Method for relieving pepper autotoxicity effect, promoting plant growth and development and increasing yield and improving quality of fruits based on exogenous silicon

Abstract

The invention discloses a method for relieving capsicum autotoxicity effect, promoting plant growth and development and increasing yield and improving quality of fruits based on exogenous silicon, which comprises the following steps: selecting capsicum seeds, soaking the capsicum seeds in warm water at 55 DEG C for 30 minutes, accelerating germination, sowing the seeds in a 72-hole tray after the seeds are white, transplanting seedlings into a nutrition pot filled with a substrate when three leaves and one core are formed, and transplanting the seedlings into a seedling tray after the seedlings are grown; the growth environment temperature is 26 DEG C / 16 DEG C, the photoperiod is 12 h / 12 h, 5 days after seedling recovery, 1 / 2 of a Japanese Kawasaki pepper nutrient solution is used as a solvent for root application of phthalic acid (PA) to induce autotoxicity stress of the peppers, meanwhile, the nutrient solution is used as a solvent for root application of exogenous nano SiO2, and the treatment capacity of each time of irrigation is 150 mL. After the flower stage is started, the nutrient solution is doubled, and the irrigation treatment capacity of each time is changed to 300mL. The root application of exogenous nano SiO2 can effectively promote the growth and development, photosynthetic process, oxidation resistance, water metabolism, carbon and nitrogen metabolism and mineral element absorption of pepper plants under autotoxicity stress, promote the growth and development, yield increase and quality improvement of pepper fruits, and significantly relieve the autotoxicity stress degree of PA on pepper.

Description

Technical Field

[0001] The invention belongs to the technical field of pepper growth and development and fruit yield and quality improvement, and specifically relates to a method for alleviating pepper self-toxicity effect and promoting plant growth and development and fruit yield and quality improvement based on exogenous silicon. Background Art

[0002] With the rapid development of modern agriculture, facility agriculture production, as a stable and efficient planting model, has become an important direction for the development of modern agriculture in my country. Among them, facility vegetable production is the top priority for the development of my country's vegetable industry. With the continuous expansion of the scale of facility vegetable planting in my country, the highly intensive and long-term single continuous planting method has led to increasingly serious problems in the continuous cropping of facility vegetables, which has restricted the sustainable development of facility agriculture in my country. Pepper (Capsicum annum L) is one of the main vegetable crops planted in my country's facility agriculture.

[0003] The allelopathic effect of pepper refers to the release of chemical substances into the surrounding environment by pepper through root secretion, decomposition of plant residues, leaching or volatilization of the aboveground parts, etc., which directly or indirectly restricts the growth and development of plants of the same species or family, microorganisms, insects and other organisms in the surrounding environment. Such chemical substances mainly include four categories: aliphatic, fatty acid, terpenoid and aromatic compounds. When such chemical substances act on plants of the same species or family, it is called plant autotoxicity. Among them, studies have confirmed that phthalic acid (PA) is one of the main autotoxic substances secreted by pepper crops. The continuous accumulation of substances in the soil tillage layer will destroy the environmental ecology of the soil, and have a great impact on the physical and chemical properties of the soil, soil enzyme activity, soil microbial structure, etc., which will in turn have an adverse effect on the plants themselves. The root systems of Solanaceae vegetable crops such as peppers and tomatoes are weak. When the concentration of autotoxic substances is higher than a certain threshold, the morphological growth and nutrient accumulation of the plants will be significantly inhibited, thereby inhibiting the plant's photosynthesis, water metabolism, antioxidant metabolism, osmotic regulation and carbon and nitrogen metabolism, and ultimately restricting the plant's growth and development and flowering and fruiting, thereby causing a decline in fruit quality and yield. Summary of the invention

[0004] The purpose of the present invention is to provide a method for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, comprising the following steps:

[0006] Step 1: Preparation for planting: Select plump pepper seeds and soak them in 55℃ warm water for 30 minutes before germination.

[0007] Step 2: sowing. When the seeds are white, sow them in a 72-hole tray. When they have three leaves and one heart, transplant the seedlings into a nutrient pot (23 cm × 23 cm) filled with a substrate. The growth environment temperature is 26°C / 16°C (day / night) and the photoperiod is 12h / 12h (day / night).

[0008] Step 3: Promote growth and development. After the seedlings have grown for 5 days, apply phthalic acid (PA) to the roots of the peppers using 1 / 2 times the Japanese Yamazaki pepper nutrient solution as a solvent to induce autotoxic stress. At the same time, apply exogenous nano-SiO2 to the roots using the nutrient solution as a solvent. The treatment volume for each irrigation is 150 mL. After entering the flowering period, the nutrient solution is changed to 1 times, and the treatment volume for each irrigation is changed to 300 mL.

[0009] Preferably, after 40 days of treatment, the third functional leaf of the pepper is taken and the leaf area is measured using a LI-3000C leaf area meter (LI-COR, USA); the number of leaves is measured using a counting method.

[0010] Preferably, after 40 days of treatment, the roots of each treatment are cleaned and scanned using a root scanner (MRS-9600TFU2L, Shanghai), and the root images are analyzed using WinRHIZO software to obtain the root surface area, total root volume, average root diameter and total root length.

[0011] Preferably, after 40 days of treatment, fresh roots of each treatment are taken and cleaned, 0.2 g of fresh root sample is put into a 10 mL centrifuge tube, 3 mL of PBS and TTC are added, and the mixture is kept at 37° C. for 1 h. 1 mL of sulfuric acid is added to terminate the reaction. The roots are taken out and wiped dry, and the volume is fixed to 10 mL with ethyl acetate. The absorbance is measured at 485 nm, and the root activity is calculated according to the formula.

[0012] Preferably, after 40 days of treatment, the second and third fully expanded functional leaves of the seedlings are selected, the midrib is removed and cut into pieces and mixed, 0.05 g is weighed and put into a 10 mL test tube, and the photosynthetic pigments are extracted with 10 mL of 96% ethanol. The test tube is sealed and placed in dark conditions for immersion for 24 hours, and shaken at irregular intervals until the leaves turn white. When measuring, 96% ethanol is used to adjust to zero, and the absorbance values ​​of the extract at 665 nm, 649 nm and 470 nm are measured.

[0013] Preferably, after 40 days of treatment, chlorophyll fluorescence is measured using a LI-6800 portable photosynthetic instrument (LI-COR, USA). Before the measurement, the pepper seedlings to be tested are dark-adapted for 30 minutes, and the second and third fully expanded functional leaves downward from the seedling growth point are selected to measure the maximum photochemical efficiency of PSII.

[0014] Preferably, after 40 days of treatment, the second functional leaf and root samples under the growth point of each treated pepper are collected, and the relative water content of the leaves is measured by water absorption specific gravity method; the leaves are ground into a homogenate, and the juice concentration of the leaves is measured by a digital saccharimeter (WYT-1, Zhejiang).

[0015] Preferably, a portable plant water potential pressure chamber (PMS1505D, USA) is used for measurement. The second functional leaf after treatment for 40 days is cut flat from the petiole and quickly loaded into the sample holder of the instrument. The incision exposes 5 mm of the sample holder gasket. The ring cover is tightened and quickly placed in the pressure chamber. Pressurization is applied at a rate of 0.05 MPa per second. When a water film appears on the petiole incision, the air valve is quickly closed and the pressure gauge reading is recorded. The negative value of the data is the leaf water potential.

[0016] Preferably, when the pepper plants enter the flowering period, pepper plants with uniform growth are selected, and the number of flower buds, the number of blossoms, the number of fruits and the number of fruits are calculated by a counting method; flowering rate = number of flower buds / number of blossoms, and after the fruits are ripe, fruit samples with uniform maturity are harvested in 3 batches, and the horizontal and vertical diameters of the fruits are measured with a vernier caliper; fruit shape index = vertical diameter of the fruit / horizontal diameter of the fruit.

[0017] Preferably, fruit samples with the same maturity in each treatment are selected, and the fresh samples are made into pulp. The soluble solid content is determined by a digital saccharimeter (WYT-1, Zhejiang); the soluble protein content is determined by the Coomassie Brilliant Blue G-250 method; the free amino acid content is determined by the hydrated ninhydrin colorimetric method, and the fruit quality is tested.

[0018] Compared with the prior art, the present invention has the following beneficial effects: the present invention uses nutrient solution as solvent to apply phthalic acid (PA) to induce autotoxicity stress of pepper (PA concentration is 1.5 mmol / L, obtained by preliminary experimental screening), wherein the nutrient solution formula uses 1 / 2 times of Japanese Yamazaki pepper nutrient solution, 150 mL of different nutrient solutions are irrigated every 3 days, and the 'Syngenta Maso' pepper variety is used as the test material, and the autotoxicity stress treatment is started when the pepper has three leaves and one heart, and at the same time, exogenous nano-SiO2 (Si concentration is 1.5 mmol / L) is applied to the roots using nutrient solution as solvent. 1.5mmol / L, obtained by preliminary experimental screening), exogenous Si fertilizer treatment was carried out every 6 days, and after entering the flowering period, the nutrient solution was changed to 1 times the Japanese Yamazaki pepper nutrient solution, and the amount of each irrigation treatment was changed to 300mL. After sampling, the study found that root application of exogenous nano-SiO2 can effectively promote the growth and development, photosynthetic process, antioxidant capacity, water metabolism, carbon and nitrogen metabolism and mineral element absorption of pepper plants under autotoxicity stress, thereby promoting the growth and development of pepper fruits and increasing yield and quality, and significantly alleviating the degree of autotoxicity stress of PA on pepper. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1Schematic diagram of the effect of exogenous Si on the physicochemical properties of pepper rhizosphere matrix under PA stress in the present invention;

[0020] Figure 2 This is a schematic diagram of the effect of exogenous Si on plant height and stem diameter of pepper plants under PA stress in the present invention;

[0021] Figure 3 This is a schematic diagram of the effect of exogenous Si on the root activity of pepper under PA stress in the present invention;

[0022] Figure 4 Schematic diagram of the effect of exogenous Si on the degree of membrane lipid peroxidation in pepper leaves and roots under PA stress in the present invention;

[0023] Figure 5 Schematic diagram of the effect of exogenous Si on ascorbic acid content in pepper leaves and roots under PA stress in the present invention;

[0024] Figure 6 Schematic diagram of the effect of exogenous Si on the content of osmotic regulating substances in pepper leaves and roots under PA stress in the present invention;

[0025] Figure 7 This is a schematic diagram of the effect of exogenous Si on the relative water content of pepper leaves under PA stress in the present invention;

[0026] Figure 8 This is a schematic diagram of the effect of exogenous Si on the juice concentration of pepper leaves under PA stress in the present invention;

[0027] Fig. 9 This is a schematic diagram of the effect of exogenous Si on the water potential of pepper leaves under PA stress in the present invention;

[0028] Fig.10 This is a schematic diagram of the effect of exogenous Si on the hydraulic conductivity of pepper root system under PA stress in the present invention;

[0029] Fig.11 This is a schematic diagram of the effect of exogenous Si on nitrogen forms in different parts of pepper under PA stress in the present invention;

[0030] Fig.12 It is a technical flow chart of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides Figure 1-12A method for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon is shown;

[0033] 1. Planting Preparation

[0034] The present invention uses pepper variety 'Syngenta Maso' as test material, purchased from Syngenta Group Co., Ltd., and the test exogenous substance nano-SiO2 (analytical grade) is purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd. The cultivation matrix adopts a composite commercial matrix (peat: vermiculite: perlite = 3:1:1), purchased from Shanxi Taigu Juxin Weiye Seedling Co., Ltd., select full pepper seeds, soak them in 55°C warm water for 30 minutes, and then germinate them, and sow them in a 72-hole hole tray after the seeds turn white;

[0035] 2. Planting seeds

[0036] When the seedlings have three leaves and one heart, transplant them into a nutrient pot (23 cm × 23 cm) filled with substrate. The growth environment temperature is 26℃ / 16℃ (day / night) and the photoperiod is 12h / 12h (day / night).

[0037] 3. Promote growth and development

[0038] After 5 days of seedling acclimatization, phthalic acid (PA) was applied to the roots of peppers with nutrient solution as solvent to induce autotoxic stress. At the same time, exogenous nano-SiO2 was applied to the roots with nutrient solution as solvent. Different treatments were started (PA and Si concentrations were obtained by preliminary experimental screening, and the detailed treatment scheme is shown in Table 1). Four treatment groups were set up, and 20 pepper seedlings were set up in each treatment. The nutrient solution formula used 1 / 2 times the Japanese Yamazaki pepper nutrient solution. 150mL of different nutrient solutions were irrigated every 3 days, and exogenous Si fertilizer was treated every 6 days. After entering the flowering period, the nutrient solution was changed to 1 times the Japanese Yamazaki pepper nutrient solution, and the amount of each irrigation was changed to 300mL. After 40 days of treatment, plant tissue and rhizosphere matrix samples were taken for the determination of plant growth and physiological indicators, and each treatment was repeated 3 times. When the fruit matured, fruit samples were taken for the determination of quality and yield indicators, and each treatment was repeated 3 times. During the experiment, management measures such as thinning flowers and fruits, pruning and forking, and pest and disease control were carried out in a timely manner.

[0039] Table 1 Experimental treatment

[0040]

[0041] Determination of physicochemical properties of rhizosphere matrix and matrix enzyme activities

[0042] Rhizosphere matrix physical and chemical properties: Rhizosphere matrix samples of pepper roots were collected, and the pH value of the matrix was measured using a soil pH meter; the EC value of the matrix was measured using a soil EC meter. Each treatment was biologically replicated three times.

[0043] Substrate enzyme activity: The rhizosphere matrix samples of pepper roots were collected, dried naturally and then passed through a 60-mesh sieve. Soil urease (URE) was determined by sodium phenol-sodium hypochlorite colorimetry; polyphenol oxidase (PPO) and peroxidase (APX) were determined by pyrogallol colorimetry; sucrase (SUC) was determined by 3,5-dinitrosalicylic acid colorimetry; acid phosphatase (ACP) was determined by disodium phenyl phosphate method; catalase (CAT) was determined by violet spectrophotometry. Three biological replicates were performed for each treatment.

[0044] 1. Determination of growth indicators

[0045] Plant height and stem diameter: pepper plants were selected at 0d, 10d, 20d, 30d, 40d, 50d and 60d of treatment, and the plant height (the distance from the cotyledon to the plant growth point) was measured with a tape measure. The diameter of the plant was measured parallel to the cotyledon with a vernier caliper with an accuracy of 0.01mm. Each treatment was biologically replicated three times.

[0046] Biomass: After 40 days of treatment, the plants were divided into aboveground and underground parts, washed with distilled water and dried, and the weight was recorded as the fresh weight of the plants. After being sterilized at 105°C for 15 min, they were dried at 65°C to constant weight and the weight was recorded as the dry weight of the plants. Root-to-shoot ratio = aboveground fresh weight / underground fresh weight. Each treatment was biologically replicated three times.

[0047] Leaf morphology index: After 40 days of treatment, the third functional leaf of each treatment was taken and the leaf area was measured using a LI-3000C leaf area meter (LI-COR, USA); the number of leaves was measured using the counting method, and each treatment was biologically replicated three times.

[0048] Root indicators: After 40 days of treatment, the roots of each treatment were cleaned and scanned using a root scanner (MRS-9600TFU2L, Shanghai). The root images were analyzed using WinRHIZO software to obtain the root surface area, total root volume, average root diameter and total root length. Each treatment was biologically replicated three times.

[0049] Root activity: After 40 days of treatment, fresh roots of each treatment were taken and cleaned, and 0.2 g of fresh root sample was placed in a 10 mL centrifuge tube, and 3 mL of PBS and TTC were added. The mixture was kept at 37 °C for 1 h, and 1 mL of sulfuric acid was added to terminate the reaction. The roots were taken out and wiped dry, and the volume was fixed to 10 mL with ethyl acetate. The absorbance was measured at 485 nm, and the root activity was calculated according to the formula. Each treatment was biologically replicated 3 times.

[0050] 2. Determination of chlorophyll content

[0051] After 40 days of treatment, select the second and third functional leaves of the seedlings that are fully expanded, cut off the midrib and mix well, weigh 0.05g and put it into a 10mL test tube, and extract the photosynthetic pigment with 10mL 96% ethanol. Seal the test tube and extract it in the dark for 24 hours, shaking it from time to time until the leaves turn white. When measuring, adjust the value to zero with 96% ethanol, measure the absorbance of the extract at 665nm, 649nm and 470nm, and calculate the chlorophyll content using the following formula, with 3 biological replicates for each treatment.

[0052] Chl a(mg g FW -1 )=(13.95×A665-6.88×A649)×V / FW;

[0053] Chl a(mg g FW -1 ) is the content of chlorophyll a per gram fresh weight (FW) of leaves, in milligrams (mg);

[0054] A665 and A649 are the absorbance values ​​at wavelengths of 665nm and 649nm, respectively, and 13.95 and 6.88 are coefficients calculated based on the absorption coefficients of chlorophyll a and chlorophyll b at different wavelengths;

[0055] V is the volume of the extract (here 10 mL);

[0056] FW is the fresh weight of the leaves (0.05 g was weighed here). The formula calculates the chlorophyll a content per gram of fresh weight of leaves through the absorbance value at a specific wavelength, the volume of the extract and the fresh weight of the leaves.

[0057] Chl b(mg g FW -1 )=(24.96×A649-7.32×A665)×V / FW;

[0058] A665 and A649 are absorbance values, 24.96 and 7.32 are coefficients, and this formula is used to calculate the chlorophyll b content per gram of fresh weight of leaves;

[0059] Car(mg g FW -1 )=(1000×A470-Chl a×2.05-Chl b×114.8) / 245;

[0060] A470 is the absorbance value at a wavelength of 470 nm; Chl a and Chl b are the contents of chlorophyll a and chlorophyll b calculated above, respectively;

[0061] 2.05 and 114.8 are coefficients determined based on the absorbance relationship between carotenoids and chlorophyll a and chlorophyll b at different wavelengths;

[0062] 245 is the absorption coefficient of carotenoids at a specific wavelength. The formula calculates the content of carotenoids per gram of fresh weight of leaves through the absorbance value at a wavelength of 470nm and the content of chlorophyll a and chlorophyll b.

[0063] Photosynthetic parameter determination

[0064] After 40 days of treatment, photosynthetic parameters were measured using a Li-6800 portable photosynthetic instrument (LI-COR, USA) from 8:30 to 11:30 a.m. The second and third fully expanded functional leaves of pepper seedlings were selected downward from the growth point, and the environmental parameter irradiation intensity was set to 800 μmol·m -2 ·s -1 , CO2 concentration is 400 μmol·mol -1 , flow rate 500 μmol·s -1 The net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), and stomatal conductance (Gs) of tomato leaves were measured. Each treatment was repeated three times.

[0065] 3. Chlorophyll fluorescence measurement

[0066] After 40 days of treatment, chlorophyll fluorescence was measured using a LI-6800 portable photosynthetic instrument (LI-COR, USA). Before the measurement, the pepper seedlings to be tested were dark-adapted for 30 minutes, and the second and third fully expanded functional leaves below the growth point of the seedlings were selected to measure the maximum photochemical efficiency of PSII [Fv / Fm=(Fm-Fo) / Fm] and the potential activity of PSⅡ [Fv / F0=(Fm-F0) / F0]; the leaves were adapted to normal light conditions for 1 hour, and their chlorophyll fluorescence was measured at 800 μmol·m -2 ·s -1 The actual photochemical efficiency of PSII under activating light [ФPSII=(Fm'-Fs) / Fm'], photochemical quenching coefficient [qP=(Fm'-Fs) / (Fm'-F0')], non-photochemical quenching coefficient [NPQ=(Fm-Fm') / Fm'] and photosynthetic electron transfer rate (ETR); where F0 and Fm are initial fluorescence and maximum fluorescence, respectively; F0', Fm' and Fs are minimum fluorescence, maximum fluorescence and steady-state fluorescence under light, respectively; Fv is variable fluorescence; and each treatment was repeated three times;

[0067] 4. Determination of Antioxidant Properties

[0068] After 40 days of treatment, fresh leaves and root samples of peppers in each treatment were collected, washed, dried, and then quickly cut into pieces and ground. The relative conductivity was measured using a conductivity meter (DDS-307A, Shanghai); the malondialdehyde (MDA) content was measured using the thiobarbituric acid method; the hydrogen peroxide (H2O2) content was measured using a kit (purchased from Solebold Biotechnology Co., Ltd.); the superoxide anion (O2ˉ·) content was measured using the p-aminobenzenesulfonic acid method; the superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) activities were measured using the ultraviolet absorption method; the ascorbic acid (AsA) content was measured using the molybdenum blue colorimetric method; and the glutathione (GSH) content was measured using the 2,6-dichloroindophenol method. Each treatment was biologically replicated three times.

[0069] 5. Determination of the content of osmotic regulating substances

[0070] After 40 days of treatment, fresh leaf and root samples of peppers in each treatment were collected, washed and dried, and the soluble sugar content was determined by the sulfuric acid-anthrone method; the soluble protein content was determined by the G-250 method; the free amino acid content was determined by the ninhydrin colorimetric method; and the proline content was determined by the sulfosalicylic acid method. Each treatment was biologically replicated three times.

[0071] 6. Determination of water metabolism indicators

[0072] Leaf relative water content and leaf juice concentration: After 40 days of treatment, the second functional leaf and root samples under the growth point of each pepper were collected, and the relative water content of the leaves was measured by the water absorption specific gravity method; the leaves were ground into a homogenate, and the leaf juice concentration was measured using a digital saccharimeter (WYT-1, Zhejiang), with 3 biological replicates for each treatment.

[0073] Leaf water potential and root hydraulic conductivity: measured using a portable plant water potential pressure chamber (PMS1505D, USA). After 40 days of treatment, take the second functional leaf and cut it flat from the petiole, quickly put it into the sample holder of the instrument, and the cut should expose 5mm of the sample holder gasket. Tighten the ring cover and quickly put it into the pressure chamber. Pressurize at a rate of 0.05MPa per second. When a water film appears on the petiole cut, quickly close the air valve and record the pressure gauge reading. The negative value of the data is the leaf water potential. A horizontal cut was made from the aboveground part 3 cm above the pepper root system, and the root system was immersed in a beaker filled with distilled water and placed in a pressure chamber together with the cut, with 5 mm of the sample holder exposed. The ring cover was tightened and the sample was quickly placed in the pressure chamber. The pressure was slowly increased from 0 to 1 MPa, and the pressure was stopped every 0.2 MPa. After the pressure stabilized, the juice was absorbed with absorbent paper for 60 s; the absorbent paper with the juice absorbed was placed in a plastic centrifuge tube, and the weight of the absorbent paper before and after the water absorption at each pressure stop stage was weighed to calculate the juice outflow rate at each stage. The root surface area was then measured using a root scanner (MRS-9600TFU2L, Shanghai), and the water flux per unit root surface area per unit time was calculated; the root water flux was plotted against the corresponding pressure difference, and the slope of the calculated regression line was the root hydraulic conductivity, with 3 biological replicates for each treatment.

[0074] 7. Determination of mineral element content

[0075] After 40 days of treatment, the leaf and root samples of peppers in each treatment were collected. When the fruit matured, the mature fruit samples with the same growth in each treatment were harvested. The samples were sterilized at 105℃ for 15 minutes, dried at 65℃ to constant weight, ground and sieved through 100 mesh to make dry powder, and the Si content of leaves, roots and fruits was determined by molybdenum blue colorimetry. The prepared dry powder was prepared by H2SO4-H2O2 digestion method to prepare digestion liquid, and the total N content of leaves, roots and fruits was determined by Kelvin method; P element was determined by molybdenum antimony colorimetry, and K, Ca, Mg, Cu, Fe, Zn and Mn elements were determined by atomic absorption spectrometry, and each treatment was biologically repeated 3 times.

[0076] 8. Determination of Sugar Metabolism Indicators

[0077] Sugar content: After 40 days of treatment, fresh leaf and root samples of peppers in each treatment were collected, and when the fruit matured, mature fruit samples with the same growth in each treatment were harvested. The reducing sugar content was determined by 3,5-dinitrosalicylic acid colorimetry; the sucrose content was determined by resorcinol colorimetry; the fructose content was determined by hydrochloric acid hydrolysis; and the starch content was determined by anthrone-sulfuric acid method.

[0078] The key enzymes of sugar metabolism: sucrose synthase (SS), sucrose phosphate synthase (SPS), acid invertase (AI) and neutral invertase (NI) were measured using kits (purchased from Solebow Biotechnology Co., Ltd.), and each treatment was repeated three times.

[0079] IX. Determination of nitrogen metabolism indicators

[0080] After 40 days of treatment, fresh leaf and root samples of peppers in each treatment were collected. When the fruit matured, fresh mature fruit samples with the same growth in each treatment were harvested and made into homogenate. The nitrate nitrogen content was determined by salicylic acid-sulfuric acid colorimetry; the ammonium nitrogen content was determined by ninhydrin colorimetry. Nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthetase (GOGAT) were determined using kits (purchased from Solebow Biotechnology Co., Ltd.), and each treatment was biologically replicated 3 times.

[0081] 10. Determination of fruit yield and quality indicators

[0082] Flowering index: When the pepper plants enter the flowering period, select pepper plants with consistent growth and use the counting method to calculate the number of flower buds, number of flowers, number of fruits and number of fruits; flowering rate = number of flower buds / number of flowers. Each treatment was biologically replicated 3 times.

[0083] Biomass: After the fruits matured, fruit samples of the same maturity were harvested in three batches, and the horizontal and vertical diameters of the fruits were measured with a vernier caliper; fruit shape index = vertical diameter of fruit / horizontal diameter of fruit; fruit hardness was measured using a fruit hardness meter (GY-4, Zhejiang); fresh fruits were washed with distilled water and wiped dry, and the weight was recorded as the fresh weight of the fruit. After being fixed at 105℃ for 15 min, they were dried at 65℃ to constant weight, and the weight was recorded as the dry weight of the fruit; all fruits of a single plant were harvested and weighed to calculate the yield of a single plant, and each treatment was biologically replicated three times.

[0084] Fruit quality: Fruit samples with the same maturity were selected from each treatment, and fresh samples were made into pulp. The soluble solid content was determined by a digital sugar meter (WYT-1, Zhejiang); the soluble protein content was determined by the Coomassie Brilliant Blue G-250 method; the free amino acid content was determined by the ninhydrin colorimetric method; the soluble sugar content was determined by the anthrone-ethyl acetate method; the reducing sugar content was determined by the 3,5-dinitrosalicylic acid colorimetric method; the sucrose content was determined by the resorcinol colorimetric method; the fructose content was determined by the hydrochloric acid hydrolysis method; and the vitamin C (VC) content was determined by the molybdenum blue colorimetric method. The nitrate (NO3 - ) content, and each treatment was repeated 3 times.

[0085] like Figure 1As shown in the results, root application of 1.5mmol / L exogenous nano-SiO2 can effectively alleviate the salinization and acidification of the matrix caused by autotoxicity stress. Compared with normal conditions, the pH of the pepper rhizosphere matrix decreased significantly by 3.03% under autotoxicity stress (P<0.05); under normal conditions, the pH of the pepper rhizosphere matrix did not change significantly after the application of exogenous Si fertilizer; compared with the autotoxicity stress treatment, the application of exogenous Si fertilizer under autotoxicity stress significantly increased the pH of the pepper rhizosphere by 58.93% (P<0.05), effectively alleviating the rhizosphere acidity environment. Autotoxicity stress significantly aggravated the salinization of the pepper rhizosphere matrix. Compared with the T1 treatment, the EC value of the pepper rhizosphere matrix under the T3 treatment was significantly increased by 14.21% (P<0.05); the application of exogenous Si fertilizer could significantly reduce the EC value of the pepper rhizosphere matrix under normal conditions and autotoxicity stress, among which, the EC value of the T4 treatment was significantly reduced by 22.01% (P<0.05) compared with the T3 treatment.

[0086] Note: In the figure, "T1" indicates the control treatment of fertilization with normal nutrient solution; "T2" indicates the normal nutrient solution with 1.5mmol·L -1 Exogenous Si fertilizer treatment; "T3" means 1.5mmol·L -1 PA-induced autotoxicity stress treatment; "T4" means 1.5mmol·L -1 PA-induced autotoxicity stress was applied with 1.5 mmol·L -1 Exogenous Si fertilizer treatment. All data are mean ± standard error. Different letters on the same type of bars in the figure indicate significant differences among the treatments (P < 0.05). Duncan's new multiple range method was used for multiple comparisons; the same below.

[0087] As shown in Table 2, root application of 1.5 mmol / L exogenous nano-SiO2 effectively alleviated the inhibition of matrix enzyme activity by autotoxicity stress. Compared with normal conditions, the activities of polyphenol oxidase, peroxidase, catalase, sucrase, acid phosphatase and urease in the rhizosphere of pepper under autotoxicity stress were significantly decreased by 28.84%, 40.98%, 34.26%, 30.96%, 34.38% and 22.02%, respectively (P<0.05); the application of exogenous Si fertilizer increased the soil enzyme activities under normal conditions and autotoxicity stress to varying degrees. Among them, compared with T1 treatment, the activities of sucrase and urease in the rhizosphere of pepper under T2 treatment were significantly increased by 12.98% and 16.72%, respectively (P<0.05); compared with T3 treatment, the activities of polyphenol oxidase, peroxidase, catalase, sucrase and urease in the rhizosphere of pepper under T4 treatment were significantly increased by 25.15%, 37.33%, 24.55%, 35.07% and 27.55%, respectively (P<0.05).

[0088] Table 2 Effects of exogenous Si on the activity of matrix enzymes in the rhizosphere of pepper under PA stress

[0089]

[0090] Note: "T1" in the table indicates the control treatment of fertilization with normal nutrient solution; "T2" indicates the normal nutrient solution with 1.5mmol·L -1 Exogenous Si fertilizer treatment; "T3" means 1.5mmol·L -1 PA-induced autotoxicity stress treatment; "T4" means 1.5mmol·L -1 PA-induced autotoxicity stress was applied with 1.5 mmol·L -1 Exogenous Si fertilizer treatment. All data are mean ± standard error. Different letters in the same column of data indicate significant differences among treatments (P < 0.05). Duncan's new multiple range method was used for multiple comparisons; the same below.

[0091] like Figure 2 As shown in Table 3, root application of exogenous nano-SiO2 effectively promoted the morphological development and biomass accumulation of pepper plants under autotoxicity stress. Figure 2 It can be seen that compared with normal conditions, the plant height and stem diameter of pepper plants under autotoxicity stress showed a continuous downward trend after 20 days of treatment. At 60 days, the plant height and stem diameter of pepper plants in T3 treatment were significantly reduced by 11.79% and 13.73% respectively compared with those in T1 treatment (P < 0.05); the application of exogenous Si fertilizer significantly increased the plant height and stem diameter of pepper plants under normal conditions and autotoxicity stress treatment. Compared with T3 treatment, the plant height and stem diameter of pepper plants in T4 treatment were significantly increased by 13.29% and 13.30% respectively (P < 0.05).

[0092] As shown in Table 3, compared with normal conditions, autotoxicity stress treatment significantly inhibited the accumulation of fresh and dry weight of pepper plants and reduced the root-to-shoot ratio of pepper plants. Compared with T1 treatment, the aboveground fresh weight, underground fresh weight, aboveground dry weight, underground dry weight and root-to-shoot ratio of pepper plants in T3 treatment were significantly reduced by 19.74%, 20.20%, 5.21%, 14.14% and 10.34% (P < 0.05), respectively; the application of exogenous Si fertilizer significantly promoted the accumulation of fresh and dry weight of pepper plants and increased the root-to-shoot ratio of plants. Among them, compared with T3 treatment, the aboveground fresh weight, underground fresh weight, aboveground dry weight, underground dry weight and root-to-shoot ratio of pepper plants in T4 treatment were significantly increased by 23.47%, 21.36%, 5.05%, 14.12% and 7.69%, respectively (P < 0.05).

[0093] Table 3 Effects of exogenous Si on fresh and dry weight and root-to-shoot ratio of pepper plants under PA stress

[0094]

[0095] like Figure 3 As shown in Table 4, root application of exogenous nano-SiO2 effectively alleviated the damage of pepper root system caused by autotoxicity stress. Figure 3 It can be seen that compared with normal conditions, autotoxicity stress significantly inhibited the root activity of pepper. Compared with T1 treatment, the root activity of pepper in T3 treatment decreased by 30.00% (P<0.05). After applying exogenous Si fertilizer, the root activity of pepper in T4 treatment was significantly increased by 28.17% (P<0.05) compared with T3 treatment, which effectively alleviated the inhibition of autotoxicity stress on the root activity of pepper.

[0096] As shown in Table 4, compared with the T1 treatment, the total root length, total surface area, average diameter and total volume of the pepper root system under the T3 treatment were significantly reduced by 18.44%, 19.20%, 22.77% and 36.66% respectively (P < 0.05); the application of exogenous Si fertilizer significantly promoted the morphological development of the pepper root system under normal conditions and autotoxicity stress. Compared with the T3 treatment, the total root length, total surface area, average diameter and total volume of the pepper root system under the T4 treatment were significantly increased by 16.23%, 16.02%, 20.51% and 27.65% respectively (P < 0.05).

[0097] Table 4 Effects of exogenous Si on pepper root morphology under PA stress

[0098]

[0099] As shown in Table 5, root application of exogenous nano-SiO2 effectively promoted the growth and development of pepper leaves under autotoxicity stress. Autotoxicity stress significantly inhibited the morphological development of pepper leaves. Compared with T1 treatment, the number of leaves, the second functional leaf area and the total leaf area of ​​pepper leaves in T3 treatment were significantly reduced by 24.69%, 31.36% and 36.44% respectively (P < 0.05); the application of exogenous Si fertilizer significantly promoted the morphological development of pepper leaves under autotoxicity stress. Compared with T3 treatment, the number of leaves, the second functional leaf area and the total leaf area of ​​pepper leaves in T4 treatment were significantly increased by 22.95%, 21.95% and 41.88% respectively (P < 0.05).

[0100] Table 5 Effects of exogenous Si on leaf number and leaf area of ​​pepper under PA stress

[0101]

[0102] As shown in Table 6, root application of exogenous nano-SiO2 effectively alleviated the inhibitory effect of autotoxicity stress on chlorophyll synthesis in pepper leaves. Autotoxicity stress significantly inhibited the synthesis of various chlorophylls in pepper leaves. Compared with T1 treatment, the contents of chlorophyll a, chlorophyll b and carotenoids in pepper leaves in T3 treatment decreased by 33.78%, 26.92% and 27.03%, respectively (P < 0.05); the application of exogenous Si fertilizer significantly alleviated the inhibitory effect of autotoxicity stress on chlorophyll synthesis in pepper leaves. Compared with T3 treatment, the contents of chlorophyll a, chlorophyll b and carotenoids in pepper leaves in T4 treatment increased by 30.61%, 26.31% and 22.22%, respectively (P < 0.05).

[0103] Table 6 Effects of exogenous Si on chlorophyll content in pepper leaves under PA stress

[0104]

[0105] As shown in Table 7, root application of exogenous nano-SiO2 effectively alleviated the inhibitory effect of autotoxicity stress on the photosynthesis efficiency of pepper. Compared with T1 treatment, the net photosynthetic rate, transpiration rate and stomatal conductance of pepper leaves in T3 treatment decreased by 45.97%, 21.79% and 23.33% (P < 0.05), respectively, and the intercellular CO2 concentration increased significantly by 24.14% (P < 0.05); compared with T3 treatment, the net photosynthetic rate, transpiration rate and stomatal conductance of pepper leaves in T4 treatment increased by 57.39%, 16.90% and 21.74% (P < 0.05), respectively, and the intercellular CO2 concentration decreased significantly by 13.51% (P < 0.05). That is, the application of exogenous Si fertilizer significantly promoted the net photosynthetic rate, transpiration rate and stomatal conductance of leaves under autotoxicity stress, and significantly reduced the intercellular CO2 concentration of leaves, alleviating the inhibitory effect of autotoxicity stress on the photosynthesis of pepper leaves.

[0106] Table 7 Effects of exogenous Si on photosynthetic parameters of pepper leaves under PA stress

[0107]

[0108] As shown in Table 8, root application of exogenous nano-SiO2 effectively alleviated the damage of self-toxicity stress to the photosynthetic functional structure of pepper. Compared with normal conditions, self-toxicity stress treatment caused the maximum photochemical efficiency of PSⅡ, actual photochemical efficiency of PSⅡ, photochemical quenching coefficient, potential activity of PSⅡ and photosynthetic electron transfer rate of pepper leaves to decrease by 6.10%, 33.33%, 12.66%, 22.22% and 11.57% respectively (P<0.05), and the non-photochemical quenching coefficient increased significantly by 20.00% (P<0.05); the application of exogenous Si fertilizer significantly increased the maximum photochemical efficiency of PSⅡ, actual photochemical efficiency of PSⅡ, potential activity of PSⅡ and photosynthetic electron transfer rate of pepper leaves under self-toxicity stress, and significantly reduced the non-photochemical quenching coefficient of leaves.

[0109] Table 8 Effects of exogenous Si on chlorophyll fluorescence parameters of pepper leaves under PA stress

[0110]

[0111]

[0112] like Figure 4 As shown in the results, root application of exogenous nano-SiO2 effectively alleviated the damage of the membrane lipid structure of pepper plants under autotoxicity stress. Autotoxicity stress significantly aggravated the membrane lipid peroxidation process of pepper leaves and root cells. Compared with T1 treatment, the relative conductivity, O2ˉ· content, MDA content and H2O2 content of pepper leaves in T3 treatment increased significantly by 17.39%, 75.62%, 48.73% and 43.51% (P<0.05), respectively, and the relative conductivity, O2ˉ· content, MDA content and H2O2 content of pepper roots increased significantly by 48.39%, 174.20%, 180.17% and 35.00% (P<0.05), respectively. 0.5); Application of exogenous Si fertilizer could significantly alleviate the degree of membrane lipid peroxidation in pepper. Compared with T3 treatment, the relative conductivity, O2ˉ· content, MDA content and H2O2 content of pepper leaves in T4 treatment were significantly reduced by 25.93%, 23.35%, 25.98% and 31.57% (P<0.05), respectively; the relative conductivity, O2ˉ· content, MDA content and H2O2 content of pepper roots were significantly reduced by 26.09%, 24.52%, 2289% and 24.36% (P<0.05), respectively.

[0113] like Figure 5 As shown in Table 9, root application of exogenous nano-SiO2 effectively improved the antioxidant capacity of pepper plants under autotoxicity stress. Figure 5It can be seen that compared with normal conditions, autotoxicity stress significantly inhibited the synthesis of AsA and GSH in pepper leaves and roots. Compared with T1 treatment, the AsA content in pepper leaves and roots under T3 treatment was significantly reduced, and the GSH content in pepper leaves and roots was significantly reduced by 45.30% and 13.02%, respectively (P < 0.05); after applying exogenous Si fertilizer under autotoxicity stress, compared with T3 treatment, the GSH content in pepper leaves under T4 treatment was significantly increased by 34.80% (P < 0.05), and the AsA and GSH contents in pepper roots were significantly increased by 37.89% and 20.54%, respectively (P < 0.05).

[0114] As shown in Table 9, autotoxicity stress inhibited the antioxidant enzyme activities in pepper leaves and roots to varying degrees. Compared with T1 treatment, the activities of SOD, POD, CAT and APX in pepper leaves under T3 treatment were significantly reduced by 30.28%, 24.27%, 40.37% and 42.98% (P < 0.05), and in pepper roots by 41.53%, 30.02%, 57.10% and 43.05% (P < 0.05), respectively. Exogenous Si significantly increased the antioxidant enzyme activities in pepper leaves and roots. Compared with T3 treatment, the activities of SOD, POD and APX in pepper leaves increased by 38.81%, 28.83% and 16.67% (P < 0.05), and in pepper roots increased by 29.01%, 40.21% and 44.82% (P < 0.05), respectively. Under normal conditions, the application of exogenous Si fertilizer also increased the antioxidant enzyme activities in pepper leaves and roots to varying degrees.

[0115] Table 9 Effects of exogenous Si on antioxidant enzyme activities in pepper leaves and roots under PA stress

[0116]

[0117] like Figure 6 As shown in the results, after applying exogenous nano-SiO2 to the roots under autotoxicity stress, the content of intracellular osmotic regulating substances in pepper plants was significantly downregulated. Compared with normal conditions, autotoxicity stress treatment increased the soluble sugar, proline and free amino acid contents in pepper leaves and roots to varying degrees, while significantly reduced the soluble protein content in pepper leaves and roots; T4 treatment compared with T3 treatment showed that after applying exogenous Si fertilizer, the soluble sugar, proline and free amino acid contents in pepper leaves and roots under autotoxicity stress were significantly reduced by 21.40%, 28.67%, 19.25% and 24.30%, 31.07%, 23.90% (P < 0.05), respectively, and the soluble protein content was significantly increased by 39.40% and 32.35% (P < 0.05).

[0118] like Figure 7-10 As shown in the figure, root application of exogenous nano-SiO2 effectively improved the water status of pepper leaves under autotoxicity stress, thereby improving the physiological metabolic process and material absorption and transport capacity of cells under stress. Figure 7 It can be seen that autotoxicity stress significantly affected the water status of pepper leaves, and the application of exogenous Si could effectively improve the water status of leaves. Compared with T1 treatment, the relative water content of pepper leaves in T3 treatment was significantly reduced; after applying exogenous Si fertilizer under normal treatment and autotoxicity stress treatment, the relative water content of pepper leaves was significantly increased to varying degrees.

[0119] like Figure 8 As shown, compared with normal conditions, the concentration of pepper leaf juice under autotoxicity stress treatment was significantly increased by 30.34% (P < 0.05); the application of exogenous Si significantly alleviated the effect of autotoxicity stress treatment on the consistency of pepper leaf juice, and the concentration of pepper leaf juice under T4 treatment was significantly reduced compared with T3 treatment.

[0120] like Fig. 9 As shown in the data, compared with normal conditions, autotoxicity stress treatment significantly reduced the water potential of pepper leaves, with a decrease of 31.51% (P < 0.05); after applying exogenous Si fertilizer under normal treatment, the water potential of pepper leaves was significantly increased by 19.71% (P < 0.05); the application of exogenous Si fertilizer under autotoxicity stress conditions effectively alleviated the effect of autotoxicity stress on leaf water potential. Compared with T3 treatment, the water potential of pepper leaves in T4 treatment was significantly increased by 12.10% (P < 0.05).

[0121] like Fig.10 As shown in the data, autotoxicity stress significantly reduced the hydraulic conductivity of the pepper root system. Compared with the T1 treatment, the hydraulic conductivity of the pepper root system in the T3 treatment was reduced by 11.12% (P < 0.05). The application of exogenous Si fertilizer could significantly increase the hydraulic conductivity of the pepper root system under normal treatment and autotoxicity stress treatment, with an increase of 13.64% (P < 0.05), respectively.

[0122] As shown in Table 10, root application of exogenous nano-SiO2 significantly increased the accumulation of Si in pepper plants and fruits. After applying exogenous Si fertilizer, the Si content in pepper plants and fruits under normal treatment and autotoxicity stress treatment was significantly increased, and autotoxicity stress had no significant effect on the absorption of Si. Among them, compared with T1 treatment, the accumulation of Si in pepper leaves, roots, stems and fruits in T2 treatment was significantly increased by 1.81 times, 0.76 times, 1.12 times and 2.96 times (P < 0.05); compared with T3 treatment, the accumulation of Si in pepper leaves, roots, stems and fruits in T4 treatment was significantly increased by 1.44 times, 1.24 times, 1.31 times and 2.34 times (P < 0.05).

[0123] Table 10 Effect of exogenous Si on the accumulation of Si content in pepper under PA stress

[0124]

[0125]

[0126] As shown in Table 11, Table 12 and Table 13, root application of exogenous nano-SiO2 significantly improved the absorption of mineral elements by pepper plants and fruits under autotoxicity stress. As shown in Table 11, autotoxicity stress has different degrees of inhibitory effect on the absorption of mineral elements in the growth and development of pepper plants and fruits. Among them, compared with T1 treatment, the content of N and K in pepper leaves and roots decreased significantly by 19.91% and 13.64% (P < 0.05) in T3 treatment; the content of N, P and K in stems decreased significantly by 26.10%, 28.68% and 8.03% (P < 0.05); the content of N, P and K in fruits decreased significantly by 44.58%, 23.87% and 6.96% (P < 0.05). The application of exogenous Si fertilizer promoted the accumulation of N, P and K elements in pepper plants and fruits under normal conditions and autotoxicity stress treatments to varying degrees. Among them, compared with T3 treatment, the contents of N, P and K in pepper leaves under T4 treatment increased significantly by 53.57%, 10.43% and 9.31% (P < 0.05), respectively; the contents of N and K in roots increased significantly by 7.90% and 4.47%, respectively (P < 0.05); the contents of P and K in stems increased significantly by 21.03% and 5.88%, respectively (P < 0.05); the contents of N, P and K in fruits increased significantly by 30.17%, 37.06% and 4.37%, respectively (P < 0.05).

[0127] Table 11 Effects of exogenous Si on the content of macroelements in pepper under PA stress

[0128]

[0129]

[0130] As shown in Table 12, compared with T1 treatment, the accumulation of Ca in pepper leaves, roots, stems and fruits was significantly reduced by 20.77%, 35.25%, 34.49% and 29.15% (P < 0.05), respectively; the accumulation of Mg in pepper leaves, roots, stems and fruits was significantly reduced by 9.49%, 14.84%, 7.91% and 13.92% (P < 0.05), respectively. Under normal conditions, the application of exogenous Si fertilizer significantly increased the accumulation of Ca and Mg in the roots, stems, leaves and fruits of pepper; after the application of exogenous Si fertilizer under autotoxicity stress, the Ca content in the leaves, stems and fruits of pepper in T4 treatment was significantly increased by 12.98%, 22.78%, 19.31% and 1769% respectively compared with T3 treatment (P < 0.05); the Mg content in the leaves, roots, stems and fruits of pepper was significantly increased by 4.90%, 9.17%, 7.03% and 7.35% respectively (P < 0.05).

[0131] Table 12 Effects of exogenous Si on the content of secondary elements in pepper under PA stress

[0132]

[0133] As shown in Table 13, autotoxicity stress significantly inhibited the accumulation of mineral trace elements in pepper plants and fruits. Compared with T1 treatment, the content of Cu, Fe, Zn and Mn in pepper leaves decreased significantly by 5.93%, 15.38%, 3.52% and 22.62% (P < 0.05) in T3 treatment, the content of Cu, Fe, Zn and Mn in roots decreased significantly by 11.81%, 23.14%, 27.93% and 27.17% (P < 0.05) in T3 treatment, the content of Cu, Fe, Zn and Mn in stems decreased significantly by 13.30%, 40.21%, 35.27% and 2278% (P < 0.05) in T3 treatment, and the content of Cu, Fe, Zn and Mn in fruits decreased significantly by 18.61%, 27.48%, 47.96% and 51.49% (P < 0.05) in T3 treatment. The application of exogenous Si promoted the accumulation of mineral trace elements in pepper plants and fruits to varying degrees. Compared with T3 treatment, the contents of Cu, Fe, Zn and Mn in pepper leaves under T4 treatment increased significantly by 3.07%, 8.01%, 26.61% and 17.03% respectively (P<0.05); the contents of Cu, Zn and Mn in roots decreased significantly by 8.41%, 19.03% and 18.06% respectively (P<0.05); the contents of Cu, Fe, Zn and Mn in stems decreased significantly by 9.30%, 32.03%, 26.28% and 18.76% respectively (P<0.05); the contents of Cu, Fe, Zn and Mn in fruits decreased significantly by 18.64%, 18.52%, 46.08% and 62.28% respectively (P<0.05). In addition, under normal conditions, the application of exogenous Si also significantly increased the accumulation of Cu, Fe, Zn, and Mn elements in pepper plants and fruits.

[0134] Table 13 Effects of exogenous Si on trace element contents of pepper under PA stress

[0135]

[0136]

[0137] As shown in Table 14, root application of exogenous nano-SiO2 effectively reduced the sugar content accumulation of pepper plants under autotoxicity stress, and significantly promoted the accumulation of sugar content in fruits. Compared with T1 treatment, the contents of reducing sugar, sucrose and fructose in pepper leaves and roots in T3 treatment were significantly increased by 52.16%, 26.47%, 113.00% and 32.65%, 38.89%, 194.74% (P < 0.05), respectively, and the starch content was significantly reduced by 33.33% and 49.76% (P < 0.05); the contents of reducing sugar, sucrose and fructose in pepper fruits were significantly decreased by 31.10%, 22.42%, 27.32% (P < 0.05), respectively, and the starch content was significantly increased by 124.65% (P < 0.05). After applying exogenous Si fertilizer under autotoxicity stress, the starch content in pepper leaves and roots increased significantly by 31.25% and 36.54% (P < 0.05), respectively, and the reducing sugar, sucrose and fructose contents in the roots showed a significant downward trend. In addition, after applying exogenous Si, the reducing sugar, fructose and sucrose contents in pepper fruits under autotoxicity stress increased significantly, while the starch content in the fruit decreased significantly by 55.51% (P < 0.05).

[0138] Table 14 Effects of exogenous Si on the content of sugars in different parts of pepper under PA stress

[0139]

[0140]

[0141] As shown in Table 15, root application of exogenous nano-SiO2 significantly increased the activity of key enzymes of sugar metabolism in pepper plants and fruits under autotoxicity stress, and alleviated the degree of inhibition of autotoxicity stress on the sugar metabolism process of pepper. Compared with normal conditions, autotoxicity stress treatment significantly inhibited the activity of key enzymes of sugar metabolism in pepper leaves, roots and fruits. Compared with T1 treatment, the activities of SPS, SS, AI and NI in pepper leaves were significantly reduced by 61.84%, 27.03%, 51.67% and 47.00% (P < 0.05), in pepper roots, by 47.13%, 30.86%, 65.16% and 52.13% (P < 0.05), and in pepper fruits, by 32.57%, 13.57%, 8.65% and 17.25% (P < 0.05); under autotoxicity stress treatment, the application of exogenous nano-SiO2 significantly increased the activity of key enzymes of sugar metabolism in pepper plants and fruits under autotoxicity stress, and alleviated the degree of inhibition of autotoxicity stress on the sugar metabolism process of pepper. Compared with normal conditions, autotoxicity stress treatment significantly inhibited the activity of key enzymes of sugar metabolism in pepper leaves, roots and fruits. Compared with T1 treatment, the activities of SPS, SS, AI and NI in pepper leaves were significantly reduced by 61.84%, 27.03%, 51.67% and 47.00% (P < 0.05), in pepper roots, by 47.13%, 30.86%, 65.16% and 52.13% (P < 0.05), and in pepper fruits, by 32.57%, 13.57%, 8.65% and 17.25% (P < 0.05). All source Si fertilizers increased the activities of key enzymes of sugar metabolism in pepper leaves, roots and fruits to varying degrees. Compared with T3 treatment, the activities of SPS, SS, AI and NI in pepper leaves under T4 treatment were significantly increased by 64.99%, 26.13%, 142.40% and 43.89% (P<0.05), respectively; the activities of SPS, SS and NI in pepper roots were significantly increased by 38.95%, 25.10% and 41.88% (P<0.05), respectively; the activities of SPS, SS, AI and NI in pepper fruits were significantly increased by 31.37%, 6.30%, 14.33% and 21.62% (P<0.05), respectively.

[0142] Table 15 Effects of exogenous Si on the activities of key enzymes in sugar metabolism in different parts of pepper under PA stress

[0143]

[0144]

[0145] like Fig.11As shown in the figure, root application of exogenous nano-SiO2 significantly promoted the absorption and transformation of nitrogen by pepper plants and fruits under autotoxicity stress. Autotoxicity stress caused the nitrate nitrogen content in pepper leaves, roots and fruits to increase to varying degrees, while the ammonium nitrogen content decreased significantly. Among them, compared with T1 treatment, the nitrate nitrogen content in leaves and fruits increased significantly by 25.51% and 44.36% (P < 0.05) in T3 treatment, respectively, while the content in roots did not change significantly. At the same time, the ammonium nitrogen content in roots and fruits decreased significantly, while the content in leaves showed a downward trend but not significantly. After applying exogenous Si fertilizer under autotoxicity stress, the nitrate nitrogen content in pepper leaves and fruits of T4 treatment was significantly reduced by 22.54% and 16.44% (P<0.05), respectively, compared with T3 treatment, while the content in the root system was significantly increased by 45.70% (P<0.05). At the same time, the ammonium nitrogen content in leaves, roots and fruits was significantly increased by 72.23%, 86.62% and 32.42% (P<0.05), respectively.

[0146] As shown in Table 16, root application of exogenous nano-SiO2 significantly alleviated the degree of inhibition of key enzymes of nitrogen metabolism in pepper plants and fruits under autotoxicity stress, thereby promoting the absorption and utilization of nitrogen by pepper plants and fruits. Compared with normal conditions, autotoxicity stress treatments inhibited the activities of key enzymes of nitrogen metabolism in pepper leaves, roots and fruits to varying degrees. Among them, compared with T1 treatment, the NR and GS activities of pepper leaves in T3 treatment were significantly reduced by 28.30% and 32.74% (P < 0.05), respectively, and the NR, GS and GOGAT activities of pepper roots and fruits were significantly reduced by 18.99%, 46.85% and 35.06% (P < 0.05), respectively. The application of exogenous Si fertilizer increased the activities of NR, GS and GOGAT in pepper leaves, roots and fruits under normal conditions and autotoxicity stress to varying degrees. Compared with the T3 treatment, the activities of NR and GOGAT in pepper roots and fruits under T4 treatment were significantly increased by 22.19%, 30.67% and 29.16%, 25.44% (P < 0.05), respectively; compared with the T1 treatment, the activities of GS and GOGAT in pepper leaves, roots and fruits under T2 treatment also showed an increasing trend to varying degrees.

[0147] Table 16 Effects of exogenous Si on the activities of key enzymes of nitrogen metabolism in different parts of pepper under PA stress

[0148]

[0149]

[0150] As shown in Table 17, root application of exogenous nano-SiO2 significantly alleviated the flowering and fruiting of pepper under autotoxicity stress. Autotoxicity stress significantly inhibited the flowering and fruiting of pepper plants during the flowering period. Compared with the T1 treatment, the number of flowers, the number of fruits and the flowering rate of pepper plants in the T3 treatment were significantly reduced by 41.67%, 31.14% and 34.85% (P < 0.05), respectively; the application of exogenous Si fertilizer significantly promoted the flowering and fruiting process of pepper plants under normal treatment and autotoxicity stress treatment. Among them, compared with the T3 treatment, the flowering rate and the number of fruits of pepper plants in the T4 treatment were significantly increased by 32.56% and 17.98%, respectively (P < 0.05).

[0151] Table 17 Effects of exogenous Si on flowering and fruiting of pepper plants under PA stress

[0152]

[0153] As shown in Table 18, root application of exogenous nano-SiO2 significantly alleviated the inhibitory effect of autotoxicity stress on the morphological growth and biomass accumulation of pepper fruit, thereby increasing the yield of pepper fruit under autotoxicity stress. Compared with normal conditions, autotoxicity stress significantly inhibited the biomass accumulation and morphological growth of pepper fruit. Among them, compared with T1 treatment, the fresh weight, dry weight, fruit hardness, fruit transverse diameter and fruit longitudinal diameter of T3 were significantly reduced by 34.79%, 38.36%, 23.44%, 25.62% and 12.08% respectively (P < 0.05); after applying exogenous Si fertilizer, the dry weight and fruit transverse diameter of pepper fruit under autotoxicity stress were significantly increased by 33.97% and 43.65% respectively (P < 0.05), and the fruit shape index was closer to 1.00.

[0154] Compared with T1 treatment, the fruit yield per pepper plant in T3 treatment was significantly reduced by 51.75% (P<0.05); after applying exogenous Si fertilizer under autotoxicity stress treatment, the fruit yield per pepper plant was significantly increased by 50.81% (P<0.05).

[0155] Table 18 Effects of exogenous Si on pepper fruit yield and morphological growth under PA stress

[0156]

[0157] As shown in Table 19, root application of exogenous nano-SiO2 can significantly improve the comprehensive nutritional quality of pepper fruit under autotoxicity stress. Compared with normal conditions, the contents of various nutrients in pepper fruit under autotoxicity stress showed a significant downward trend. Compared with T1 treatment, the soluble solid content of pepper fruit in T3 treatment was significantly reduced by 16.89% (P < 0.05), and the contents of soluble sugar, VC, soluble protein and free amino acids were significantly reduced by 16.78%, 16.88%, 13.33% and 12.28% (P < 0.05), respectively. In addition, the titratable acid and nitrate contents of pepper fruit under autotoxicity stress treatment were significantly increased by 9.10% and 25.00% (P < 0.05), respectively. After applying exogenous Si fertilizer, the contents of various nutrients in pepper fruit under normal conditions and autotoxicity stress treatment showed a significant upward trend. Among them, compared with T3 treatment, the soluble solid content of pepper fruit in T4 treatment was significantly increased by 15.44% (P<0.05), and the contents of soluble sugar, VC, soluble protein and free amino acids were significantly increased by 19.01%, 12.50%, 7.69% and 7.95%, respectively (P<0.05), and the titratable acid and nitrate contents of pepper fruit were significantly decreased by 25.56% and 14.29%, respectively (P<0.05).

[0158] Table 19 Effects of exogenous Si on the nutritional quality of pepper fruit under PA stress

[0159]

[0160] The present invention uses nutrient solution as solvent to apply phthalic acid (PA) to induce pepper autotoxicity stress (PA concentration is 1.5mmol / L, obtained by preliminary experimental screening), wherein the nutrient solution formula uses 1 / 2 times Japanese Yamazaki pepper nutrient solution, and 150mL of different nutrient solutions are irrigated every 3 days. The 'Syngenta Maso' pepper variety is used as a test material, and the autotoxicity stress treatment is started when the three leaves and one heart are formed. At the same time, exogenous nano-SiO2 (Si concentration is 1.5mmol / L, obtained by preliminary experimental screening) is applied to the roots using nutrient solution as solvent, and exogenous Si fertilizer treatment is performed every 6 days. After entering the flowering period, the nutrient solution is changed to 1 times Japanese Yamazaki pepper nutrient solution, and the irrigation treatment amount is changed to 300mL each time. After sampling, the study found that root application of exogenous nano-SiO2 can effectively promote the growth and development, photosynthetic process, antioxidant capacity, water metabolism, carbon and nitrogen metabolism and mineral element absorption of pepper plants under autotoxicity stress, thereby promoting the growth and development of pepper fruits and increasing yield and quality, and significantly alleviating the degree of autotoxicity stress of PA on peppers.

[0161] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: The following steps are involved: Step 1: Preparation for planting: Select plump pepper seeds and soak them in 55℃ warm water for 30 minutes before germination. Step 2: sowing. When the seeds are white, sow them in a 72-hole tray. When the seedlings have three leaves and one heart, transplant them into a nutrient pot filled with a substrate. The growth environment temperature is 26℃ / 16℃ and the photoperiod is 12h / 12h. Step three, promote growth and development. After the seedlings have grown for 5 days, apply phthalic acid to the roots using the nutrient solution as a solvent to induce autotoxic stress on the peppers. At the same time, apply exogenous nano-SiO2 to the roots using 1 / 2 times the Japanese Yamazaki pepper nutrient solution as a solvent. The treatment volume for each irrigation is 150 mL. After entering the flowering period, the nutrient solution is changed to 1 times, and the treatment volume for each irrigation is changed to 300 mL.

2. The method of claim 1 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: After 40 days of treatment, the third functional leaf of the pepper was taken and the leaf area was measured using a LI-3000C leaf area meter; the number of leaves was measured using the counting method.

3. The method of claim 1 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: After 40 days of treatment, the roots of each treatment were cleaned and scanned using a root scanner. The root images were analyzed using WinRHIZO software to obtain the root surface area, total root volume, average root diameter and total root length.

4. The method of claim 1 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: After 40 days of treatment, fresh roots of each treatment were taken and cleaned, and 0.2 g of fresh root samples were placed in a 10 mL centrifuge tube, and 3 mL of PBS and TTC were added. The samples were kept at 37 °C for 1 h, and 1 mL of sulfuric acid was added to terminate the reaction. The roots were taken out and wiped dry, and the volume was fixed to 10 mL with ethyl acetate. The absorbance was measured at 485 nm, and the root activity was calculated according to the formula.

5. The method of claim 1 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: After 40 days of treatment, select the second and third fully expanded functional leaves of the seedlings, remove the midrib, cut into pieces and mix well, weigh 0.05 g and put it into a 10 mL test tube, use 10 mL 96% ethanol to extract the photosynthetic pigments, seal the test tube, and place it in the dark for 24 hours. During the period, shake it occasionally until the leaves turn white. When measuring, adjust to zero with 96% ethanol and measure the absorbance of the extract at 665nm, 649nm and 470nm.

6. The method of claim 1 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: After 40 days of treatment, chlorophyll fluorescence was measured using a LI-6800 portable photosynthetic instrument. Before the measurement, the pepper seedlings to be tested were dark-adapted for 30 minutes, and the second and third fully expanded functional leaves below the growth point of the seedlings were selected to measure the maximum photochemical efficiency of PSII.

7. The method of claim 1 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: After 40 days of treatment, the second functional leaf and root samples under the growth point of each pepper were collected, and the water content of the leaves was measured by water absorption specific gravity method; The leaves were ground into a homogenate and the concentration of the leaf juice was measured using a digital saccharimeter.

8. The method of claim 7 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: Use a portable plant water potential pressure chamber for measurement. Take the second functional leaf after 40 days of treatment, cut it flat from the petiole, and quickly put it into the sample holder of the instrument. The incision should expose 5mm of the sample holder gasket. Tighten the ring cover and quickly put it into the pressure chamber. Apply pressure at a rate of 0.05MPa per second. When water film appears on the petiole incision, quickly close the air valve and record the pressure gauge reading. The negative value of the data is the leaf water potential.

9. The method of claim 1 for alleviating the self-toxic effect of pepper and promoting plant growth and development and increasing fruit yield and quality based on exogenous silicon, characterized in that: When the pepper plants enter the flowering period, select pepper plants with consistent growth and use the counting method to calculate the number of flower buds, number of blossoms, number of fruits and number of fruits; flowering rate = number of flower buds / number of blossoms. After the fruits are ripe, harvest fruit samples with consistent maturity in 3 batches, and use a vernier caliper to measure the horizontal and vertical diameters of the fruits; fruit shape index = vertical diameter of the fruit / horizontal diameter of the fruit.

10. The method of claim 9 for alleviating the self-toxicity of pepper and promoting the yield and quality improvement of pepper based on exogenous silicon, characterized in that: Fruit samples with the same maturity were selected from each treatment, and the fresh samples were made into pulp. The soluble solids content was determined by a digital saccharimeter; the soluble protein content was determined by the Coomassie Brilliant Blue G-250 method; the free amino acid content was determined by the ninhydrin colorimetric method, and the fruit quality was tested.

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