Photosynthetic cell model, simulation method and applications

Abstract

The application provides a photosynthesis cell model, a simulation method and application. The model is a three-dimensional cell reaction diffusion model, comprising a structure part and a reaction diffusion model. The structure part is a three-dimensional structure, comprising simulated mesophyll cells and vascular sheath cells, and the two types of cells are close to each other. The cells comprise a cell wall, a plasma membrane, a cytoplasmic matrix and orderly arranged organelles. The carbon dioxide concentration at the boundary of the cell wall of the two types of cells reaches equilibrium with the partial pressure in the intercellular space. The reaction diffusion model is used to define the material metabolism and material and energy flow relationship of each element in the cells of the structure part, and comprises a material conservation model, a biochemical reaction diffusion model, a boundary condition setting / conductivity calculation model, a parameter setting / calculation model and the like. The application further provides a method for simulating and analyzing cell photosynthesis or photosynthetic activity by using the model and application.

Description

Technical Field

[0001] This invention relates to a photosynthesis simulation model, and more specifically, to a photosynthetic cell model, simulation method, and application. Background Technology

[0002] In recent years, technicians have been dedicated to simulating the process of photosynthesis, exploring new ways to create clean energy through artificial photosynthesis technology. These technologies attempt to reproduce steps in photosynthesis, such as light absorption, charge separation, water splitting, and energy storage, under laboratory conditions using artificially designed materials and catalysts.

[0003] Photosynthesis simulation models are models developed by engineers to understand and simulate the process of photosynthesis in plants in nature. These models help to gain a deeper understanding of the mechanisms of photosynthesis and explore its potential applications in fields such as clean energy, agriculture, and medicine.

[0004] In photosynthesis simulation, mathematical models and computer simulations can be combined to optimize and predict system performance. The core of this approach lies in constructing accurate mathematical models to describe the various biochemical reactions and mass transport processes during photosynthesis, and then using computer simulations to achieve a deeper understanding of the photosynthetic process and to predict its performance. Mathematical models provide the theoretical foundation for photosynthesis simulation.

[0005] In this field, existing photosynthesis simulation models, such as the leaf-scale Farquhar photochemical model, are based on the leaf-scale Farquhar photochemical model to simulate photosynthesis. The instantaneous photosynthetic rate of a leaf can be expressed by specific mathematical formulas, which involve multiple factors such as carboxylase activity limitation, photon conduction limitation, and leaf dark respiration during the day.

[0006] Another type of photosynthesis simulation model is the crop canopy photosynthesis model, where canopy photosynthesis is the sum of photosynthetic activities carried out by the above-ground parts of numerous individual plants. A canopy photosynthesis model is a mathematical model used to simulate plant photosynthesis. By considering factors such as plant canopy structure, light conditions, and meteorological factors, it simulates and predicts the intensity and efficiency of photosynthesis in different environments. Depending on the degree of simplification of the plant canopy, canopy photosynthesis models can be divided into various types, such as large-leaf models, light-shade models, multi-layer models, and three-dimensional canopy models.

[0007] Photosynthesis simulation has many applications in the medical field. Photosynthesis simulation technology can be applied to the treatment of human diseases, such as photodynamic therapy using photosensitizers that simulate chlorophyll electron absorption and transfer, and the treatment of hypoxic diseases such as heart disease and tumors using oxygen produced by algal photosynthesis.

[0008] To increase grain yield, various methods have been employed to improve the efficiency of photosynthesis, the process of converting solar energy into crop biomass. C4 photosynthesis, due to its unique carbon dioxide concentration mechanism, exhibits higher photosynthetic efficiency than C3 photosynthesis under high light or drought conditions. This carbon dioxide concentration mechanism requires close cooperation between C4 photosynthetic metabolism and leaf structure. The general process is as follows: carbon dioxide diffuses from the intercellular air into mesophyll cells and is fixed by carbonic anhydrase and PEPC enzymes, entering the C4 acid cycle; after a series of reactions and transports, C4 acids are decarboxylated in the bundle sheath cells, releasing carbon dioxide; the released carbon dioxide is then fixed by Rubisco enzymes in the bundle sheath chloroplasts, entering the Calvin cycle. Although the basic metabolic and structural characteristics of C4 photosynthesis have been clearly elucidated, the mechanistic mechanism by which these two processes interact to achieve efficient C4 photosynthesis remains unresolved.

[0009] With ongoing research and technological advancements, photosynthesis simulation technology is expected to play a significant role in future energy, agriculture, and medicine. Despite substantial progress, photosynthesis simulation technology still faces many challenges, including how to efficiently absorb sunlight of different wavelengths and how to design stable reaction centers. Summary of the Invention

[0010] The purpose of this invention is to provide a photosynthetic cell model, simulation method, and application.

[0011] In a first aspect of the present invention, a method for simulating and analyzing cellular photosynthesis or photosynthetic activity is provided, the method comprising:

[0012] (a) Provide a photosynthetic cell model, which is a three-dimensional cell reaction-diffusion model, comprising: a structural component and a reaction-diffusion model (equations and parameters); the structural component is a three-dimensional structure, including simulated mesophyll cells and bundle sheath cells, the two types of cells being close to each other (adjacent or connected by cell walls); the cells include: cell walls, plasma membranes (protoplasmic membranes), cytoplasm, and orderly arranged organelles; the carbon dioxide concentration at the cell wall boundary of the two types of cells is in equilibrium with the partial pressure in the intercellular space; the reaction-diffusion model (which may include equations or parameters) is used to define the material metabolism and material and energy flow relationships of each component in the cells of the structural component, including: a matter conservation model, a biochemical reaction-diffusion model, a boundary condition setting and conductivity calculation model, and a parameter setting and calculation model;

[0013] (b) The photosynthetic cell model of (a) was used to simulate and analyze cell photosynthesis.

[0014] In one or more embodiments, the photosynthesis includes C4 photosynthesis; the method includes (but is not limited to) analyzing C4 photosynthetic efficiency or conductance; preferably, the method for simulating and analyzing cellular photosynthesis or photosynthetic activity includes (but is not limited to): simulating and calculating the diffusion process of carbon dioxide within or between cells, analyzing the involved biochemical reaction processes, and obtaining the carbon dioxide concentration, diffusion rate, and / or diffusion conductance at various sites within the cell; or, adjusting cell structural parameters and analyzing the influence of structural parameters on C4 photosynthesis.

[0015] In another aspect of the present invention, a photosynthetic cell model is provided, which is a three-dimensional cell reaction-diffusion model. The model includes: a structural part and a reaction-diffusion model; the structural part is a three-dimensional structure, including simulated mesophyll cells and bundle sheath cells, the two types of cells being close to each other (adjacent or connected by cell walls); the cells include: cell walls, plasma membranes, cytoplasm, and orderly arranged organelles; the carbon dioxide concentration at the cell wall boundary of the two types of cells is in equilibrium with the partial pressure in the intercellular space; the reaction-diffusion model is used to define the material metabolism and material and energy flow relationships of each element in the cells of the structural part, including: a material conservation model, a biochemical reaction-diffusion model, a boundary condition setting / derivative calculation model, and a parameter setting / calculation model.

[0016] In one or more embodiments, the mesophyll cell includes chloroplasts and vacuoles; the chloroplasts are located near the intercellular spaces and are randomly distributed, and the vacuoles are located in the middle (including the central position) of the mesophyll cell.

[0017] In one or more embodiments, the bundle sheath cell includes: a layer of chloroplasts, a layer of mitochondria, and vacuoles; the chloroplasts are located in the bundle sheath cell near the mesophyll cells, and the vacuoles are located away from the mesophyll cells.

[0018] In one or more embodiments, the mesophyll cells include 30-70 chloroplasts, preferably 35-65 chloroplasts, more preferably 40-60 chloroplasts, such as 45, 47, 50, or 55.

[0019] In one or more embodiments, in a bundle sheath cell, the layer of chloroplasts comprises a plurality of chloroplasts arranged as a whole layer.

[0020] In one or more embodiments, the photosynthesis is C4 photosynthesis, and the reaction-diffusion model includes simulated metabolites (such as carbon dioxide or bicarbonate), photosynthetic enzymes (such as carbonic anhydrase (CA), Rubisco, or PEPC enzyme (PEPC)), and decarboxylases (including NADP-ME or PEPCK); wherein, after carbon dioxide enters the mesophyll cells, it is fixed by photosynthetic enzymes (such as CA, PEPC) to form C4 acid; the C4 acid enters the bundle sheath cells through the C4 cycle, and is then decarboxylated by decarboxylases (such as ADP-ME, PEPCK) to release carbon dioxide, which is then fixed by photosynthetic enzymes (such as Rubisco enzyme) and enters the Calvin cycle (PCR, PCO).

[0021] In one or more embodiments, the mass conservation model considers only the limiting effect of PEPC enzymes on the C4 acid cycle, sets the sum of the carbon fixation rate of PEPC enzymes in mesophyll cells and the decarboxylation rate in bundle sheath cells to be equal, sets all enzymes to be uniformly distributed in specific organelles, and sets metabolites to participate in biochemical reactions and diffuse simultaneously in mesophyll cells and bundle sheath cells; the metabolite is carbon dioxide, and its mass conservation equation during reaction and diffusion is:

[0022]

[0023] in, D c (m 2 s -1 [CO2](mol m) is the liquid-phase diffusion coefficient of carbon dioxide, and η is a dimensionless coefficient representing the relative viscosity of the space where diffusion occurs. -3 ) represents the carbon dioxide concentration, v c (mol m -3 s -1 ) and v o (mol m -3 s -1 These represent the rate at which carbon dioxide is fixed by Rubisco enzyme in bundle sheath cells and the rate at which carbon dioxide is released during photorespiration, respectively.

[0024] h(mol m -3 s -1 ) is the rate of carbon dioxide hydration reaction, r m and r bs (mol m -3 s -1 (v) represents the respiration rate in mesophyll cells and bundle sheath cells, respectively. p (mol m -3 s -1 ) represents the carboxylation rate of PEPC enzyme, v me (mol m-3 s -1 ) and v pepck (mol m -3 s -1 These represent the decarboxylation rates of chloroplasts in bundle sheath cells catalyzed by NADP-ME and PEPCK-catalyzed in the cytoplasm, respectively.

[0025] In one or more embodiments, in the mass conservation model, the metabolite is bicarbonate, and the mass conservation equation for bicarbonate during the reaction-diffusion process is:

[0026]

[0027] in, D b (m 2 s -1 ) is the liquid-phase diffusion coefficient of bicarbonate; v c v me r m r bs v o v p The definitions of h and v are the same as above; c ≠ 0 and v me ≠0 occurs only in the chloroplasts of bundle sheath cells, r m ≠0 and r bs ≠0 occurs only in the mitochondria of mesophyll cells and bundle sheath cells, respectively. o ≠0 occurs only in the mitochondria of bundle sheath cells, v p ≠0 occurs only in the cytoplasm of mesophyll cells, while h≠0 occurs only in the vacuoles of both types of cells.

[0028] In one or more embodiments, the reactive diffusion model is a C4 NADP-ME type reactive diffusion model. In this biochemical reactive diffusion model, only linear electron transport is set in the photosystem of mesophyll cells and bundle sheath cells chloroplasts, and the total electron transport chain rate J (mol m) is... -2 s -1 The equation is:

[0029]

[0030] Where I is the total light intensity, J max It is the total maximum electron transport rate per unit leaf area.

[0031] In one or more embodiments, formulas (3) / (4) are based on the premise that there is only a linear electron transport chain in the photosystem of mesophyll cells and bundle sheath cells chloroplasts.

[0032] In one or more embodiments, the biochemical reaction diffusion model is set as follows: the photosynthetic rate is limited only by ATP under light-dependent conditions; the photosystem has a Q cycle; and the ratio of the proton velocity across the thylakoid membrane to the electron flux velocity in the electron transport chain (H) is defined as follows: + / e - The ratio of proton rate to ATP production rate (H) is 3; + The ratio of ATP / electron flux is 4; therefore, the ratio of ATP generated to electron flux (ATP / e) is 4. - ) is 3 / 4 photosynthetic enzymes, including photosynthetic enzymes;

[0033] The rate (v) of carbon dioxide fixation by Rubisco enzyme in chloroplasts of bundle sheath cells c mol m -3 s -1 )for:

[0034]

[0035] Among them, K m =K c (1+[O2] / K o ), Γ * =r·[O2],[CO2] ch_bs (mol m -3 V is the concentration of carbon dioxide in the chloroplasts of the bundle sheath cells. cmax (μmol m -2 s -1 f is the maximum carboxylation rate of Rubisco enzyme per unit leaf area. V_ms and f V_bs K represents the ratio of the volume of chloroplasts in mesophyll cells and bundle sheath cells to the total volume of chloroplasts, respectively. m (mol m -3 ) is the effective Michaelis-Menten constant of Rubisco enzyme in mesophyll cells, Γ * (mol m -3 () is the carbon dioxide compensation point without considering mitochondrial respiration, r is half the reciprocal of the carboxyl-oxygen ratio of Rubisco enzyme, K c (mol m -3 ) is the Michaelis-Menten constant for the carboxylation of Rubisco enzymes, K o (mol m -3 [O2](mol m) is the Michaelis-Menten constant for the oxidation of Rubisco enzymes. -3 S is the concentration of oxygen in the chloroplasts of the bundle sheath cells. mes (m2 m -2 V is the surface area of ​​mesophyll cells exposed to intercellular air per unit leaf area. ch_bs (m 3 m -2 () is the volume of chloroplasts in bundle sheath cells per unit surface area of ​​mesophyll cells exposed to intercellular air.

[0036] In one or more embodiments, the biochemical reaction diffusion model is set such that the respiration rate per unit leaf area is the same in mesophyll cells and bundle sheath cells, and that respiration in mesophyll cells occurs in the cytoplasm; the respiration rate per unit volume of mitochondria in both types of cells is r. m and r bs for:

[0037]

[0038] Where R d (mol m -2 s -1 V is the respiration rate per unit leaf area. cy_ms (m 3 m -2 V is the volume of mesophyll matrix per unit surface area of ​​a mesophyll cell exposed to intercellular air. mi_bs (m 3 m -2 S represents the volume of mitochondria in the bundle sheath cells per unit surface area of ​​a mesophyll cell exposed to intercellular air; mes It is the surface area of ​​mesophyll cells exposed to intercellular air.

[0039] In one or more embodiments, the biochemical reaction diffusion model is configured such that the peroxisomes and mitochondria of the bundle sheath cells are in one space, and the photorespiration rate v per unit volume is... o (mol m -3 s -1 The expression represents the rate of Rubisco enzyme carboxylation in the chloroplasts of bundle sheath cells multiplied by Γ. * Divide by the carbon dioxide concentration, make an integral over the chloroplast, and then divide by the volume of the mitochondria in the bundle sheath cell:

[0040]

[0041] The rate of carbon dioxide net hydration reaction h (mol m) -3 s -1 )for:

[0042]

[0043] Among them [HCO3]- ](mol m -3 V is the concentration of bicarbonate ions. ca (mol m -2 s -1 ) represents the maximum catalytic activity of CA enzyme per unit leaf area, x ca V(m) is the partition coefficient of CA enzyme in different organelles. 3 m -2 K is the volume of different organelles per unit surface area of ​​a mesophyll cell exposed to intercellular air. e_ca (mol m -3 K is the equilibrium constant of the CA enzyme. m,c_ca and K m,b_ca (mol m -3 ) are the Michaelis-Menten constants for the hydration and dehydration reactions of CA enzyme, respectively, and pH is the pH value.

[0044] In one or more embodiments, the biochemical reaction diffusion model is set to have only linear electron transport chains in mesophyll cells, and to have a Q cycle in the photosystem. The ratio of the proton velocity across the thylakoid membrane in the linear electron transport chain to the electron flux velocity in the electron transport chain (H) is defined as follows: + / e - The ratio of proton rate to ATP production rate (H) is 3; + The ratio of ATP / electron flux is set to 4; therefore, the ratio of ATP generated to electron flux (ATP / e) is... - The value is 3 / 4; the carboxylation rate of PEPC enzyme is:

[0045]

[0046] Among them, V pepc (mol m -2 s -1 [CO2] represents the maximum carboxylation rate of PEP. cy_ms (mol m -3 K is the concentration of carbon dioxide in the cytoplasm of mesophyll cells. p (mol m -3 ) is the Michaelis-Menten constant for carbon dioxide in PEPC enzyme; v me Represented as v p The integral in the mesophyll cell cytoplasm multiplied by the proportion allocated to the NADP-ME decarboxylation pathway, f me Divide by the volume of the chloroplasts in the bundle sheath cells:

[0047]

[0048] v pepckRepresented as v p The integral in the mesophyll cell cytoplasm multiplied by the proportion allocated to the PEPCK decarboxylation pathway (1-f) me Divide by the volume of the cytoplasm of the bundle sheath cells:

[0049]

[0050] In one or more embodiments, the boundary condition setting and conductivity calculation model is configured such that carbon dioxide can diffuse from intercellular air into mesophyll cells but cannot diffuse directly from intercellular air into bundle sheath cells, and bicarbonate cannot pass through the cell walls of mesophyll cells or bundle sheath cells; the process by which metabolites pass through the membranes of chloroplasts, mitochondria, and vacuoles, cell membranes, and plasmodesmata is as follows:

[0051]

[0052] The left side of equation (13) represents the flow through the boundary, where r is the resistance of metabolites at the boundary, and C1 and C2 (mol m) -3 () represents the concentration of metabolites on both sides of the boundary.

[0053] In one or more embodiments, the boundary condition setting and conductance calculation model are configured such that metabolites can pass through the membranes of chloroplasts, mitochondria, and vacuoles; the resistance of metabolites (such as carbon dioxide or bicarbonate) to passing through the membranes is:

[0054] r = P co2 -1 (14)

[0055] Where P co2 It refers to the permeability of carbon dioxide on the membrane.

[0056] In one or more embodiments, in the boundary condition setting and conductance calculation model, the resistance of metabolites (such as carbon dioxide or bicarbonate) at the interface between the two types of cells is:

[0057]

[0058] Among them, S w / S l φ is the ratio of the interface area between mesophyll cells and bundle sheath cells to the leaf area; φ is the proportion of the interface area covered by plasmodesmata; L pd (m) is the length of plasmodesmata.

[0059] In one or more embodiments, in the boundary condition setting and conductivity calculation model, for the cell wall boundary of mesophyll cells exposed to intercellular air, a conductivity constant G encompassing the cell wall and plasma membrane is defined. wall(mol m -2 s -1 If the velocity of carbon dioxide entering the mesophyll cell at each point on this cell wall is (mol / m³), then... -2 s -1 )for:

[0060]

[0061] Where P (Pa) is atmospheric pressure, s c (mol m -3 Pa -1 ) represents the solubility of carbon dioxide, C i (mol m -3 C is the concentration of carbon dioxide in the intercellular space. wall (mol m -3 () represents the concentration of carbon dioxide on the cell walls of mesophyll cells;

[0062] Furthermore, the average flow rate of carbon dioxide entering the three-dimensional structural portion is defined as the integral of the flow rates at all points on the cell wall boundary exposed to intercellular air in the mesophyll cells, divided by the area of ​​the cell wall exposed to intercellular air in the mesophyll cells. The net photosynthetic rate A (mol m²) per unit leaf area is then calculated. -2 s -1 )for:

[0063]

[0064] In one or more embodiments, the boundary condition setting and conductivity calculation model is used to define the leakage rate L (mol m) of carbon dioxide from the bundle sheath cells to the mesophyll cells. -2 s -1 The rate of C4 acid decarboxylation per unit leaf area is defined as the rate of carbon dioxide fixation by Rubisco enzymes in the chloroplasts of bundle sheath cells, minus the rate of respiration in the mitochondria and the rate of photorespiration in the cytoplasm of bundle sheath cells.

[0065]

[0066] Among them, V cy_bs (m 3 m -2 () is the volume of the bundle sheath cell cytoplasm per unit surface area of ​​a mesophyll cell exposed to intercellular air; therefore:

[0067] vascular bundle sheath conductance g bs (mol m -2 s -1 bar -1 )for:

[0068]

[0069] in, and These represent the average concentrations of carbon dioxide in the chloroplasts of bundle sheath cells and the cytoplasm of mesophyll cells:

[0070]

[0071] Mesophyll conductance g m (mol m -2 s -1 bar -1 )for:

[0072]

[0073] In one or more embodiments, the cells are C4 plant cells; preferably, the plants include: monocotyledonous C4 plants or dicotyledonous C4 plants; more preferably, the plants include (but are not limited to): monocotyledonous plants of the Poaceae, Cyperaceae, and Dioscoreaceae families, and dicotyledonous plants of the Chenopodiaceae, Cirsaceae, Amaranthaceae, Asteraceae, Polygonaceae, Acanthaceae, Portulacaceae, Caryophyllaceae, or Zygophyllaceae families; more preferably, the Poaceae plants include (but are not limited to): plants of the genus *Zea* (such as corn), plants of the genus *Setaria* (such as millet), plants of the genus *Sorghum* (such as sorghum), and plants of the genus *Saccharum* (such as sugarcane).

[0074] In another aspect of the invention, the use of any of the cell models described above in the preparation of apparatus or systems for simulating and analyzing cellular photosynthesis or photosynthetic activity is provided.

[0075] In one or more embodiments, the simulation analysis of cellular photosynthesis or photosynthetic activity includes (but is not limited to): the effects of various reaction rates and conductances in the simulation model under different intercellular carbon dioxide concentrations (Ci) and light intensities (PPFD); and the simulation analysis of the total conductance (G) of the cell wall and protoplasmic membrane. wall The effects of carbonic anhydrase activity on photosynthetic efficiency or conductance were simulated; the effects of PEPC enzyme activity on photosynthetic rate or conductance were simulated; the effects of carbon dioxide permeability on chloroplast membranes in bundle sheath cells on photosynthesis or conductance were simulated; or the effects of Rubisco enzyme maximum carboxylation activity (V) were simulated. cmax The impact on photosynthetic efficiency or conductivity.

[0076] In another aspect of the invention, an apparatus or system for simulating and analyzing cellular photosynthesis or photosynthetic activity is provided, wherein any of the cell models or combinations of cell models described above are integrated.

[0077] Other aspects of the invention will be apparent to those skilled in the art from the disclosure herein. Attached Figure Description

[0078] Figure 1 Three-dimensional structural diagram of mesophyll cells (top left) and connected bundle sheath cells (bottom right) in maize (maize leaves perform C4 photosynthesis). a: Chloroplast; b: Mitochondria; c: Vacuole; d: Cytoplasm.

[0079] Figure 2 A schematic diagram of the biochemical reactions in the NADP-ME type C4 reaction diffusion model. Black represents metabolites and biochemical reactions. Blue represents enzymes. All metabolites in the diagram can diffuse and shuttle through the organelles of mesophyll cells and bundle sheath cells. Gray arrows represent carbon dioxide flow. CA: carbonic anhydrase; PEPC: phosphoenolpyruvate carboxylase.

[0080] Figure 3 The response curves of various reaction rates simulated by the two-cell C4 reactive diffusion model under different intercellular carbon dioxide concentrations and light intensities, based on carbon dioxide concentrations in different organelles. (a) At a light intensity (PPFD) of 2000 μmol m -2 s -1 Under certain conditions, the model predicted the carboxylation rate of PEPC enzyme, the carboxylation rate of Rubisco enzyme, the photorespiration rate, and the leakage rate at different intercellular carbon dioxide concentrations (C). i (b) Response curve under C i The response curves of the carboxylation rate of PEPC enzyme, the carboxylation rate of Rubisco enzyme, the photorespiration rate, and the leakage rate under different light intensities simulated by the model at a light intensity of 150 μbar. (c) At a light intensity of 2000 μmol m -2 s -1 Under the conditions of the model simulation, the different C i Response curves of carbon dioxide concentration in the cytoplasm and chloroplasts of lower leaf mesophyll cells and bundle sheath cells. (d) In C i The model simulates the response curves of carbon dioxide concentration in the cytoplasm and chloroplasts of mesophyll cells and bundle sheath cells under different light intensities at a light intensity of 150 μbar.

[0081] Figure 4 The response curves of mesophyll conductance, leakage rate, and bundle sheath conductance simulated by a two-cell C4 reactive diffusion model under different intercellular carbon dioxide concentrations and light intensities. (a, c) At a light intensity (PPFD) of 2000 μmol / m². -2 s -1 Under certain conditions, the model predicted mesophyll conductance (a), leakage rate, and bundle sheath conductance (c) at different intercellular carbon dioxide concentrations (Ci The response curves under (b,d) conditions. i The model simulates the response curves of mesophyll conductance (b), leakage rate, and bundle sheath conductance (d) under different light intensities at a light intensity of 150 μbar.

[0082] Figure 5 The two-cell C4 reactive diffusion model simulated net photosynthetic rate (a), leakage rate (b), mesophyll conductance (c), and bundle sheath conductance (d) under different intercellular carbon dioxide concentrations, with varying total conductance (G) at different cell walls and protoplasmic membranes. wall The response curve under the given light intensity was set to 2000 μmol / m². -2 s -1 All the vertical dashed lines in the diagram represent G. wall The value is the initial value in Table 1 or Table 2.

[0083] Figure 6 The two-cell C4 reactive diffusion model simulates the response curves of net photosynthetic rate (a), leakage rate (b), mesophyll conductance (c), and bundle sheath conductance (d) under different intercellular carbon dioxide concentrations, assuming the maximum catalytic activity of carbonic anhydrase in mesophyll cells is at 2% of the initial value. The light intensity in the simulation was set to 2000 μmol / m². -2 s -1 .

[0084] Figure 7 The two-cell C4 reactive diffusion model simulates mesophyll cells with the maximum catalytic activity of PEPC enzyme at the initial values ​​in Table 1 or 2, and at 150% and 50% of the initial values. The response curves of net photosynthetic rate (a), leakage rate (b), mesophyll conductance (c), and bundle sheath conductance (d) under different intercellular carbon dioxide concentrations are shown. The light intensity in the simulation was set to 2000 μmol / m². - 2 s -1 .

[0085] Figure 8 The two-cell C4 reactive diffusion model simulated the following changes in net photosynthetic rate (a), leakage rate (b), mesophyll conductance (c), and bundle sheath conductance (d) with plasmodesmata length (L) under different proportions (φ) of plasmodesmata at the mesophyll-to-bundle sheath interface. pd The response curve shows the change in light intensity. In the simulation, the light intensity was set to 2000 μmol / m². -2 s -1 All the vertical dashed lines in the figure represent plasmodesmata lengths with initial values ​​from Table 1 or Table 2.

[0086] Figure 9Net photosynthetic rate and leakage rate simulated by a two-cell C4 reactive diffusion model (a), mesophyll conductance and bundle sheath conductance (b) as a function of carbon dioxide permeability across the chloroplast membrane of bundle sheath cells (P co2 The response curves to the changes in bicarbonate ions on the chloroplast membrane of the bundle sheath cells. The simulated net photosynthetic rate and leakage rate (c), mesophyll conductance, and bundle sheath conductance (d) change with the permeability of bicarbonate ions on the chloroplast membrane of the bundle sheath cells (P). hco3 The response curve shows the change in light intensity. In the simulation, the light intensity was set to 2000 μmol / m². -2 s -1 All the vertical dashed lines in the figure represent the corresponding permeability values ​​from the initial values ​​in Table 1 or Table 2.

[0087] Figure 10 The two-cell C4 reactive diffusion model simulates mesophyll cells with the maximum carboxylation activity of Rubisco enzyme at the initial values ​​in Table 1 or Table 2, and at 150% and 50% of the initial values, showing the response curves of net photosynthetic rate (a), leakage rate (b), mesophyll conductance (c), and bundle sheath conductance (d) under different intercellular carbon dioxide concentrations. The light intensity in the simulation was set to 2000 μmol / m². -2 s -1 . Detailed Implementation

[0088] Through in-depth research, the inventors have constructed a three-dimensional reaction-diffusion model of C4 photosynthetic cells, utilizing both cell types. The model includes a three-dimensional structural component, reaction-diffusion equations, and parameter settings.

[0089] As used in this invention, the C4 plant is also called a carbon-4 plant, which is a plant that absorbs carbon dioxide from the air during its growth process and first synthesizes compounds containing four carbon atoms, such as malic acid or aspartic acid.

[0090] In this invention, the C4 plants may include: monocotyledonous C4 plants or dicotyledonous C4 plants; more preferably, the plants include (but are not limited to): monocotyledonous plants of the Poaceae, Cyperaceae, and Dioscoreaceae families, and dicotyledonous plants of the Chenopodiaceae, Cirsaceae, Amaranthaceae, Asteraceae, Polygonaceae, Acanthaceae, Portulacaceae, Caryophyllaceae, or Zygophyllaceae families; more preferably, the Poaceae plants include (but are not limited to): plants of the genus *Zea* (such as corn), plants of the genus *Setaria* (such as millet), plants of the genus *Sorghum* (such as sorghum), plants of the genus *Saccharum* (such as sugarcane), etc.

[0091] Given that C4 plants have essentially the same mechanism in photosynthesis, those skilled in the art will understand that the C4 plants suitable for applying the technical solutions of the present invention are not limited to those listed in the present invention, but may also include other C4 plants.

[0092] In this invention, unless otherwise stated, " / " can mean "and" or "or".

[0093] This invention utilizes systems biology methods to overcome the challenge of studying metabolic and structural interactions using experimental techniques. By constructing a C4 photosynthesis model, it systematically analyzes the effects of different combinations of structural and metabolic features related to C4 photosynthesis on C4 photosynthetic efficiency, identifies key factors controlling CO2 diffusion within two types of C4 cells, and explores the necessary structural and metabolic modifications for current C4 rice engineering.

[0094] C4 photosynthesis can be divided into different categories based on the type of decarboxylase, and the leaf structures of different C4 types also differ. In monocotyledonous NADP-ME type C4 plants, chloroplasts in bundle sheath cells are generally distributed near mesophyll cells; while in NAD-ME type C4 plants, chloroplasts in bundle sheath cells are generally distributed near vascular bundles. The physiological significance of the synergistic relationship between metabolism and leaf structure among these C4 types remains unknown. Therefore, this invention established a C4 photosynthetic system model including three decarboxylation pathways and parameters reflecting leaf structure, and quantitatively studied the effects of different combinations of decarboxylation pathways and leaf structural characteristics on photosynthetic efficiency. The results showed that in monocotyledonous NADP-ME type plants, chloroplast location, light energy distribution in the two cell types, and the synergy between decarboxylation pathways and organelles are beneficial to improving C4 photosynthetic efficiency. This indicates that the synergy between metabolism and structure is an important factor limiting the distribution and evolution of C4 plants.

[0095] This invention establishes a C4 photosynthetic reaction-diffusion model that effectively integrates metabolic and cellular structural characteristics, targeting the NADP-ME+PEPCK C4 pathway. It quantitatively analyzes the effects of C4-related structures (conductivity of mesophyll cell walls and protoplasts, plasmodesmata conductance, and carbon dioxide and bicarbonate permeability on the chloroplast membranes of bundle sheath cells) and metabolic characteristics (carbonic acid enzymes, PEPC enzymes, and Rubisco enzymes) on C4 photosynthetic efficiency, mesophyll conductance, and bundle sheath conductance. The model developed in this study provides an important theoretical tool for C4 physiological ecology and engineering modification research, and identifies important modification targets for the optimization and improvement of C4 plants.

[0096] The coordination of metabolism and structure in C4 plants is crucial not only for improving the light energy utilization efficiency of existing C4 plants but also for influencing the selection of C4 transformation schemes for C3 plants. One key issue is whether retaining some of the original leaf structure and metabolism from C3 plants significantly impacts the effectiveness of C4 transformation – a problem that remains unsolved. To address this, this invention uses rice leaves as the research object and establishes a three-dimensional leaf photosynthetic reaction-diffusion model. This model includes a mesophyll cell and an adjacent bundle sheath cell, simultaneously incorporating both C3 and C4 photosynthetic metabolic processes. Using this model, it was found that under atmospheric carbon dioxide conditions, retaining the original structure and metabolism of C3 plants and modifying the C4 acid cycle metabolic pathway in rice improves photosynthetic efficiency. Several physiological factors that may affect the photosynthetic rate were also analyzed, including the surface area of ​​mesophyll chloroplasts facing the intercellular air, the cell wall thickness of bundle sheath cells, the permeability of the chloroplast membrane in bundle sheath cells, the distribution of Rubisco enzymes between mesophyll cells and bundle sheath cells, and the energy distribution between C3 and C4 photosynthesis. Among these factors, the distribution ratio of Rubisco enzymes between the two cell types and the distribution ratio of energy between C3 and C4 photosynthesis have a decisive influence on this modified C3-C4 photosynthesis.

[0097] The photosynthetic cell model described in this invention uses C4 plant cells as the simulation object. Based on the photosynthetic metabolic processes and energy flow within the cells, the C4 plant cells are divided into different cellular functional units. The stoichiometric expressions of the cellular functional units are determined. According to the material metabolism and energy flow relationships between the cellular functional units, corresponding stoichiometric equations and process rate expressions are established to construct a C4 plant cell model for simulating or predicting photosynthesis or photosynthetic activities of C4 plant cells.

[0098] The photosynthetic cell model described in this invention is a three-dimensional cell reaction-diffusion model, which includes: a structural part and a reaction-diffusion model (equations and parameters).

[0099] In a preferred embodiment of the present invention, the photosynthetic cell model is a leaf cell model. The structural component is a three-dimensional structure, including simulated mesophyll cells and bundle sheath cells. The two types of cells are close to each other, adjacent, or connected by cell walls, thereby simulating the photosynthetic process of C4 plants. That is, in order to simulate C4 plants, the present invention breaks down photosynthesis into two independent parts for simulation: mesophyll cells capture carbon dioxide, and bundle sheath cells produce it.

[0100] The cell includes: a cell wall, a plasma membrane (protoplasmic membrane), a cytoplasmic matrix, and orderly arranged organelles. Other organelles or special structures may also be included when needed.

[0101] In a preferred embodiment of the invention, the three-dimensional structure comprises a mesophyll cell and an adjacent bundle sheath cell, and is based on the equilibrium between the concentration of carbon dioxide at the cell wall boundary of the mesophyll cell and the partial pressure in the intercellular spaces. In the model, the mesophyll cell contains multiple (e.g., 10-70, specifically 47) randomly distributed chloroplasts near the intercellular spaces, and the vacuoles are located in the center of the mesophyll cell. The bundle sheath cell has a layer of chloroplasts near the mesophyll cell and a layer of mitochondria, and the vacuoles in the bundle sheath cell are located away from the mesophyll cell. An exemplary three-dimensional structure of the model is shown below. Figure 1 In the preferred embodiment, the structural parameters related to cell structure and organelles are shown in Table 1.

[0102] The reaction-diffusion model is used to define the material metabolism and energy flow relationships of various components within the cells of the structure, including: a matter conservation model, a biochemical reaction-diffusion model, a boundary condition setting and conductivity calculation model, and a parameter setting and calculation model. Other models may be included when needed to facilitate diverse research and analysis using the three-dimensional structure.

[0103] In a preferred embodiment of the present invention, the reaction-diffusion equation includes: the mass conservation equation of the reaction-diffusion model, the biochemical reaction equation of the reaction-diffusion model, the setting of boundary conditions and the calculation of the derivative in the reaction-diffusion model, and the setting and calculation of reaction-diffusion model parameters. These equations are described in detail in the embodiments. These equations are used to simulate and calculate the diffusion process of CO2 within and between cells, the biochemical reaction processes involved, and ultimately obtain the CO2 concentration, diffusion rate, diffusion derivative, etc., at various locations within the cell.

[0104] In the model described in this invention, the parameters of the cell structure can also be adjusted to analyze and calculate the effect of each structural parameter on C4 photosynthesis.

[0105] By combining systems theory with mathematics, those skilled in the art utilize mathematical models to describe the complex system structure of photosynthesis. These models typically involve multiple variables and parameters, such as light intensity, temperature, CO2 concentration, and enzyme activity, which collectively influence the rate and efficiency of photosynthesis. Mathematical models can comprehensively consider these factors, thereby exploring the process of photosynthesis. Computer simulation provides a tool for the application of mathematical models. Computer simulation technology is used to solve and simulate mathematical models in a virtual environment. However, while existing technologies in the field have explored the simulation analysis of biochemical reaction processes, they do not include the three-dimensional structure of cells, and cannot analyze the impact of differences in cellular and subcellular structures on C4 photosynthetic efficiency and conductance. The C4 photosynthetic metabolic model of this invention is three-dimensional and includes multiphysics simulation formulas and parameter settings, which can effectively realize the simulation analysis of structural differences.

[0106] This invention provides a novel model and a theoretical analysis method for studying C4 photosynthesis based on this model. It can theoretically simulate and analyze processes that cannot be achieved or measured by experimental methods, and provides analytical models and methods for designing and guiding the improvement of C4 photosynthesis efficiency.

[0107] The model of this invention can also be used to study key enzymes and reaction mechanisms in photosynthesis. By simulating enzyme-catalyzed reaction processes, a deeper understanding of enzyme mechanisms and catalytic efficiency can be achieved, providing a theoretical basis for developing novel enzyme preparations and improving crop varieties. The solution of this invention can provide a deeper understanding and prediction of the performance of photosynthetic processes, offering strong support for agricultural production, enzyme preparation development, and other fields.

[0108] This invention allows for in-depth optimization and prediction of the photosynthetic process. For example, by adjusting parameters in the model, the photosynthetic process under different environmental conditions can be simulated, thereby predicting crop growth and yield. This has significant guiding implications for agricultural production, helping farmers develop more rational planting strategies and improve crop yield and quality.

[0109] The structural parameters and default values ​​used in the embodiments of the present invention are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] The structural and metabolic parameters and some constants (25°C) in the two-cell C4 reaction diffusion model of this invention are shown in Table 2.

[0114] Table 2

[0115]

[0116]

[0117] Example 1: Model Establishment

[0118] 1. The mass conservation equation of the reaction-diffusion model (module)

[0119] As shown in the metabolic diagram ( Figure 2 As shown in the two-cell C4 reaction-diffusion model, metabolites such as carbon dioxide and bicarbonate are included, along with photosynthetic-related enzymes (carbonic anhydrase, Rubisco, and phosphoenolpyruvate carboxylase). Carbon dioxide enters the mesophyll cells from the intercellular space and is fixed by carbonic anhydrase and PEPC enzymes to form C4 acid. The C4 acid then enters the bundle sheath cells after a series of reactions and transport. In maize, decarboxylases include NADP-ME and PEPCK, located in chloroplasts and the cytoplasm, respectively. C4 acid is decarboxylated by these two enzymes, releasing carbon dioxide, which is then fixed by Rubisco enzyme and enters the Calvin cycle. Here, only the limiting effect of PEPC enzyme on the C4 acid cycle is considered, assuming that the rate of carbon fixation by PEPC enzyme in mesophyll cells is equal to the sum of the decarboxylation rate in bundle sheath cells. All enzymes are assumed to be uniformly distributed in specific organelles, and all metabolites can diffuse simultaneously in mesophyll cells and bundle sheath cells while participating in biochemical reactions.

[0120] The mass conservation equation for carbon dioxide during reaction and diffusion is:

[0121]

[0122] in D c (m 2 s -1 [CO2](mol m) is the liquid-phase diffusion coefficient of carbon dioxide, and η is a dimensionless coefficient representing the relative viscosity of the space where diffusion occurs. -3 ) represents the carbon dioxide concentration, v c (mol m -3 s -1 ) and v o (mol m -3 s -1 The values ​​represent the rates of carbon dioxide fixation by Rubisco enzyme in bundle sheath cells and the rate of carbon dioxide release during photorespiration, respectively. The carbon dioxide generated during photorespiration is assumed to be released into the mitochondria of bundle sheath cells, h (mol / m³). -3 s -1 ) is the rate of carbon dioxide hydration reaction, r m and rbs (mol m -3 s -1 (v) represents the respiration rate in mesophyll cells and bundle sheath cells, respectively. p (mol m -3 s -1 ) is the carboxylation rate of phosphoenolpyruvate carboxylase, v me (mol m -3 s -1 ) and v pepck (mol m -3 s -1 These are the decarboxylation rates of chloroplasts in bundle sheath cells catalyzed by NADP-ME enzyme and PEPCK enzyme in the cytoplasm, respectively.

[0123] Similarly, the mass conservation equation for bicarbonate ions during the reaction and diffusion process is:

[0124]

[0125] in D b (m 2 s -1 ) is the liquid-phase diffusion coefficient of bicarbonate.

[0126] In this model, v c ≠ 0 and v me ≠0 occurs only in the chloroplasts of bundle sheath cells, r m ≠0 and r bs ≠0 occurs only in the mitochondria of mesophyll cells and bundle sheath cells, respectively. o ≠0 occurs only in the mitochondria of bundle sheath cells, v p ≠0 occurs only in the cytoplasm of mesophyll cells, while h≠0 occurs only in the vacuoles of both types of cells.

[0127] 2. Biochemical reaction equations for the reaction-diffusion model

[0128] Electron transport chain rate

[0129] In this C4 NADP-ME reactive diffusion model, only a linear electron transport chain is assumed in the photosystem of mesophyll cells and bundle sheath cells chloroplasts. The electron transport chain in the C4 metabolic model is calculated based on equations (3) and (4) to determine the total electron transport chain rate J (mol m⁻¹) in the model. -2 s -1 ):

[0130]

[0131] Where I is the total light intensity, and J maxThis is the maximum total electron transport rate per unit leaf area. The electron transport chain generated by the photosystem is assumed to be primarily used for the C4 acid cycle in C4 photosynthesis (mainly the reaction catalyzed by PEPC enzymes in this model), the Calvin cycle, and photorespiration. Let the coefficient x represent the proportion of the total energy generated by the two-cell photosystem allocated to the PEPC enzyme-catalyzed reaction; then the corresponding rate of the photosystem electron transport chain allocated to the PEPC enzyme carboxylation reaction is J. m =x·J, and then the rate allocated to the photosystem electron transport chain used for Calvin cycle and photorespiration is J. b = (1-x)·J.

[0132] Biochemical reaction rate

[0133] In this study, the photosynthetic rate was set to be limited only by ATP under light-dependent conditions; simultaneously, the photosystem was set to have a Q cycle (Sacksteder C et al., Proc Natl Acad Sci USA 2000; 97:14283–14288; Kramer DM et al., Plant Physiol 2011; 155:70–78), and the ratio of the proton rate across the thylakoid membrane to the electron flux rate in the linear electron transport chain (H) was established. + / e - The ratio of the proton rate to the rate of ATP production is 3. + The ratio of ATP to electron flow varies depending on the measurement method (Kramer DM et al., Plant Physiol 2011; 155:70–78), and here we set the ratio to 4 (JE S et al., Elsevier; 2000). Therefore, the ratio of ATP generated to electron flow rate (ATP / e) is... - The value is 3 / 4. Therefore, according to (Ubierna N et al., J Exp Bot 2011; 62:3119–3134), the rate at which carbon dioxide is fixed by Rubisco enzyme in the chloroplasts of bundle sheath cells (v...) c mol m -3 s -1 It can be described as:

[0134]

[0135] Where K m =K c (1+[O2] / K o ), Γ * =r·[O2],[CO2] ch_bs (mol m -3V is the concentration of carbon dioxide in the chloroplasts of the bundle sheath cells. cmax (μmol m -2 s -1 f is the maximum carboxylation rate of Rubisco enzyme per unit leaf area. V_ms and f V_bs K represents the ratio of the volume of chloroplasts in mesophyll cells and bundle sheath cells to the total volume of chloroplasts, respectively. m (molm -3 ) is the effective Michaelis-Menten constant of Rubisco enzyme in mesophyll cells, Γ * (mol m -3 () is the carbon dioxide compensation point without considering mitochondrial respiration, r is half the reciprocal of the carboxyl-oxygen ratio of Rubisco enzyme, K c (mol m -3 ) is the Michaelis-Menten constant for the carboxylation of Rubisco enzymes, K o (mol m -3 [O2](mol m) is the Michaelis-Menten constant for the oxidation of Rubisco enzymes. -3 ) is the concentration of oxygen in the chloroplasts of the bundle sheath cells (assumed to be a constant), S mes (m 2 m -2 V is the surface area of ​​mesophyll cells exposed to intercellular air per unit leaf area. ch_bs (m 3 m -2 () is the volume of chloroplasts in bundle sheath cells per unit surface area of ​​mesophyll cells exposed to intercellular air.

[0136] Furthermore, the respiration rate per unit leaf area was set to be the same in both mesophyll cells and bundle sheath cells, and respiration in mesophyll cells occurred in the cytoplasm. The respiration rate per unit volume of mitochondria was calculated for both cell types. m and r bs It can be represented as:

[0137]

[0138] Where R d (mol m -2 s -1 V is the respiration rate per unit leaf area. cy_ms (m 3 m -2 V is the volume of mesophyll matrix per unit surface area of ​​a mesophyll cell exposed to intercellular air. mi_bs (m 3 m-2 S represents the volume of mitochondria in the bundle sheath cells per unit surface area of ​​a mesophyll cell exposed to intercellular air; mes It is the surface area of ​​mesophyll cells exposed to intercellular air.

[0139] In the C3 biochemical model, the photorespiration rate is calculated by multiplying the carboxylation rate of Rubisco enzyme by the carbon dioxide compensation point (ignoring mitochondrial respiration), and then dividing by the carbon dioxide concentration in the chloroplasts. In the C4 plant photorespiration pathway, carbon dioxide is released in the peroxisomes of the bundle sheath cells; here, the peroxisomes and mitochondria of the bundle sheath cells are assumed to be in the same space. According to (Tholen D et al., Plant Physiol 2011; 156:90–105), the photorespiration rate per unit volume, v, can be calculated. o (mol m -3 s -1 The expression represents the rate of Rubisco enzyme carboxylation in the chloroplasts of bundle sheath cells multiplied by Γ. * Divide by the carbon dioxide concentration, then perform an integral over the chloroplasts, and finally divide by the volume of the mitochondria in the bundle sheath cells:

[0140]

[0141] For the carbon dioxide net hydration reaction rate h (mol m) -3 s -1 Based on (Spalding MH et al., Planta 1985; 164:308–320), modified, it is expressed as:

[0142]

[0143] Among them [HCO3] - ](mol m -3 V is the concentration of bicarbonate ions. ca (mol m -2 s -1 ) represents the maximum catalytic activity of CA enzyme per unit leaf area, x ca V(m) is the partition coefficient of CA enzyme in different organelles. 3 m -2 K is the volume of different organelles per unit surface area of ​​a mesophyll cell exposed to intercellular air. e_ca (mol m -3 K is the equilibrium constant of the CA enzyme. m,c_ca and K m,b_ca (mol m -3(x) represent the Michaelis-Menten constants for the hydration and dehydration reactions of CA enzymes, respectively, and pH is the pH value. ca The pH value varies in different organelles.

[0144] We assume that only linear electron transport chains exist in mesophyll cells. We assume the photosystem has a Q cycle (Sacksteder Cetal., Proc Natl Acad Sci USA 2000; 97:14283–14288; Kramer DM et al., Plant Physiol 2011; 155:70–78), and the ratio of the proton velocity across the thylakoid membrane to the electron flux velocity along the linear electron transport chain (H0) is given. + / e - The ratio of the proton rate to the rate of ATP production is 3. + The ratio of ATP to electron flow rate was set to 4 (JE Set al., Elsevier; 2000). Therefore, the ratio of ATP generated to electron flow rate (ATP / e) was... - The value is 3 / 4. According to (Von Caemmerer S. Csiro publishing; 2000), the carboxylation rate of PEPC enzyme can be expressed as:

[0145]

[0146] Where V pepc (mol m -2 s -1 [CO2] represents the maximum carboxylation rate of PEP. cy_ms (mol m -3 K is the concentration of carbon dioxide in the cytoplasm of mesophyll cells. p (mol m -3 (v) is the Michaelis-Menten constant for carbon dioxide in PEPC enzymes. In this model, it is assumed that the total decarboxylation rate in chloroplasts and cytoplasm of bundle sheath cells should be the same as the total carboxylation rate of PEPC enzymes in mesophyll cell cytoplasm, i.e., v me It can be represented as v p The integral in the mesophyll cell cytoplasm multiplied by the proportion allocated to the NADP-ME decarboxylation pathway, f me Divide by the volume of the chloroplasts in the bundle sheath cells:

[0147]

[0148] Similar v pepck It can be represented as v pThe integral in the mesophyll cell cytoplasm multiplied by the proportion allocated to the PEPCK decarboxylation pathway (1-f) me Divide by the volume of the cytoplasm of the bundle sheath cells:

[0149]

[0150] 3. Setting boundary conditions and calculating derivatives in the reaction-diffusion model

[0151] In the two-cell reactive diffusion model, carbon dioxide is assumed to diffuse from the intercellular air into the mesophyll cells, but not directly into the bundle sheath cells. Bicarbonate cannot cross the cell walls of either mesophyll or bundle sheath cells. The process of metabolites crossing the membranes of chloroplasts, mitochondria, and vacuoles, as well as the cell membrane and plasmodesmata, is represented as follows:

[0152]

[0153] The left side of equation (13) represents the flow through the boundary, where r is the resistance of metabolites at the boundary, and C1 and C2 (mol m) -3 () represents the concentration of metabolites on both sides of the boundary.

[0154] Assume that all metabolites can pass through the membranes of chloroplasts, mitochondria, and vacuoles. Taking carbon dioxide as an example, the resistance to carbon dioxide passing through the membrane is expressed as:

[0155] r = P co2 -1 (14)

[0156] Where P co2 This refers to the permeability of carbon dioxide across the membrane. Similar conditions can be set for bicarbonate ions.

[0157] When calculating the resistance of metabolites across the interface between mesophyll cells and bundle sheath cells, maize has a cork layer at the interface, allowing metabolites to pass only through plasmodesmata. For example, the resistance of carbon dioxide at the interface can be expressed as:

[0158]

[0159] Where S w / S l φ is the ratio of the interface area between mesophyll cells and bundle sheath cells to the leaf area; φ is the proportion of the interface area covered by plasmodesmata; L pd (m) is the length of plasmodesmata. The calculation method for the resistance of bicarbonate ions through the interface between two types of cells is similar to that for carbon dioxide.

[0160] For the cell wall boundary of mesophyll cells exposed to intercellular air (where only carbon dioxide and oxygen can pass through), a conductivity constant G is defined that includes the cell wall and plasma membrane. wall (mol m -2 s -1 So, at each point on this cell wall, the flow rate of carbon dioxide into the mesophyll cell (mol / m³) -2 s -1 It can be set to:

[0161]

[0162] Where P (Pa) is atmospheric pressure, s c (mol m -3 Pa -1 ) represents the solubility of carbon dioxide, C i (mol m -3 C is the concentration of carbon dioxide in the intercellular space. wall (mol m -3 The concentration of carbon dioxide on the cell walls of mesophyll cells is denoted as A(mol / m²). The average velocity of carbon dioxide entering this three-dimensional model structure can then be defined as the integral of the velocities at all points on the cell wall boundaries exposed to intercellular air within the mesophyll cells, divided by the area of ​​the cell wall exposed to intercellular air within the mesophyll cells. Therefore, the net photosynthetic rate A per unit leaf area is calculated as A(mol / m²). -2 s -1 ) can be represented as:

[0163]

[0164] In this reaction-diffusion model, the leakage rate of carbon dioxide from bundle sheath cells to mesophyll cells, L (mol m⁻¹), is... - 2 s -1 It can be defined as the rate of C4 acid decarboxylation per unit leaf area minus the rate of carbon dioxide fixation by Rubisco enzyme in the chloroplasts of bundle sheath cells, plus the respiration rate in the mitochondria of bundle sheath cells and the photorespiration rate in the cytoplasm:

[0165]

[0166] Where V cy_bs (m 3 m -2 The bundle sheath conductance (g) is the volume of the vascular bundle sheath cell cytoplasm per unit surface area of ​​a mesophyll cell exposed to intercellular air; thus, the bundle sheath conductance (g) is... bs (mol m -2 s -1 bar -1 This can be represented as:

[0167]

[0168] in and These represent the average concentrations of carbon dioxide in the chloroplasts of bundle sheath cells and the cytoplasm of mesophyll cells:

[0169]

[0170] Mesophyll conductance g m (mol m -2 s -1 bar -1 ) is represented as:

[0171]

[0172] 4. Parameter setting and calculation of reaction-diffusion model

[0173] The parameters for this reaction-diffusion model are shown in Tables 1 and 2. Hatch et al., using isotope labeling, determined that 75% of the carbon entering the NADP-ME decarboxylation pathway accounts for 75% of the total fixed carbon in maize photosynthetic metabolism (Hatch MD et al., Biochem J 1971; 125:425–432). Arrivault et al. determined that 10%–14% of the carbon entering the PEPCK decarboxylation pathway accounts for 10%–14% of the total fixed carbon in maize (Arrivault S et al., J Exp Bot 2016: erw414). Here, we assume that 15% of the carbon entering the PEPCK decarboxylation pathway accounts for 15% of the total fixed carbon. Carbonic anhydrases in C4 plants are mainly distributed in the cytoplasm of mesophyll cells (Poincelot RP et al., Plant Physiol 1972; 50:336–40; Burnell JN et al., Plant Physiol 1988; 86:1252–6). The measured values ​​of carbonic anhydrase activity vary considerably. Studer et al. measured the carbonic anhydrase activity in maize to be approximately 230 μmol m. -2 s -1 (Studer AJ et al., Plant Physiol 2014; 165:608–617); The carbonic anhydrase activity in Flavorea bidentis was measured to be approximately 2000 μmol m -2 s -1 Or 800 μmol m -2 s -1(Cousins ​​AB et al., Plant Physiol 2006; 141:232–242; Von CaemmererS et al., A transgenic analysis. Plant Cell Environ 2004; 27:697–703); The carbonic anhydrase activity in Setariaviridis was measured to be approximately 560–1500 μmol m -2 s -1 (Osborn HL et al., J ExpBot 2017; 68:299–310). The carbonic anhydrase activity (200,000 μmol m) in (Wang Y et al., Plant Physiol 2014; 164:2231–46) was used here. -2 s -1 The distribution ratio of carbonic anhydrase in mesophyll cells and bundle sheath cells was set at 4:1 (Poincelot RP et al., Plant Physiol 1972; 50:336–40; Burnell JN et al., Plant Physiol 1988; 86:1252–6). Regarding the distribution of carbonic anhydrase in the two types of organelles, the distribution ratios in the mesophyll cell cytoplasm, mesophyll cell chloroplasts, bundle sheath cell cytoplasm, bundle sheath cell chloroplasts, and bundle sheath cell mitochondria were set to 0.64, 0.16, 0.1, 0.05, and 0.05, respectively.

[0174] The structure of the reaction-diffusion model was decomposed into 580,988 small units. After the biochemical reactions and boundary conditions of each metabolite in different subspaces were set, the entire model could be solved using the finite element method. A steady-state solution method was used in the solution process. After obtaining the numerical solution, the net photosynthetic rate and conductance could be calculated using equations (16)-(22).

[0175] Example 2: Effects of reaction rate and conductance in the simulation model under different intercellular carbon dioxide concentrations (Ci) and light intensities (PPFD)

[0176] This two-cell maize reactive diffusion model was used to simulate the response curves of various reaction rates and conductances under different intercellular carbon dioxide concentrations (Ci) and light intensities (PPFD).

[0177] With increasing intercellular carbon dioxide concentration, the carboxylation rates of both PEPC and Rubisico enzymes increased, reaching a maximum at an intercellular carbon dioxide concentration of approximately 500 μbar and then stabilizing. Figure 3a) The rate of photorespiration decreases with increasing carbon dioxide concentration. In this model, the rate of carbon fixation by PEPC enzymes per unit leaf area is set to be equal to the total rate of decarboxylation by NADP-ME and PEPCK enzymes in the bundle sheath cells. Thus, the leakage rate can be expressed as the carboxylation rate of PEPC enzymes plus the respiration rate in the bundle sheath cells (set to a constant) and the rate of carbon dioxide production through photorespiration, minus the carboxylation rate of Rubisco enzymes. Figure 3 The leakage rate in cells a also increases with increasing intercellular carbon dioxide concentration, reaching a maximum and then leveling off. The carbon dioxide concentration in mesophyll cells and bundle sheath cells also increases with increasing intercellular carbon dioxide concentration. Figure 3 c). In simulations with different light intensities, the carboxylation rate and photorespiration rate of both PEPC and Rubisco enzymes increased with increasing light intensity. The carboxylation rate of PEPC enzyme increased at a light intensity of approximately 1300 μmol / m². -2 s -1 It reaches its maximum value and then experiences slow fluctuations. Figure 3 b). Because the carboxylation rate of PEPC enzyme reaches its maximum value, the carbon fixation rate of Rubisco enzyme continues to increase with increasing light intensity, while the leakage rate initially increases with increasing light intensity and then gradually decreases until it reaches a stable value. Figure 3 b). Simultaneously, the carbon dioxide concentration in the bundle sheath cells first increases and then decreases with increasing light intensity, while the carbon dioxide concentration in the mesophyll cells slowly decreases with increasing light intensity. Figure 3 d).

[0178] The results above demonstrate that the model can simulate and analyze specific enzyme reaction rates and specific intracellular local conductance. These simulation results are in line with expectations and can provide more accurate dynamic changes.

[0179] In addition, the response curves of conductance to intercellular carbon dioxide concentration and light intensity were simulated. The simulated mesophyll conductance values ​​were on the same order of magnitude as those estimated by combining experimental measurements and model data (Ubierna N et al., New Phytol 2017; 214:66–80; Barbour MM et al., New Phytol 2016; 59:86–90; Osborn Hl et al., JExp Bot 2017; 68:299–310). Mesophyll conductance decreased with increasing intercellular carbon dioxide concentration, and then remained essentially unchanged with concentration after the intercellular carbon dioxide concentration reached approximately 200 μbar. Figure 4a) This trend is consistent with the results in (Osborn HL et al., J Exp Bot 2017; 68:299–310). Mesophyll conductance also decreases with increasing light intensity, reaching a certain level at a light intensity of approximately 300 μmol / m². -2 s -1 After that, it basically does not change with the increase of light intensity. Figure 4 b). The conductance of the vascular bundle sheath decreases with increasing intercellular carbon dioxide concentration (by approximately 15%). Figure 4 c). Its variation with increasing light intensity is very small (the maximum and minimum values ​​do not exceed approximately 9.3%). Figure 4 d), which is consistent with the trend of the estimated value of the bundle sheath conductance of maize grown under high light as a function of light intensity in (Bellasio C et al., Plant, Cell Environ 2014; 37:1046–1058). Figure 1 The leakage rate is defined as the ratio of the leakage rate to the rate at which PEPC enzymes carboxylate and fix total carbon, reflecting the efficiency of C4 photosynthetic carbon utilization. Figure 4 c shows the response curve of leakage rate to changes in intercellular carbon dioxide concentration and light intensity. This trend is roughly the same as the estimated trend in (Yin X et al., J Exp Bot 2016; 2:1–42). The phenomenon that leakage rate decreases with increasing light intensity ( Figure 4 d) This trend is consistent with previous experimental observations (Kromdijk J et al., Plant, Cell Environ 2010; 33:1935–1948; Bellasio C et al., Plant, Cell Environ 2014; 37:1046–1058; Ubierna N et al., Plant, Cell Environ 2013; 36:365–381; Henderson SA et al., Aust J Plant Physiol 1992; 19:263–85). The carboxylation rate of Rubisco enzyme, the photorespiration rate, and the carboxylation rate of PEPC enzyme all increase with increasing light intensity. Figure 4 (b) However, among the proportions of Rubisco enzyme carboxylation rate, photorespiration rate, and leakage rate in the PEPC enzyme carboxylation rate, only the proportion of Rubisco enzyme carboxylation rate increases with increasing light intensity. Therefore, the increase in leakage rate under low light conditions is not significantly related to photorespiration or the difference in energy distribution under high and low light conditions.

[0180] The above results show that the model can simulate and analyze to obtain the expected results, and can produce specific dynamic curves.

[0181] Example 3: Simulated total conductivity (G) of cell wall and protoplasmic membrane wall Impact on photosynthetic efficiency and conductance

[0182] Due to limitations in methods for measuring C4 mesophyll conductance and bundle sheath conductance or leakage rate, most current methods rely on indirect estimation through a combination of experiments and models. Here, we use a two-celled C4 maize reactive diffusion model to systematically analyze some biochemical and structural parameters that may affect the diffusion conductance (including mesophyll conductance and bundle sheath conductance) of carbon dioxide as it diffuses from the intercellular air into the mesophyll cells, undergoes a series of diffusion and reactions, and is ultimately fixed by Rubisco enzymes in the bundle sheath cells.

[0183] First, carbon dioxide dissolves from the intercellular air into the water and enters the mesophyll cell cytoplasm through the cell wall and plasma membrane. The plasma membrane is usually tightly connected to the cell wall; for simplicity, the resistance of the cell wall and plasma membrane can be considered as a single unit (G). wall ). Figure 5 G was displayed wall The effects of changes on C4 photosynthetic rate, leakage rate, mesophyll conductance, and bundle sheath conductance. According to (Evans JR et al., J Exp Bot 2009;60:2235–2248), G... wall The range is approximately 8.7 × 10⁻⁶. -3 ~0.45mol m -2 s -1 Within this range, G wall The impact on C4 photosynthetic efficiency is relatively large. Figure 5 a, b). Mesophyll conductance with G wall Increased by the increase ( Figure 5 c) vascular bundle sheath conductance as a function of G wall The increase was relatively small, approximately 22%. Figure 5 d). Simulated photosynthesis at different intercellular carbon dioxide concentrations: under low carbon dioxide concentrations, photosynthetic efficiency, leakage rate, mesophyll conductance, and bundle sheath conductance increased with G. wall The increase in the magnitude of change is the largest. Figure 5 ).

[0184] The results above demonstrate that the model accurately simulates and calculates the influence of cell wall and protoplasmic membrane conductance on photosynthetic efficiency.

[0185] Example 4: Analysis of the effect of the maximum catalytic activity of carbonic anhydrase in mesophyll cells on the photosynthetic efficiency and conductance of C4 cells.

[0186] Carbon dioxide passes through the cell wall and protoplasmic membrane of mesophyll cells and enters the mesophyll cell cytoplasm, where it is immediately fixed by carbonic anhydrase and PEPC enzymes and enters the C4 acid cycle. The potential effects of these two enzymes on C4 photosynthetic efficiency and conductance were simulated. Reducing the catalytic activity of carbonic anhydrase in mesophyll cells to 2% of its initial value had little effect on the photosynthetic rate (the maximum reduction in net photosynthetic rate was approximately 21%). Figure 6 a). The leakage rate also decreased with the decrease in carbonic anhydrase activity in mesophyll cells. Figure 6 b). Figure 6 Figure c shows that mesophyll conductance decreases by approximately 57% with decreasing carbonic anhydrase activity in mesophyll cells. In contrast, the decrease in bundle sheath conductance due to decreased carbonic anhydrase activity is smaller (approximately 16%). Figure 6 d).

[0187] The above results demonstrate that this model accurately analyzes the effect of carbonic anhydrase activity on C4 photosynthetic efficiency.

[0188] Example 5: Simulation analysis of the effect of PEPC enzyme activity on C4 photosynthetic rate and conductance.

[0189] Increased PEPC enzyme activity reduces C4 photosynthetic rate and increases leakage rate, while having little effect on mesophyll conductance and bundle sheath conductance. Figure 7 Mesophyll conductance increases with increasing PEPC enzyme activity, but this increase only occurs when the intercellular carbon dioxide concentration is below 150 μbar. Figure 7 c). Decreased PEPC enzyme activity led to varying degrees of decrease in C4 photosynthetic rate, leakage rate, and mesophyll conductance, while vascular bundle sheath conductance showed a slight increase. Figure 7 ).

[0190] Example 6: Analysis of the effect of the ratio (φ) of plasmodesmata to the interface between mesophyll cells and bundle sheath cells on photosynthesis and conductance.

[0191] After carbon dioxide is fixed in mesophyll cells and enters the C4 acid cycle, the C4 acid undergoes a series of transport and reactions in the bundle sheath cells, where it is decarboxylated by NADP-ME enzymes in chloroplasts and PEPCK enzymes in the cytoplasm, releasing carbon dioxide. The re-released carbon dioxide is then fixed by Rubisco enzymes in the chloroplasts of the bundle sheath cells and enters the Calvin cycle. The C4 acid cycle leads to a high concentration of carbon dioxide in the bundle sheath cells, creating a concentration gradient between the bundle sheath cells and mesophyll cells. Some of the carbon dioxide released in the bundle sheath cells diffuses back into the mesophyll cells. The effects of structural and biochemical parameters on photosynthetic efficiency and conductance during the diffusion of carbon dioxide from the bundle sheath cells to the mesophyll cells can be simulated. The effects of plasmodesmata length and the proportion of plasmodesmata to the intercellular interface area (φ) on C4 photosynthetic efficiency were simulated. The simulation results show that increasing the length of plasmodesmata or decreasing φ both reduce the leakage rate and increase the photosynthetic rate. Figure 8 a, b). This model does not consider the transport of C4 acid between the two cells, and assumes that carbon dioxide is fixed in the mesophyll cell cytoplasm and immediately released into the bundle sheath cell. Therefore, increasing the length of plasmodesmata or decreasing φ is equivalent to increasing the resistance to carbon dioxide diffusion at the cell interface, i.e., reducing the diffusion capacity of carbon dioxide from the bundle sheath cell to the mesophyll cell. Increasing the length of plasmodesmata or decreasing φ will slightly increase mesophyll conductance (…). Figure 8 c), and reduces the conductivity of the vascular bundle sheath ( Figure 8 d).

[0192] Example 7: Simulation of the effect of carbon dioxide permeability on chloroplast membranes of bundle sheath cells on C4 photosynthesis and conductance.

[0193] The effects of carbon dioxide and bicarbonate permeability on the chloroplast membrane of bundle sheath cells on C4 photosynthetic efficiency and conductance were then simulated. The simulation results showed that as carbon dioxide permeability on the chloroplast membrane of bundle sheath cells increased, the C4 photosynthetic rate first increased and then decreased, while the leakage rate and bundle sheath conductance first decreased and then increased, and mesophyll conductance showed an increasing trend. Figure 9 a, b). With the increase of bicarbonate permeability on the chloroplast membrane of the bundle sheath cells, the C4 photosynthetic rate showed a decreasing trend, while the leakage rate, mesophyll conductance, and bundle sheath conductance all showed an increasing trend. Figure 9 c, d). Furthermore, the effect of bicarbonate permeability on C4 photosynthesis and conductivity is greater than its effect on carbon dioxide permeability. Figure 9 ).

[0194] Example 8, Maximum carboxylation activity of Rubisco enzyme (V) cmax The effect on C4 photosynthetic efficiency and conductance

[0195] Finally, the maximum carboxylation activity (V) of Rubisco enzyme was simulated. cmax The effect of C4 photosynthetic efficiency and conductance. cmax The initial value was set to 65 μmol m -2 s -1 The figure shows that when the maximum carboxylation activity of Rubisco enzyme was increased to 1.5 times its original value, the response curves of C4 photosynthetic rate and mesophyll conductance to carbon dioxide concentration remained essentially unchanged, while the leakage rate only decreased at low carbon dioxide concentrations and subsequently correlated with V. cmax There was no difference at the initial value; the vascular bundle sheath conductance only increased at low intercellular carbon dioxide concentrations, and then remained unchanged. However, when V... cmax Interestingly, when reduced to half of the initial value, both photosynthetic rate and mesophyll conductance decreased, while leakage rate increased. Vascular bundle sheath conductance only increased at low intercellular carbon dioxide concentrations, and then remained unchanged. Figure 10 ).

[0196] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for simulating and analyzing cellular photosynthesis or photosynthetic activity, the method comprising: (a) Provide a photosynthetic cell model, which is a three-dimensional cell reaction-diffusion model, the model including: structural parts and reaction-diffusion model; The structure is a three-dimensional structure, including simulated mesophyll cells and bundle sheath cells, which are close to each other. Each cell includes a cell wall, plasma membrane, cytoplasm, and orderly arranged organelles. The carbon dioxide concentration at the cell wall boundary between the two types of cells is in equilibrium with the partial pressure in the intercellular space. The reaction-diffusion model is used to define the material metabolism and material and energy flow relationships of each element in the cell of the structural part, including: material conservation model, biochemical reaction-diffusion model, boundary condition setting and conductivity calculation model, and parameter setting and calculation model; (b) The photosynthetic cell model of (a) was used to simulate and analyze cell photosynthesis.

2. The method as described in claim 1, characterized in that, The photosynthesis includes C4 photosynthesis; the method includes analyzing C4 photosynthetic efficiency or conductance; preferably, the method for simulating and analyzing cellular photosynthesis or photosynthetic activity includes: simulating and calculating the diffusion process of carbon dioxide within or between cells, analyzing the involved biochemical reaction processes, and obtaining the carbon dioxide concentration, diffusion rate, and / or diffusion conductance at various sites within the cell; or, adjusting cell structural parameters and analyzing the influence of structural parameters on C4 photosynthesis.

3. A photosynthetic cell model, which is a three-dimensional cellular reaction-diffusion model, the model comprising: Structural components, reaction-diffusion model; The structure is a three-dimensional structure, including simulated mesophyll cells and bundle sheath cells, which are close to each other. Each cell includes a cell wall, plasma membrane, cytoplasm, and orderly arranged organelles. The carbon dioxide concentration at the cell wall boundary between the two types of cells is in equilibrium with the partial pressure in the intercellular space. The reaction-diffusion model is used to define the material metabolism and material and energy flow relationships of each element in the cell of the structural part, including: material conservation model, biochemical reaction-diffusion model, boundary condition setting / derivative calculation model, and parameter setting / calculation model.

4. The method according to any one of claims 1-2 or the photosynthetic cell model according to claim 3, characterized in that, The mesophyll cells include chloroplasts and vacuoles; the chloroplasts are located near the intercellular spaces and are randomly distributed, and the vacuoles are located in the middle of the mesophyll cells. The bundle sheath cell comprises: a layer of chloroplasts, a layer of mitochondria, and vacuoles; the chloroplasts are located in the bundle sheath cell near the mesophyll cells, and the vacuoles are located away from the mesophyll cells.

5. The method according to any one of claims 1-2 or the photosynthetic cell model according to claim 3, characterized in that, The photosynthesis is C4 photosynthesis, and the reaction-diffusion model includes simulated metabolites, photosynthetic enzymes, and decarboxylases. Carbon dioxide enters the mesophyll cells and is fixed by photosynthetic enzymes to form C4 acids. The C4 acids enter the bundle sheath cells through the C4 cycle, where they are decarboxylated by decarboxylases to release carbon dioxide, which is then fixed by photosynthetic enzymes and enters the Calvin cycle.

6. The method or cell model as described in claim 5, characterized in that, In the aforementioned mass conservation model, only the limiting effect of PEPC enzymes on the C4 acid cycle is considered. The sum of the carbon fixation rate of PEPC enzymes in mesophyll cells and the decarboxylation rate in bundle sheath cells is assumed to be equal. All enzymes are assumed to be uniformly distributed in specific organelles, and metabolites can participate in biochemical reactions and diffuse simultaneously in mesophyll cells and bundle sheath cells. The metabolite is carbon dioxide, and its mass conservation equation during the reaction and diffusion process is: in, D c (m 2 s -1 [CO2](mol m) is the liquid-phase diffusion coefficient of carbon dioxide, and η is a dimensionless coefficient representing the relative viscosity of the space where diffusion occurs. -3 ) represents the carbon dioxide concentration, v c (mol m -3 s -1 ) and v o (mol m -3 s -1 These represent the rate at which carbon dioxide is fixed by Rubisco enzyme in bundle sheath cells and the rate at which carbon dioxide is released during photorespiration, respectively. h(molm -3 s -1 ) is the rate of carbon dioxide hydration reaction, r m and r bs (molm -3 s -1 (v) represents the respiration rate in mesophyll cells and bundle sheath cells, respectively. p (molm -3 s -1 ) represents the carboxylation rate of PEPC enzyme, v me (mol m -3 s -1 ) and v pepck (mol m -3 s -1 These represent the decarboxylation rates of chloroplasts in bundle sheath cells catalyzed by NADP-ME and PEPCK in the cytoplasm, respectively.

7. The method or cell model as described in claim 5, characterized in that, In the aforementioned mass conservation model, the metabolite is bicarbonate, and the mass conservation equation for bicarbonate during the reaction and diffusion process is: in, D b (m 2 s -1 ) is the liquid-phase diffusion coefficient of bicarbonate; v c v me r m r bs v o v p The definition of h is the same as in claim 6; v c ≠ 0 and v me ≠0 occurs only in the chloroplasts of bundle sheath cells, r m ≠0 and r bs ≠0 occurs only in the mitochondria of mesophyll cells and bundle sheath cells, respectively. o ≠0 occurs only in the mitochondria of bundle sheath cells, v p ≠0 occurs only in the cytoplasm of mesophyll cells, while h≠0 occurs only in the vacuoles of both types of cells.

8. The method or cell model as described in claim 5, characterized in that, The reaction-diffusion model is a C4 NADP-ME type reaction-diffusion model. In this biochemical reaction-diffusion model, only linear electron transport is assumed in the photosystem of mesophyll cells and bundle sheath cells chloroplasts, and the total electron transport chain rate J (mol / m²) is [not specified]. -2 s -1 The equation is: Where I is the total light intensity, J max It is the total maximum electron transport rate per unit leaf area.

9. The method or cell model as described in claim 5, characterized in that, In the aforementioned biochemical reaction diffusion model, it is set that: the photosynthetic rate, under light-reaction-limited conditions, is only limited by ATP; the photosystem has a Q cycle, and the ratio of the proton velocity across the thylakoid membrane to the electron flux velocity in the electron transport chain (H) is given. + / e - The ratio of proton rate to ATP production rate (H) is 3; + The ratio of ATP / electron flux is 4; therefore, the ratio of ATP generated to electron flux (ATP / e) is 4. - ) is 3 / 4 photosynthetic enzymes, including photosynthetic enzymes; The rate (v) of carbon dioxide fixation by Rubisco enzyme in chloroplasts of bundle sheath cells c mol m -3 s -1 )for: Among them, K m =K c (1+[O2] / K o ), Γ * =r·[O2],[CO2] ch_bs (mol m -3 V is the concentration of carbon dioxide in the chloroplasts of the bundle sheath cells. cmax (μmolm -2 s -1 f is the maximum carboxylation rate of Rubisco enzyme per unit leaf area. V_ms and f V_bs K represents the ratio of the volume of chloroplasts in mesophyll cells and bundle sheath cells to the total volume of chloroplasts, respectively. m (mol m -3 ) is the effective Michaelis-Menten constant of Rubisco enzyme in mesophyll cells, Γ * (mol m -3 () is the carbon dioxide compensation point without considering mitochondrial respiration, r is half the reciprocal of the carboxyl-oxygen ratio of Rubisco enzyme, K c (mol m -3 ) is the Michaelis-Menten constant for the carboxylation of Rubisco enzymes, K o (molm -3 [O2](mol m) is the Michaelis-Menten constant for the oxidation of Rubisco enzymes. -3 S is the concentration of oxygen in the chloroplasts of the bundle sheath cells. mes (m 2 m -2 V is the surface area of ​​mesophyll cells exposed to intercellular air per unit leaf area. ch_bs (m 3 m -2 () is the volume of chloroplasts in bundle sheath cells per unit surface area of ​​mesophyll cells exposed to intercellular air.

10. The method or cell model as described in claim 5, characterized in that, In the aforementioned biochemical reaction diffusion model, the respiration rate per unit leaf area is set to be the same in mesophyll cells and bundle sheath cells, and respiration in mesophyll cells occurs in the cytoplasm; the respiration rate per unit volume of mitochondria in both types of cells is r. m and r bs for: Where R d (mol m -2 s -1 V is the respiration rate per unit leaf area. cy_ms (m 3 m -2 V is the volume of mesophyll matrix per unit surface area of ​​a mesophyll cell exposed to intercellular air. mi_bs (m 3 m -2 S represents the volume of mitochondria in the bundle sheath cells per unit surface area of ​​a mesophyll cell exposed to intercellular air; mes It is the surface area of ​​mesophyll cells exposed to intercellular air.

11. The method or cell model as described in claim 5, characterized in that, In the aforementioned biochemical reaction diffusion model, the peroxisomes and mitochondria of the bundle sheath cells are set in a single space, and the photorespiration rate v per unit volume is... o (molm - 3 s -1 The expression represents the rate of Rubisco enzyme carboxylation in the chloroplasts of bundle sheath cells multiplied by Γ. * Divide by the carbon dioxide concentration, make an integral over the chloroplast, and then divide by the volume of the mitochondria in the bundle sheath cell: The rate of carbon dioxide net hydration reaction h (mol / m) -3 s -1 )for: Among them [HCO3] - ](mol m -3 V is the concentration of bicarbonate ions. ca (mol m -2 s -1 ) represents the maximum catalytic activity of CA enzyme per unit leaf area, x ca V(m) is the partition coefficient of CA enzyme in different organelles. 3 m -2 K is the volume of different organelles per unit surface area of ​​a mesophyll cell exposed to intercellular air. e_ca (mol m -3 K is the equilibrium constant of the CA enzyme. m,c_ca and K m,b_ca (mol m -3 ) are the Michaelis-Menten constants for the hydration and dehydration reactions of CA enzyme, respectively, and pH is the pH value.

12. The method or cell model as described in claim 5, characterized in that, In the aforementioned biochemical reaction diffusion model, it is assumed that only linear electron transport chains exist in mesophyll cells, and that the photosystem contains a Q cycle. The ratio of the proton velocity across the thylakoid membrane in the linear electron transport chain to the electron flux velocity in the electron transport chain (H) is also considered. + / e - The ratio of proton rate to ATP production rate (H) is 3; + The ratio of ATP to electron flow rate is set to 4; therefore, the ratio of ATP generated to electron flow rate (ATP / e) is... - The value is 3 / 4; the carboxylation rate of PEPC enzyme is: Among them, V pepc (mol m -2 s -1 [CO2] represents the maximum carboxylation rate of PEP. cy_ms (mol m -3 K is the concentration of carbon dioxide in the cytoplasm of mesophyll cells. p (mol m -3 ) is the Michaelis-Menten constant for carbon dioxide in PEPC enzyme; v me Represented as v p The integral in the mesophyll cell cytoplasm multiplied by the proportion allocated to the NADP-ME decarboxylation pathway, f me Divide by the volume of the chloroplasts in the bundle sheath cells: v pepck Represented as v p The integral in the mesophyll cell cytoplasm multiplied by the proportion allocated to the PEPCK decarboxylation pathway (1-f) me Divide by the volume of the cytoplasm of the bundle sheath cells:

13. The method or cell model as described in claim 5, characterized in that, In the boundary condition setting and conductivity calculation model, carbon dioxide is set to diffuse from intercellular air into mesophyll cells, but not directly from intercellular air into bundle sheath cells; bicarbonate cannot pass through the cell walls of mesophyll cells or bundle sheath cells. The process by which metabolites cross these boundaries through the membranes of chloroplasts, mitochondria, and vacuoles, cell membranes, and plasmodesmata is as follows: The left side of equation (13) represents the flow through the boundary, where r is the resistance of metabolites at the boundary, and C1 and C2 (mol m) -3 () represents the concentration of metabolites on both sides of the boundary.

14. The method or cell model as described in claim 5, characterized in that, In the boundary condition setting and conductance calculation model, it is assumed that all metabolites can pass through the membranes of chloroplasts, mitochondria, and vacuoles; the resistance to metabolite passage through the membranes is: r＝P co2 -1 (14) Where P co2 It refers to the permeability of carbon dioxide on the membrane.

15. The method or cell model as described in claim 5, characterized in that, In the boundary condition setting and conductance calculation model, the resistance of metabolites at the interface between the two types of cells is: Among them, S w / S l φ is the ratio of the interface area between mesophyll cells and bundle sheath cells to the leaf area; φ is the proportion of the interface area covered by plasmodesmata; L pd (m) is the length of plasmodesmata.

16. The method or cell model as described in claim 5, characterized in that, In the boundary condition setting and conductivity calculation model, for the cell wall boundary of mesophyll cells exposed to intercellular air, a conductivity constant G encompassing both the cell wall and plasma membrane is defined. wall (mol m -2 s -1 If the velocity of carbon dioxide entering the mesophyll cell at each point on this cell wall is (mol / m³), then... -2 s -1 )for: Where P (Pa) is atmospheric pressure, s c (molm -3 Pa -1 ) represents the solubility of carbon dioxide, C i (molm -3 C is the concentration of carbon dioxide in the intercellular space. wall (molm -3 () represents the concentration of carbon dioxide on the cell walls of mesophyll cells; Furthermore, the average flow rate of carbon dioxide entering the three-dimensional structural portion is defined as the integral of the flow rates at all points on the cell wall boundary exposed to intercellular air in the mesophyll cells, divided by the area of ​​the cell wall exposed to intercellular air in the mesophyll cells. The net photosynthetic rate A (mol / m²) per unit leaf area is then calculated. -2 s -1 )for:

17. The method or cell model as described in claim 5, characterized in that, In the boundary condition setting and conductivity calculation model, the leakage rate L (molm) of carbon dioxide from the bundle sheath cells to the mesophyll cells is used. -2 s -1 The rate of C4 acid decarboxylation per unit leaf area is defined as the rate of carbon dioxide fixation by Rubisco enzymes in the chloroplasts of bundle sheath cells, minus the rate of respiration in the mitochondria and the rate of photorespiration in the cytoplasm of bundle sheath cells. Among them, V cy_bs (m 3 m -2 () is the volume of the bundle sheath cell cytoplasm per unit surface area of ​​a mesophyll cell exposed to intercellular air; therefore: vascular bundle sheath conductance g bs (molm -2 s -1 bar -1 )for: in, and These represent the average concentrations of carbon dioxide in the chloroplasts of bundle sheath cells and the cytoplasm of mesophyll cells: Mesophyll conductance g m (molm -2 s -1 bar -1 )for:

18. The method according to any one of claims 1-2 or the photosynthetic cell model according to claim 3, characterized in that, The cells were C4 plant cells; Preferably, the plant comprises: monocotyledonous C4 plants or dicotyledonous C4 plants; more preferably, the plant comprises: monocotyledonous plants of the Poaceae, Cyperaceae, and Dioscoreaceae families, and dicotyledonous plants of the Chenopodiaceae, Cirsaceae, Amaranthaceae, Asteraceae, Polygonaceae, Acanthaceae, Portulacaceae, Caryophyllaceae, or Zygophyllaceae families; more preferably, the Poaceae plant comprises: plants of the genus *Zea*, *Setaria*, *Sorghum*, and *Saccharum*.

19. The use of the cell model according to any one of claims 3-18 in the preparation of an apparatus or system for simulating and analyzing cellular photosynthesis or photosynthetic activity; Preferably, the simulated analysis of cellular photosynthesis or photosynthetic activity includes: The effects of various reaction rates and conductances in the simulation model under different intercellular carbon dioxide concentrations and light intensities; Simulation analysis of the total conductivity (G) of the cell wall and protoplasmic membrane wall The effect on photosynthetic efficiency or conductance; Simulation analysis of the effect of maximum catalytic activity of carbonic anhydrase in mesophyll cells on photosynthetic efficiency or conductance; The effect of PEPC enzyme activity on photosynthetic rate or conductance was simulated and analyzed. Simulation analysis of the effect of carbon dioxide permeability on chloroplast membranes of bundle sheath cells on photosynthesis or conductance; or Simulation analysis of the maximum carboxylation activity (V) of Rubisco enzyme cmax The impact on photosynthetic efficiency or conductivity.

20. An apparatus or system for simulating and analyzing cellular photosynthesis or photosynthetic activity, wherein a cell model or combination of cell models as described in any one of claims 3-18 is integrated.

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