Oyster shell-starch sludge carbon quantum dot and application thereof as pepper growth promoter

Abstract

The invention discloses oyster shell-starch sludge carbon quantum dots and application thereof as a pepper growth promoter, and belongs to the technical field of organic fertilizers, soil improvement and waste utilization. Comprising the following steps: crushing oyster shells, mixing the crushed oyster shells with starch sludge, performing hydrothermal reaction, centrifuging, taking supernate, dialyzing, freezing and drying. The promoter can be used for enhancing photosynthesis of pepper leaves, promoting growth and yield increase of pepper in saline-alkali soil, and can be used as a promoter for growth and yield increase of pepper in saline-alkali soil. The plant height, stem diameter, leaf length, leaf width and fresh weight of the pepper treated by the oyster shell starch sludge carbon quantum dots are obviously improved. The maximum quantum yield, the actual photosynthesis efficiency, the absolute electron conductivity and the non-photochemical quenching coefficient of pepper plants can be obviously improved. The plant height, stem diameter, leaf area and single plant yield of pepper plants can be obviously improved when the fertilizer is applied to the field. After the calcium-doped carbon quantum dots are treated, the growth and development of the saline-alkali soil peppers are promoted, the photosynthesis of the saline-alkali soil peppers is promoted, and the yield of the peppers is increased.

Description

Technical Field

[0001] This invention relates to oyster shell-starch sludge carbon quantum dots and their application as a chili pepper growth promoter, belonging to the fields of organic fertilizer, soil improvement and waste utilization technology. Background Technology

[0002] Photosynthesis is the core process of plant growth and development. It converts light energy into chemical energy, synthesizes organic matter, and releases oxygen, providing plants with energy and carbon sources. The efficiency of photosynthesis directly affects plant biomass accumulation, growth, development, and stress resistance. First, photosynthesis generates ATP and NADPH through light and dark reactions and fixes carbon dioxide to form carbohydrates. These products are the material basis for plant cell division, elongation, and differentiation. Second, photosynthesis is closely related to plant nutrient absorption and metabolism. For example, the assimilation of nutrients such as nitrogen and phosphorus depends on the energy and carbon skeleton provided by photosynthesis. Studies have shown that plants with high photosynthetic efficiency typically exhibit stronger growth potential, higher yields, and better stress resistance (such as salt and drought resistance). Therefore, optimizing photosynthetic efficiency is one of the key ways to improve plant growth performance and agricultural productivity. Chloroplasts, as important organelles in plant photosynthesis, can only absorb light of specific wavelengths, and less than 10% of solar energy is absorbed and utilized by plants. This means that cells participating in photosynthesis cannot maximize the use of solar energy. Therefore, improving the utilization rate of solar energy in photosynthesis is crucial for promoting plant growth.

[0003] Carbon quantum dots (CQDs) are carbon-based zero-dimensional nanomaterials with excellent optical properties, good water solubility, and low toxicity. The fluorescence properties of CQDs can maximize solar absorption and its conversion into effective radiation for photosynthesis by regulating plant absorbance and fluorescence. CQDs can increase chlorophyll content in the light-dependent reactions, enabling chloroplasts to capture more light energy and simultaneously improving electron transfer efficiency, thus enhancing the activity of the photosystem and promoting ATP production, providing more impetus for carbon fixation in the dark reactions. Particularly noteworthy is that CQDs prepared from biomass raw materials not only possess the aforementioned photosynthetic-promoting properties but also demonstrate greater potential for agricultural applications due to their excellent biocompatibility and environmental friendliness.

[0004] Sweet potato starch is a common commodity, and its production process generates a large amount of sludge. However, the utilization rate of this sludge is very low; it is usually transported to a drying plant for stockpiling after simple mechanical dehydration, resulting in a significant waste of resources. Starch sludge is rich in organic matter and can provide a carbon source for the preparation of carbon quantum dots. China has the world's largest number and scale of shellfish farming, with more than 20 main farmed species including clams, oysters, and scallops. Oyster shells, as waste generated during aquatic product processing, are rich in calcium carbonate, a natural calcium source. Calcium plays an important role in plant growth and development and is one of the essential nutrients for plant growth. In particular, it participates in the structure of the oxygen-evolving complex of photosystem II (PSII) in plant photosynthesis, regulating the activity of cytochromes in the photosynthetic electron transport chain. Calcium deficiency can lead to chloroplast structure damage, hindered electron transport, and reduced enzyme activity, all of which affect plant growth and development. However, research on the properties of carbon quantum dots prepared by co-pyrolysis of oyster shell powder and sweet potato starch sludge, and their effects on pepper growth and photosynthesis, is still lacking. Summary of the Invention

[0005] The purpose of this invention is to provide oyster shell-starch sludge carbon quantum dots made from oyster shell powder and starch sludge produced in factories; to provide the application of the above-mentioned oyster shell-starch sludge carbon quantum dots in enhancing the photosynthesis of pepper leaves, promoting the growth and yield of peppers in saline-alkali land, and the application of the above-mentioned oyster shell-starch sludge carbon quantum dots as a growth and yield promoter for peppers in saline-alkali land; and to provide a method for promoting the growth and increasing the yield of peppers in saline-alkali land by enhancing the photosynthesis of pepper leaves, so as to overcome the defects and deficiencies of the prior art.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution: An oyster shell-starch sludge carbon quantum dots (CQDs / Ca) method is characterized in that the oyster shell-starch sludge carbon quantum dots are prepared according to the following method: Mix the crushed oyster shells with starch sludge. The above mixture was subjected to a hydrothermal reaction; The product after the hydrothermal reaction was centrifuged, the supernatant was collected and dialyzed, and the resulting liquid was freeze-dried to obtain powdered oyster shell-starch sludge carbon quantum dots.

[0007] The oyster shell crushing process involves washing the oyster shells, crushing them, and then passing them through a 50-mesh sieve.

[0008] The starch sludge is sweet potato starch sludge.

[0009] The crushed oyster shells and sweet potato starch sludge are mixed in a ratio of 1~1:1~2.

[0010] The temperature of the hydrothermal reaction is 180~220℃.

[0011] The hydrothermal reaction time is 6-8 hours.

[0012] The oyster shell-starch sludge carbon quantum dots provided by the above-described method of the present invention are used to enhance the photosynthesis of pepper leaves and promote the growth and yield of peppers in saline-alkali land. This relates to the application of the above-described oyster shell-starch sludge carbon quantum dots as a growth and yield promoter for peppers in saline-alkali land.

[0013] A method for promoting the growth and increasing the yield of chili peppers in saline-alkali land is characterized by applying oyster shell-starch sludge carbon quantum dots to the soil where chili peppers are planted every 7-30 days.

[0014] The concentration of carbon quantum dots from oyster shells and starch sludge applied each time is 0.1~0.5 μg / dot.

[0015] The calcium-doped carbon quantum dots produced by this invention using oyster shell powder and starch sludge from factories have the following beneficial effects: This invention proposes a method for the resource utilization of starch sludge and oyster shell waste from sweet potato factories, which can make full use of waste resources, is low in cost and conforms to the concept of environmental protection.

[0016] In this invention, carbon quantum dots (CQDs / Ca) from oyster shell sludge have a synergistic effect on the early growth of chili pepper plants, including plant height, stem diameter, leaf length, leaf width, and fresh weight.

[0017] In this invention, the maximum quantum yield, actual photosynthetic efficiency, absolute electron conductivity, and non-photochemical quenching coefficient of the pepper plants after the addition of CQDs / Ca were significantly higher than those of the control group.

[0018] In this invention, the application of CQDs / Ca in the field increases the plant height, stem diameter, and leaf area of ​​chili pepper plants. Furthermore, the addition of CQDs / Ca increases the yield per plant and the length of the fruit. Attached Figure Description

[0019] Figure 1 The image shows the structural characterization of CQDs / Ca prepared in Example 1, where A is the fluorescence spectrum of CQDs / Ca and B is the Fourier transform infrared spectrum of CQDs / Ca.

[0020] Figure 2 The images show the phenotypic patterns of small potted chili pepper plants after application of calcium-doped carbon quantum dots and before application. In the image, A shows the phenotypic patterns of chili pepper plants after 20 days of application and before application; B shows the phenotypic patterns of chili pepper plants after 40 days of application and before application.

[0021] Figure 3This is a statistical chart showing the morphological data of chili pepper plants in small pots after application of calcium-doped carbon quantum dots and before application. In the chart, A represents the plant height at 20 and 40 days; B represents the stem diameter at 20 and 40 days; C represents the leaf length at 20 and 40 days; D represents the leaf width at 20 and 40 days; E represents the fresh weight of the chili peppers at 20 and 40 days; and F represents the root activity at 20 and 40 days.

[0022] Figure 4 This is a statistical chart showing the chlorophyll a and b content of pepper leaves in small potted plants after application of calcium-doped carbon quantum dots and before application. In the chart, A represents the chlorophyll a content of pepper leaves after 20 and 40 days; B represents the chlorophyll b content of pepper leaves after 20 and 40 days; and C represents the total chlorophyll content of pepper leaves after 20 and 40 days.

[0023] Figure 5 Statistical graphs of chlorophyll fluorescence data of pepper leaves after application and without application of calcium-doped carbon quantum dots in small potted plants. A represents the maximum photochemical quantum yield of pepper leaves at 20 and 40 days; B represents the light energy utilization rate of pepper leaves at 20 and 40 days; C represents the electron transport rate of pepper leaves at 20 and 40 days; and D represents the non-photochemical quenching of pepper leaves at 20 and 40 days.

[0024] Figure 6 These are in vivo images of small potted pepper plants after 40 days. Image A is an in vivo image of a pepper plant without calcium-doped carbon quantum dots after 40 days; image B is an in vivo image of a pepper plant with calcium-doped carbon quantum dots after 40 days; image C is an in vivo image of a leaf after 40 days without calcium-doped carbon quantum dots; and image D is an in vivo image of a leaf after 40 days with calcium-doped carbon quantum dots.

[0025] Figure 7 Confocal images of root, stem, and leaf sections of chili peppers after application and without calcium-doped carbon quantum dots (CQDs / Ca) in small potted plants are shown. A is a 40-day confocal image of the root system of the control group; B is a 40-day confocal image of the root system after CQDs / Ca application; C is a 40-day confocal image of the stem system of the control group; D is a 40-day confocal image of the stem system after CQDs / Ca application; E is a 40-day confocal image of the leaf system of the control group; and F is a 40-day confocal image of the leaf system after CQDs / Ca application.

[0026] Figure 8 Microscopic images of chloroplasts under bright field, 515-565 nm and 361-389 nm excitation.

[0027] Figure 9 Microscopic imaging of chloroplasts and CQDs / Ca complexes under bright field excitation at 515–565 nm and 361–389 nm.

[0028] Figure 10The apparent morphology of peppers in saline-alkali soil with and without CQDs / Ca applied in field experiments.

[0029] Figure 11 Plant height of peppers in saline-alkali soil with and without CQDs / Ca applied in field experiments.

[0030] Figure 12 The stem diameter of peppers in saline-alkali soil with and without CQDs / Ca application was compared in a field experiment.

[0031] Figure 13 Leaf area of ​​peppers in saline-alkali soil with and without CQDs / Ca applied in field experiments.

[0032] Figure 14 The yield per plant of chili peppers in saline-alkali soil with and without CQDs / Ca application was compared in a field experiment.

[0033] Figure 15 The apparent morphology of peppers in saline-alkali soil with and without CQDs / Ca applied in field experiments. Detailed Implementation Plan

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the following embodiments are commercially available.

[0035] I. Synthesis of CQDs / Ca Nanomaterials Oyster shell powder and starch sludge were mixed by ball milling at a mass ratio of 1:1:1:2. For example, 30 g of oyster shell powder and 30-60 g of starch sludge were placed in a reaction vessel through a 100-mesh sieve, and 100 mL of distilled water was added. The mixture was then subjected to hydrothermal reaction at 200℃ for 8 h. After cooling, the mixture was centrifuged at 4000 r / min for 10 min. The supernatant was filtered through a 0.22 μm hydrophilic membrane and dialyzed using a 1000 Da dialysis bag for 24 h. Finally, the resulting liquid was freeze-dried to obtain CQDs / Ca powder.

[0036] II. Characterization of CQDs / Ca nanomaterials The surface functional group structure of CQDs / Ca was analyzed using Fourier transform infrared spectroscopy. For example... Figure 1 Fourier transform infrared spectrum at 3020 cm⁻¹ is shown in Figure A. -1 2270-2100 cm -1 1506 cm -1The peak at 1460 cm⁻¹ corresponds to the NH / OH, C≡C, and C=O functional groups. -1 and 900 cm -1 The differences are attributed to the -Ca and Ca-O bonds, respectively. Infrared data shows that CQDs / Ca is rich in oxygen-containing functional groups, which determines its ideal water solubility and makes it easier for plants to absorb and utilize. This also demonstrates the successful doping of calcium.

[0037] As can be seen from the fluorescence spectrum ( Figure 1 (B) CQDs / Ca exhibit wavelength-dependent emission under excitation light in the range of 330 nm to 420 nm. The fluorescence intensity initially increases and then decreases with increasing excitation wavelength, reaching a maximum of 2299 au under excitation at 380 nm.

[0038] III. Phenotypic and morphological indicators of small potted peppers grown in saline-alkali soil on days 20 and 40 after applying CQDs / Ca. Experimental methods: Chili seeds were soaked in a water bath at 50℃ for 15 minutes, then continued to soak at room temperature for 8 hours, and finally placed in the dark for 3 days. Once the seeds showed signs of germination, they were sown in seedling trays (the substrate was peat moss: perlite: vermiculite = 2:1:1). After germination to the three-leaf stage, seedlings with uniform growth were selected for transplanting, with two seedlings transplanted per pot of saline-alkali soil. At transplanting, 5 mL of nutrient solution was added to each pot. The nutrient solution consisted of urea (7.43 g / L), dipotassium hydrogen phosphate (2.16 g / L), and potassium sulfate (3.87 g / L).

[0039] The control group of potted pepper plants received no further treatment. The treatment group of potted plants were watered with 5 mL of 0.5 mg / L CQDs / Ca solution on days 7, 14, 21, 28, and 35.

[0040] Plant height, stem diameter, leaf length, leaf width, chlorophyll content, and chlorophyll fluorescence were measured on days 20 and 40 after the peppers were transplanted into pots. Destructive sampling was performed on the plants on days 20 and 40.

[0041] Experimental results: Figure 2 A, Figure 2 B represents the morphological differences between the control and treatment groups of chili pepper plants on days 20 and 40. It can be seen that the addition of CQDs / Ca has a significant growth-promoting effect on chili pepper plants.

[0042] Figure 3A, B, C, and D show that the plant height, stem diameter, leaf length, and leaf width were significantly increased after adding CQDs / Ca compared to the control group. Figure 3 Figures E and F show a significant improvement in both the fresh weight of the peppers and root activity. This indicates that the application of CQDs / Ca can promote the early growth of pepper plants.

[0043] Figure 4 A, B, and C represent the chlorophyll a, b, and total chlorophyll contents of pepper leaves in the control and experimental groups on days 20 and 40, respectively. It can be seen that the chlorophyll content of pepper plants treated with CQDs / Ca is significantly higher than that in the control group. This indicates that the addition of CQDs / Ca can increase the chlorophyll content in leaves, thereby enhancing photosynthesis.

[0044] Figure 5 A, B, C, and D represent the chlorophyll fluorescence intensity values ​​of pepper leaves in the control and experimental groups after 20 and 40 days, respectively. It can be seen that the chlorophyll fluorescence data of pepper plants treated with CQDs / Ca are all greater than those in the control group, further indicating that the addition of CQDs / Ca has a certain promoting effect on photosynthesis in pepper leaves.

[0045] IV. In vivo imaging of CQDs / Ca-treated pepper plants Experimental methods: Destructive sampling was performed on chili plants from the control and experimental groups after 40 days. The entire plant and leaves were placed in a live imaging instrument with an excitation wavelength of 380 nm.

[0046] Experimental results: Figure 6 Carbon quantum dots were observed in various parts of the chili pepper plants treated with CQDs / Ca 40 days later. Fluorescence was also observed on the leaf veins, indicating that CQDs / Ca was absorbed by the chili pepper roots and transported upwards to the leaves.

[0047] V. Confocal microscopy of roots, stems, and leaves of CQDs / Ca-treated pepper plants Experimental plan: Pepper roots, stems, and leaves from the above experimental materials were embedded in paraffin and sectioned. The samples were imaged using a laser confocal microscope. The parameters were set to 10x objective lens and PMT1: 405, 488 laser excitation.

[0048] Experimental results: Figure 7 The distribution of CQDs / Ca in the roots, stems, and leaves of the control and experimental groups was measured after 40 days. The results showed that CQDs / Ca was present in the roots, stems, and leaves of peppers treated with CQDs / Ca, indicating that CQDs / Ca can enter and exert its effects in various parts of the pepper plant.

[0049] VI. Exposure of isolated chloroplasts to CQDs / Ca and their photosynthetic activity Experimental plan: A chloroplast suspension containing 10 mg / L chlorophyll was mixed with CQDs / Ca at 10 mg / L in the dark. After 1 hour, the chloroplast-CQDs / Ca complex (CQDs / Ca@Chl) was obtained by centrifugation at 3000 rpm for 3 min at 4 °C. The distribution of CQDs / Ca in the chloroplasts was observed using a Nikon ECLIPSE Ti 2-U microscope equipped with a Nikon DS-Ri 2 camera. The fluorescence of the chloroplasts and the CQDs / Ca@Chl suspension was recorded.

[0050] Experimental results: Compared with the control, CQDs / Ca induced no significant changes in chloroplast morphology. Figure 8 and Figure 9 Under inverted fluorescence microscopy with excitation at 361-389 nm, CQDs / Ca@Chl emitted a blue fluorescent signal, indicating that CQDs / Ca@Chl were internalized by chloroplasts; under excitation at 515-565 nm, chlorophyll molecules on the thylakoid membrane emitted a red fluorescent signal. Figure 3 In F, the blue fluorescence signal overlaps with the red fluorescence signal, indicating that CQDs / Ca and chlorophyll molecules are distributed similarly in chloroplasts. These results confirm that CQDs / Ca excited by UV light can be absorbed by chloroplasts.

[0051] VII. Field Experiment Application Experimental plan: In the field experiment, 500 mL of CQDs / Ca (0.03 g / mL) was added to 4 L of water to form a homogeneous mixture. Three 3 m x 3 m quadrats were divided into five replicates in saline-alkali soil, and the mixture was applied via root drenching. Application was performed once a week for a total of four times.

[0052] Four months later, when the peppers mature, the plant height, stem diameter, leaf area, and yield per plant are measured.

[0053] Experimental results: Figure 10 The images show the morphology of chili peppers grown in saline-alkali soil with and without CQDs / Ca application. The three plants on the left are chili peppers grown in saline-alkali soil without CQDs / Ca application, while the three plants on the right are chili peppers grown in saline-alkali soil with CQDs / Ca application. The chili peppers grown in saline-alkali soil with CQDs / Ca application showed a significant increase in height and sturdiness.

[0054] Figure 11The plant height of peppers in saline-alkali soil with and without CQDs / Ca application was compared. The plant height of peppers in saline-alkali soil with CQDs / Ca application increased by 26.40% compared to those without CQDs / Ca application.

[0055] Figure 12 The stem diameter of peppers grown in saline-alkali soil with and without CQDs / Ca application was compared. The stem diameter of peppers grown in saline-alkali soil with CQDs / Ca application increased by 15.92% compared to those grown in saline-alkali soil without CQDs / Ca application.

[0056] Figure 13 Leaf area of ​​saline-alkali peppers with and without CQDs / Ca application. Leaf area of ​​saline-alkali peppers with CQDs / Ca application increased by 77.10% compared to those without CQDs / Ca application.

[0057] Figure 14 The yield per plant of chili peppers in saline-alkali soil with and without CQDs / Ca application was compared. The yield per plant of chili peppers in saline-alkali soil with CQDs / Ca application increased by 20.97% compared to those in saline-alkali soil without CQDs / Ca application.

[0058] Figure 15 The images show the morphology of peppers grown in saline-alkali soil with and without CQDs / Ca application. The top image shows peppers grown in saline-alkali soil without CQDs / Ca application, and the bottom image shows peppers grown in saline-alkali soil with CQDs / Ca application. The three peppers at the top are significantly smaller than the three at the bottom, indicating that applying CQDs / Ca to saline-alkali soil promotes pepper growth.

[0059] Table 1 deal with Fruit length (cm) Fruit width (cm) CK 5.80±0.28 1.13±0.08 CQDs / Ca 6.90±0.17*** 1.23±0.08* P<0.05(*), P<0.01(**), P<0.001(***) Table 1 shows the fruit length and width of chili peppers grown in saline-alkali soil with and without CQDs / Ca application. The application of CQDs / Ca resulted in a significant increase in both fruit length and width for the chili peppers grown in saline-alkali soil.

[0060] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A type of oyster shell-starch sludge carbon quantum dots, characterized in that... The oyster shell-starch sludge carbon quantum dots were prepared according to the following method: (1) Mix the crushed oyster shells and starch sludge. (2) The above mixture is subjected to a hydrothermal reaction; (3) Centrifuge the product after hydrothermal reaction, take the supernatant and dialyze it, freeze-dry the obtained liquid to obtain powdered oyster shell-starch sludge carbon quantum dots.

2. The oyster shell-starch sludge carbon quantum dots according to claim 1, characterized in that... The crushing process of oyster shells in step (1) involves washing the oyster shells, crushing them, and passing them through a 50-mesh sieve.

3. The oyster shell-starch sludge carbon quantum dots according to claim 1, characterized in that... The starch sludge mentioned in step (1) is sweet potato starch sludge.

4. The oyster shell-starch sludge carbon quantum dots according to claim 1, characterized in that... In step (1), the crushed oyster shells and starch sludge are mixed in a ratio of 1~1:1~2.

5. The oyster shell-starch sludge carbon quantum dots according to claim 1, characterized in that... The temperature of the hydrothermal reaction in step (2) is 180~220℃.

6. The oyster shell-starch sludge carbon quantum dots according to claim 5, characterized in that... The hydrothermal reaction time in step (2) is 6-8 h.

7. The application of any one of the oyster shell-starch sludge carbon quantum dots described in claims 1-6 in enhancing photosynthesis of chili pepper leaves, promoting the growth and yield of chili peppers in saline-alkali land.

8. The application of any one of the oyster shell-starch sludge carbon quantum dots as described in claims 1-6 as a growth and yield-increasing promoter for chili peppers in saline-alkali land.

9. A method for promoting the growth and increasing the yield of chili peppers in saline-alkali land, characterized in that... Apply oyster shell-starch sludge carbon quantum dots to the soil where saline-alkali peppers are grown every 7-30 days.

10. The method according to claim 9, characterized in that... The concentration of carbon quantum dots from oyster shells and starch sludge applied each time is 0.1~0.5 μg / dot.

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