Nitrogen-doped biomass carbon dots, method for promoting plant root growth and application of nitrogen-doped biomass carbon dots
Nitrogen-doped biomass carbon dots prepared by hydrothermal method solve the problems of easy degradation and limited growth under salt stress of traditional plant growth regulators. They achieve the effect of promoting plant root growth under normal and salt stress conditions, and have good biocompatibility and low cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2026-02-10
- Publication Date
- 2026-05-12
AI Technical Summary
Existing traditional plant growth regulators are easily degraded under light and microbial action, have a short period of action, and frequent application increases costs and may cause chemical residues. They are also difficult to effectively promote root growth under salt stress.
Nitrogen-doped biomass carbon dots, prepared by hydrothermal method using corn stalks as carbon source and urea as nitrogen source, are used for seed soaking, root irrigation and foliar spraying to promote plant root growth.
The prepared nitrogen-doped biomass carbon dots broadly promote the root growth of various plants under normal and salt stress conditions. The process is simple, low-cost, and biocompatible, making it suitable for large-scale production.
Smart Images
Figure CN122010095A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of agricultural nanomaterials technology, specifically relating to a nitrogen-doped biomass carbon dot method for promoting plant root growth and its application. Background Technology
[0002] With the increasing scarcity of arable land and the expansion of salinization areas globally, developing efficient and safe modern agricultural technologies has become a key strategy for ensuring food security. Currently, traditional plant growth regulators are widely used in agricultural production. For example, while naphthaleneacetic acid (NAA) can effectively promote crop growth, it is easily degraded under light and microbial influences, resulting in a short-lived effect and frequent application. This not only increases labor and economic costs but may also cause chemical residues, posing risks to soil microecology and agricultural product safety. Furthermore, under adverse growth environments such as salt stress, the promoting effect of traditional plant growth regulators on plant root growth is often significantly limited, making it difficult to sustain their regulatory role.
[0003] Against this backdrop, agricultural nanomaterials technology has emerged. Among them, carbon dots (CDs), as a novel carbon-based nanomaterial, have shown broad application prospects in plant growth regulation and stress resistance enhancement due to their small particle size, good water solubility, high biocompatibility, and tunable surface functions, and have become a current research hotspot.
[0004] Traditional methods for preparing carbon dots that promote plant growth often utilize small-molecule chemical raw materials such as citric acid, glucose, ethylenediamine, and polyethyleneimine, obtained through hydrothermal, microwave, or solvothermal methods. While traditional methods offer some controllability in structure and properties, their preparation relies on chemical precursors, resulting in relatively high raw material costs. Furthermore, potential environmental residues and ecological safety issues must be considered when applying these methods in agriculture. Patent application CN114190188A discloses a method and application for alleviating plant growth inhibition under high-concentration rare earth element stress. This patent describes a method for preparing carbon quantum dots using citric acid and urea as raw materials, synthesized via a microwave method, although the raw material costs are relatively high.
[0005] Therefore, there is an urgent need to develop a biomass carbon dot material that uses green raw materials, has a simple preparation process, and can promote plant root growth under both normal growth conditions and salt stress conditions, so as to provide new technical means for plant growth vitality and environmental adaptability as well as the utilization of saline-alkali land. Summary of the Invention
[0006] The first objective of this invention is to provide a nitrogen-doped biomass carbon dot that is small in size and has good biocompatibility and water solubility.
[0007] A second objective of this invention is to provide an application of nitrogen-doped biomass carbon dots.
[0008] A third objective of this invention is to provide a method for promoting plant root growth.
[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0010] In a first aspect, the present invention provides an application of nitrogen-doped biomass carbon dots, which promotes plant root growth under normal or salt stress conditions; the concentration of nitrogen-doped biomass carbon dots is 0.1–100 mg / L.
[0011] Preferably, the salt stress is salt stress caused by sodium chloride, and the concentration of sodium chloride is 100-150 mM.
[0012] Preferably, the average particle size of the nitrogen-doped biomass carbon dots is 1.4–4.2 nm.
[0013] Preferably, the nitrogen-doped biomass carbon dots are prepared by hydrothermal reaction using corn stalks as the carbon source and urea as the nitrogen source; the hydrothermal reaction temperature is 180-220 °C, and the hydrothermal reaction time is 6-10 h; the mass ratio of corn stalks to urea is 1:(0.6-3).
[0014] Preferably, the plant is one or more of the following: food crops, vegetables, model plants, and ornamental plants.
[0015] Preferably, the application method of the nitrogen-doped biomass carbon dots includes one or more of seed soaking, root irrigation, and foliar spraying.
[0016] Secondly, the present invention provides a method for promoting plant root growth, comprising the following steps: soaking seeds and / or irrigating roots and / or spraying leaves with a nitrogen-doped biomass carbon dot solution with a concentration of 0.1 to 100 mg / L.
[0017] Thirdly, the present invention provides a nitrogen-doped biomass carbon dot, the preparation method of which includes the following steps: pre-treating corn stalks and then acid washing them; dispersing the acid-washed corn stalks and urea in water; and purifying them after hydrothermal reaction; the nitrogen-doped biomass carbon dot promotes plant root growth under normal conditions or salt stress conditions.
[0018] Preferably, the pretreatment involves crushing the corn stalks and sieving them to 80-100 mesh, and the acid washing involves soaking them in a 0.05-0.1 mol / L HCl solution for 12-24 hours.
[0019] Preferably, the mass-to-volume ratio of corn stalks to water is 1 g:(10-30) mL; the mass ratio of corn stalks to urea is 1:(0.6-3); the temperature of the hydrothermal reaction is 180-220 °C; and the time of the hydrothermal reaction is 6-10 h.
[0020] Preferably, the purification includes centrifugation and dialysis.
[0021] Preferably, the centrifugation speed is 4000-5000 rpm; the centrifugation time is 10-15 min.
[0022] Preferably, the molecular weight cutoff for dialysis is 500–1000 Da; and the dialysis time is 24–48 h.
[0023] The beneficial effects of this invention are:
[0024] This invention utilizes nitrogen-doped biomass carbon dots to broadly promote root growth in various types of plants, including food crops, vegetables, model plants, and ornamental plants, under normal or salt stress conditions.
[0025] In the application of nitrogen-doped biomass carbon dots of the present invention, the application method of nitrogen-doped biomass carbon dots is flexible and adaptable to various application methods such as seed soaking, root irrigation, and foliar spraying, and is suitable for different production scenarios.
[0026] This invention uses agricultural waste as a carbon source and urea as a nitrogen source. Through a hydrothermal process, nitrogen-doped biomass carbon dots with a surface rich in carboxyl and amino groups are specifically prepared. The raw materials are widely available, the operation is simple, the cost is low, and it is green and sustainable, which is in line with the concept of circular economy.
[0027] The nitrogen-doped biomass carbon dots prepared by this invention are small in size, rich in carboxyl and amino groups on the surface, exhibit good biocompatibility, and low toxicity. The preparation method of this nitrogen-doped biomass carbon dots has the advantages of simple process, ease of operation, low cost, and no pollution, with a yield as high as 22.3%, and can be used for large-scale production. Attached Figure Description
[0028] Figure 1 The properties of Bio-CDs in Example 1 are characterized. Figure 1 In the image, A represents the TEM image of Bio-CDs. Figure 1 In the diagram, B represents the particle size distribution histogram of Bio-CDs. Figure 1 In this context, C represents the XPS energy spectrum of Bio-CDs. Figure 1 In this context, D represents the C1s spectrum of the XPS of Bio-CDs. Figure 1 E in the figure represents the N1s spectrum of XPS for Bio-CDs;
[0029] Figure 2This illustrates the effects of different treatments under normal conditions on wheat plant development in Example 3. Figure 2 In the diagram, A represents the phenotypic figures of wheat plants in the control and treatment groups. Figure 2 B in the image represents a root scan of wheat plants from the control group. Figure 2 C in the image represents a root scan of wheat plants in the treatment group. Figure 2 In the graph, D represents the root length data of wheat plants in the control and treatment groups;
[0030] Figure 3 This illustrates the effects of different treatments under normal conditions on tomato plant development in Example 4. Figure 3 In the diagram, A represents the phenotypic figures of tomato plants in the control and treatment groups. Figure 3 B in the image represents a root scan of the control group tomato plants. Figure 3 C in the image represents a root scan of tomato plants in the treatment group. Figure 3 In the graph, D represents the root length data of tomato plants in the control and treatment groups.
[0031] Figure 4 This illustrates the effects of different treatments under normal conditions on Arabidopsis seedling development in Example 5. Figure 4 In the diagram, A represents the phenotypic figures of Arabidopsis thaliana seedlings in the control and treatment groups. Figure 4 B in the figure represents the root length data of Arabidopsis thaliana seedlings in the control and treatment groups;
[0032] Figure 5 This illustrates the effects of different treatments under normal conditions on the development of jasmine plants in Example 6. Figure 5 In the diagram, A represents the phenotypic figures of jasmine plants in the control and treatment groups. Figure 5 B in the graph represents the root length data of jasmine plants in the control and treatment groups;
[0033] Figure 6 This illustrates the effects of different treatments under salt stress on wheat plant development in Example 7. Figure 6 In the diagram, A represents the phenotypic figures of wheat plants in the control and treatment groups. Figure 6 In the graph, B represents the root length data of wheat plants in the control and treatment groups. Figure 6 C in the image represents a root scan of the control group wheat plants. Figure 6 In the image, D represents a root scan of wheat plants in the treatment group;
[0034] Figure 7 This illustrates the effects of different treatments under salt stress on cotton plant development in Example 8. Figure 7 In the diagram, A represents the phenotypic figures of cotton plants in the control and treatment groups. Figure 7 Figure B in the diagram shows a comparison of the fresh weight of cotton plants in the control group and the treatment group. Figure 7 C in the figure represents the root length data of cotton plants in the control group and the treatment group. Detailed Implementation
[0035] The present invention will be further described below with reference to the embodiments and accompanying drawings.
[0036] Example 1
[0037] The method for preparing nitrogen-doped biomass carbon dots in Example 1 includes the following steps:
[0038] The corn stalks were pretreated and then acid-washed. The pretreatment involved crushing the corn stalks to 80 mesh. The acid washing involved soaking the stalks in a 0.1 mol / L HCl solution for 24 hours to remove ash and metallic impurities. The mixture was then filtered and washed with plenty of deionized water until the filtrate was neutral. After drying, the corn stalk powder was obtained.
[0039] 5 g of corn stalk powder was weighed and dispersed in 100 mL of deionized water, followed by the addition of 3 g of urea. The mixture was then sonicated for 35 min to obtain a solution. The solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted for 8 h to obtain a nitrogen-doped biomass carbon dot solution. The reaction temperature was 200 °C.
[0040] After the nitrogen-doped biomass carbon dot solution was naturally cooled to 25 °C, it was centrifuged for 15 min at a speed of 5000 rpm. After centrifugation, the supernatant was collected to obtain the crude extract of nitrogen-doped biomass carbon dots.
[0041] The crude extract of nitrogen-doped biomass carbon dots was transferred to a dialysis bag with a molecular cutoff of 1000 Da, dialyzed with deionized water for 48 h, and then freeze-dried to obtain nitrogen-doped biomass carbon dots. The nitrogen-doped biomass carbon dots in Example 1 were named Bio-CDs. The yield of Bio-CDs was 22.3%.
[0042] The properties of Bio-CDs in Example 1 are characterized as follows: Figure 1 As shown.
[0043] Figure 1 In the image, A is a TEM image of Bio-CDs. The image shows that Bio-CDs are nearly spherical in shape. Figure 1 B in the figure is the particle size distribution histogram of Bio-CDs. It can be seen from the figure that the average particle size of Bio-CDs is about 1.4 to 4.2 nm.
[0044] Figure 1 In this context, C represents the XPS energy spectrum of Bio-CDs, derived from... Figure 1As can be seen from D, Bio-CDs are mainly composed of three elements: C, O, and N, with atomic percentages of 58.71%, 28.61%, and 12.68%, respectively. The nitrogen content of 12.68% indicates that the urea hydrothermal method has successfully achieved efficient nitrogen doping of biomass carbon dots, laying a solid foundation for enriching nitrogen-containing functional groups on their surface.
[0045] Figure 1 In the figure, D represents the C1s spectrum of the XPS of Bio-CDs. Three characteristic peaks were observed at 284.6 eV, 286.2 eV, and 288.8 eV, corresponding to sp... 2 / sp 3 The presence of carbon (CC / C=C), carbon nitrite (CO / CN), and carbonyl carbon (C=O) indicates that the surface of Bio-CDs is rich in oxygen-containing functional groups.
[0046] Figure 1 E in the figure represents the N1s spectrum of the XPS of Bio-CDs. The N1s spectrum shows that the binding energies are located at 399.1 eV (CN) and 397.8 eV (C=N). The peak area of amide nitrogen (-NH2) at 399.1 eV accounts for about 65.1%, indicating that the doped nitrogen mainly exists in the form of amino groups, which directly constitutes the main source of surface amino functional groups.
[0047] XPS spectra of Bio-CDs show that Bio-CDs are rich in amino and carboxyl groups. This unique surface structure not only ensures excellent water dispersibility, but also provides multiple sites for its interaction with plant cell walls, membrane systems and rhizosphere environment.
[0048] Example 2
[0049] The preparation method of nitrogen-doped biomass carbon dots in Example 2 includes the following steps:
[0050] The corn stalks were pretreated and then acid-washed. The pretreatment involved crushing the corn stalks to 100 mesh. The acid washing involved soaking the stalks in a 0.1 mol / L HCl solution for 24 hours to remove ash and metallic impurities. The mixture was then filtered and washed with plenty of deionized water until the filtrate was neutral. After drying, the corn stalk powder was obtained.
[0051] 5 g of corn stalk powder was weighed and dispersed in 150 mL of deionized water, followed by the addition of 15 g of urea. The mixture was then sonicated for 35 min to obtain a solution. The solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted for 10 h to obtain a nitrogen-doped biomass carbon dot solution. The reaction temperature was 220 °C.
[0052] After the nitrogen-doped biomass carbon dot solution was naturally cooled to 25 °C, it was centrifuged for 15 min at a speed of 5000 rpm. After centrifugation, the supernatant was collected to obtain the crude extract of nitrogen-doped biomass carbon dots.
[0053] The crude extract of nitrogen-doped biomass carbon dots was transferred to a dialysis bag with a molecular cutoff of 1000 Da, dialyzed with deionized water for 48 h, and then freeze-dried to obtain nitrogen-doped biomass carbon dots.
[0054] Example 3
[0055] Application of nitrogen-doped biomass carbon dots in promoting wheat root growth under normal conditions in Example 3:
[0056] Example 3 uses nitrogen-doped biomass carbon dots prepared in Example 1 to promote wheat root growth under normal conditions.
[0057] Zhengmai 1860 was selected as the application variety. Wheat seeds with plump and uniform grain size were selected and randomly divided into a treatment group (Bio-CDs group) and a control group (CK group). The treatment group was soaked in a 100 mg / L Bio-CDs aqueous solution for 12 h, while the control group was soaked in an equal volume of deionized water for 12 h as a blank control.
[0058] After soaking, wheat seeds were sown in pots containing the same substrate, 10 seeds per pot. The pots were then placed in a greenhouse at 25℃, 60% relative humidity, and a photoperiod of 16 h light / 8 h dark. Regular, measured watering was maintained to ensure consistent moisture supply. After 21 days of cultivation, the intact plants were carefully removed, the roots were washed clean of any attached material, and samples were randomly taken and photographed.
[0059] Figure 2 The image shows the phenotypic pattern of wheat plants in Example 3. Figure 2 A in Figure 2 B and Figure 2 As can be seen from C, compared to the control group, wheat plants treated with Bio-CDs not only showed advantages in plant height and biomass, but also exhibited particularly outstanding root development. For example... Figure 2 As shown in Figure D, the average length of the primary root in the treatment group increased by 15.61%, and the root system became denser and more developed, forming a larger root system, indicating that Bio-CDs can effectively promote the growth and development of wheat roots under normal conditions.
[0060] Example 4
[0061] Application of nitrogen-doped biomass carbon dots in promoting tomato root growth under normal conditions in Example 4:
[0062] Zhongza 9 tomato was selected as the application variety. First, tomato seeds were placed in 15 mL centrifuge tubes, and deionized water was added until the seeds were completely submerged. The centrifuge tubes were then placed in a 55 ℃ water bath for 15 min. After the water bath, two layers of ordinary filter paper were placed in a 90 mm petri dish and moistened with deionized water. The water-baked seeds were then evenly spread on the surface of the filter paper and cultured in the dark for 3–4 days, keeping the filter paper moist. After germination, seeds with uniform germination were transplanted into 50-cell seedling trays and cultured for 15 days with only supplemental water, until the seedlings reached the two-leaf-one-heart stage. Subsequently, tomato seedlings with uniform growth were selected from the seedling trays and transplanted into flowerpots containing the same substrate. After transplanting, a treatment group (Bio-CDs group) and a control group (CK group) were set up. The treatment group was regularly treated with a 50 mg / L Bio-CDs solution by root drenching, while the control group was treated with an equal amount of water. Treatment was carried out once a week, with each plant irrigated with 20 m³ of water each time. L After 30 days of cultivation, carefully remove the complete plant, wash off any attached material from the roots, and then randomly sample and photograph it.
[0063] Figure 3 The tomato plant phenotypic diagram for Example 4 is shown below. Figure 3 A in Figure 3 B and Figure 3 As shown in C, compared to the control group, the tomato plants in the treatment group had more developed root systems, denser root hairs, a significantly increased number of lateral roots, and overall stronger growth with dark green leaves. Figure 3 As shown in Figure D, the root length of tomato plants in the treatment group increased significantly by 21.16%, indicating that Bio-CDs have a significant promoting effect on the root growth of cherry tomatoes under normal conditions.
[0064] Example 5
[0065] Application of nitrogen-doped biomass carbon dots in promoting Arabidopsis root growth under normal conditions (Example 5):
[0066] Arabidopsis thaliana Col-0 seeds were selected as the application variety. After sterilization with 10% NaClO solution for 5 min, the seeds were randomly divided into a treatment group (Bio-CDs group) and a control group (CK group). The treatment group was soaked in a 100 mg / L Bio-CDs solution (sterilized by 0.22 µm filtration) for 12 h, while the control group was soaked in an equal volume of sterile water for 12 h. After soaking, the Arabidopsis seeds were sown on 1 / 2 MS medium and placed at 4 ℃ for 3 days. Then, they were placed in a greenhouse for 5 days of vertical growth. Finally, intact plants were carefully removed, sampled, and photographed.
[0067] Figure 4 The image shows the phenotypic pattern of Arabidopsis thaliana seedlings in Example 5. Figure 4It can be seen that, compared with the control group, the Arabidopsis seedlings in the treatment group had significantly longer root systems and better growth.
[0068] Example 6
[0069] Application of nitrogen-doped biomass carbon dots in promoting jasmine root growth under normal conditions (Example 6):
[0070] Jasmine plants propagated by cuttings were used as the target species and planted in the field. A treatment group (Bio-CDs group) and a control group (CK group) were set up. After the jasmine plants were propagated by cuttings, the treatment group was sprayed with a 100 mg / L Bio-CDs solution on the leaves and irrigated the roots every 10 days. The control group was treated with an equal amount of water at the same time. After 60 days of treatment, the whole plants were carefully removed, the root attachments were removed, and samples were randomly taken and photographed.
[0071] Figure 5 This is a phenotypic diagram of the jasmine plant from Example 6, by... Figure 5 It can be seen that, compared with the control group, the jasmine plants in the treatment group showed particularly outstanding root development, with a significant increase in root length and the number of lateral roots, forming a more developed root structure. Figure 5 As shown in Figure A, the jasmine plants in the treatment group have already flowered, indicating that the vegetative growth of the jasmine plants in the treatment group has been promoted, the number of stem nodes has increased significantly, and the flowering time has been advanced; this proves that Bio-CDs, when applied to both roots and leaves, can effectively promote the root development of jasmine and improve its overall growth under normal conditions.
[0072] Example 7
[0073] Application of nitrogen-doped biomass carbon dots in promoting wheat root growth under salt stress (Example 7):
[0074] Zhengmai 1860 was selected as the application variety. Plump, uniformly sized wheat seeds were chosen and allowed to germinate until the flag leaf emerged. Wheat seedlings of uniform growth were transplanted into pots containing the same substrate, with 10 seedlings per pot, and randomly divided into treatment and control groups. The treatment group was irrigated with a solution of 150 mM NaCl and 100 mg / L Bio-CDs, while the control group received an equal amount of 150 mM NaCl as a control. Irrigation was performed every 3 days, with 100 mL of solution applied each time. Both groups were cultivated in a greenhouse at 25 ℃, 60% relative humidity, and a photoperiod of 16 h light / 8 h dark. After 15 days of cultivation, intact plants were carefully removed, roots were washed to remove any attached material, and samples were randomly taken and photographed.
[0075] Figure 6 The image shows the phenotypic pattern of wheat plants in Example 7. Figure 6It can be seen that, compared with the control group, the wheat plants in the treatment group showed significantly improved root growth, with the main root length and overall root development being better than the control group. The root length increased by 23.79%, indicating that Bio-CDs can promote wheat root growth under salt stress.
[0076] Example 8
[0077] Application of nitrogen-doped biomass carbon dots in promoting cotton root growth under salt stress in Example 8:
[0078] Zhongmian 1813 was selected as the application variety. Plump and uniformly sized cotton seeds were soaked in a 10% hydrogen peroxide solution for 20 minutes for disinfection, followed by soaking in pure water for 1–2 hours. Ten uniformly sized cotton seeds were planted in flowerpots, randomly divided into treatment and control groups. The treatment group was irrigated with a 150 mM NaCl and 100 mg / L Bio-CDs solution, while the control group was irrigated with an equal volume of 150 mM NaCl solution, 100 mL each time, every 3 days. Both groups were cultivated in a greenhouse at 25 ℃, 60% relative humidity, and a photoperiod of 16 h light / 8 h dark. After 18 days of cultivation, intact plants were carefully removed, roots were cleaned of any attached substances, and samples were randomly taken and photographed.
[0079] Figure 7 The image shows the phenotypic diagram of cotton plants in Example 8. The results indicate that under the same salt stress conditions, the cotton plants in the treatment group showed better growth, significantly increased fresh weight, and more developed root system. The root length was significantly better than that of the control group, increasing by 26.93%, indicating that Bio-CDs can promote cotton root growth under salt stress conditions.
[0080] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.
[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the content of the present invention's specification shall also be included within the scope of protection of the present invention.
Claims
1. An application of nitrogen-doped biomass carbon dots, characterized in that, Application of nitrogen-doped biomass carbon dots in promoting plant root growth under normal or salt stress conditions; the concentration of nitrogen-doped biomass carbon dots is 0.1–100 mg / L.
2. The application of nitrogen-doped biomass carbon dots according to claim 1, characterized in that, The salt stress is salt stress caused by sodium chloride, and the concentration of sodium chloride is 100-150 mM.
3. The application of nitrogen-doped biomass carbon dots according to claim 1, characterized in that, The average particle size of the nitrogen-doped biomass carbon dots is 1.4–4.2 nm.
4. The application of nitrogen-doped biomass carbon dots according to claim 1, characterized in that, The nitrogen-doped biomass carbon dots are prepared by hydrothermal reaction using corn stalks as the carbon source and urea as the nitrogen source; the hydrothermal reaction temperature is 180-220℃ and the hydrothermal reaction time is 6-10 h; the mass ratio of corn stalks to urea is 1:(0.6-3).
5. The application of nitrogen-doped biomass carbon dots according to claim 1, characterized in that, The plant is one or more of the following: food crops, vegetables, model plants, and ornamental plants.
6. The application of nitrogen-doped biomass carbon dots according to claim 1, characterized in that, The application methods of the nitrogen-doped biomass carbon dots include one or more of the following: seed soaking, root irrigation, and foliar spraying.
7. A method for promoting plant root growth, characterized in that, Includes the following steps: Plants were treated with nitrogen-doped biomass carbon dot solutions at concentrations of 0.1–100 mg / L for seed soaking and / or root irrigation and / or foliar spraying.
8. A nitrogen-doped biomass carbon dot, characterized in that, The preparation method of nitrogen-doped biomass carbon dots includes the following steps: pre-treating corn stalks and then acid washing them; dispersing the acid-washed corn stalks and urea in water; and purifying them after hydrothermal reaction; the nitrogen-doped biomass carbon dots promote plant root growth under normal conditions or salt stress conditions.
9. The nitrogen-doped biomass carbon dots according to claim 8, characterized in that, The pretreatment involves crushing the corn stalks and sieving them to 80-100 mesh, and the acid washing involves soaking them in a 0.05-0.1 mol / L HCl solution for 12-24 hours.
10. The nitrogen-doped biomass carbon dots according to claim 8, characterized in that, The mass-to-volume ratio of corn stalks to water is 1 g:(10-30) mL; the mass-to-urea ratio of corn stalks to urea is 1:(0.6-3); the temperature of the hydrothermal reaction is 180-220 ℃; and the time of the hydrothermal reaction is 6-10 h.