CN112369296A

CN112369296A - Cultivation management method for improving photosynthesis of flue-cured tobacco seedlings under lead and cadmium stress

Info

Publication number: CN112369296A
Application number: CN202011256482.9A
Authority: CN
Inventors: 姜永雷; 邹聪明; 李军营; 赵高坤; 陈颐; 胡彬彬; 刘加红; 马二登; 邓小鹏
Original assignee: Yunnan Academy of Tobacco Agricultural Sciences
Current assignee: Yunnan Academy of Tobacco Agricultural Sciences
Priority date: 2020-11-11
Filing date: 2020-11-11
Publication date: 2021-02-19
Anticipated expiration: 2040-11-11
Also published as: CN112369296B

Abstract

The invention discloses a cultivation management method for improving photosynthesis of flue-cured tobacco seedlings under the stress of lead and cadmium, which comprises the steps of applying silicon fertilizer in tobacco fields with excessive lead and cadmium according to the dosage of 154-308 kg/mu for pre-intervention before the seedlings are planted; transplanting tobacco seedlings into the plots treated in the step A, and watering for rooting; and applying silicon fertilizer for intervention 15-20 days after the seedlings are transplanted according to the dosage of 66-132 kg/mu. According to the method, the silicon fertilizer with the appropriate amount is applied to the land with the excessive lead and cadmium before transplanting for pre-intervention, and then the silicon fertilizer is continuously applied after transplanting for intervention, so that the problem that the photosynthesis of the flue-cured tobacco seedlings is inhibited in the lead and cadmium stress environment is effectively solved, the net photosynthetic rate of the seedlings can be remarkably improved, the healthy growth of tobacco is promoted, and a solid foundation is laid for improving the yield and the quality of tobacco leaves.

Description

Cultivation management method for improving photosynthesis of flue-cured tobacco seedlings under lead and cadmium stress

Technical Field

The invention belongs to the technical field of tobacco cultivation, and particularly relates to a cultivation management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress, which can effectively solve the problem that photosynthesis of the flue-cured tobacco seedlings is inhibited under the lead-cadmium stress environment and can obviously improve net photosynthetic rate of the seedlings.

Background

The healthy growth of the cured tobacco seedlings is an important link for determining the final yield and quality of tobacco leaves. The growth and development of the plants cannot be separated from photosynthesis, which is the material basis of all material metabolism and energy metabolism in the biological world, provides important materials and energy for the growth and development of the plants and is an important factor for determining the yield and quality of final agricultural products. Therefore, the normality or normality of photosynthesis of flue-cured tobacco seedlings is the key for healthy growth of the flue-cured tobacco seedlings.

Research shows that when plants are stressed by environment, plant cells are damaged, cell membrane structural disorder and tissue death are caused, chloroplast structures are damaged, chlorophyll content is reduced, photosynthesis is changed, photosynthesis rate is obviously reduced, photosynthetic electron transfer activity is weakened, and photosynthesis phosphorylation is inhibited.

Lead (Pb) and cadmium (Cd) are non-essential heavy metal elements for plant growth, have the characteristics of strong toxicity, difficult degradation in soil and easy absorption and accumulation in vivo by plants, can have adverse effects on the growth and development of plants when the concentration in the soil exceeds a certain range, and can cause the plants to be poisoned and even die when the concentration is too high. Therefore, the characteristic that heavy metal affects plant growth through contaminated soil and enters edible parts of plants through roots to produce toxic action on organisms is a remarkable characteristic of heavy metal pollution, so that the heavy metal pollution is one of the most widely-affected environmental problems at present. The tobacco has strong lead and cadmium enrichment capacity, lead and cadmium in the soil are main sources of the lead and cadmium in the tobacco, the lead and cadmium pollution can inhibit photosynthesis and respiration of the tobacco, the yield and the quality of the tobacco are reduced, and the lead and cadmium in the tobacco enter a human body in an aerosol form in the smoking process and can cause certain harm to the human body.

Silicon is a potential beneficial element for higher plants, and has an important role in maintaining plant growth. Researches show that the organic silicon fertilizer can reduce the accumulation of Cd in rice and corn and improve the tolerance of plants, but the related detoxification mechanism is lack of deep explanation, and the research on whether the silicon fertilizer can relieve the photosynthesis of plants under the stress of lead and cadmium and even relieve the toxic action of the stress of lead and cadmium on the growth of tobacco seedlings has not been well researched. Therefore, the key point for solving the problems is to develop a cultivation management method for improving the photosynthesis of the flue-cured tobacco seedlings under the lead-cadmium stress, which can effectively solve the problem that the photosynthesis of the flue-cured tobacco seedlings is inhibited under the lead-cadmium stress environment and can obviously improve the net photosynthetic rate of the seedlings.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a cultivation management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress, which can effectively solve the problem that photosynthesis of the flue-cured tobacco seedlings is inhibited under the lead-cadmium stress environment and can obviously improve net photosynthetic rate of the seedlings.

The purpose of the invention is realized as follows: the method comprises the steps of land pre-intervention, seedling transplantation and post-cultivation intervention, and specifically comprises the following steps:

A. pre-intervention of the land parcel: before seedling planting, applying a silicon fertilizer in tobacco fields with excessive lead and cadmium according to the dosage of 154-308 kg/mu for pre-intervention;

B. transplanting seedlings: transplanting tobacco seedlings into the plots treated in the step A, and watering for rooting;

C. intervention after planting: and applying silicon fertilizer for intervention 15-20 days after the seedlings are transplanted according to the dosage of 66-132 kg/mu.

The invention has the beneficial effects that:

1. according to the method, the silicon fertilizer with the appropriate amount is applied to the land with the excessive lead and cadmium before transplanting for pre-intervention, and then the silicon fertilizer is continuously applied after transplanting for secondary intervention, so that the problem that the photosynthesis of the flue-cured tobacco seedlings is inhibited in the lead and cadmium stress environment is effectively solved, the net photosynthetic rate of the seedlings can be remarkably improved, the healthy growth of tobacco is promoted, a solid foundation is laid for improving the yield and quality of tobacco leaves, and theoretical and technical supports are provided for preventing and controlling the lead and cadmium stress of the field flue-cured tobacco seedlings.

2. The invention has the advantages of simple operation and low cost: the effect of improving the photosynthesis of the flue-cured tobacco seedlings can be achieved only by applying appropriate silicon fertilizers before and after transplanting, the applicability is strong, and the method is suitable for large-area popularization and application; and the organic silicon fertilizer and the inorganic silicon fertilizer are low in price, and have the advantages of low investment and high benefit compared with other methods for relieving the damage caused by lead and cadmium stress by adopting a growth regulator.

3. The invention has obvious effect of relieving lead and cadmium stress. The invention is adopted before and after the field seedlings are transplanted and is compared with the blank group, which shows that the net photosynthetic rate of the leaves of the tobacco seedlings is reduced under the lead-cadmium stress environment, the photosynthetic mechanism is damaged to a certain degree, and the photosynthetic rate is reduced due to the influence on the transmission of photosynthetic electrons. After the silicon fertilizer is applied according to the invention, the net photosynthetic rate of the tobacco leaves can be improved, the growth of the tobacco is promoted, wherein the net photosynthetic rate of the organic silicon fertilizer treatment is improved to the maximum; the application of the silicon fertilizer can improve the number of the PS II reaction centers stressed in tobacco units, optimize the energy flow of the PS II reaction centers, increase the conversion rate of captured electrons, improve the net photosynthetic rate and relieve the damage of lead and cadmium stress on the photosynthetic mechanism of the flue-cured tobacco seedlings.

Drawings

FIG. 1 shows the effect of different silicon fertilizers on the photosynthesis parameter Pn of lead and cadmium stress treatment in the example;

FIG. 2 is a graph showing the effect of different silicon fertilizers on the photosynthesis parameter Gs of lead and cadmium stress treatment in the example;

FIG. 3 shows the effect of different silicon fertilizers on the photosynthesis parameter Ci of lead and cadmium stress treatment in the example;

FIG. 4 shows the effect of different silicon fertilizers on photosynthesis parameters Tr of lead and cadmium stress treatment in the example.

Detailed Description

The invention is further illustrated by the following figures and examples, which are not intended to limit the invention in any way, and any variations or modifications which are based on the teachings of the invention are intended to be within the scope of the invention.

The method comprises the steps of land pre-intervention, seedling transplantation and post-cultivation intervention, and specifically comprises the following steps:

A. pre-intervention of the land parcel: before seedling planting, applying a silicon fertilizer in a tobacco field with excessive lead and cadmium according to the dosage of 154-308 kg/mu (converted by the addition amount of 1-2 g/kg of soil) for pre-intervention;

C. intervention after planting: and applying silicon fertilizer for intervention 15-20 days after the seedlings are transplanted according to the dosage of 66-132 kg/mu (0.43-0.86 g/kg of addition amount of soil).

The method also comprises at least one subsequent intervention step, wherein the subsequent intervention step is to identify the lead-cadmium stress characterization of the seedlings 25-30 days after the previous intervention after the transplantation is finished, the seedlings with the physical indexes of leaf length, leaf width, stem girth and opening degree which are obviously different from those of the blank control group are executed according to half of the application amount of the step C, and the subsequent intervention step is stopped until the lead-cadmium stress characterization identified at the last time is not obvious.

The silicon fertilizer in each intervention step comprises organic silicon fertilizer and/or inorganic silicon fertilizer, and the silicon fertilizer is directly applied to the surface of the land or buried shallow, or the aqueous solution of the silicon fertilizer is irrigated to the land.

And C, transplanting the tobacco seedlings in the step B to 6 leaves and 1 heart.

And in the step A, the silicon fertilizer is applied to tobacco fields with excessive lead and cadmium 5-10 days before seedling transplantation.

When the lead concentration in the tobacco field soil in the step A is less than or equal to 100 mg/kg and the cadmium concentration is less than or equal to 10 mg/kg, the application amount of the silicon fertilizer is 154-220 kg/mu; when the lead concentration is more than 100 mg/kg and the cadmium concentration is more than 10 mg/kg, the application amount of the silicon fertilizer is 221-308 kg/mu.

And step A and/or step C, applying the silicon fertilizer on rainfall-free days.

When the lead concentration in the tobacco field soil in the step C is less than or equal to 100 mg/kg and the cadmium concentration is less than or equal to 10 mg/kg, the application amount of the silicon fertilizer is 66-95 kg/mu; when the lead concentration is more than 100 mg/kg and the cadmium concentration is more than 10 mg/kg, the application amount of the silicon fertilizer is 96-132 kg/mu.

The tobacco seedling varieties comprise K326, KRK26, Honghuadajinyuan and Yunyan tobacco series.

Examples

S100: mixing red soil (dug in field in a rear mountain experiment base of southwest forestry university) and humus soil according to the proportion of 1:1.5 to serve as a transplanting matrix, and filling 5kg of the matrix into a plastic basin with the inner diameter of 30 cm and the height of 40 cm to serve as a transplanting foundation; adding Pb (NO)₃)₃And CdCl₂Mixing to form lead-cadmium aqueous solution, and applying the lead-cadmium aqueous solution to a substrate in a plastic basin for 10 days before transplanting, wherein the lead-cadmium aqueous solution is added with Pb (NO) to form a test group PC₃)₃And CdCl₂The application amount of the composition is as follows: the lead concentration is 0.1g/kg, and the cadmium concentration is 0.005 g/kg; meanwhile, a group of water solutions without lead and cadmium is set as a blank control group CK. Then, the test group CK and the blank control group CK are respectively divided into 4 treatment groups, PC-CK special for tobacco (urea: 0.4g/kg, monopotassium phosphate: 0.35g/kg, potassium sulfate: 0.12 g/kg) is applied 5d (no rainfall) before seedling transplantation, two organic silicon fertilizers PC-OSiFA and PC-OSiFB and inorganic silicon fertilizer PC-InOSiF are applied, the application amount of all fertilizers is 1.0g/kg, each treatment group comprises 5 repetitions, and each repetition comprises 3 tobacco seedlings.

S200: the test tobacco variety is K326, provided by tobacco agricultural science research institute in Yunnan province, the method comprises the steps of raising seedlings in a floating mode by using a matrix, selecting seedlings with excellent growth vigor and consistent growth when the seedlings grow to 6 leaves and 1 heart, transplanting the seedlings into the material pot matrix of the fertilized test group CK and the blank control group CK, and watering and rooting.

S300: and (5) after the seedlings are transplanted for 15 days, correspondingly applying the special compound fertilizer PC-CK for tobacco, the organic silicon fertilizers PC-OSiFA and PC-OSiFB and the inorganic silicon fertilizer PC-InOSiF to the test group CK and the blank control group CK in the S100 respectively according to the application amount of 0.43 g/kg.

1. Determination of photosynthesis and fluorescence parameters

1.1, determination of photosynthesis parameters: selecting a day of clear weather when the tobacco plants grow to the stem-growing period, randomly selecting a tobacco plant without plant diseases and insect pests and with consistent growth vigor, measuring photosynthetic parameters by using a Li-6400 portable photosynthetic apparatus, repeating the treatment for 5 times, taking an average value, and measuring the net photosynthetic rate (Pn) of the leaf, the stomatal conductance (Gs) and intercellular CO of the tobacco plant₂Concentration (intercellular CO)₂concentration, Ci) and transpiration rate (Tr). The measurement time is 9: 00-11: 00 (temperature is 24-28 ℃, and relative air humidity is 60-70%) of the photosynthetic activity.

1.2, measuring fluorescence parameters: dark processing the tobacco leaves for 30min, selecting the 4 th leaf from the top of the tobacco plant, and measuring chlorophyll fluorescence parameters of the tobacco leaves by using a modulated chlorophyll fluorescence instrument PAM-2100 (WALZ): initial fluorescence (Fo), PS ii maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (yii), Electron Transfer Rate (ETR), photochemical quenching coefficient (qP), non-photochemical quenching coefficient (qN), and non-chemical quenching coefficient (NPQ).

2. Statistics and analysis

The data were simply collated by Excel, compared at the 0.05 level for differences between the different data sets by One-way ANO-VA and independent T-test in SPSS (19.0), and finally tabulated by Excel and charted by origin.

2.1, the influence of different silicon fertilizers on tobacco photosynthesis parameters under the stress of lead and cadmium:

as can be seen from FIGS. 1 to 4, the net photosynthesis rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of PC-CK treatment were significantly decreased compared to CK under the stress of Pb and Cd54.41%, 30.19% and 37.47% decrease, respectively, in intercellular CO₂The concentration (Ci) increased by 34.03%. The lead and cadmium stress inhibits the photosynthetic carbon assimilation capability of the tobacco leaves and influences the photosynthesis of the tobacco leaves. Compared with the PC-CK treatment, the net photosynthesis rate (Pn) and the porosity conductance (Gs) of the silicon fertilizer are increased, and the PC-OSiFA, the PC-OSiFB and the PC-InOSiF are respectively increased by 111.00% and 49.28%, 151.97% and 61.22%, 91.12% and 21.72%. And intercellular CO₂The concentration (Ci) and the transpiration rate (Tr) were reduced by 32.37% and 24.49%, 34.35% and 35.13%, 28.17% and 22.73%, respectively, for PC-OSiFA, PC-OSiFB and PC-InOSiF. The organic silicon fertilizer is more effective for improving the net photosynthetic rate of the tobacco under the stress of lead and cadmium, probably because the organic silicon fertilizer can reduce the biological effectiveness of cadmium in soil and enhance the antagonism between cadmium and silicon, the absorption and accumulation of the cadmium by the tobacco are reduced, and the heavy metal toxicity is reduced. In this test, the lead-cadmium stress without the addition of the silicon fertilizer resulted in a very significant reduction in the net photosynthesis rate (Pn) of tobacco, accompanied by a reduction in the stomatal conductance (Gs) and intercellular CO₂The increase of the concentration (Ci) shows that the influence of lead and cadmium stress on the tobacco photosynthesis rate is mainly non-stomatal factors, the lead and cadmium stress can cause the damage of an active oxygen defense system in a plant body, so that oxygen free radicals in chloroplast are increased, a chloroplast membrane system is damaged, the chloroplast degradation is caused, the heavy metal content of lead and cadmium stress tobacco chloroplast can be reduced by adding silicon, the tobacco superoxide anion free radical generation rate is reduced, the plant carbon assimilation capability is improved, and the photosynthesis rate is increased.

2.2, influence of different silicon fertilizers on the fluorescence parameters of the tobacco under the stress of lead and cadmium:

TABLE 1 influence of different silicon fertilizers on chlorophyll fluorescence parameters of tobacco under different lead and cadmium stresses

As shown in the table 1 below, the following examples,under lead-cadmium stress treatment, the values of initial fluorescence (Fo), psii maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (yii), Electron Transfer Rate (ETR), photochemical quenching coefficient (qP), non-photochemical quenching coefficient (qN), and non-chemical quenching coefficient (NPQ) of PC-CK were all decreased by 23.81%, 14.80%, 18.15%, 12.70%, 2.51%, 20.35%, and 40.71%, respectively, compared to CK. The maximum photosynthetic efficiency (Fv/Fm) is remarkably reduced, which indicates that the tobacco leaf photosynthetic mechanism is damaged to a certain extent due to the stress of lead and cadmium, the integrity is damaged, the activity and the opening degree of a PSII reaction center of the leaf are reduced, and the transmission of photosynthetic electrons is inhibited. The reduction of the actual photosynthetic efficiency (YII) shows that the leaf cell membrane of the tobacco is damaged under the stress of lead and cadmium, the efficiency of capturing excitation energy is reduced, the photosynthetic electron transfer rate and the photosynthetic assimilation rate are influenced, and the photosynthetic intensity is weakened. Meanwhile, the Electron Transfer Rate (ETR) of the stress tobacco is lower than that of CK, which shows that the photosynthetic electron transfer rate is reduced under stress, and the excitation energy capture rate of PSII is also reduced. The photochemical quenching coefficient (qP) of the stressed tobacco is reduced, which shows that the proportion of the open reaction center in the PS II and the participation in CO₂The fixed electrons are reduced and photosynthesis is affected to some extent. NPQ and qN of the stressed tobacco are reduced, which shows that the lead and cadmium stress inhibits an energy dissipation mechanism of tobacco leaves, the inhibition effect on a photosynthetic mechanism is increased, the redundant accumulation of light energy is caused, the activity of a PS II reaction center is reduced, and the net photosynthetic rate of the tobacco is influenced finally. And the reduction amplitude of NPQ is obviously higher than qN, which shows that the non-radiative energy dissipation mechanism depending on the lutein cycle is more sensitive to cadmium stress. Compared with PC-CK, the F0 value of PC-OSiFA, PC-OSiFB and PC-InOSiF is not changed greatly, Fv/Fm, YII and ETR are increased as same as the silicon fertilizer added into the N-PC group, and PC-OSiFA is increased by 15.41%, 42.98% and 47.71% respectively; the PC-OSiFB is increased by 22.21 percent, 34.50 percent and 41.42 percent respectively; PC-InOSiF increased by 12.70%, 20.63% and 17.54%, respectively. Meanwhile, the qP of PC-OSiFA, PC-OSiFB and PC-InOSiF are all increased by 7.02 percent, 2.06 percent and 24.24 percent respectively. The NPQ of OSiFA and OSiFB was increased by 31.91% and 5.66%, respectively, while that of InOSiF was decreased by 16.60%. After addition of silicon fertilizer, FvThe values of/Fm, YII and ETR are increased, which shows that the silicon adding treatment can relieve the damage degree on the PS II donor side and the acceptor side of the stressed tobacco leaves, increase the opening degree of a PSII reaction center and increase the electron transfer rate, and the reasons for the increase of the enzyme activity, the reduction of the active oxygen content, the relief of the membrane lipid peroxidation degree, the influence on the increase of the net photosynthetic rate (Pn) of the tobacco leaves and the relief of the toxic action of lead and cadmium stress on the tobacco can be probably caused by the silicon adding treatment. After different silicon fertilizers are added for treatment, qN and NPQ treated by the organic silicon fertilizer are increased to some extent, which shows that silicon can improve the energy dissipation mechanism of tobacco under the stress of lead and cadmium, optimize energy flow and avoid the phenomenon of photoinhibition, and simultaneously shows that the silicon fertilizer is favorable for improving the efficiency of photosynthetic pigments for converting captured electrons into chemical energy, thereby providing more sufficient energy for carbon assimilation and improving the photosynthetic property.

2.3, correlation analysis of tobacco determination indexes of different treatments:

TABLE 2 Pearson correlation of tobacco assay indices

Note: indicates significant correlation (P < 0.05); indicates very significant correlation (P < 0.01).

As shown in Table 2, net photosynthetic Rate (Pn) and intercellular CO₂The concentration (Ci) appears to be very significantly negatively correlated (P < 0.01), very significantly positively correlated with the maximum photosynthetic efficiency (Fv/Fm), the actual photosynthetic efficiency (YII) and the Electron Transfer Rate (ETR), and very significantly positively correlated with the initial fluorescence (F0) (P < 0.05). In addition, the maximum photosynthetic efficiency (Fv/Fm) is also related to intercellular CO₂The concentration (Ci) is in an extremely obvious negative correlation (P is less than 0.01) and is in an extremely obvious positive correlation (P is less than 0.01) with the actual photosynthetic efficiency (YII). The Electron Transfer Rate (ETR) is in very obvious positive correlation with the stomatal conductance (Gs), the maximum photosynthetic rate (Fv/Fm) and the actual photosynthetic rate (YII) (P is less than 0.01). In addition, the initial fluorescence (F0) is in very significant positive correlation (P < 0.01) with the transpiration rate (Tr) and is in actual photosynthetic rate(YII) exhibits significant positive correlation (P < 0.05).

2.4, analyzing main components of tobacco determination indexes of different treatments:

TABLE 3 principal Components analysis of measurement indices

As shown in Table 3, 4 main components are extracted from the test paper according to the principle that the minimum characteristic root is greater than 1, the cumulative contribution rate reaches 88.16%, and the basic characteristics of 11 measurement indexes can be reflected. The eigenvalue of the 1 st principal component is 5.38, the contribution rate is 38.39%, and the highest eigenvector is the net photosynthetic rate (Pn) which is 0.36; the eigenvalue of the 2 nd principal component is 3.35, the contribution rate is 23.92%, and the highest eigenvector is the optical quenching coefficient (qP) of 0.37; the 3 rd principal component had a characteristic value of 2.03, a contribution rate of 14.51%, and a porosity conductance (Gs) of 0.57 as an index for a characteristic vector amount higher than 0.50; the feature position of the 4 th principal component is 1.59, the contribution rate is 11.33%, and the feature vectors of the 4 th principal component are the highest transpiration rate (Tr) and intercellular CO₂Concentrations (Ci) of 0.49 and 0.48, respectively.

2.5, the experiment of the embodiment proves that the net photosynthetic rate of the tobacco leaves is reduced due to the stress of lead and cadmium, the photosynthetic mechanism is damaged to a certain extent, and the photosynthetic rate is reduced due to the influence on the transmission of photosynthetic electrons; the net photosynthetic rate of the tobacco can be improved and the growth of the tobacco can be promoted by applying different silicon fertilizers, wherein the net photosynthetic rate of the organic silicon fertilizer treatment is improved to the maximum; the application of the silicon fertilizer can improve the number of the PS II reaction centers stressed by the tobacco unit, optimize the energy flow of the PS II reaction centers, increase the conversion rate of captured electrons, improve the net photosynthetic rate and relieve the damage of lead and cadmium stress to the tobacco photosynthetic mechanism.

Claims

1. A cultivation management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress is characterized by comprising the steps of pre-intervention of plots, seedling transplantation and post-cultivation intervention, and specifically comprises the following steps:

2. The cultivation and management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress according to claim 1, characterized by further comprising at least one subsequent intervention step, wherein the subsequent intervention step is to identify lead-cadmium stress characterization of seedlings 25-30 days after the previous intervention after transplantation is finished, the seedlings with physical indexes of leaf length, leaf width, stem circumference and opening degree which are significantly different from those of a blank control group are executed according to half of the application amount of the step C, and the subsequent intervention step is stopped until the lead-cadmium stress characterization identified at the last time is not obvious.

3. The cultivation and management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress according to claim 1, wherein the silicon fertilizer in each intervention step comprises organic silicon fertilizer and/or inorganic silicon fertilizer, and the silicon fertilizer is directly applied to the surface of the land or buried shallowly or the silicon fertilizer aqueous solution is irrigated to the land.

4. The cultivation and management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress according to claim 1, wherein the tobacco seedlings transplanted in the step B are 6-leaf 1-heart seedlings.

5. The cultivation and management method for improving photosynthesis of flue-cured tobacco seedlings under the stress of lead and cadmium according to any one of claims 1 to 4, characterized in that the silicon fertilizer in the step A is applied to tobacco fields with lead and cadmium exceeding standards 5-10 days before seedling transplantation.

6. The cultivation and management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress according to claim 5, characterized in that when the lead concentration in the tobacco field soil in the step A is less than or equal to 100 mg/kg and the cadmium concentration is less than or equal to 5 mg/kg, the application amount of the silicon fertilizer is 154-220 kg/mu; when the lead concentration is more than 100 mg/kg and the cadmium concentration is more than 5 mg/kg, the application amount of the silicon fertilizer is 221-308 kg/mu.

7. The cultivation and management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress according to claim 6, wherein silicon fertilizer is applied in the step A and/or the step C in rainfall-free days.

8. The cultivation and management method for improving photosynthesis of flue-cured tobacco seedlings under lead-cadmium stress according to claim 6, wherein when the lead concentration in the tobacco field soil in the step C is less than or equal to 100 mg/kg and the cadmium concentration is less than or equal to 5 mg/kg, the application amount of the silicon fertilizer is 66-95 kg/mu; when the lead concentration is more than 100 mg/kg and the cadmium concentration is more than 5 mg/kg, the application amount of the silicon fertilizer is 96-132 kg/mu.