A kind of tomato straw carbon dots, their preparation method and application

Abstract

The present invention provides a tomato straw carbon dot and its preparation method and application, belonging to the field of nanotechnology and nanomaterials. The method is to crush tomato straw, add water in a mass ratio of 1: (90-110), heat at 130-200 ° C for 6-10h after ultrasonic treatment; after centrifugation, filtration, and dialysis, freeze-drying is performed to prepare tomato straw carbon dots. The tomato straw carbon dots of the present application are used as root promoters or plant growth aids, which can effectively improve the germination potential, germination rate, radicle and lateral root number of melon seeds, promote the melon seedling root system to be more robust, and the plant growth is more vigorous. In saline-alkali land environment, good results can also be obtained by treating melon seeds with the tomato straw carbon dot aqueous solution of the present application. The melon root system can reach the growth level in non-saline-alkali land, with significant effect.

Description

Technical Field

[0001] The present invention belongs to the field of nanotechnology and nanomaterials, and particularly relates to tomato straw carbon dots and a preparation method and application thereof. Background Art

[0002] Every summer harvest and autumn and winter, vast quantities of straw accumulate in farmland. Burning straw in rural areas can cause environmental pollution, fire hazards, soil damage, and waste land resources. Unlike the straw of ordinary grain crops, the straw of nightshade vegetables like tomatoes, eggplants, and peppers inhibits the growth of the next crop, so it cannot be directly returned to the fields. Furthermore, if too much is returned or tillage is uneven, it can lead to nutrient conflicts between soil microorganisms and young crop seedlings, potentially causing yellowing and seedling death, and reduced yields. The comprehensive development and utilization of straw faces the dilemma of immature technology, high investment, and poor results.

[0003] Carbon quantum dots (CQDs), also known as carbon dots (CDs), are a new type of fluorescent nanomaterial that exhibits many excellent properties, such as photostability, good biocompatibility, hydrophilicity, and easy surface modification. They have been widely used in agriculture, bioimaging, biosensing, fluorescent labeling, and optoelectronic devices.

[0004] my country boasts the world's largest tomato planting area and highest tomato production. By 2022, the planting area and production were projected to reach 1.1692 million hectares and 69.7077 million tons, respectively. This has led to a significant accumulation and unused tomato straw, triggering a series of environmental problems. The harmless disposal and resource utilization of tomato straw have become a major concern in horticultural production (Zhang Feixue et al., 2023). However, current research on the preparation of carbon quantum dots from biomass carbon sources has not yet utilized tomato straw as a carbon source.

[0005] Melon roots develop early, but their regenerative capacity is relatively weak, making them difficult to recover after root damage. If seedlings are transplanted, they should be transplanted as early as possible to avoid root damage. Melon roots are prone to corking, and the older the seedlings, the more corky they become, making rooting difficult. Recovery from root damage is difficult. If root damage occurs before pollination, the roots can slowly recover after the stress is lifted. However, if root damage occurs after pollination, the plant will have difficulty recovering and will experience persistent wilting and decay. Therefore, any problems with the melon root system will directly affect its healthy growth. Currently, relatively little research has been conducted on melon root problems, and few products or methods are available to address them. Summary of the Invention

[0006] The present application aims to overcome at least one of the deficiencies of the prior art. To this end, in a first aspect, the present application provides tomato straw carbon dots and a method for preparing the same.

[0007] The second aspect of the present application provides the application of tomato straw carbon dots in promoting plant root growth, especially plant root growth in saline-alkali soil environments.

[0008] The third aspect of the present application provides a melon root promoter and a plant growth aid in a saline-alkali soil environment.

[0009] The fourth aspect of the present application provides a method for growing melon seedlings and a method for growing plants in a saline-alkali land environment.

[0010] The technical solution adopted in this application is:

[0011] A method for preparing tomato straw carbon dots (TS-CDs) comprises the following steps:

[0012] (1) Crush the tomato straw;

[0013] (2) Weigh tomato straw powder, add water at a mass ratio of 1:(90-110), and continue ultrasonic treatment for 25-35 minutes; transfer the suspension to a reactor and heat at 130-200°C for 6-10 hours;

[0014] (3) centrifuging the resulting mixture at 3000 rpm to 8000 rpm for 15 to 35 min; after centrifugation, collecting the supernatant and filtering it to obtain a liquid product;

[0015] (4) dialyzing the obtained liquid product;

[0016] (5) The dialysis solution was freeze-dried to prepare tomato straw carbon dots.

[0017] In some embodiments, in step (2), heating is performed at 160-180° C. for 8-9 h.

[0018] In some embodiments, in step (3), the obtained mixture is centrifuged at 4000-5000 r / min for 20-30 min.

[0019] The rotation speed and time during centrifugation are used to separate the quantum dot solution and the reactant residue, thereby speeding up the filtration process and preventing the residue from clogging the filter paper to the greatest extent.

[0020] In some embodiments, the filtration in step (3) is vacuum filtration, and the pore size of the filter membrane used in the vacuum filtration is 0.22 μm-0.6 μm.

[0021] The purpose of filtration is to remove the residues that have not been completely reacted.

[0022] In some embodiments, the dialysis bag used for dialysis in step (4) has a specification of a dialysis bag with a molecular weight cut-off of 3500 μm.

[0023] Disclosed are tomato straw carbon dots, wherein the raw material for preparing the tomato straw carbon dots is tomato straw.

[0024] In some embodiments, the raw material for preparing the tomato straw carbon dots is tomato straw, which is obtained using the above-mentioned preparation method.

[0025] Application of tomato straw carbon dots in promoting root growth of plants, including melon.

[0026] Application of tomato straw carbon dots in promoting root growth of plants in saline-alkali soil environments, including melons.

[0027] A melon root promoter, wherein the active ingredient of the root promoter is tomato straw carbon dots, with a concentration of no more than 200 μg ml -1 .

[0028] A plant growth aid for saline-alkali land environments, wherein the active ingredient of the plant growth aid is tomato straw carbon dots, with a concentration of no more than 200 μg·ml -1 The main function of the adjuvant is to promote root growth. The root growth includes but is not limited to root growth during seed germination, promoting root regrowth of plants after root cutting after transplantation, and / or root growth of plants after transplantation.

[0029] A method for growing melon seedlings, comprising soaking seeds and accelerating germination, wherein the concentration of 50-200 μg·ml is used during the soaking and germination process. -1 Melon seeds were treated with an aqueous solution of tomato straw carbon dots.

[0030] In some embodiments, seeds are dried in the sun before soaking and germination. For example, 2 to 3 days before sowing, melon seeds are placed in a sunny place for 1 to 2 days to increase the vitality of the melon seeds.

[0031] A method for planting plants in a saline-alkali land environment comprises the following steps: during the plant planting process, treating plant seeds with a tomato straw carbon dot aqueous solution and then transplanting them to saline-alkali land; and / or treating plant seedlings with a tomato straw carbon dot aqueous solution and then transplanting them to saline-alkali land; and / or, after planting plant seeds or plants in the saline-alkali land, watering them with the tomato straw carbon dot aqueous solution.

[0032] The beneficial effects of this application are:

[0033] In this application, tomato straw carbon dots (TS-CDs) were prepared from discarded tomato straw by a hydrothermal method, thereby utilizing the discarded straw, reducing the accumulation of discarded straw, and avoiding environmental pollution caused by incineration.

[0034] The tomato straw carbon dots described in this application can effectively promote the root growth of melons. Experiments have shown that treating melon seeds with a tomato straw carbon dot aqueous solution during the seed soaking and germination process can effectively increase germination potential, germination rate, and the number of radicles and lateral roots. Continued spraying of the tomato straw carbon dot aqueous solution during seedling cultivation in plug trays can promote stronger root systems and more vigorous plant growth.

[0035] In a saline-alkali land environment, good results can be achieved by treating melon seeds with the tomato straw carbon dot aqueous solution of the present application. The melon root system can reach the growth level in non-saline-alkali land, with significant results. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the hydrothermal synthesis process of CDs.

[0037] Figure 2 Characterization of carbon dots prepared using tomato straw as the carbon source, where A is the TEM image of TS-CDs and B is the particle size distribution diagram.

[0038] Figure 3 Figure 2 is the fluorescence emission spectra of carbon dots at different excitation wavelengths.

[0039] Figure 4 is the UV-visible absorption spectrum of TS-CDs.

[0040] Figure 5 is the Fourier transform infrared spectrum of TS-CDs.

[0041] Figure 6 X-ray diffraction of TS-CDs.

[0042] Figure 7 is the X-ray photoelectron spectrum of TS-CDs.

[0043] Figure 8 For cytotoxicity experiments, the viability of African green monkey kidney epithelial cells was evaluated under treatment with different concentrations of TS-CDs.

[0044] Figure 9 The phenotypes of adventitious root regeneration in melon at different time periods.

[0045] Figure 10 The diagram shows the changes in the root primordium during adventitious root regeneration of melon at different time periods (the white arrow in the figure indicates the protrusion of the root primordium).

[0046] Figure 11were water and 150 μg·ml -1 Related indices of root regeneration from adventitious roots of melon after treatment with TS-CDs.

[0047] Among them, (A) is the root length of melon adventitious root regeneration induced by TS-CDs at different days; (B) is the root surface area of melon adventitious root regeneration induced by TS-CDs at different days; (C) is the root projection area of melon adventitious root regeneration induced by TS-CDs at different days; (D) is the root volume of melon adventitious root regeneration induced by TS-CDs at different days; (E) is the average root diameter of melon adventitious root regeneration induced by TS-CDs at different days; (F) is the total number of root tips of melon adventitious root regeneration induced by TS-CDs at different days; (G) is the number of branches of melon adventitious root regeneration induced by TS-CDs at different days; (H) is the number of intersections of melon adventitious root regeneration induced by TS-CDs at different days.

[0048] Figure 12 Longitudinal paraffin sections of melon seedling stems with different treatments.

[0049] Figure 13 The phenotypes of adventitious root regeneration in melon after treatment with water and different concentrations of TS-CDs for 7 days.

[0050] Figure 14 Figure 2 is the fluorescence emission spectra of carbon dots at different reaction temperatures at the same excitation wavelength.

[0051] Figure 15 Figure 2 is the fluorescence emission spectra of carbon dots at the same excitation wavelength with different reaction times.

[0052] Figure 16 The phenotypes of carbon dots in melon adventitious root regeneration at different reaction temperatures.

[0053] Figure 17 The phenotypes of adventitious root regeneration of melon with carbon dots at different reaction times.

[0054] Figure 18 The phenotype of TS-CDs on adventitious root regeneration in tomato.

[0055] Figure 19 TS-CDs promote melon seed germination phenotype.

[0056] Figure 20 TS-CDs alleviate the salt tolerance phenotype of melon seeds.

[0057] Figure 21 Spray 150 μg ml after the cotyledons are flattened -1 The carbon dot solution can promote the growth phenotype of melon seedlings.

[0058] Figure 22150 μg·ml for irrigation after planting -1 Carbon dot solution can promote the survival phenotype. DETAILED DESCRIPTION

[0059] The experimental methods in the following examples of the present invention, where specific conditions are not specified, are generally carried out under conventional conditions or conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0060] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0061] The terms "comprise," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product, or device comprising a series of steps is not limited to the listed steps or modules but may optionally include steps not listed, or other steps inherent to the process, method, product, or device.

[0062] In this application, "plurality" refers to two or more. "And / or" describes the relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates that the related objects are in an "or" relationship.

[0063] This application uses a hydrothermal method to synthesize tomato straw CDs. The process diagram is shown in Figure 1 .

[0064] A method for preparing tomato straw carbon dots (TS-CDs) comprises the following steps:

[0065] (1) Crush the tomato straw;

[0066] (2) Weigh tomato straw powder, add water at a mass ratio of 1:(90-110), and continue ultrasonic treatment for 25-35 minutes; transfer the suspension to a reactor and heat at 130-200°C for 6-10 hours;

[0067] (3) centrifuging the resulting mixture at 3000 rpm to 8000 rpm for 15 to 35 min; after centrifugation, collecting the supernatant and filtering it to obtain a liquid product;

[0068] (4) dialyzing the obtained liquid product;

[0069] (5) The dialysis solution was freeze-dried to prepare tomato straw carbon dots.

[0070] In the process of preparing straw carbon dots, the role of ultrasound is mainly reflected in the following aspects: accelerating the dispersion and exfoliation of materials, increasing the surface activity of materials, promoting physical reactions, improving the uniformity of materials, etc.

[0071] In some embodiments, in step (2), the ultrasonic power is 150W and the frequency is 40kHz. The ultrasonic device used in the technical solution of this application is a laboratory ultrasonic device. Those skilled in the art can adjust the parameters of the ultrasonic device according to actual conditions.

[0072] In some embodiments, in step (2), heating is performed at 160-180° C. for 8-9 h.

[0073] In some embodiments, in step (3), the obtained mixture is centrifuged at 4000-5000 r / min for 20-30 min.

[0074] The rotation speed and time during centrifugation are used to separate the quantum dot solution and the reactant residue, thereby speeding up the filtration process and preventing the residue from clogging the filter paper to the greatest extent.

[0075] In some embodiments, the filtration in step (3) is vacuum filtration, and the pore size of the filter membrane used in the vacuum filtration is 0.22 μm-0.6 μm.

[0076] The purpose of filtration is to remove the residues that have not been completely reacted.

[0077] In some embodiments, the dialysis bag used for dialysis in step (4) has a specification of a dialysis bag with a molecular weight cut-off of 3500 μm.

[0078] The purpose of dialysis is to retain the desired large molecules and remove extremely small molecules.

[0079] In some embodiments, the freeze-drying in step (5) is performed using a freeze dryer.

[0080] Disclosed are tomato straw carbon dots, wherein the raw material for preparing the tomato straw carbon dots is tomato straw.

[0081] In some embodiments, the raw material for preparing the tomato straw carbon dots is tomato straw, which is obtained using the above-mentioned preparation method.

[0082] Application of tomato straw carbon dots in promoting root growth of plants, including melon.

[0083] A melon root promoter, wherein the active ingredient of the root promoter is tomato straw carbon dots, with a concentration of no more than 200 μg ml -1 .

[0084] A method for growing melon seedlings, comprising soaking seeds and accelerating germination, wherein the concentration of 50-200 μg·ml is used during the soaking and germination process. -1 Melon seeds were treated with an aqueous solution of tomato straw carbon dots.

[0085] In some embodiments, seeds are dried in the sun before soaking and germination. For example, 2 to 3 days before sowing, melon seeds are placed in a sunny place for 1 to 2 days to increase the vitality of the melon seeds.

[0086] To air-dry, carefully selected seeds are spread evenly on clean paper or straw mats and aired in clear, windless, sunny weather. Turn the seeds every two hours to ensure even sunlight exposure. Air-drying promotes seed ripening, enhances seed vitality, and improves germination potential and germination rate. Furthermore, the ultraviolet rays and high temperatures in the sun kill some pathogens carried by the seeds, reducing the risk of seed-borne diseases. Furthermore, the drier the seeds are, the faster they absorb water during soaking, promoting germination.

[0087] A method for planting plants in a saline-alkali land environment comprises the following steps: during the plant planting process, treating plant seeds with a tomato straw carbon dot aqueous solution and then transplanting them to saline-alkali land; and / or treating plant seedlings with a tomato straw carbon dot aqueous solution and then transplanting them to saline-alkali land; and / or, after planting plant seeds or plants in the saline-alkali land, watering them with the tomato straw carbon dot aqueous solution.

[0088] The following is a description of the specific examples. The muskmelon seeds used in the following examples and comparative examples are all of the "Yangjiaomi" variety.

[0089] The tomato straw used in the present application is the dried product of the entire tomato plant (including the stems and leaves) obtained after the tomato fruits are harvested and air-dried or oven-dried. Since the leaves of the entire plant are easily lost during air-drying or oven-drying and subsequent transportation, the tomato straw mainly consists of the stems, with a small amount of leaves retained.

[0090] Example 1: Preparation of tomato straw carbon dots

[0091] (1) Wash and dry the tomato straw, then grind it into powder using a grinder and sieve it.

[0092] (2) Weigh 3 g of tomato straw powder and 300 mL of double-distilled water into a beaker (1:100) and treat with ultrasound (power 150 W, frequency 40 kHz) for 30 min. Transfer the suspension to a 500 mL polyvinyl fluoride reactor and heat at 200 °C for 6 h. Allow the reactor to cool to room temperature.

[0093] (3) The resulting mixture was centrifuged at 8000 rpm for 15 min. After centrifugation, the supernatant was collected and filtered under reduced pressure using a 0.22 μm filter membrane to obtain an orange-yellow liquid product.

[0094] (4) The obtained product was transferred into a dialysis bag with a molecular weight cutoff of 3500 μm, placed in a large beaker filled with deionized water, and dialyzed for 3 days, changing the water every 24 hours until the liquid was basically colorless.

[0095] (5) The solution in the dialysis bag is tomato straw carbon dots (TS-CDs). After freezing, it is placed in a freeze dryer and freeze-dried into carbon dot powder, which is then collected and stored at 4°C for future use.

[0096] Example 2: Preparation of tomato straw carbon dots

[0097] (1) Wash and dry the tomato straw, then grind it into powder using a grinder and sieve it.

[0098] (2) Weigh 3 g of tomato straw powder and 300 mL of double-distilled water into a beaker (1:100) and treat with ultrasound (power 150 W, frequency 40 kHz) for 30 min. Transfer the suspension to a 500 mL polyvinyl fluoride reactor and heat at 180°C for 8 h. Allow the reactor to cool to room temperature.

[0099] (3) The resulting mixture was centrifuged at 4000 r / min for 20 min. After centrifugation, the supernatant was collected and filtered under reduced pressure using a 0.22 μm filter membrane to obtain an orange-yellow liquid product.

[0100] (4) The obtained product was transferred into a dialysis bag with a molecular weight cutoff of 3500 μm, placed in a large beaker filled with deionized water, and dialyzed for 3 days, changing the water every 24 hours until the liquid was basically colorless.

[0101] (5) The solution in the dialysis bag is tomato straw carbon dots (TS-CDs). After freezing, it is placed in a freeze dryer and freeze-dried into carbon dot powder, which is then collected and stored at 4°C for future use.

[0102] Test Example 1

[0103] The tomato straw carbon dots prepared in Example 2 were characterized.

[0104] In the characterization of carbon dots, (1) TEM is used to observe the structure, size and dispersibility of carbon quantum dots and determine whether their particle size range meets the requirements of the nanoscale. (2) Fluorescence emission spectra under different excitation wavelengths are used to observe the luminescence characteristics of carbon quantum dots under different excitation wavelengths and determine the optical properties of the prepared carbon dots. (3) UV-visible absorption spectra can provide information on the electronic structure of nanoparticles. In the measurement of the biological effects of nanomaterials, the UV-visible absorption of nanoparticles will cause signal interference in the biological effect experiment. (4) In the Fourier transform infrared spectroscopy experiment, because the vibration of different chemical bonds of carbon dots has a specific absorption frequency in the infrared region, the structure of carbon quantum dots can be determined by observing the position and intensity of each peak in the spectrum image. (5) In the identification of material state, different material states have different diffraction effects on X-rays. Therefore, X-ray diffraction spectra (XRD) can be used to distinguish between crystalline and amorphous states. Generally, the XRD spectrum of amorphous materials is a straight line. The XRD spectrum of diffuse peaks that appear at low 2θ angles is generally composed of liquid-type solids and gas-type solids. (6) X-ray photoelectron spectroscopy (XPS) can confirm the presence of hydrophilic groups on the surface of carbon quantum dots, proving that they have good water solubility.

[0105] In the characterization experiments described below, transmission electron microscopy (TEM) images of CDs were obtained. Photoluminescence (PL) spectra were measured using a fluorescence spectrophotometer. Ultraviolet-visible (UV-Vis) absorption spectra were measured using an ultraviolet-visible absorption spectrometer. Fourier transform infrared (FT-IR) spectra were measured using a Fourier transform infrared spectrometer. X-ray photoelectron spectrum (XPS) and diffraction (XRD) were measured using an electron spectrometer and an X-ray diffractometer, respectively.

[0106] See the results Figure 2-Figure 7 .

[0107] Figure 2 Characterization of carbon dots prepared using tomato straw as the carbon source, where A is the TEM image of TS-CDs and B is the particle size distribution diagram. Figure 3 Figure 2 is the fluorescence emission spectra of carbon dots at different excitation wavelengths. Figure 4 is the UV-visible absorption spectrum of TS-CDs. Figure 5 is the Fourier transform infrared spectrum of TS-CDs. Figure 6 is the X-ray diffraction spectrum of TS-CDs. Figure 7 is the X-ray photoelectron spectrum of TS-CDs.

[0108] like Figure 2 As shown in Figure A, it can be seen with the naked eye that the carbon dots prepared using tomato straw as the carbon source in this application are approximately spherical, uniform in size, well dispersed, and have no agglomeration. Figure 2 B is the particle size distribution diagram after TEM image analysis. Figure 2 B shows that the average diameter of TS-CDs is 2.17 nm, which meets the particle size requirements of nanomaterial carbon dots.

[0109] Figure 3 A is the fluorescence emission spectrum of tomato straw carbon dots at different excitation wavelengths. The TS-CDs (Tomato straw carbon dots) prepared in Example 2 were irradiated with excitation light of 300, 325, 350, 375, 400, 425, 450, 475, 500, and 525 nm, respectively. It can be seen that the fluorescence intensity is highest when irradiated with 350 nm excitation light ( Figure 3 A). Then, the TS-CDs were irradiated with 350nm excitation light. It can be seen that the peak of the emitted light is around 455nm. The wavelength range of blue light is 450-480nm. Therefore, it can be proved that the TS-CDs prepared in Example 2 are carbon dots that emit blue fluorescence, and the fluorescence intensity emitted is the strongest when irradiated with 350nm excitation light ( Figure 3 B). This indicates that the prepared tomato straw carbon dots have good optical properties.

[0110] from Figure 4 It can be seen from the UV-visible absorption spectrum of TS-CDs that in the ultraviolet wavelength range of 200-800nm, the absorbance of TS-CDs gradually decreases with the increase of excitation wavelength, and it has a strong absorption capacity in the ultraviolet region of 200-470nm ( Figure 4 ); Simultaneously, a strong absorption peak at 286 nm is exhibited, attributed to the chromophore transition. This 286 nm absorption peak in the UV-visible spectrum can be attributed to the π→π* transition of electrons in the conjugated carbon core, demonstrating the excellent luminescence capability of Ts-CDs. The emission characteristics of Ts-CDs can be attributed to the energy characteristics of down-conversion, demonstrating their optoelectronic properties.

[0111] The surface functional groups of TS-CDs were detected by Fourier transform infrared spectroscopy, such as Figure 5 As shown, 3421cm -1 and 1649cm -1The stretching vibration regions of OH and C=O are 1103cm -1 The stretching vibrations of CO and CN and the single-bond skeleton vibrations of CC are located at the bottom. This indicates that the synthesized tomato straw carbon dots have various organic functional groups, which can improve the hydrophilicity and stability of carbon dots in aqueous systems and promote the further functionalization and application of carbon dots.

[0112] exist Figure 6 In the X-ray diffraction spectrum of TS-CDs, the characteristic peaks of carbon dots usually appear in the 2θ angle range of 20-30°. Among them, the strongest peak is usually around 25°. Figure 6 As shown in the figure, a very broad diffraction package appears near the peak at around 25°, which proves that the prepared carbon dots are amorphous in structure ( Figure 6 ).

[0113] Figure 7 The X-ray photoelectron spectrum of TS-CDs shows that the TS-CDs prepared in Example 2 contain three elements: C, N, and O. TS-CDs contain three peaks, located at 284.03, 398.95, and 532.26 eV, corresponding to C1s (71.6%), N1s (23.36%), and O1s (5.04%), respectively. The N1s spectrum can be fitted with a peak at 398.98 eV, which is attributed to CN. The two peaks of O1s are located at 531.68 and 532.82 eV, which are attributed to OH and CO, respectively. The C1s spectrum shows the presence of CC / C=C (283.99 eV), CN (285.19 eV), C=O (287.88 eV), and OCO (285.96 eV). The above FTIR and XPS spectra both show that the surface of the TS-CDs of the present application is rich in hydrophilic groups (-OH and -COOH), which is consistent with the excellent water dispersibility.

[0114] Test Example 2

[0115] In order to ensure the biosafety of TS-CDs, African green monkey kidney epithelial cells were treated with TS-CDs prepared in Example 2 at different concentrations to conduct cytotoxicity experiments, and the cell survival rates were calculated 3 days after treatment.

[0116] Cytotoxicity test method: African green monkey kidney epithelial cells (Marc-145) with good growth status were transferred to 96-well plates and inoculated into each well with about 1×10 4Cells were plated three times with the same sample and incubated in a constant temperature incubator for 24 hours. After discarding the culture medium and washing with phosphate buffered saline (PBS), 200 μL of CDs culture medium dilutions of different concentrations were added to each well, with water as a control, and incubated for 24 hours. Then 10 μL of CCK-8 solution (CCK-8 kit) was added to each well. After adding the reagent, the culture plate was gently shaken to help mix. After returning to the incubator and incubating for 2 hours, the OD value at 450 nm was measured using a microplate reader to calculate cell viability. The experiment was set up with three independent biological replicates.

[0117] See the results Figure 8 , Figure 8 The results showed that when the concentration of TS-CDs did not exceed 150 μg·mL -1 Under the conditions of 150 μg·mL, the cell survival rate was stable at more than 95% with no obvious toxic side effects. However, when the concentration was higher than 150 μg·mL -1 The cell survival rate decreased gradually with the increase of TS-CDs concentration, and reached 250 μg·mL -1 When the concentration of tomato straw carbon dots was not higher than 200 ng / ml, the cell survival rate dropped to 67%, which was 33% lower than that of the control, showing a certain degree of cytotoxicity.

[0118] Example 3: Application of the Tomato Straw Carbon Dots Prepared in Example 2 as a Root Promoter in Muskmelon Growth

[0119] After germination, the seeds of the melon variety 'Yangjiaomi' were selected and sown with uniform whitening. When the cotyledons of the seedlings were flattened, the seedlings with uniform growth were selected for root cutting (root cutting was performed at the junction of green and white stems with a sharp blade). After root cutting, the seedlings were fixed with a sponge in a centrifuge tube with reconstituted 150 μg mL -1 The TS-CDs aqueous solution (prepared in Example 2) and water were used as two treatments, and three replicates were set for each.

[0120] Measurement of root parameters during TS-CD-induced adventitious root regeneration in melon: On the third day, seedlings were placed in a root scanner to photograph and analyze relevant root parameters. Analysis was continued daily until the seventh day, when treatment was complete. Root parameters were measured using a root scanner.

[0121] To determine changes in root primordium and cytological number during TS-CDs-induced adventitious root regeneration in melon, the same treatment method was used. After treatment, the solution on the roots of the seedlings was gently wiped dry with paper and photographed and observed under a stereomicroscope. The seedlings were returned to the centrifuge tubes and continued to culture. The roots were photographed and observed daily until roots had grown from both treatments on the fourth day. To ensure experimental consistency, the same seedlings were observed each day. Root primordium changes were measured using a stereomicroscope, and paraffin sections were obtained by Wuhan Sevier Biotechnology.

[0122] Figure 9 were water and 150 μg·ml -1 Phenotype of melon adventitious root regeneration after TS-CDs treatment. Figure 9 The results showed that on the third day, no roots grew in either treatment group; on the fourth day, only the 150 μg·ml -1 The melon seedlings treated with TS-CDs took root; after the fifth day, both treatment groups had grown roots. As time went on, the regenerated root system of melon adventitious roots became longer. In the same period of time, from the fourth to the seventh day, after 150 μg·ml -1 The roots of the TS-CDs-treated plants were longer and denser than those of the control group, indicating that TS-CDs can promote the regeneration of adventitious roots in melons earlier.

[0123] Water treatment, similar to rooting by cuttings, produced weak, small, and thin adventitious roots, hindering subsequent growth. Melon seedlings treated with tomato straw carbon dots outperformed water treatment in both root strength and number. Furthermore, carbon dot treatment enhanced photosynthesis, promoting the accumulation of organic matter.

[0124] Depend on Figure 10 As can be seen, no adventitious root primordia appeared in the hypocotyls immediately after root removal. On the first day, no obvious root primordia were observed in the melon adventitious roots treated with water or TS-CDs. On the second day, one root primordium appeared in the melon adventitious roots treated with TS-CDs, while none appeared in the control group. On the third and fourth days, it was clearly evident that the root primordia regenerated from the melon adventitious roots treated with TS-CDs were more densely populated than those in the water control group. This suggests that TS-CDs can promote the formation of root primordia during melon adventitious root regeneration, and the number of root primordia is greater than in the control group.

[0125] Figure 11 were water and 150 μg·ml -1 Related indices of regeneration root system of melon adventitious roots after TS-CDs treatment. Figure 11 A shows that in the same period of time, after 150 μg ml -1The length of regenerated roots of melon adventitious roots treated with TS-CDs was significantly increased compared with the water control group ( Figure 11 A); from the third to the seventh day, after 150 μg ml -1 The surface area of regenerated roots of melon adventitious roots treated with TS-CDs was significantly higher than that of the water control group ( Figure 11 B); in the same time period, after 150 μg·ml -1 The projected root area of melon adventitious roots regenerated by TS-CDs treatment was significantly higher than that of the control group ( Figure 11 C); from the third to the seventh day, after 150 μg ml -1 The volume of regenerated root system of melon adventitious roots treated with TS-CDs was significantly higher than that of the control group ( Figure 11 D); treated for the same period of time, after 150 μg ml -1 The average diameter of regenerated roots of melon adventitious roots treated with TS-CDs was significantly higher than that of the control group ( Figure 11 E); treated for the same period of time, after 150 μg ml -1 The number of regenerated root branches of melon adventitious roots treated with TS-CDs was significantly higher than that of the control group ( Figure 11 F); from the same number of days, after 150μg·ml -1 The total number of root tips regenerated from adventitious roots of melons treated with TS-CDs was significantly higher than that of the control group ( Figure 11 G); in the same time period, after 150 μg ml -1 The number of crossovers of regenerated roots of melon adventitious roots treated with TS-CDs was significantly higher than that of the control group ( Figure 11 H). This indicates that TS-CDs can promote the growth of melon roots earlier.

[0126] Figure 12 This is a longitudinal paraffin section of a melon seedling stem. It can be seen that 24 hours after treatment, the TS-CDs-treated seedlings produced root primordia protruding from the vascular bundle, while the control group showed no root primordia protrusions at the same time. At 60 hours after treatment, the control group had only one root primordium protruding, while the TS-CDs-treated seedlings had three protruding root primordia, significantly more than the control group. 72 hours (3 days) after treatment, the control group had numerous root primordia protruding from the vascular bundle, while the TS-CDs-treated seedlings had already broken through the epidermis, forming adventitious roots.

[0127] Screening experiment of TS-CDs growth-promoting concentration: After the melon seedlings were grown to the point where the cotyledons were flattened, the roots were cut off and the root-cut seedlings were placed in a 0 μg·mL -1 , 100 μg·mL -1 , 150 μg·mL-1 and 200 μg mL -1 After 7 days of treatment with TS-CDs aqueous solution, 9 seedlings were randomly selected for phenotypic observation to evaluate the phenotype of melon adventitious root regeneration.

[0128] Depend on Figure 13 It can be seen that the adventitious roots of melons treated with TS-CDs were longer and more numerous than those treated with water. -1 The regeneration root system of melon adventitious roots treated with TS-CDs was significantly higher than that of melon adventitious roots treated with 100 μg·mL -1 The results of TS-CDs treatment were significantly better and more consistent. This indicates that with the increase of TS-CDs concentration, the regeneration of melon adventitious roots grew better until the concentration increased to 200 μg·mL -1 When the concentration of TS-CDs was less than 150 μg·mL, the effect of TS-CDs on adventitious root regeneration of melon became smaller, indicating that the concentration of TS-CDs was less than 150 μg·mL -1 There is concentration dependence; when the concentration is 150μg·mL -1 When the concentration of TS-CDs was more than 150 μg·mL, the effect of TS-CDs on adventitious root regeneration of melon was the most significant and uniform. -1 Therefore, the effective concentration of this application is finally determined to be 150 μg·mL -1 optimal.

[0129] The relevant data are shown in Table 1:

[0130] Table 1

[0131]

[0132]

[0133] Example 4: Preparation of tomato straw carbon dots and application of tomato straw carbon dots in promoting adventitious root growth in melon seedlings

[0134] The temperature and time of the reaction in the reactor in step (2) were adjusted to explore the effects of the reaction temperature and reaction time on the tomato straw carbon dots. The other steps were the same as in Example 2.

[0135] The specific steps are as follows:

[0136] (1) Wash and dry the tomato straw, then grind it into powder using a grinder and sieve it.

[0137] (2) Weigh 3 g of tomato straw powder and 300 mL of double-distilled water into a beaker (1:100) and treat with ultrasound for 30 min. Transfer the suspension into a 500 mL polyvinyl fluoride reactor and react at 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C for 8 h or at 180°C for 6 h, 7 h, 8 h, 9 h, and 10 h, respectively. Wait for the reactor to cool to room temperature.

[0138] (3) The resulting mixture was centrifuged at 4000 r / min for 20 min. After centrifugation, the supernatant was collected and filtered under reduced pressure using a 0.22 μm filter membrane to obtain an orange-yellow liquid product.

[0139] (4) The obtained product was transferred into a dialysis bag with a molecular weight cutoff of 3500 μm, placed in a large beaker filled with deionized water, and dialyzed for 3 days, changing the water every 24 hours until the liquid was basically colorless.

[0140] (5) Freeze-dry the obtained carbon dot powder in a freezer and store it at 4°C.

[0141] The fluorescence emission spectra of carbon quantum dots prepared at different reaction temperatures were observed at an excitation wavelength of 450 nm. It can be seen from the spectrum that the fluorescence signal is strongest when the reaction temperature is 180°C ( Figure 14 ); At the same time, the fluorescence emission spectra of carbon quantum dots prepared at different reaction times were observed at an excitation wavelength of 450nm. It can be seen from the spectrum that the fluorescence signal is strongest when the reaction temperature is 8h ( Figure 15 To further verify the effects of different reaction temperatures and reaction times on the promotion of adventitious roots in melon seedlings, the inventors conducted rooting experiments at different preparation times and temperatures. The experimental results confirmed the fluorescence emission spectrum results at an excitation wavelength of 450nm. The experimental results showed that the adventitious root growth at a reaction temperature of 180°C and a reaction time of 8h was better than that at other times and temperatures ( Figure 16 、 Figure 17 ).in Figure 14 and Figure 16 Corresponding to the step (2), tomato straw carbon dots were prepared by reacting at 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C for 8 h, wherein Figure 15 and Figure 17 Correspondingly, tomato straw carbon dots were prepared by reacting at 180°C for 6h, 7h, 8h, 9h, and 10h in step (2).

[0142] It can be seen that the reaction time and reaction temperature in step (2) of the technical solution of the present application are crucial. Too high a temperature or too long a time will lead to severe carbonization of the quantum dots produced, resulting in a decrease in their quality.

[0143] Example 5: Application of the Tomato Straw Carbon Dots Prepared in Example 2 as a Root Promoter in Tomato Growth

[0144] In order to further prove that the root promoter can be applied to other crops, the tomato straw carbon dots were tested in tomato seedlings. The results showed that 150 μg ml -1 On the third day after the tomato seedlings were treated with TS-CDs, the control group had no roots, while the TS-CDs treated group had adventitious roots. On the fourth day, both groups had adventitious roots. However, after 150 μg·ml -1 The adventitious roots of tomato seedlings treated with TS-CDs were superior to those of the control group, which proved that 150 μg·ml -1 TS-CDs treatment of tomato seedlings can significantly promote the production of adventitious roots ( Figure 18 ).

[0145] Example 6: Use of the tomato straw carbon dots prepared in Example 2 as a root promoter

[0146] Select the melon seeds with full grains and place them in the prepared carbon dot solution (50, 100, 150 μg ml -1 ) and 0 μg·ml -1 For the control (equivalent to the water treatment), the seeds were soaked for 10 hours and then spread on moistened filter paper (using the same carbon dot solution or water as used for soaking) and placed in a dark incubator at 28°C for germination. During this process, the filter paper was kept moist to ensure normal growth. Three plants were randomly selected under different concentrations for observation and parameter measurement.

[0147] 16 hours after treatment, it was found that the germination potential of the seeds treated with carbon dots was better than that of the control, and the germination rate was better than that of the control at 72 hours. After 72 hours, the growth of the seeds was observed and it was found that the epicotyls and hypocotyls of the seeds treated with carbon dots were better than those treated with control water, and the number of lateral roots in the carbon dot treatment group was better than that in the control group. In addition, the growth of the melon seedlings treated with carbon dots was uniform and overall better than that of the control treatment. Therefore, soaking seeds with carbon dot solution can effectively improve the germination potential, germination rate, and number of radicles and lateral roots of melon seeds ( Figure 19 ).

[0148] Specifically, at 16 h, 50, 100, and 150 μg·ml were compared with CK. -1 The germination potential of carbon dots treated with 50, 100 and 150 μg·ml -1 The germination rates of carbon dots treated with 50, 100 and 150 μg·ml-1 The number of lateral roots treated with carbon dots increased by 22.90%, 31.00%, and 29.95% respectively; at 72h, the lateral roots of 50, 100, and 150 μg·ml -1 The epicotyls treated with carbon dots increased by 20.69%, 19.76%, and 29.19% respectively; at 72h, the 50, 100, and 150 μg·ml -1 The hypocotyls treated with carbon dots increased by 6.91%, 22.43% and 14.42% respectively.

[0149] Conventional melon cultivation primarily relies on direct seeding, a method that, to a certain extent, fails to ensure uniform germination. Furthermore, the radicles that develop after direct seeding are weak, with fewer lateral roots, hindering growth and subsequent seedbed management. This requires workers to screen and remove poorly grown and deformed seedlings, undoubtedly increasing production costs. The technical solution of this application effectively addresses this issue by addressing germination rates and potential, avoiding problems such as deformed seedlings caused by poor root growth, reducing the number of workers involved in screening and significantly reducing production costs.

[0150] Example 7: Use of tomato straw carbon dots in saline-alkali soil

[0151] To further explore whether carbon dots can alleviate the salt tolerance of melon seeds, the inventors selected full melon seeds and soaked them in water at 60°C for sterilization. -1 TS-CDs, 150mM NaCl+100μg·ml -1 TS-CDs, 150mM NaCl+150μg·ml -1 For TS-CDs treatment, soak the seeds for 10 h, spread them on a culture dish covered with two layers of filter paper, add an equal amount of water to the filter paper, culture them in an incubator in the dark, and observe them in time.

[0152] Among them, the water treatment group simulated the growth of melon seeds in a normal environment, the 150mM NaCl treatment group simulated the growth of melon seeds in a saline-alkali environment, and the 150mM NaCl+50μg·ml -1 TS-CDs, 150mM NaCl+100μg·ml -1 TS-CDs, 150mM NaCl+150μg·ml -1 The TS-CDs treatment group simulated the growth of melon seeds in a saline-alkali soil environment, thereby investigating the effects of different concentrations of carbon dot solutions on the growth of melon seeds under salt stress.

[0153] At 16 h after treatment, the germination rates of the water treatment group (CK) and the 150 mM NaCl group were 41.66% and 21.66%, respectively; 150 mM NaCl + 50 μg ml -1 TS-CDs, 150mM NaCl+100μg·ml -1 TS-CDs, 150mM NaCl+150μg·ml - 1 The germination rates of TS-CDs were 30%, 40%, and 30%, respectively. That is, after 16 hours, under saline-alkali conditions, the melon seeds treated with TS-CDs could recover to the level under normal conditions.

[0154] See the results Figure 20 The phenotype diagram shows the melon root system after 72 hours of culture. The analysis of the melon root system after 7 days of culture showed that compared with the control group, the melon root system treated with 150mM / L NaCl was significantly weaker than the control group and had fewer lateral roots. The epicotyls grew delicately. The 150mM / L NaCl treatment affected the normal growth of the melon epicotyls. -1 TS-CDs, 150mM NaCl+100μg·ml -1 TS-CDs, 150mM NaCl+150μg·ml -1 TS-CDs were soaked in the seeds at the same time and found that the -1 and 150 μg·ml -1 When treated with carbon dot solution, the growth of melon root system (hypocotyl) returned to normal level (the level of water treatment group), and after 150mM NaCl + 150μg ml -1 The epicotyls treated with TS-CDs were slightly stronger than those in the control (water treatment group), but there was no significant difference. At the same time, the ratio of lateral roots and epicotyls after 150mM NaCl+TS-CDs treatment returned to the normal level of the control (water treatment group), proving that the salt tolerance of seeds treated with carbon dots increased and it could effectively alleviate the damage caused by salt stress ( Figure 20 ).

[0155] Saline-alkali land refers to land with high salt content in the soil, which affects the normal growth of vegetation. Generally speaking, the salinity level of saline-alkali land is classified as follows: slightly saline-alkali land has a salt content of 0.1-0.2%, moderately saline-alkali land has a salt content of 0.2-0.4%, and severely saline-alkali land has a salt content of 0.4-0.6%.

[0156] In other words, 100g of soil in mild saline-alkali soil contains approximately 0.1g of sodium chloride, and 150mM / L NaCl is equivalent to adding approximately 4.39g of NaCl to 500ml of water, which is roughly the salinity range of severely saline-alkali soil. Therefore, the salt concentration in this embodiment is consistent with the salinity of normal saline-alkali soil. This also provides a theoretical basis for the use of this technical solution in saline-alkali soil.

[0157] Based on a general calculation of the germination rate of all crops after 72 hours or longer (no more than 7 days), the emergence rate of general crops can reach over 95%. However, in saline-alkali soils, due to the high salt content in the soil, seeds may have difficulty germinating or easily die after germination. Therefore, the emergence rate in saline-alkali soil is generally lower, perhaps only 60%-70% (Liu Jie et al., 2020). According to existing technology, the emergence rate of crop seeds in mild saline-alkali soil is around 70% to 80%. The emergence rate in moderate saline-alkali soil is not described in detail (Yang Kai, 2020), and the emergence rate in severely saline-alkali soil is less than 50%. In other words, the germination rate of any crop in severely saline-alkali soil will be significantly lower than that of crops grown in conventional soil.

[0158] Therefore, through comparison, it was found that even in a severely saline-alkali environment, good results can be achieved by treating melon seeds with the tomato straw carbon dot aqueous solution of the present application. The melon root system can reach the growth level in non-saline-alkali land, with significant results.

[0159] In practice, using a tomato straw carbon dot aqueous solution during seed soaking and germination can effectively promote the growth and development of the melon radicle and lateral roots, improving the resistance of the melon plant. After planting, it can also enhance its ability to absorb nutrients and increase salt tolerance. By treating melon seeds with a tomato straw carbon dot aqueous solution, the damage caused by salinity and alkali to the melon plant can be effectively alleviated.

[0160] In addition, after the melon seedlings are transferred to saline-alkali land for planting, they can be treated with tomato straw carbon dot solution from time to time. They can be sprayed or watered to alleviate the problem of poor melon growth caused by saline-alkali land.

[0161] Example 8: Use of the Tomato Straw Carbon Dots Prepared in Example 2 as a Root Promoter

[0162] Soak the selected melon seeds in warm water (50-60℃) for 12 hours, and then sow them in 5×10 hole trays containing substrate for seedling cultivation.

[0163] Soaking seeds in warm water is a commonly used seed treatment method. This involves soaking seeds in hot water at a specific temperature to eliminate pathogens lurking on or within the seeds, while also promoting water absorption and accelerating germination. This simple, economical, and effective method is suitable for seed treatment of a wide range of crops.

[0164] The matrix is composed of peat, vermiculite and perlite in a volume ratio of 6:2:2, and is stirred with water until it forms a ball when held by hand and then falls to the ground. The organic matter content of the ball is 45%, and the pH value is 5.8-6.5.

[0165] After the cotyledons of the melon seedlings are flattened, spray the prepared 150μg ml for three consecutive days. -1 The carbon dot aqueous solution and the control group (CK) continued to be sprayed with water. After 3 days, it was found that the melon seedlings sprayed with carbon dot solution had stronger root systems and more vigorous plant growth ( Figure 21 The melon seedlings can be transplanted when they have about two leaves and one heart. It takes about 25 days from sowing to transplanting.

[0166] Example 9: Use of the Tomato Straw Carbon Dots Prepared in Example 2 as a Root Promoter

[0167] Transplant the melon seedlings into the soil. The specific operation method is: when the melon seedlings grow to two leaves and one heart, use a hole puncher to make a planting hole 1 to 2 days in advance, and pour in about 1.5 kg of planting water. After the water in the hole has seeped dry, carefully and completely place the melon seedlings into the hole. The depth should be 1 cm below the bed surface. Use loose fine soil to fix the seedlings. Cover the surface of the soil ball with 1 cm thick fine dry soil and then level it with the ridge surface. After surrounding the soil, water it thoroughly again (about 0.5 kg per hole) to make the soil ball in close contact with the surrounding soil. Afterwards, check one by one whether the soil covering the seedling ball has been washed away by watering. If it has been washed away, take fine dry soil and cover it again to prevent the root system from being damaged due to rapid water loss of the matrix.

[0168] The roots are easily injured during transplanting, causing root damage. After planting, water once every three days with 150μg·ml -1 The control group CK was irrigated with normal seedling-accelerating water every three days.

[0169] Seedling hardening refers to the period of time plants need to adapt to their new environment and recover their growth capacity after transplanting, repotting, or changing environments. During this process, the plant's root system primarily grows and recovers, while above-ground growth is less pronounced. The duration of this hardening period depends on the plant species and specific circumstances. Large, woody plants may experience a longer hardening period, lasting from one week to two months, while small seedlings and herbaceous plants may experience a shorter hardening period, requiring only one to two days to recover. Melon hardening typically takes about seven days.

[0170] After 7 days, the transplanted seedlings survived successfully. Compared with the control group (CK) irrigated with normal seedling water, the transplanted seedlings irrigated with carbon dot aqueous solution had longer roots, more root hairs, and stronger plant growth ( Figure 22 ).

[0171] Comparative Example 1

[0172] In order to further prove whether carbon quantum dots prepared from other plants have the same effect on the growth of adventitious roots of melon seedlings, the inventors used cucumber straw (specifically cucumber stems) to prepare corresponding carbon quantum dots (the preparation method is the same as that in Example 2).

[0173] After the roots of the normally growing melon seedlings were cut off, they were placed in 150 μg·mL -1 tomato straw carbon dots aqueous solution and 150 μg·mL -1 The cucumber straw carbon dots were treated in aqueous solution for 7 days, and seedlings were randomly selected for phenotypic observation. The data were statistically analyzed and the results are shown in Table 2, where CK is water treatment:

[0174] Table 2

[0175]

[0176] According to phenotypic observations, although the carbon quantum dots prepared from cucumber straw promoted the adventitious roots of melon seedlings, their effect was weaker than that of the carbon quantum dots prepared from tomato straw (Table 2).

[0177] Data in Table 2 show that the TS-CDs-treated melon root length, root surface area, root projected area, root volume, average root diameter, total root tips, number of branches, and number of intersections increased by 21.89%, 29.85%, 29.83%, 36.67%, 33.25%, 14.77%, 40.94%, and 44.33%, respectively, compared to the CK. The CS-CDs-treated melon root length, root surface area, root projected area, root volume, average root diameter, total root tips, number of branches, and number of intersections increased by 2.47%, 5.60%, 5.59%, 9.36%, 5.63%, 10.49%, 12.81%, and 1.03%, respectively, compared to the CK. The TS-CDs-treated melon showed a more significant effect.

[0178] Comparative Example 2

[0179] Li Jingrui et al. (2020) used the melon variety 'Xizhou Mi No. 25' as the experimental material and used GR24 and IAA to experiment on the growth of melon radicle and adventitious roots. They found that GR24 and IAA treatments had significant regulatory effects in promoting the growth of melon radicle and adventitious roots, and the interaction and concentration effects were obvious.

[0180] GR24 is a synthetic chemical based on the strigol framework. In 2008, researchers in France, Japan, Australia, and other countries confirmed that strigol can inhibit aerial branching in plants, along with other hormones. It is the seventh major class of plant hormones. Due to its instability in soil, GR24 is currently primarily used as a laboratory research material. This is because GR24 is affected by soil temperature and concentration, degrading more rapidly at higher temperatures and at higher concentrations. Therefore, it is not suitable for conventional agricultural promotion.

[0181] Indole-3-acetic acid (IAA) is a plant growth regulator. It is a plant hormone analogue and plays an important role in plant growth and development.

[0182] Because the concentration effect of growth hormone is trace, and it has either a growth-promoting or growth-inhibiting effect at different concentrations, it is inconvenient to use. The inventors found that the tomato straw carbon dots of the present application can promote growth at a concentration of no more than 200ng / ml.

[0183] At the same time, some growth hormones not only have a certain effect on plants, but also affect other organisms to a certain extent after decomposition, affecting the ecological balance. Carbon dots, as a carbon source, have good safety and stability, and are not suspected of affecting other organisms while maintaining ecological balance.

[0184] In addition, the price of growth hormone is relatively expensive, which increases unnecessary production costs. Carbon dots, as the main way to utilize waste, greatly reduce production costs, can greatly reduce expenses in price, increase product revenue, and can be suitable for agricultural promotion.

[0185] In addition, both macroelements and trace elements can promote plant rooting. For example, fertilizers that promote plant rooting are mainly nitro-based fertilizers, and high nitrogen and high phosphorus can promote root growth (Rui Wenli et al., 2012). However, due to the excessive use of chemical fertilizers and hormone substances, the soil has become seriously salinized, the soil has become compacted, and the soil microbial environment has become disordered, resulting in a decline in the yield and quality of most fruits, vegetables and crops. Therefore, in the process of field fertilization, organic fertilizers and pollution-free effective substances should be preferred to contribute to the early realization of "carbon neutrality" and "carbon peak". Therefore, the tomato straw carbon dots in the technical solution of this application have good prospects for agricultural promotion.

[0186] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing tomato straw carbon dots, characterized in that: The following steps are involved: (1) Crush the tomato straw; (2) Weigh tomato straw powder, add water at a mass ratio of 1:(90-110), and continue ultrasonic treatment for 25-35 minutes; transfer the suspension to a reactor and heat at 160-180°C for 8-9 hours; (3) Centrifuging the resulting mixture at 3000 r / min-8000 r / min for 15-35 min; after centrifugation, collecting the supernatant and filtering it to obtain a liquid product; (4) dialyzing the obtained liquid product; (5) The dialysis solution was freeze-dried to prepare tomato straw carbon dots with down-conversion energy properties.

2. The preparation method according to claim 1, wherein: The filtration in step (3) is vacuum filtration, and the pore size of the filter membrane used in the vacuum filtration is 0.22 μm-0.6 μm.

3. A tomato straw carbon dot, characterized in that: The tomato straw carbon dots are prepared from tomato straw, which is obtained using the preparation method described in any one of claims 1-2. The tomato straw carbon dots have down-conversion energy characteristics, and the peak value of the emitted light is at 455 nm under 350 nm excitation light. The tomato straw carbon dots have an amorphous structure, and the surface of the carbon dots contains hydrophilic groups.

4. Use of the tomato straw carbon dots according to claim 3 in promoting the growth of melon roots.

5. The use of the tomato straw carbon dots according to claim 3 in promoting the root growth of melons in saline-alkali soil environments, characterized in that: The salt content of the saline-alkali land includes 0.1-0.2%, 0.2-0.4%, and 0.4-0.6%.

6. A melon root promoting agent, characterized in that The active ingredient of the root promoting agent is the tomato straw carbon dots described in claim 3, with a concentration not higher than 200 μg·ml -1 .

7. A melon growth aid in saline-alkali land environment, characterized in that: The active ingredient of the melon growth promoter is the tomato straw carbon dots described in claim 3, with a concentration not higher than 200 μg·ml -1 .

8. A method for growing melon seedlings, characterized in that: The method includes soaking seeds and accelerating germination, wherein the concentration used in the soaking and germination process is 50-200 μg·ml -1 Melon seeds are treated with the tomato straw carbon dot aqueous solution according to claim 3.

9. A method for growing muskmelon in a saline-alkali soil environment, characterized in that: The method comprises the following steps: during the melon planting process, treating the melon seeds with a tomato straw carbon dot aqueous solution and then transplanting them to saline-alkali land, and / or treating the melon seedlings with a tomato straw carbon dot aqueous solution and then transplanting them to saline-alkali land, and / or planting the melon seeds or melon seedlings in the saline-alkali land and then watering them with the tomato straw carbon dot aqueous solution; the tomato straw aqueous solution is the tomato straw carbon dot aqueous solution according to claim 3; the salt content of the saline-alkali land comprises 0.1-0.2%, 0.2-0.4%, and 0.4-0.6%.

Images