Wheat root growth model established through root-rhizosphere-soil coupling by using water-carbon flux and method thereof

Abstract

The invention relates to a wheat root system growth model established through root system-rhizosphere-soil coupling by using water-carbon flux and a method thereof, and the wheat root system growth model is established through root system-rhizosphere-soil coupling by using water-carbon flux on the basis of response of wheat root system parameters, root system density and root system activity to moisture. Therefore, a crop root growth model system with applicability is formed. The wheat root growth model is further coupled with a rhizosphere model on the basis of CA and L-System, and a root-rhizosphere-soil model with water carbon flux as an internal relation is constructed, so that the tobacco root growth model is fully applied and developed. Model results show that root mean square error (RMSE) of test values and model values of root length distribution of moisture stress treatment and moisture sufficient treatment are 0.0261 and 0.0396 respectively, model precision R2 is 0.9179 and 0.8758 respectively, simulation precision is relatively close, and precision is very high.

Description

Technical Field

[0001] The invention relates to a wheat root growth model established by using water-carbon flux to carry out root-rhizosphere-soil coupling and a method thereof, and belongs to the technical field of vegetation root model simulation. Background Art

[0002] The root system is an important organ for plants to obtain water and nutrient resources from the soil during their growth. The range and extent of root growth in the soil are closely related to the soil environment. The interaction between roots and soil directly affects the growth of the aboveground parts of plants, thereby affecting crop yields. Therefore, the root growth model is one of the main directions of crop research and has practical production guidance significance for future agricultural development. The root system of wheat (Triticum aestivum L.) consists of primary roots and secondary roots. The secondary roots are divided into primary and secondary lateral roots. The secondary roots are the main components of the wheat root system, and their development status is one of the signs of seedling growth. The primary roots play a greater role in the early stage, and their growth is more stable than that of the secondary roots. They play a role until the late growth period of wheat; the secondary roots have a long rooting time and a large amount of roots. When conditions are suitable, they play an important role in significantly increasing yields. The main functions of wheat root system are absorption, metabolism and support. Part of the water and nutrients absorbed by the roots are retained in the roots for use, and the other part enters the conducting tissue in the original form or in the form of other compounds, and is transported to various parts of the plant with the rise of transpiration flow to meet the needs of the growth and development of organs such as leaves, stems, and ears. The root system has both horizontal distribution and vertical growth, forming a good support and pulling force to support the plant to stand upright. It can be seen that strong seedlings must first have strong roots, and deep roots and lush leaves. A strong root system is the basis for strong seedlings, strong stalks, and large ears. In general clay soil, wheat roots are slender and have many branches; in sandy soil, wheat roots are thick and have few branches. Appropriate soil drought can promote the root system to go down, and the number and amount of secondary roots of a single plant increase significantly with the improvement of soil water and fertilizer. The root system is deep in the soil and evenly distributed. A well-developed root system is the basis for high wheat yield. With the development of wheat production, the relationship between the distribution of roots in the soil and yield is increasingly valued by people. Most of the existing wheat root system models are simulated based on the influence of wheat's own growth factors. However, many environmental factors have a huge impact on wheat growth. If wheat's own growth factors are used as the main factor, the simulated model will be different from the actual one, resulting in an unsatisfactory simulated model and little practical significance. Summary of the invention

[0003] The present invention provides a wheat root growth model established by using water-carbon flux to conduct root-rhizosphere-soil coupling, analyzes wheat root parameters to verify model results, and establishes an applicable crop root growth model, thereby solving the problem that the existing wheat model is not ideal and has little practical significance because the model is obtained by using wheat's own production factors or single water as an indicator.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A wheat root growth model was established by using water-carbon flux for root-rhizosphere-soil coupling, including

[0006] (1) Relationship formula between root weight density and root length density:

[0007] RLD=a+b*ln(RWD+c),

[0008] Wherein, RLD is the root length density, cm cm-3; RWD is the root weight density, g cm-3; a, b, and c are the fitting parameters for calculating the root length density by fitting the root weight density measured by the experiment;

[0009] (2) The relationship between root length density and soil water suction is:

[0010] RLD=m+n*ln(S+e l ),

[0011] Where RLD is the root length density; S is the soil water suction value, which is normalized; m, n, and l are the fitting parameters representing the root-soil-water relationship in the fitting process of root length density and soil water suction;

[0012] (3) The dynamic root growth model of water absorption after root-soil coupling is as follows:

[0013]

[0014] Where t represents time, θ represents soil volume moisture content, d represents buffering capacity, and D l represents the diffusion coefficient, f represents the resistance coefficient, and f(s) represents the water absorbed by the root system, which is based on the root length density distribution and soil hydraulic distribution;

[0015] Here we demonstrate the coupling between L-System root growth and soil model. To simplify the definition:

[0016]

[0017] Among them, F m Indicates the maximum flow rate into the root system, K m represents the Michaelis Menten constant;

[0018] (4) Root growth function;

[0019] Assuming the initial value: t = 0, the root topology stage i, i at t = 0, the root growth function is:

[0020]

[0021] Among them, K i Maximum root length, R i The initial growth rate of the ith root, interpolated (age) which describes the age of the nearest root surface,

[0022] (5) A root fractal model was established by combining Cellular Automata (CA) and L-System (Lindenmayer-System). At the beginning of the simulation (t = 0), the boundary conditions of all root surfaces were set to no flow;

[0023] The coupling in soil is illustrated using the following code: iterate i, where i is the current time step, from 0 to N-1, where N is the total number of time steps. In this loop, the soil water suction S is first calculated. Based on S, the root growth is simulated, and the xylem water pressure Sr of the root is calculated. Based on the root structure, xylem pressure and soil saturation (soil water suction calculation), the root water absorption rate is calculated;

[0024] for i in range(N):

[0025] Si+1=soil_model(S,i)

[0026] root_architecturei+1=root_system_growth(S,i+1)

[0027] Sr,i+1=model(root_architecture,ps,i+1)

[0028] Si+1=root_water_uptake(root_architecturei+1,Sr,i+1,S,i+1).

[0029] The present invention also provides a method for establishing a wheat root growth model by using water-carbon flux to perform root-rhizosphere-soil coupling, comprising the following steps:

[0030] (1) Collect and analyze local data of actual wheat growth;

[0031] (2) constructing a wheat root growth model using the model of claim 1 based on the data obtained in step (1);

[0032] (3) To analyze the accuracy of the fit between the model value and the experimental value, two statistical criteria are used: the mean square error (RMSE) and the coefficient of determination (R2), as shown in the following formula:

[0033]

[0034] Where Mi and Pi are measured values ​​and model values ​​respectively, where i = 1, 2, 3, ..., n, is the mean of Mi, and n is the number of observations in the validation dataset. R2 values ​​range from 0 (least accurate) to 1.0 (most accurate), and 0≤RMSE values ​​are not less than zero.

[0035] Further, preferably: the local data of wheat include soil moisture, wheat root density, moisture in wheat plants, carbon flux and nitrogen flux.

[0036] The wheat root growth model of the present invention is used in calculating the energy of various organs of the plant.

[0037] Beneficial effects of the present invention:

[0038] The present invention establishes a wheat root growth model based on the response of wheat root parameters, root density and root activity to water, and uses water-carbon flux to perform root-rhizosphere-soil coupling, thereby forming an applicable crop root growth model system.

[0039] The application of crop root growth model uses biochar as a soil environmental factor to study the root growth of water-regulated wheat under sufficient soil water and stress conditions. The study shows that the growth of secondary lateral roots is more vigorous when the soil water is sufficient, and water stress treatment inhibits the generation of new roots. Under sufficient water treatment, the wheat root system grows in a balanced horizontal and vertical direction. The root system mainly absorbs surface water, so the root angle is slightly larger; while under water stress treatment, the root angle is smaller and mainly grows downward. Analysis of root rhizosphere enzymes showed that the enzyme activity in the surface soil of water stress treatment was significantly lower than that of sufficient water treatment, but the depth of the bottom soil was obviously greater than that of sufficient water treatment. This shows that water stress forces the root system to grow deep and the root system is deep and long. Based on CA and L-System, the wheat root growth model further couples the rhizosphere model to construct a root-rhizosphere-soil model with water and carbon flux as the intrinsic connection, so that the tobacco root growth model can be fully applied and developed. The model results show that the root mean square error (RMSE) of the experimental value and the model value of the root length distribution under water stress treatment and water sufficient treatment is 0.0261 and 0.0396 respectively, and the model accuracy R2 is 0.9179 and 0.8758 respectively. The simulation accuracy is relatively close and the accuracy is very high. This model can simulate the flow of water and carbon in reality in a complete crop root structure, forming an applicable crop root growth model. By simulating the aboveground part of wheat root growth and simulating the process of each aboveground wheat organ, the digital characteristics and structure of crop root configuration and crop growth are revealed, thus forming an applicable crop root growth model system, providing theoretical support for the development of crop growth models. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 It is the test setup and process diagram of the present invention;

[0042] Figure 2 This is a graph of root growth rate of wheat primary roots;

[0043] Figure 3 This is the root length density diagram of wheat at different soil depths;

[0044] Figure 4 This is a schematic diagram of water carbon flux in the wheat model;

[0045] Figure 5 This is the root system simulation process analysis diagram;

[0046] Figure 6 Describe the model process diagram;

[0047] Figure 7 This is a simulation diagram of dissolved carbon content under steady state;

[0048] Figure 8 A simulated diagram of dissolved carbon in symbiotic and oligobiotic organisms in soil under steady state;

[0049] Fig. 9 Simulation results of wheat root length under water stress treatment;

[0050] Fig.10 This is the simulation result of wheat root length under the treatment of sufficient water;

[0051] Fig.11 The simulation results of the growth of various organs of wheat plants;

[0052] Fig.12 This is the total carbon content of wheat plant structure. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Example 1

[0055] A method for establishing a wheat root growth model by coupling root system, rhizosphere and soil using water and carbon flux, and a method for establishing a wheat root growth model by coupling root system, rhizosphere and soil using water and carbon flux, including

[0056] (1) Relationship formula between root weight density and root length density:

[0057] RLD=a+b*ln(RWD+c),

[0058] Wherein, RLD is the root length density, cm cm-3; RWD is the root weight density, g cm-3; a, b, and c are the fitting parameters for calculating the root length density by fitting the root weight density measured by the experiment;

[0059] (2) The relationship between root length density and soil water suction is:

[0060] RLD=m+n*ln(S+e l ),

[0061] Where RLD is the root length density; S is the soil water suction value, which is normalized; m, n, and l are the fitting parameters representing the root-soil-water relationship in the fitting process of root length density and soil water suction;

[0062] (3) The dynamic root growth model of water absorption after root-soil coupling is as follows:

[0063]

[0064] Where t represents time, θ represents soil volume moisture content, d represents buffering capacity, and D l represents the diffusion coefficient, f represents the resistance coefficient, and f(s) represents the water absorbed by the root system, which is based on the root length density distribution and soil hydraulic distribution;

[0065] Here we demonstrate the coupling between L-System root growth and soil model. To simplify the definition:

[0066]

[0067] Among them, F m represents the maximum flow rate into the root system, K m represents the Michaelis Menten constant;

[0068] (4) Root growth function;

[0069] Assuming the initial value: t = 0, the root topology stage i, i at t = 0, the root growth function is:

[0070]

[0071] Among them, K i Maximum root length, R i The initial growth rate of the ith root, interpolated (age) which describes the age of the nearest root surface,

[0072] (5) A root fractal model was established by combining Cellular Automata (CA) and L-System (Lindenmayer-System). At the beginning of the simulation (t = 0), the boundary conditions of all root surfaces were set to no flow;

[0073] The coupling in soil is illustrated using the following code: iterate i, where i is the current time step, from 0 to N-1, where N is the total number of time steps. In this loop, the soil water suction S is first calculated. Based on S, the root growth is simulated, and the xylem water pressure Sr of the root is calculated. Based on the root structure, xylem pressure and soil saturation (soil water suction calculation), the root water absorption rate is calculated;

[0074] for i in range(N):

[0075] Si+1=soil_model(S,i)

[0076] root_architecturei+1=root_system_growth(S,i+1)

[0077] Sr,i+1=model(root_architecture,ps,i+1)

[0078] Si+1=root_water_uptake(root_architecturei+1,Sr,i+1,S,i+1).

[0079] The present invention also provides a method for establishing a wheat root growth model by using water-carbon flux to perform root-rhizosphere-soil coupling, comprising the following steps:

[0080] (1) Collect and analyze local data of actual wheat growth;

[0081] (2) constructing a wheat root growth model using the model of claim 1 based on the data obtained in step (1);

[0082] (3) To analyze the accuracy of the fit between the model value and the experimental value, two statistical criteria are used: the mean square error (RMSE) and the coefficient of determination (R2), as shown in the following formula:

[0083]

[0084] Where Mi and Pi are measured values ​​and model values ​​respectively, where i = 1, 2, 3, ..., n, is the mean of Mi, and n is the number of observations in the validation dataset. R2 values ​​range from 0 (least accurate) to 1.0 (most accurate), and 0≤RMSE values ​​are not less than zero.

[0085] The specific process is as follows:

[0086] 1. Experimental introduction

[0087] 1.1 Overview of the test area

[0088] The wheat experiment was conducted in a greenhouse from May to August 2021. The experimental area has a temperate marine climate, with an average annual temperature of 8.8°C and an average annual precipitation of 809.3 mm. The soil texture is sandy loam, 24.8% sand, 55.1% silt, 20.1% clay, and the soil bulk density is 1.29 g / cm3 , soil carbon content was 14.1g / kg, microbial carbon was 73μg / g, soil nitrogen content was 0.8g / kg, and the average soil pH was 6.5. The experiment used soil columns to plant wheat, and the size of the soil column was 20cm×10cm×60cm (length×width×height). The soil was sieved through a 5mm sieve and loaded into the soil column.

[0089] 1.2 Experimental design

[0090] The wheat experiment mainly used water as a control factor to study the interaction between plant roots and soil and the flow of water and carbon in the root-soil environment. The experimental treatments were: Non-drought (65%-75% WHC) and Drought (30%-40% WHC), each with 3 replicates, and another soil column without crops, for a total of 7 soil columns.

[0091] Once the wheat plants are large enough, they 13 C is marked, and the process diagram is shown in 1. After the wheat planting soil column is drought-treated for 7 days, it is placed in a closed transparent room (length × width × height: 1.0m × 1.0m × 1.5m). Circulation fans are installed on the side and top, and detection sensors are installed to measure the indoor CO2 concentration and indoor temperature in real time.

[0092] Carbon is injected with CO2 (99atom% 13 C) After the wheat plants are grown in a soil rich in 13 C-CO2 environment for 2 hours to allow the absorption and incorporation of carbon isotopes. The total CO2 concentration in the chamber was raised to 1000ppm, and the CO2 concentration in the transparent chamber was reduced to 700ppm within 2 hours (MG811, CO2 gas module, DFRobot, Shanghai, China). After CO2 pulse labeling, the plants were given 2 days to increase the photosynthetic rate. 13 C-CO2 is conducted underground. Then the leaves and stems are sampled, and a 50mm diameter soil column is collected and immediately passed through a 2mm sieve to separate the living roots and soil; finally, the soil column is moved to the laboratory for decomposition and sampling of soil and roots. 13 The movement track marked by C is: photosynthesis 13 C (Photosynthetic 13 C) → In the leaves and stems of plants 13 C( 13 C in plant) → in the root system 13 C( 13 C in roots)→in the rhizosphere 13 C( 13 C in rhizodeposits) → in soil13 C( 13 C in soil). The ultimate goal is biological processes 13 C decomposition, the process of C flow from photosynthesis to plant roots or plant residues to soil microorganisms and from soil organic matter to CO2. 13 The purpose of C labeling is to study the growth of plant roots in the soil, track the distribution and transportation of labeled carbon in plant roots, and understand the soil depth and type selected by plant roots when absorbing nutrients, so as to calculate the carbon flux during root-soil interaction.

[0093] 2 Test items and methods

[0094] 2.1 Wheat plant analysis

[0095] In order to determine the water, carbon, and nitrogen fluxes in various parts of the wheat plants, after the wheat experiment, the wheat was cut from the soil layer and the total weight of the wheat plants was weighed. After removing some yellow and dead leaves from the wheat plants, take each organ of the wheat plant (stem, ear and leaf) and weigh the fresh weight of each part. Finally, put each organ into a kraft paper bag, put it into an oven, and dry it at 75°C for 72 hours. After closing the oven to a constant temperature, weigh the dry weight of each part. Grind or chop the dried samples of various parts of the wheat plant to make the samples uniform, put them into glass bottles and carry out for subsequent weighing. Use an electronic balance with an accuracy of 0.001 mg to weigh 3 mg of samples from various parts of the plant and 25 mg of soil samples and put them into tin bags for TC, TN, 13 C and 15 N measurement. For every 10 samples, one standard (1 mg of glutamic acid) is required. In addition, three tin capsules containing standard soil need to be weighed for standard comparison.

[0096] 2.2 Analysis of wheat root morphological parameters

[0097] WinRhizo Pro 2020a was used to analyze the morphological parameters of wheat roots. After the wheat root samples were obtained, samples were taken from different locations and depths of three replicates of two treatments for root analysis.

[0098] 2.3 Data Statistics and Analysis

[0099] Image processing and analysis in this paper were completed using the open source software imageJ. SPSS22.0, Origin2022b and Excel 2016 were used for statistical analysis, drawing graphs and other data processing, and Matlab R2016a was used for simulation and model verification.

[0100] To analyze the accuracy of the fit between the model value and the experimental value, two statistical criteria were used: the mean square error (RMSE) and the coefficient of determination (R2 ), the formula is as follows:

[0101]

[0102] Where M i and P i are measured values ​​and model values, respectively, where i = 1, 2, 3, ..., n, It is M i The mean value of R, where n is the number of observations in the validation dataset. 2 Values ​​range from 0 (least accurate) to 1.0 (most accurate), and 0≤RMSE values ​​are not less than zero.

[0103] 3. Analysis of test results

[0104] 3.1 Analysis of root structure parameters

[0105] The results of the wheat test were mainly analyzed through wheat root parameters, which were mainly analyzed through wheat primary roots (Basel roots), first order lateral roots (1st order lateral roots) and second order lateral roots (2nd order lateral roots). The root parameters of the sufficient water treatment and water stress treatment are shown in Table 1. For the total root length of wheat, the primary roots, first order lateral roots and second order lateral roots of the water stress treatment were all greater than those of the sufficient water treatment. The total length of the first order lateral roots of the water stress treatment was 72.22 cm, which was significantly greater than the total length of 47.00 cm of the non-drought treatment; the total length of the second order lateral roots was 104.13 cm, which was also significantly greater than the total length of 65.42 cm of the sufficient water treatment.

[0106] For the water stress treatment, the mean and median of the primary root lateral distance were 0.43 cm and 0.44 cm, respectively, while the sufficient water treatment showed that the mean and median of the primary root lateral distance were greater than the water stress treatment, 0.55 cm and 0.53 cm, respectively. This indicates that the primary root lateral distance is higher in the sufficient water treatment, and the root growth tends to extend horizontally rather than vertically. However, the mean (0.44 cm) and median (0.44 cm) of the primary lateral root lateral distance in the water stress treatment were slightly greater than the mean (0.39 cm) and median (0.41 cm) of the primary lateral root lateral distance in the sufficient water treatment. The results showed that there was no significant difference in the lateral distance of the lateral roots.

[0107] The results of the test on the root growth rate of primary roots within 12 days showed that the root growth rate of primary roots treated with water stress was 2.91 cm / day; the root growth rate of primary roots treated with sufficient water was 3.81 cm / day. Figure 2As shown. Within 11.3 days of water stress treatment, the root growth rate of the primary root was 2.9 cm / day; after 11.3 days, the total length of the primary root was 39.0 cm. Within 8.6 days of water sufficient treatment, the root growth rate of the primary root was 3.8 cm / day, and after that, the root length of the primary root was 40.4 cm. The experimental observation and simulation results are similar, indicating that after a certain period of time, the primary root no longer continues to grow, and the root growth is mainly lateral root growth. It also shows that there are more roots in the surface soil of the water sufficient treatment, while the roots of the water stress treatment grow more towards the deep soil and require more water. The average value (0.26 cm / day) and median value (0.28 cm / day) of the secondary lateral root growth rate of the water sufficient treatment are significantly faster than the average value (0.10 cm / day) and median value (0.10 cm / day) of the water stress treatment, and its speed is nearly 3 times the growth rate of the water stress treatment. This indicates that the growth of secondary lateral roots is more vigorous when there is sufficient water, and conversely it also indicates that water stress inhibits the production of new roots.

[0108] As for the root angle, the root angle under water stress treatment is smaller at 34.8°, indicating that water mainly grows downward. Under sufficient water treatment, the primary root angle is 37.1°, indicating that in a soil environment with sufficient water, the wheat root system grows in a balanced horizontal and vertical direction, and the root system mainly absorbs surface water, so the root angle is slightly larger.

[0109] Table 1 Wheat root parameters under different water distributions

[0110]

[0111]

[0112] Note: * indicates the mean value calculated from the transformed data; ±sd indicates the standard deviation; NA indicates not applicable.

[0113] 3.2 Analysis of wheat root morphological parameters

[0114] Table 2 shows the root morphological parameters of wheat in different treatments and soil depths. As can be seen from the table, there are obvious differences in the root morphological parameters between the sufficient water treatment and the water stress treatment.

[0115] Table 2 Root indexes of wheat in different treatments and soil depths

[0116]

[0117] For the treatment with sufficient water, the total root length at each soil depth is greater than that of the treatment with water stress, especially at a soil depth of 0-30 cm. For the root length of the water stress treatment, it is relatively small at 0-30 cm, and the total root length increases significantly at a soil depth of 30-60 cm, especially at 50-60 cm, which is nearly three times that of 0-10 cm. This shows that under water stress, the wheat root system extends to the deep layer, and the longitudinal growth is greater than the lateral growth. The total root length of the treatment with sufficient water at a soil depth of 0-10 cm (1113.237 cm) is about twice that of the treatment with water stress (638.723 cm), and the total root length at each soil depth is relatively stable. This shows that when water is sufficient, the longitudinal and lateral growth of the root system is relatively balanced. At the same time, the total root length at a soil depth of 50-60 cm was close to that of the water stress treatment (1818.935 cm) and the water sufficient treatment (1860.998 cm). This indicates that the root growth in the deep soil may be due to the lack of deep water infiltration in the soil column test, and the soil moisture environment is similar. On the other hand, it reflects that the roots in the water stress treatment grow more vigorously in the deep soil.

[0118] Tables 3-6 divide the total root length, root surface area, estimated area, and root volume of wheat in the two treatments into 10 levels for analysis and comparison of root occupancy of different lengths, different surface area ranges, different area ranges, and different volume ranges. As can be seen from Table 3, in the treatments of sufficient water and water stress, only the root distribution range of 0-10cm surface soil is relatively wide, while the root length of 10-60cm soil depth is all concentrated in the length range of 0<.L.<=0.500cm. For the treatment of sufficient water, the analysis of the root length within the ten length levels shows that the surface root's ability to absorb water and grow is greater than that of the water stress treatment. However, in the root length range of 2.000<.L.<=2.500cm, 2.500<.L.<=3.000cm, 3.000<.L.<=3.500cm, 3.500<.L.<=4.000cm, the root length of water stress treatment was 3.421cm, 3.942cm, 4.097cm, 2.691cm, respectively, which was greater than that of the well-watered treatment (the values ​​were 1.058cm, 2.134cm, 1.650cm, 2.334cm, respectively). As for the root surface area of ​​wheat, it can be seen from Table 4 that, similar to the root length, only the root surface area of ​​the 0-10cm surface soil was distributed in all levels in the well-watered and water stress treatments, while the root surface area of ​​the 10-60cm soil depth was mainly concentrated in the 0<.SA.<=0.500cm 2 and 0.500<.SA.<=1.000cm 2 Range. The root surface area range is 2.000<.SA.<=2.500cm 2、2.500<.SA.<=3.000cm 2 、3.000<.SA.<=3.500cm 2 、3.500<.SA.<=4.000cm 2 The root surface areas under water stress were 2.398 cm 2 、3.409cm 2 、4.098cm 2 、3.136cm 2 Water treatment (values ​​are 0.742cm 2 、1.812cm 2 、1.674cm 2 、2.778cm 2 ), which is the same as the root length. As can be seen from Tables 5 and 6, the distribution range of root area and root volume is the same as that of root surface area, with distribution in all levels of 0-10 cm surface soil and 10-60 cm soil depth mainly concentrated in 0<.PA.<=0.500cm 2 and 0.500<.PA.<=1.000cm 2 Range, 0<.SA.<=0.500cm 3 and 0.500<.SA.<=1.000cm 3 scope.

[0119] Table 3 Range of wheat root lengths in different treatments and soil depths

[0120]

[0121]

[0122] Note: L represents the root length within 10 levels.

[0123] Table 4 Range of wheat root surface area in different treatments and soil depths

[0124]

[0125]

[0126] Note: SA represents the root surface area within 10 levels.

[0127] Note:SA is root surface area in the range of ten class by class.

[0128] Table 5 Estimated range of wheat root area in different treatments and soil depths

[0129]

[0130] Note: PA represents the estimated root area within 10 levels.

[0131] Table 6 Range of wheat root volume at different soil depths under different treatments

[0132]

[0133]

[0134] Note: V represents the root volume within 10 levels.

[0135] This shows that in addition to the physiological factors of root growth, the roots treated with water stress compete for soil resources within a certain range, and appropriate water stress promotes root growth. It proves that wheat roots can grow deeply under moderate drought, and the plants do not wilt. In the case of water shortage, crops can enhance their root growth ability through root hair absorption.

[0136] 3.3 Analysis of wheat root density

[0137] Figure 3 The root density in different soil layers of the treatments with sufficient water and water stress calculated according to Table 2. As can be seen from the figure, the root density at each soil depth of the treatment with sufficient water is greater than that of the treatment with water stress, and the root volume decreases within the volume range of 20-30cm soil layer. The reason may be that due to the physiological characteristics of the root growth stage, the root diameter becomes thicker rather than the length increases; or during the wheat growth stage, when the roots grow to this soil depth, the lower layer is dry and the root growth is hindered. At the same time, this issue also needs further study. However, at a depth of 50-60cm in the bottom soil, the root density of the two treatments gradually approaches, and the root density value of the treatment with sufficient water is 0.021cm cm greater than that of the treatment with water stress. -3 This indicates that the growth of deep soil layers under water stress treatment is greater than that of surface soil layers. In addition, the root density research results also verified the conclusion of 5.1.3 above, proving that the surface soil roots are mainly used to stabilize crop seedlings in the early growth period, with a large root diameter and a slow increase in length; the deep soil roots are mainly fine roots, and the roots mainly grow through root hairs to find resources.

[0138] 4. Construction of wheat root growth model

[0139] The model principles used were CA and L-System, with carbon flux added as the validation medium for the wheat root system model, and root system simulation analysis was performed using the above simulation method. Figure 4It is a description of the state of the water-carbon flux model when simulating the wheat root system. As can be seen from the figure, first, a plant consisting of nodes connected by segments is constructed in the article, like a directed graph; secondly, the water flow in the root (xylem) and the photosynthesis rate of the plant are calculated, and the soil water model uses the absorption rate as the source term to give the average soil water potential of each soil voxel. The new carbon flow and carbon sink are calculated based on the xylem water potential and carbon input. The amount of carbon required for the growth of each organ is obtained, which is used to simulate the expansion or creation of plant parts in the next time step, and the rhizosphere model will be added to the soil-plant framework. For each root segment, the radial root flux will give the internal boundary conditions of the rhizosphere model, and the soil module will give the external boundary conditions.

[0140] At the same time, from Figure 4 It can be seen that the growth of the aboveground plants is mainly photosynthesis, plant water flux, carbon flux and utilization. The underground soil is mainly soil water flux, accompanied by root water absorption and rhizosphere and soil secretions. When simulating the wheat root system, the flow process analysis of the water and carbon flux used is as follows Figure 5 As shown in the figure, the plant growth process is as follows: plant water flux and photosynthesis are the basis of soil water flux, while circulating plant carbon flux, with root water absorption and soil matrix potential as the medium to circulate soil resources.

[0141] Figure 6 = represents the rhizosphere model process description, which is a graphical explanation of the root-rhizosphere integration process in the establishment of the wheat root growth model. The figure describes the spatial distribution of dissolved carbon content and microbial biomass in the rhizosphere. The model divides the carbon content into two parts, namely dissolved carbon in the soil solution and insoluble carbon. The insoluble carbon area is large molecular carbon, such as lignin, selenide, plant residues, and belongs to oligotrophs, an organism that can live in an environment that provides very low nutrient levels. Dissolved carbon is small molecular carbon, which will cause the growth of copiotrophs in the microbial consortium, an organism that prefers nutrient-rich environments, especially those found in carbon-rich environments. Copiotrophic bacteria are a key component of the C cycle in the soil and exude a large amount of C compounds.

[0142] 5. Wheat root system model verification results

[0143] 5.1 Rhizosphere model results

[0144] Figure 7 and 8 The rhizosphere simulation results for two treatments are shown, and the figures are all obtained under steady state. Figure 7In the figure, we can see the dissolved carbon concentration (mg cm -3 ). Due to the exudation of root secretions, the concentration of dissolved carbon is higher near the roots, with a value of 0.20 mg cm -3 ; it decreases slightly to approximately 0.19 mg cm- -3 .from Figure 8 It can be seen that the spatial distribution of the two functional groups is plotted in the same graph. Due to the high carbon content, the concentration of copiotrophs near the roots is high, with values ​​greater than 0.30 mg cm -3 The concentration of symbiotic biomass decreased from the root center to the soil, and was close to 0 mg cm at a distance of 1 cm from the root system. -3 Oligotrophs, on the other hand, have a lower concentration of dissolved carbon near the roots, with a value of 0.07-0.08 mg cm at a distance of 1 cm from the root surface. -3 The common point between the two is that the concentration value tends to be stable at the root surface. The reason may be the supply of substrate near the root and the decrease of substrate concentration in the soil direction.

[0145] The wheat root-rhizosphere model is a model of the wheat root system and the soil microbial community around it. Such models usually involve factors such as soil physical properties, chemical properties, and biological properties, and use mathematical and computer simulation methods to analyze and predict the ecosystem functions of the rhizosphere of wheat plants. These functions include nutrient cycling, carbon and nitrogen metabolism, soil carbon fixation and nitrogen capture, plant-microbe interactions, etc. The study of wheat root-rhizosphere models is the direction of future research and development, which can provide useful information for the understanding of wheat growth and development and ecosystem functions, and provide guidance for optimizing wheat production.

[0146] 5.2 Model Results Analysis

[0147] The root system model results of water flow and carbon flow in the root system-rhizosphere-soil of wheat under conditions of sufficient soil moisture and soil moisture stress showed that the root growth was significantly different. The lateral root growth of wheat roots under water stress treatment was mainly lateral root growth, while the root growth under sufficient water treatment was mainly horizontal growth. Under the water control factor, the initial response of the root system to water stress was a decrease in the expansion pressure of the root tip, a decrease in the elongation rate of the root system, and an acceleration of the elongation rate of the root tip. The model results and the root length distribution scores in the experiment were distributed at each soil depth as shown in the following figure. Fig. 9 and 10As shown in the figure, it can be seen that the model effect of the treatment with sufficient water is better, and the model value of root length distribution is closer to the experimental value, while the treatment with water stress is second. Secondly, the comparison results between the measured values ​​and the model values ​​show that the distribution of the two treatments in the upper soil (0-30cm) is larger than the measured value, and in the deep soil (30-60cm), the model value is larger. RMSE and R were calculated by regression analysis 2 The model error was obtained by analyzing the simulation results. The root mean square error (RMSE) between the experimental value and the model value of the root length distribution under water stress treatment and water sufficient treatment was 0.0261 and 0.0396, respectively. The model accuracy R 2 The RMSE range of the measured value and the model value of the root length distribution of tobacco is 0.0016-0.0259 and the model accuracy R 2 The range is 0.5969-0.9044, and the simulation effect of wheat is better, indicating that the model with soil moisture as a single factor control has higher accuracy. Crop root growth simulation is a complex process involving multiple fields such as soil mechanics, plant physiology and biomechanics, so it is also very challenging to accurately simulate root growth. The simulation method used in this study makes the root growth model accuracy much greater than the root simulation accuracy of other crops, indicating that the model method in this paper is more applicable.

[0148] At the same time, the results of this model are similar to the results of the wheat experiment, that is, the growth of wheat roots under water stress treatment and sufficient water treatment. Specifically, compared with the sufficient water treatment, the wheat roots under water stress treatment extended more to the deep soil to find more resources. This shows that under water shortage, plants are more inclined to extend their roots to find water and nutrients. In addition, under the sufficient water treatment, the wheat roots grew faster in the horizontal direction, but grew relatively less in the vertical direction, especially at a depth of 40 cm below the soil layer. This shows that under sufficient water conditions, plants are more inclined to use water and nutrient resources in the horizontal direction, so that the roots can grow and expand rapidly. In addition, in terms of the angle between the root system and the vertical direction, the root system with balanced growth is slightly larger. This means that this root system has a more balanced growth mode, which can not only obtain sufficient water and nutrients in the horizontal direction, but also go deep into the soil in the vertical direction to obtain deeper water and nutrients. These results reveal the adaptation strategy of wheat roots under different water conditions, which can provide a certain reference for people to better understand the growth law of plant roots.

[0149] 5.3 Wheat simulation application plant analysis

[0150] Based on the wheat root growth model, further simulation analysis of wheat plants was conducted. Fig.11 To simulate wheat plants13 C-labeled, simulated plant organ growth for 100 days was performed, and then the growth process of each organ of the simulated wheat plant from the 30th to the 33rd day was extracted through the C-flow. The sucrose concentration of each organ of the simulated plant was simulated and the sucrose concentration of wheat grains, roots, stems, and leaves was respectively measured under photosynthesis. 13 Growth amount under C labeling. As can be seen from the figure, the amount of sucrose in the leaves is the largest. Due to photosynthesis, the amount of sucrose in the leaf organs increases during the day; followed by the stems. After the leaves photosynthesize, the sucrose is first transferred to the stem organs; and finally to the roots. The main reason for this is that the accumulation capacity of plant organs at night is used for plant maintenance, growth or root exudation. This also shows that the carbon circulation rate is very high, and it can reach the root soil environment in a short time, and accumulates fastest in the roots. Under pulse isotope labeling, the conclusion that carbon flows to the roots is consistent with the shorter time. During the simulation of plant organ growth, the plant reached its maximum length on the 33rd day. At the same time, the amount of sucrose used for growth decreased, and the maximum sucrose concentration obtained in each organ increased.

[0151] Fig.12 Indicated in Fig.11 The total amount of structural carbon in wheat plants is analyzed on the basis of expressing the sucrose concentration in each organ of wheat plants. As can be seen from the figure, the total amount of structural carbon increased by nearly 0.20 mol from the 30th day to the 33rd day, indicating that as the plant growth time increases, the total amount of structural carbon continues to increase during the simulation process. Among them, the increase on the 30th day was at most 0.08 mol, and the growth was slower on the 33rd day, increasing by less than 0.05 mol. This is closely related to the C concentration. The rate of increase is consistent with the increase in concentration of each organ of the plant, that is, it increases rapidly during the day and slowly at night. Under photosynthesis, the leaves of the plant absorb carbon dioxide for reaction, and the carbon flows to the stem of the plant and finally to the root, which is of great significance to the study of the overall model of the plant. The two figures simultaneously verify the plant simulation results. The model of the present invention can simulate the flow of realistic water and carbon in a complete plant root structure, and can also be reversed to the leaves of the plant to simulate the growth of the aboveground plant. By inverting the simulation process of wheat root architecture and reversely simulating the growth process of plant structural carbon, we further reflect the local ecological to regional carbon sink simulation, thereby studying the dynamic response of plants to the climate environment.

[0152] The wheat root system can be used to simulate wheat plant growth, which can further explore the impact of carbon distribution in various plant organs on plant growth and development. Carbon is an important circulating substance for plant photosynthesis. Future research aims to link plant growth function with local soil carbon content, which will be able to explore the feedback relationship between plants, soil and environment. The applicability of the crop root system crop model established by the present invention also provides a theoretical support for the feasibility of other crop root system research.

[0153] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A wheat root growth model established by using water-carbon flux for root-rhizosphere-soil coupling, characterized in that: include (1) Relationship formula between root weight density and root length density: RLD=a+b*ln(RWD+c), Where RLD is the root length density, cm cm -3 ; RWD is root weight density, g cm -3 ; a, b, c are the fitting parameters of the root length density calculated by fitting the root weight density measured by the experiment; (2) The relationship between root length density and soil water suction is: RLD=m+n*ln(S+e l ), Where RLD is the root length density; S is the soil water suction value, which is normalized; m, n, and l are the fitting parameters representing the root-soil-water relationship in the fitting process of root length density and soil water suction; (3) The dynamic root growth model of water absorption after root-soil coupling is as follows: Where t represents time, θ represents soil volume moisture content, d represents buffering capacity, and D l represents the diffusion coefficient, f represents the resistance coefficient, and f(s) represents the water absorbed by the root system, which is based on the root length density distribution and soil hydraulic distribution; Here we demonstrate the coupling between L-System root growth and soil model. To simplify the definition: Among them, F m represents the maximum flow rate into the root system, K m represents the Michaelis Menten constant; (4) Root growth function; Assuming the initial value: t = 0, the root topology stage i, i at t = 0, the root growth function is: Among them, K i Maximum root length, R i The initial growth rate of the ith root, interpolated (age) which describes the age of the nearest root surface, (5) A root fractal model was established by combining cellular automata and L-system. At the beginning of the simulation (t = 0), the boundary conditions of all root surfaces were set to no flow; The coupling in soil is illustrated using the following code: iterate i, where i is the current time step, from 0 to N-1, where N is the total number of time steps. In this loop, the soil water suction S is first calculated. Based on S, the root growth is simulated, and the xylem water pressure Sr of the root is calculated. Based on the root structure, xylem pressure and soil saturation (soil water suction calculation), the root water absorption rate is calculated; for i in range(N): Si+1=soil_model(S,i) root_architecturei+1=root_system_growth(S,i+1) Sr,i+1=model(root_architecture,ps,i+1) Si+1=root_water_uptake(root_architecturei+1,Sr,i+1,S,i+1).

2. A method for establishing a wheat root growth model by using water-carbon flux to couple root-rhizosphere-soil, characterized in that: The following steps are involved: (1) Collect and analyze data on actual wheat growth; (2) constructing a wheat root growth model using the model of claim 1 based on the data obtained in step (1); (3) To analyze the accuracy of the fit between the model value and the experimental value, two statistical criteria are used: the mean square error (RMSE) and the coefficient of determination (R2), as shown in the following formula: Where Mi and Pi are measured values ​​and model values ​​respectively, where i = 1, 2, 3, ..., n, is the mean value of Mi, n is the number of observations in the validation dataset, and R 2 Values ​​range from 0 (least accurate) to 1.0 (most accurate), and 0≤RMSE values ​​are not less than zero.

3. The method according to claim 2, characterized in that: The local data of wheat include soil moisture, wheat root density, moisture in wheat plants, carbon flux and nitrogen flux.

4. Use of the wheat root growth model according to claim 1 in calculating the energy of various organs of a plant.

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