Method for improving crop growth and stress resistance through seed germination accelerating treatment by using carbon dots

Abstract

The invention belongs to the technical field of agriculture, and particularly relates to a method for improving crop growth and stress resistance through seed germination acceleration treatment by using carbon dots. The method comprises the following steps: preparing carbon dots into a carbon dot solution, soaking crop seeds of which the surfaces are disinfected by using the carbon dot solution, carrying out shading constant-temperature culture until the crop seeds germinate and grow into seedlings, and then transplanting the seedlings to light without carbon dot exposure for culture. The carbon dots are prepared from a carbon-containing chemical reagent or a biomass material through microwave heating in a medium. According to the method, the effects of promoting plant growth and improving stress resistance for a long time are achieved through one-time germination accelerating treatment, the economic cost and the labor cost of agricultural production are reduced to the maximum extent, and the influence of agricultural input on the environment is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of agriculture, and in particular relates to a method for improving crop growth and stress resistance by using carbon dots through seed germination treatment. Background Art

[0002] In recent years, human activities and industrial emissions have become increasingly frequent, climate change and extreme weather have become increasingly severe, and agricultural production is currently facing bottlenecks in reducing costs and increasing production, the deterioration of the natural environment for crop growth, the degradation of arable land conditions, and a high degree of dependence on resource inputs. Current agricultural production urgently needs to transform its production model towards low-cost, low-pollution, environmentally friendly and sustainable production.

[0003] Agronomic measures are traditional methods for ensuring crop growth and resisting environmental changes in agricultural production, covering tillage management, fertilizer and water management, and adjusting planting patterns. This method does not rely on the use of chemicals. It provides a suitable growth environment for crops through various measures, with controllable costs and environmental friendliness. However, this method greatly increases the labor cost of agricultural production, is not conducive to large-scale and intensive production, and has poor effects on mitigating environmental changes. Cultivating new high-yield and stress-resistant crop varieties can not only solve the purpose of maintaining and increasing crop yields, but also reduce dependence on agrochemical products and alleviate environmental burdens. However, the cultivation of new varieties is a high-cost, long-cycle job, and continuous environmental changes can easily invalidate the excellent shape of new varieties. Reasonable application of pesticides and fertilizers can effectively prevent and control pests and diseases and supplement the nutrients required by crops, promote the healthy growth of crops, and enhance their adaptability to adverse environments. This method is convenient, effective, and cost-controlled. However, excessive or improper use can lead to problems such as soil pollution, reduced crop quality, and environmental and health risks. At present, agricultural production that relies on high input of resources such as agrochemicals has entered a bottleneck period, and even a phenomenon of reduced production has occurred.

[0004] In recent years, the penetration and application of nanotechnology in agriculture have shown diversified characteristics, especially in the slow-release and precise delivery of pesticides and fertilizers, pest and disease control, plant growth and development, agricultural product quality and safety testing, and agricultural product processing, opening up an important scientific path for mankind to solve problems such as food security, resource shortages, and environmental pollution.

[0005] Carbon dots are a type of carbon-based nanomaterial with fluorescent properties. They are quasi-spherical core-shell structures with a size of less than 10 nanometers. Carbon dots have tunable photoluminescence, high water solubility, biocompatibility and negligible toxicity. They are low in cost and simple in process, making them very suitable for use in the biological, environmental and agricultural fields. In recent years, carbon dots have shown significant growth-promoting effects on plants: photoluminescence can effectively improve plant photosynthetic efficiency and become a photosynthetic enhancer; hydrophilicity can accelerate plant seed germination and plant water absorption, promoting plant growth; antibacterial and antioxidant properties can help alleviate plant biotic and abiotic stresses and improve plant health. In addition, agricultural sensors based on carbon dots can also detect plant growth status, agricultural pests and diseases, pesticide residues, etc., supporting the development of future smart sensors.

[0006] In previous research reports, carbon dots were mostly treated on plants by foliar spraying, and a few studies added carbon dots to hydroponic nutrient solutions. The effects on plants mostly depended on the continuous exposure of carbon dots, which required regular and quantitative spraying or adding of carbon dots, increasing the application dosage of carbon dots and the workload. Summary of the invention

[0007] The purpose of the present invention is to provide a method for improving crop growth and stress resistance by seed germination treatment using carbon dots, so as to achieve a single germination treatment, a long-term effect of promoting seedling growth and improving crop stress resistance.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: A method for improving crop growth and stress resistance by using carbon dots through seed germination treatment, the method comprising preparing carbon dots into a carbon dot solution, soaking surface-sterilized crop seeds with the carbon dot solution, culturing them in a light-shielding and constant-temperature environment until they germinate and grow into seedlings, and then culturing the seedlings under light without exposure to the carbon dots.

[0009] Furthermore, the carbon dots are prepared by using carbon-containing chemical reagents or biomass materials through microwave heating in a medium, wherein the carbon-containing chemical reagent is citric acid or a mixture of citric acid and ethanolamine.

[0010] Furthermore, the concentration of the carbon dot solution is 10-50 μg / mL, preferably 20 μg / mL.

[0011] Furthermore, the surface-sterilized crop seeds are obtained by soaking the crop seeds in 75% ethanol for 20 minutes.

[0012] Furthermore, the light-shielding constant temperature culture condition is culture in a dark environment at 30° C. for 3 days.

[0013] Furthermore, the stress resistance refers to the ability of crops to resist environmental stress.

[0014] Furthermore, the environmental stress is salt stress, heavy metal stress or herbicide stress.

[0015] Furthermore, the seedlings were transplanted on the 7th day after the surface-sterilized crop seeds were soaked in the carbon dot solution.

[0016] The present invention also provides application of the above method in the agricultural field.

[0017] The present invention also provides a method for promoting the development of plant cell walls and root systems using carbon dots, the method comprising preparing carbon dots into a carbon dot solution, soaking surface-sterilized plant seeds in the carbon dot solution, culturing them in a light-shielded and constant temperature environment until they germinate and grow into seedlings, and then culturing the seedlings under light without exposure to the carbon dots; the carbon dots are prepared by microwave heating in a medium using carbon-containing chemical reagents or biomass materials.

[0018] Compared with the prior art, the present invention has the following beneficial effects: Different from the immediate effects of conventional crop treatments (seed treatment focuses on seed germination, seedling treatment focuses on seedling growth, etc.), the present invention utilizes carbon dots to achieve long-term promotion of crop seedling growth and stress resistance through seed germination treatment, and does not rely on continuous exposure of carbon dots.

[0019] The method of the present invention achieves the effect of promoting plant growth and improving its stress resistance in a long term through a single germination treatment, which not only reduces the economic cost and labor cost of agricultural production to the greatest extent, but also limits the application of materials to the hydroponic seedling stage, and the nutrient solution containing the materials can be centrally processed, which greatly reduces the release of materials into the environment, thereby reducing the impact of agricultural inputs on the environment. At the same time, the carbon dots used in the method of the present invention are biodegradable in the natural environment and will not cause pollution to the soil and water environment.

[0020] In addition, in the present invention, after the surface-sterilized crop seeds are germinated by using carbon dots, the physical barrier and tolerance to environmental stress are improved by inducing the formation and strengthening of the root cell wall of the crop seedlings, while promoting the development and nutritional metabolism of the root system, enhancing its absorption, assimilation and metabolic activity of nutrients, and ultimately making the crop seedlings show vigorous growth metabolic activity and stress tolerance (resistance), so that they can maintain a high growth activity after being exposed to environmental stress. This is obviously different from the role of carbon dots in promoting growth and development by improving crop photosynthesis and antioxidant defense systems in previous research reports. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1The characterization results of the carbon dot material prepared in Example 1: Figures (a)-(d) are the transmission electron microscopy, particle lattice fringes, particle size distribution and diffraction spot diagram of carbon dots; Figure (e) is the FTIR spectrum of carbon dots; Figures (f)-(h) are the XPS full spectrum and C1s, O1s high-resolution spectrum of carbon dots; Figure (i) is the thermogravimetric spectrum of carbon dots; Figures (j)-(k) are the 1 H and 13 C NMR spectrum.

[0022] Figure 2 Figure 3 shows the growth of rice seedlings treated with carbon dot solutions of different concentrations. Figure (a) shows the growth photos of rice seedlings on the 5th, 7th and 14th days; Figures (b)-(e) show the root length, root surface area, root volume and stem and leaf surface area of ​​rice seedlings on the 5th and 7th days, respectively; Figures (f)-(g) show the plant height, root length, stem and leaf length and total fresh weight, root fresh weight and stem and leaf fresh weight of rice seedlings on the 24th day, respectively.

[0023] Figure 3 Figures 2 and 3 show the root characteristics of rice seedlings treated with 20 μg / mL carbon dot solution for germination, where (a)-(b) are scanning electron micrographs of the roots of rice seedlings treated with carbon dots and in the control group, respectively; (c)-(d) are transmission electron micrographs of the roots of rice seedlings treated with carbon dots and in the control group, respectively; (e)-(f) are paraffin sections of the roots of rice seedlings treated with carbon dots and stained with safranin-fast green, respectively.

[0024] Figure 4 Figure 1 shows the germination of rice seeds and the nutrient assimilation activity of seedling roots after being germinated with carbon dots at different concentrations. Figures (a) and (b) show the imbibition rate and germination rate of rice seeds germinated with carbon dots, respectively. Figures (c) and (e) show the Ca2+ activity of rice seedling roots in the control and carbon dots-treated rice seedlings tested with non-damage micro-measurement technology, respectively. 2+ , K + and Na + Figure (f) shows the root activity of rice seedlings treated with carbon dots and in the control group; Figure (g) shows the relative expression levels of water channel protein genes and salt stress resistance genes in the roots of rice seedlings treated with carbon dots and in the control group.

[0025] Figure 5 The growth of rice seedlings germinated with 20 μg / mL carbon dot solution and then exposed to salt stress, heavy metal cadmium stress, and herbicide 2,4-D stress: (a) root length, (b) root surface area, (c) root volume, (d) stem and leaf area, (e) stem and leaf length, and (f) total fresh weight of seedlings. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0027] Example 1 Preparation of carbon dot materials Carbon dots were prepared by microwave-assisted method using citric acid as raw material. First, citric acid (2.1 g) was dissolved in ultrapure water (20 mL) and heated in a household microwave oven at medium heat (350 W) until a yellow colloidal substance was formed. Shake every 5 min to ensure uniform reaction. The reaction will undergo two processes: rapid water removal and carbonization. The obtained carbon dot sample was redispersed in ultrapure water and filtered with a filter head with a pore size of 0.22 μm. The sample was freeze-dried and fixed to 100 mg / mL and stored at room temperature.

[0028] like Figure 1 As shown in ad, the carbon dot material prepared by the present invention is a nearly spherical nanoparticle with clear lattice fringes, a lattice spacing of 0.21 nm, an average particle size of 3.44 nm, and its symmetrical transmission electron microscope diffraction spots indicate that it has good crystallinity.

[0029] Fourier infrared spectrum of carbon dots ( Figure 1 e) shows that the carbon dots have stretching vibration peaks of OH, C=O, and CO and bending vibration peaks of OH, indicating that the surface of the carbon dots has a carboxyl (-COOH) or hydroxyl (-OH) structure, which makes the carbon dots have excellent hydrophilicity and colloidal stability.

[0030] By X-ray photoelectron spectroscopy (XPS) ( Figure 1 fh) It can be seen that the carbon dots mainly contain two elements, C and O, and exist mainly in the forms of CC, CO and C=O, corresponding to the carbonaceous core, carboxyl and hydroxyl surface chemical structures of the carbon dots.

[0031] Thermogravimetric analysis found that the carbon dot material decomposed rapidly between 150-235°C, which was an endothermic reaction ( Figure 1 i). Utilization 1 H and 13 C NMR analysis revealed that both fatty chain structures and ring structures exist in carbon dot materials ( Figure 1 jk).

[0032] Through the above characterization results, it can be found that the carbon dots prepared by the present invention are carbon nanoparticles with a core-shell structure of extremely small particle size, with a carbonaceous core inside and carboxyl-like and hydroxyl-like functional groups on the surface, which make the carbon dots have good water solubility and colloidal stability, and facilitate their application in biological systems to pass through biological barriers into cells and interact with biological components, and can keep the carbon dots stable in biological cells, avoid damage to biological structures and components, and improve the biocompatibility of carbon dots. At the same time, the extremely small particle size of the carbon dots gives them extremely high specific surface area and reactivity, and in the interaction with biological systems, they can exert the maximum biological efficacy with the minimum dosage, reduce resource input, reduce environmental release, and alleviate environmental burden. The low thermal decomposition temperature of the carbon dot material indicates that its chemical structure is easy to decompose, and its carbonaceous components make it easy to degrade in the environment, avoiding environmental accumulation and environmental toxicity.

[0033] Example 2 Effect of seed germination treatment using carbon dots on the growth of rice seedlings The rice seedling experiment was conducted in a greenhouse. First, rice seeds (Huahang 31) were surface sterilized by soaking in 75% ethanol for 20 min, and then cultured in a dark environment at 30°C with deionized water (control) and 10 μg / mL, 20 μg / mL, and 50 μg / mL carbon dot solutions. After 3 days, the germinated rice seeds were cultured under light without carbon dot exposure. On the 7th day, the rice seedlings were transplanted into square plastic pots filled with seedling substrate. Three parallel replicates were set for all treatments. All rice seedlings were cultured in a greenhouse (about 30°C during the day and about 26°C at night). After 3 weeks, the rice seedlings of each treatment were collected and their plant height, biomass, and chlorophyll content were measured.

[0034] Figure 2 The growth status of rice seedlings after the seeds were treated with carbon dot solutions of different concentrations prepared in Example 1 for germination. It can be found from the figure that the root growth of rice seeds can be significantly promoted on the 5th day of carbon dot solution germination treatment, among which the promotion effect of the 20μg / mL carbon dot solution treatment group is the best. After the germination of rice seedlings is removed from the carbon dots, its growth advantage can be maintained until the 24th day (longer data are not measured). At the appropriate treatment dose, the length, surface area and volume of the root system of rice seedlings and the surface area of ​​stems and leaves are significantly promoted on the 7th and 14th days ( Figure 2 ae). At 24 days after treatment, the plant height, stem and leaf length, root length, total fresh weight, stem and leaf fresh weight, and root fresh weight of rice seedlings treated with carbon dots were also significantly increased ( Figure 2 fg).

[0035] The above results show that the method of the present invention achieves the effect of promoting the growth of crop seedlings in a long term through a single germination treatment. In the application, the carbon dots exposed the root system of the rice seedlings and promoted the development of the root system. The root system is the main nutritional organ of the plant, responsible for obtaining water and nutrients from the environment. Carbon dots promote the development of the rice root system, which can improve the nutrient assimilation and metabolic capacity of rice seedlings and promote plant growth vitality.

[0036] Figure 3 The microscopic and anatomical structures of the roots of rice seedlings treated with the control and 20 μg / mL carbon dot solution were shown. Figure 3 The scanning electron microscopy images of ab show that the amount of microorganisms attached to the root surface of rice seedlings treated with carbon dots increased significantly compared with the control group. Figure 3 The projection electron micrograph of cd shows that the root cells of rice seedlings treated with carbon dots have increased in volume, irregular shapes, thickened cell walls, and the distribution of carbon dots can be observed in the cells. Figure 3 ef), it was found that the lignification and corkification of the root cell walls of rice seedlings treated with carbon dots increased, and the vascular tissue was more developed.

[0037] The above results show that the roots of rice seedlings treated with carbon dots can recruit and attach more microorganisms, mediate interactions with microorganisms and promote nutrient assimilation activity. In addition, carbon dots also enhance the physical barrier protection of seedling roots against the external environment and the transport capacity for nutrient absorption by strengthening cell walls and high tube tissue. The enlargement and irregular morphology of root cells indicate that carbon dots enhance the metabolic activity and cell proliferation activity in root cells.

[0038] Figure 4 Figure 3 shows the imbibition rate and development rate of rice treated with different concentrations of carbon dot solution (Figure a, b) and the nutrient assimilation capacity of the seedling root system (Figure ce). It can be seen that during the seed soaking process, carbon dots had no significant effect on the imbibition and germination process of rice seeds, but promoted the Ca assimilation of the rice seedling root system. 2+ The inflow, K + outflow, improving root vitality (Figure f) and aquaporin genes ( OsPIP1 1. OsPIP1 ;3) and salt stress tolerance genes ( OsSOS1 , OxY ) expression (Figure g).

[0039] The above results show that soaking seeds in the carbon dot solution of the present invention does not significantly affect the germination process of seeds. Instead, the carbon dots are absorbed into the rice seedling tissue during seed germination, which improves the metabolic activity of the rice seedling root system and its ability to absorb water and nutrients. At the same time, the carbon dot treatment regulates the Ca content of the rice seedling root system. 2+ and K + The steady state of the seedlings can promote the osmotic balance of the root system and improve the tolerance of the seedlings to environmental stress. This phenomenon is obviously different from the results of promoting germination by soaking seeds in other inventions.

[0040] Example 3 Effect of seed germination treatment using carbon dots on stress resistance of rice seedlings After the rice germinated with 20 μg / mL carbon dot solution was transplanted to an environment exposed to stress (salt stress, heavy metal cadmium stress, herbicide 2,4-D stress), Figure 5 As shown, compared with the control, the seedlings treated with carbon dots showed significantly increased growth and development rate, including root length (a), root surface area (b), root volume (c), stem and leaf area (d), stem and leaf length (e) and total fresh weight of seedlings (f).

Claims

1. A method for improving crop growth and stress resistance by seed germination treatment using carbon dots, characterized in that: The method comprises preparing carbon dots into a carbon dot solution, soaking surface-sterilized crop seeds in the carbon dot solution, culturing them at a constant temperature and in a shaded manner until they germinate and grow into seedlings, and then culturing the seedlings under light without exposure of the carbon dots.

2. The method according to claim 1, characterized in that The carbon dots are prepared by using carbon-containing chemical reagents or biomass materials through microwave heating in a medium.

3. The method according to claim 2, characterized in that The carbon-containing chemical reagent is citric acid or a mixture of citric acid and ethanolamine.

4. The method according to claim 1, characterized in that: The concentration of the carbon dot solution is 10-50 μg / mL.

5. The method according to claim 1, characterized in that The surface-sterilized crop seeds are obtained by soaking the crop seeds in 75% ethanol for 20 minutes.

6. The method according to claim 1, characterized in that The light-shielding constant temperature culture condition is culture in a dark environment at 30° C. for 3 days.

7. The method according to claim 1, characterized in that The stress resistance refers to the ability of crops to resist environmental stress.

8. The method according to claim 7, characterized in that The environmental stress is salt stress, heavy metal stress or herbicide stress.

9. Application of the method according to any one of claims 1 to 8 in the agricultural field.

10. A method for promoting plant cell wall and root development using carbon dots, characterized in that: The method comprises the following steps: preparing carbon dots into a carbon dot solution, soaking surface-sterilized plant seeds in the carbon dot solution, culturing them under light-shielding and constant temperature to make them germinate and grow into seedlings, and then culturing the seedlings under light without exposure of carbon dots; the carbon dots are prepared by using carbon-containing chemical reagents or biomass materials through microwave heating in a medium.

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