Glu is significantly increased by 281.1%, 259.5% and 302.8% respectively.

[0054] It indicates that spraying glutamic acid in a cadmium-polluted environment can alleviate the inhibition effect of cadmium on the chlorophyll synthesis of Aster subulatus, and spraying 20mg / L glutamic acid has a relatively obvious promotion effect on the chlorophyll synthesis of Aster subulatus under cadmium pollution.

[0055] 1.5.3 Effect on cadmium content in roots of Aster subulatus

[0056] The results are shown in Figure 3 .

[0057] It can be seen from Figure 3 that compared with Cd, the cadmium content in roots of Aster subulatus in the 0.5Glu, 5Glu and 20Glu treatment groups is increased by 53.7%, 55.3% and 70.3% respectively.

[0058] 1.5.4 Effect on cadmium accumulation of Aster subulatus

[0059] The results are shown in Figure 4 .

[0060] It can be seen from Figure 4 that compared with Cd, the cadmium accumulation of Aster subulatus in the 0.5Glu, 5Glu and 20Glu treatment groups is increased by 89.7%, 69.3% and 118.0% respectively. This shows that spraying glutamic acid can enhance the cadmium enrichment ability of Aster subulatus, and spraying 20mg / L glutamic acid has a better enhancement effect on the cadmium enrichment ability of Aster subulatus.

[0061] In conclusion, glutamic acid can enhance the stress resistance of *Aster tataricus* under cadmium stress, increase its survival ability, promote its growth and development, increase its biomass, and increase its cadmium accumulation. Compared with phytoremediation alone, exogenous application of glutamic acid can improve the remediation efficiency of *Aster tataricus* for cadmium pollution, thereby reducing the cadmium content in the environment.

[0062] 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. A method for using exogenous glutamic acid to promote the remediation of cadmium pollution by *Aster tataricus*, characterized in that, Specifically, during the growth period of Aster tataricus, a glutamic acid solution is sprayed on the leaves every 3 days for a total of 6 times; and the Aster tataricus is harvested 10 days after the end of the foliar spraying; the concentration of the glutamic acid solution is 0.5-20 mg / L.

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