Method and system for calculating utilization rate of nitrogen in soil under action of arbuscular mycorrhiza

Abstract

The invention provides a method and system for calculating the utilization rate of soil nitrogen under the action of arbuscular mycorrhiza, and relates to the technical field of calculation of the utilization rate of soil nitrogen under the action of arbuscular mycorrhiza. Soil nitrogen absorption amount data of an experimental group and a control group are collected, meanwhile, the total amount of externally input nitrogen is recorded, and related photosynthetic parameters of plants are measured; in addition, through an in-vitro mycelium culture experiment, mycelium nitrogen absorption rates under different nitrogen concentrations are measured, and a semi-saturation constant and a nitrogen effectiveness index are calculated, so that a carbon-nitrogen coupling factor is calculated, morphological parameters of mycelia are collected, and a relation equation of a pipe diameter and a transport rate is established; calculating the total flux of the hypha network, calculating the original nitrogen utilization rate in combination with the nitrogen absorption amount difference value of the experimental group and the control group and externally input nitrogen data, and introducing a transportation continuity coefficient for dynamic correction to finally obtain the soil nitrogen utilization rate of the target area.

Description

Technical Field

[0001] The present invention relates to the technical field of calculation of soil nitrogen utilization rate under the action of arbuscular mycorrhizae, and in particular to a method and system for calculating soil nitrogen utilization rate under the action of arbuscular mycorrhizae. Background Art

[0002] In agricultural ecosystems, nitrogen is a crucial nutrient required for plant growth and development. However, soil nitrogen exists in complex forms, and its availability to plants is influenced by a variety of factors. Arbuscular mycorrhizal fungi, through their symbiotic relationship with plant roots, significantly enhance plants' ability to absorb soil nitrogen. This process not only promotes plant growth but also positively impacts the soil nitrogen cycle. Therefore, accurately calculating the soil nitrogen use efficiency (NUE) under the influence of arbuscular mycorrhizal fungi is of great scientific and practical significance. For example, in agricultural production, optimizing the inoculation and management of arbuscular mycorrhizal fungi can improve crop nitrogen uptake efficiency, thereby reducing the use of chemical fertilizers, lowering production costs, and minimizing environmental pollution. Furthermore, during the restoration of damaged ecosystems, the effective use of arbuscular mycorrhizal fungi can promote the recovery of soil fertility. Therefore, studying the NUE under the influence of arbuscular mycorrhizal fungi is not only important for improving agricultural production efficiency but also helps promote the practice of sustainable agriculture and ecological restoration.

[0003] Existing technologies usually evaluate the contribution of arbuscular mycorrhizae to soil nitrogen utilization through simple nitrogen uptake measurements. These methods are mainly based on the comparison of nitrogen uptake between the experimental group and the control group. Although they can provide preliminary data support, they lack a comprehensive analysis of nitrogen utilization efficiency. For example, existing technologies often fail to comprehensively consider multiple factors such as the photosynthetic efficiency of plants, the nitrogen uptake rate of mycelium and its morphological characteristics, thereby limiting the in-depth understanding of the mechanism of action of arbuscular mycorrhizae. This single evaluation method makes it difficult to reveal the multiple influencing factors of nitrogen utilization efficiency, resulting in reduced accuracy and reliability of the evaluation results.

[0004] Existing technologies have many shortcomings in the study of arbuscular mycorrhizae promoting nitrogen utilization. First, there is a lack of a systematic method to comprehensively consider the relationship between photosynthesis and the nitrogen uptake rate of mycelium, and the cross-research results of plant physiology and microbial ecology are not fully utilized; second, existing evaluation methods often ignore the influence of the morphological characteristics of the mycelial network on nitrogen transport efficiency, and fail to accurately quantify the role of mycelial branching degree, tube diameter and fractal dimension on nitrogen uptake capacity; in addition, existing technologies do not consider the dynamic changes of nitrogen transport under different environmental conditions and cannot provide a highly adaptable evaluation system, resulting in the obtained nitrogen utilization rate often lacking practicality and pertinence.

[0005] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and system for calculating soil nitrogen utilization rate under the action of arbuscular mycorrhizae to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae comprises the following steps:

[0009] Step 1: Within a preset time window, synchronously acquire experimental group data and control group data in the target area, wherein the experimental group data is the soil nitrogen uptake measured by the arbuscular mycorrhizal fungus inoculation group, and the control group data is the soil nitrogen uptake measured by the uninoculated group, and record the total amount of external nitrogen input in the target area;

[0010] Step 2: Synchronously measure the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of plants in the target area, and construct a light response curve. Calculate the actual photosynthetic efficiency based on the integral of the light response curve. Measure the nitrogen uptake rate of mycelium at different nitrogen concentrations through in vitro mycelial culture experiments. Use the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index. Combine the actual photosynthetic efficiency with the fitted results of the mycelial nitrogen uptake rate to calculate the carbon-nitrogen coupling factor.

[0011] Step 3: Collect morphological parameters of hyphae in the target area, including hyphal branching degree, hyphal diameter, and fractal dimension. Based on the relationship between hyphal diameter and hyphal transport rate, establish a diameter-transport rate equation, and combine it with hyphal branching degree to calculate the total flux of the hyphal network.

[0012] Step 4: Based on the difference in nitrogen uptake between the experimental and control groups and the total amount of external nitrogen input, the original nitrogen utilization rate was calculated. This was then combined with the carbon-nitrogen coupling factor and the total flux of the mycelial network to obtain the comprehensive efficiency factor. The transport persistence coefficient was then introduced to correct for the dynamic changes in transport efficiency, ultimately yielding the soil nitrogen utilization rate in the target area.

[0013] The formula for calculating the soil nitrogen utilization efficiency NUE is:

[0014]

[0015] Among them, N AM is the soil nitrogen absorption of the experimental group, N conis the nitrogen absorption of the soil in the control group, N inp is the total amount of external nitrogen input, α is the actual photosynthetic efficiency, K m is the half-saturation constant of nitrogen absorption by mycelium, [N soil ] is the soil available nitrogen concentration, f(T leaf ,g s ) is the environmental correction function for photosynthetic efficiency; d is the mycelial diameter, ΔP is the osmotic pressure difference at the root-soil interface, μ is the cytoplasmic viscosity, L is the average mycelial length, B is the mycelial branching degree, B is the fractal dimension; PC is the transport persistence coefficient.

[0016] Furthermore, the logic for synchronously acquiring the experimental group data and the control group data in the target area within the preset time window is as follows:

[0017] The preset time window is the hyphae expansion period of the plant growing season in the target area. The experimental group is the rhizosphere soil sample of the plant inoculated with arbuscular mycorrhizal fungi, and the control group is the rhizosphere soil sample of the plant not inoculated. The specific steps for obtaining the soil nitrogen absorption are as follows:

[0018] Rhizosphere soil samples were collected weekly from the 0-30 cm rhizosphere layer during the active period of AM fungi symbiotic with plant roots. Using the 1N isotope pulse labeling method, 1N-labeled NHCl and KNO solutions were injected into the experimental group soil weekly at concentrations of 10 mg / kg and 15 mg / kg, respectively. A control group was treated simultaneously with equal amounts of unlabeled NHCl and KNO solutions to eliminate interference from fertilization.

[0019] Spatially resolved isotope analysis of hyphae and plant roots was performed by laser ablation inductively coupled plasma mass spectrometry to distinguish ammonium nitrogen specifically absorbed by hyphae. 15 NH4 + Nitrate 15 NO3 - content;

[0020] Calculate the soil nitrogen absorption N in the experimental group AM : in and The nitrogen absorption amount of the control soil was obtained by measuring the amount of nitrogen absorbed by the roots in the same soil without mycorrhiza inoculation using the same method. con ;

[0021] Total external nitrogen input N inp It is calculated by the accumulation of atmospheric wet deposition nitrogen, fertilizer input and mineralized nitrogen. Precipitation is collected by rain gauge and NO3 in precipitation is determined by chemiluminescence method.- -N and NH4 + -N concentration was used to calculate the amount of atmospheric wet nitrogen deposition, and the total amount of nitrogen applied was calculated by fertilization records, and the NH4 in fertilizers was determined by flow injection analysis. + -N and NO3 - -N content was used to calculate the fertilizer input, and the mineralized nitrogen content was determined by anaerobic culture combined with KCl extraction-colorimetry.

[0022] Furthermore, the net photosynthetic rate, photosynthetically active radiation, leaf temperature and stomatal conductance of the target plant are measured simultaneously, and the logic for constructing the light response curve is as follows:

[0023] Use a portable photosynthetic meter to measure the photosynthetic rate of plants in the target area during the average daily light period. The measurement parameters are: the net photosynthetic rate is set as P n , photosynthetically active radiation is set as PAR, and leaf temperature is set as T leaf and the stomatal conductance is set to g s , each time point was measured three times, and the average was taken after removing outliers;

[0024] For the light response curve, a non-rectangular hyperbolic model was used to fit P n The relationship with PAR is based on the formula:

[0025]

[0026] in, is the apparent quantum efficiency, P max is the maximum photosynthetic rate, R d is the dark respiration rate;

[0027] Based on the light response curve, the actual photosynthetic efficiency α is calculated by integration of the formula:

[0028]

[0029] Among them, the integration time window is the average daily light period, t day =4h, t is the time variable, PAR(t) is the photosynthetic active radiation value that changes with time, P n (t) is the net photosynthetic rate that changes with time.

[0030] Furthermore, the nitrogen uptake rate of mycelium under different nitrogen concentrations was measured by in vitro mycelial culture experiments, and the logic of fitting the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index was as follows:

[0031] The isolated mycelium was cultured in agar medium and NH4 + The concentration gradient was 0, 50, 100, 150, 200 μM, and each concentration was repeated 3 times. 32The P-ATP labeling method was used to determine the nitrogen uptake rate of mycelium. The specific steps included: 32 P-labeled ATP and NH4 + The solutions were mixed and the mycelia were incubated for 30 min. The 32P radioactivity intensity in the mycelia was measured using a liquid scintillation counter and converted into nitrogen uptake rate;

[0032] The Michaelis-Menten equation was used to fit the nitrogen absorption rate:

[0033]

[0034] Where V is the nitrogen absorption rate of mycelium at a specific nitrogen concentration, [N] is the nitrogen concentration in the environment, and V max is the maximum nitrogen absorption rate, K m is the half-saturation constant;

[0035] The Levenberg-Marquardt algorithm was used for nonlinear least squares fitting, requiring the coefficient of determination to be greater than or equal to 0.95, and PAR < 200 μmol / m 2 / s low-light data points to avoid noise interference;

[0036] The soil available nitrogen concentration [N soil ]: Fresh soil samples were mixed with 1MKCl solution at a ratio of 1:5, shaken for 30 minutes and then centrifuged. The supernatant was measured by flow analyzer for NH4 + -N and NO3 - -N concentration, sum to get [N soil ];

[0037] The nitrogen availability index is Among them, [N soil ] is the available nitrogen concentration in soil, K m is the half-saturation constant;

[0038] When [N soil ] is much larger than K m When [N soil ] is much smaller than K m When , it means that soil nitrogen is severely limited and the nitrogen availability index approaches 0;

[0039] The carbon-nitrogen coupling factor C N The calculation formula is:

[0040]

[0041] in, is the nitrogen availability index, f(T leaf ,gs ) is the environmental correction function for photosynthetic efficiency;

[0042] f(T leaf ,g s ) Specifically:

[0043]

[0044] in, is the temperature response function, T leaf It's Ye Wen, T opt =25℃ is the optimum temperature for mycelium, τ=10℃ is the temperature decay constant, is the regulation of stomatal conductance, g s,max It is the highest historical observed value of pore conductance.

[0045] Furthermore, the logic for collecting the morphological parameters of target crop mycelium, including mycelial branching degree, mycelial tube diameter, and fractal dimension, is as follows:

[0046] The three-dimensional reconstruction of the hyphal network was performed using confocal microscopy combined with fluorescence staining, with a spatial resolution of 0.2 μm / pixel. Hyphae with diameters between 0.5 μm and 3 μm and lengths between 5 μm and 200 μm were counted as effective hyphal segments, excluding aging or abnormally enlarged hyphae. The cross-sectional diameters of each hypha in the effective hyphal segment were measured using transmission electron microscopy, and the mean was taken as the hyphal tube diameter d. The path of the hyphae in the effective hyphal segment was marked pixel by pixel along its central axis, and the actual length was calculated using the three-dimensional Euclidean distance formula. Outliers that deviated from the mean by ±3 times the standard deviation were eliminated, and the arithmetic mean of the remaining effective hyphal segments was taken to obtain the average hyphal length. The hyphal branching degree B is defined as the number of branch nodes per cubic millimeter of hyphal volume.

[0047] The fractal dimension D was calculated using the box counting method. The box size gradient was set to ∈ = [2 μm, 32 μm], and the minimum number of boxes N(∈) that covered the mycelial network for each size ∈ was counted. The formula used was:

[0048]

[0049] Where N(∈1) is the minimum number of boxes covering the mycelial network when the box size is ∈1, ∈1=2μm,∈2=32μm is the box size, and D∈[1,2] quantifies the spatial expansion efficiency. The closer D is to 2, the denser and more efficient the network is.

[0050] Based on the modified Poiseuille law, the transport rate v of a single hypha is:

[0051]

[0052] Where ΔP = ψ root -ψ soilis the osmotic pressure difference at the root-soil interface, and the root water absorption potential ψ root =-0.5MPa, soil water potential ψ soil =-0.1MPa, μ is the cytoplasmic viscosity, L is the average length of hyphae;

[0053] Total flux of mycelial network Q total The calculation formula is:

[0054] Q total =v·B·D 2

[0055] Among them, the single hypha velocity v provides the basic transport capacity, the branching degree B increases the transport path density, and the fractal dimension squared D 2 Amplifying the synergistic effects of complex networks.

[0056] Furthermore, based on the difference in nitrogen absorption between the experimental and control groups and the total amount of external nitrogen input, the original nitrogen utilization rate was calculated. The logic of the comprehensive efficiency factor was calculated by combining the carbon-nitrogen coupling factor with the total flux of the mycelial network:

[0057] Based on the difference in nitrogen absorption between the experimental group and the control group, combined with the total amount of external nitrogen input, the original utilization rate NUE was calculated. base The formula is:

[0058]

[0059] Among them, N con is the nitrogen absorption of the soil in the control group, N AM is the soil nitrogen absorption of the experimental group, N inp is the total amount of external nitrogen input;

[0060] The comprehensive efficiency factor F is calculated by combining the carbon-nitrogen coupling factor and the total flux of the mycelial network. rff , based on the formula:

[0061] F eff =NUE base Q total ·C N

[0062] Among them, C N is the carbon-nitrogen coupling factor, Q total is the total flux of the hyphal network;

[0063] Live hyphae were marked green and dead hyphae were marked red by fluorescent double staining, and the proportion of surviving hyphae was recorded by confocal microscopy, and an exponential decay model was fitted:

[0064] S(t)=e -λt

[0065] Among them, S(t) is the survival rate of hyphae at time t, λ is the decay rate constant, t is the time variable, and t is defined as act is the time when the survival rate drops to 50%, that is, S(t act )=0.5, calculated

[0066] The formula for calculating the transport continuity coefficient is:

[0067]

[0068] Where k is the environmental pressure coefficient, It is affected by the life span of mycelium. It is environmental pressure suppression.

[0069] The present invention further provides a system for calculating soil nitrogen utilization rate under the action of arbuscular mycorrhizae. The system is used to execute the above-mentioned method for calculating soil nitrogen utilization rate under the action of arbuscular mycorrhizae, comprising:

[0070] A data acquisition module is used to synchronously acquire experimental group data and control group data in the target area within a preset time window, wherein the experimental group data is the soil nitrogen uptake measured by the arbuscular mycorrhizal fungus inoculated group, and the control group data is the soil nitrogen uptake measured by the uninoculated group, and record the total amount of external nitrogen input in the target area;

[0071] A coupled calculation module is used to simultaneously measure the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of plants in the target area, construct a light response curve, calculate the actual photosynthetic efficiency based on the integral of the light response curve, measure the nitrogen uptake rate of mycelium at different nitrogen concentrations through in vitro mycelial culture experiments, and use the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index. The actual photosynthetic efficiency is combined with the fitting results of the mycelial nitrogen uptake rate to calculate the carbon-nitrogen coupling factor;

[0072] The mycelial network module is used to collect morphological parameters of mycelium in the target area, including mycelial branching degree, mycelial diameter, and fractal dimension. Based on the relationship between mycelial diameter and mycelial transport rate, a diameter-transport rate equation is established, and the total flux of the mycelial network is calculated in combination with mycelial branching degree.

[0073] The comprehensive results module is used to calculate the original nitrogen utilization rate based on the difference in nitrogen absorption between the experimental group and the control group, combined with the total amount of external nitrogen input, and combine it with the carbon-nitrogen coupling factor and the total flux of the mycelial network to calculate the comprehensive efficiency factor. The transport sustainability coefficient is then introduced to correct the dynamic changes in transport efficiency, and finally the soil nitrogen utilization rate in the target area is obtained.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] The present invention simultaneously obtains soil nitrogen uptake in the experimental group (arbuscular mycorrhizal fungus inoculated group) and the control group (uninoculated group), and records the total amount of external nitrogen input, providing basic data for subsequent calculation of nitrogen utilization rate. The comprehensiveness of this data collection solves the problem of the lack of systematic evaluation of nitrogen absorption sources in the existing technology.

[0076] The present invention measures the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of plants, constructs a light response curve, combines the mycelial nitrogen uptake rate obtained from in vitro mycelial culture experiments, and fits the obtained half-saturation constant and nitrogen availability index to calculate the carbon-nitrogen coupling factor. This process quantifies the relationship between photosynthetic efficiency and nitrogen absorption capacity, thus overcoming the limitation of traditional methods that ignore the impact of plant photosynthetic status on nitrogen utilization.

[0077] The present invention collects morphological parameters of mycelium, including mycelial branching degree, tube diameter and fractal dimension, and establishes a relationship equation between tube diameter and transport rate, and further calculates the total flux of the mycelial network; this technical feature solves the problem of lack of comprehensive evaluation of the contribution of mycelial network complexity to nitrogen absorption in the existing technology; the original nitrogen utilization rate is calculated by combining the difference in nitrogen absorption between the experimental group and the control group with the total amount of external nitrogen input, and the carbon-nitrogen coupling factor and the total flux of the mycelial network are combined to finally obtain the comprehensive efficiency factor. By introducing the transport continuity coefficient, the nitrogen transport efficiency is dynamically corrected so that the evaluation results can reflect changes under actual environmental conditions. This technical feature solves the problem of inaccurate evaluation of nitrogen utilization efficiency in a dynamic environment in the existing technology, and provides more practical data support for agricultural management. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 Schematic diagram of the overall method flow of the present invention;

[0079] Figure 2 This is a flow chart of the overall system module of the present invention. DETAILED DESCRIPTION

[0080] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0081] It should be noted that, unless otherwise defined, the technical or scientific terms used in the present invention should have the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0082] Example:

[0083] See also Figure 1 , the present invention provides a technical solution:

[0084] A method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae comprises the following steps:

[0085] Step 1: Within a preset time window, synchronously acquire experimental group data and control group data in the target area, wherein the experimental group data is the soil nitrogen uptake measured by the arbuscular mycorrhizal fungus inoculation group, and the control group data is the soil nitrogen uptake measured by the uninoculated group, and record the total amount of external nitrogen input in the target area;

[0086] The logic for synchronously acquiring experimental and control group data in the target area within the preset time window is as follows:

[0087] The preset time window is the hyphae expansion period of the plant growing season in the target area. The experimental group is the rhizosphere soil sample of the plant inoculated with arbuscular mycorrhizal fungi, and the control group is the rhizosphere soil sample of the plant not inoculated. The specific steps for obtaining the soil nitrogen absorption are as follows:

[0088] Rhizosphere soil samples were collected weekly from the 0-30 cm rhizosphere layer during the active period of AM fungi symbiotic with plant roots. Using the 1N isotope pulse labeling method, 1N-labeled NHCl and KNO solutions were injected into the experimental group soil weekly at concentrations of 10 mg / kg and 15 mg / kg, respectively. A control group was treated simultaneously with equal amounts of unlabeled NHCl and KNO solutions to eliminate interference from fertilization.

[0089] Spatially resolved isotope analysis of hyphae and plant roots was performed by laser ablation inductively coupled plasma mass spectrometry to distinguish ammonium nitrogen specifically absorbed by hyphae.15 NH4 + Nitrate 15 NO3 - content;

[0090] Calculate the soil nitrogen absorption N in the experimental group AM : in and are the amount of ammonium nitrogen absorbed by mycelium and the amount of nitrate nitrogen absorbed by mycelium determined by the isotope abundance method;

[0091] N AM is the total nitrogen absorbed by mycorrhizal fungi in the soil of the experimental group. The absolute nitrogen absorption capacity of AMF for soil is the total amount of nitrogen actively absorbed from the soil by mycelium and transported to the plant roots. It refers to the functional strength of mycelium in the soil nitrogen cycle and directly reflects the contribution of AM fungi to plant nitrogen nutrition. AM The larger the value, the higher the total amount of ammonium nitrogen and nitrate nitrogen absorbed by the mycelium, indicating that the nitrogen absorption capacity of AM fungi is stronger and the utilization rate of soil nitrogen by plants is higher; AM The smaller the size, the lower the efficiency of AM fungi-plant symbiosis or the available nitrogen form (NH4 + or NO3 - ) content is insufficient;

[0092] or Any increase, N AM The mycelial absorption capacity of the two nitrogen forms jointly determines the total nitrogen absorption. Mycelial activity, soil nitrogen concentration, and the symbiotic efficiency of AM fungi and host plants will affect the value of the independent variable.

[0093] In the same soil without mycorrhiza inoculation, the nitrogen absorption of the roots in the uninoculated soil was measured using the same method to obtain the nitrogen absorption of the control soil N con ;

[0094]

[0095] in, is the ammonium nitrogen content directly absorbed by the plant roots in the control group without AM fungi inoculation, is the nitrate nitrogen content directly absorbed by plant roots in the control group without AM fungi inoculation, N con is the total nitrogen directly absorbed by plant roots in the control soil;

[0096] N con It is the nitrogen absorption capacity of plant roots in the absence of AM fungi, that is, the total amount of nitrogen that plants obtain from the soil through their roots. It refers to the nitrogen utilization efficiency baseline of plants in their natural state and is used to compare the synergistic effect of mycorrhizal symbiotic systems.con The more nitrogen the plant has, the stronger its ability to absorb soil nitrogen is. However, it may also indicate that soil nitrogen availability is high or the plant's own root system is well developed. con The smaller the value, the more likely it is to reflect limited root uptake, such as low soil nitrogen availability or poor root development;

[0097] N con and and If the plant roots' absorption efficiency of ammonium nitrogen or nitrate nitrogen is improved, such as an increase in root biomass or high soil nitrogen availability, then N con Increase;

[0098] Total external nitrogen input N inp It is calculated by the accumulation of atmospheric wet nitrogen deposition, fertilizer input and mineralized nitrogen. Precipitation is collected by rain gauges, and the concentrations of NO3-N and NH4-N in precipitation are determined by chemiluminescence to calculate atmospheric wet nitrogen deposition. The total amount of nitrogen applied is calculated by fertilization records, and NH4 in fertilizers is determined by flow injection analysis. + -N and NO3 - -N content was used to calculate the fertilizer input, and the mineralized nitrogen content was determined by anaerobic culture combined with KCl extraction-colorimetry;

[0099] N inp =N wet +N fert +N min

[0100] Among them, N wet The amount of atmospheric wet nitrogen deposition is determined by collecting precipitation through a rain gauge and measuring NH4 by chemiluminescence. + -N and NO3 - -N concentration, N fert Input nitrogen amount for fertilizer, calculate total amount by fertilization record, and determine NH4 in fertilizer by flow injection analysis + -N and NO3 - -N content, N min The amount of mineralized nitrogen was determined by anaerobic culture combined with KCl extraction-colorimetry;

[0101] N inp Reflects the external environment's ability to supplement the soil nitrogen pool, N wet ,N fert ,N min Represents nitrogen input from different sources; N inp With N wet ,N fert ,N min There is a positive correlation. If the precipitation increases, N wetIncrease, increase the amount of fertilizer, that is, N fert Increase or mineralization rate increases, that is, N min Increase, then N inp Increase;

[0102] N inp The larger the value, the richer the soil nitrogen source, which may accelerate the nitrogen utilization of plants and microorganisms, but may also lead to nitrogen loss such as leaching or volatilization. inp The smaller the value, the more likely it is that the soil nitrogen supply is insufficient and the plant needs to rely on internal circulation, such as mycelium or root absorption, to meet plant needs.

[0103] like This indicates that mycelium prefers ammonium nitrogen; conversely, it prefers nitrate nitrogen, which may be affected by soil pH, oxygen content and AM fungal species. For example, ammonium nitrogen in acidic soil is more easily absorbed by mycelium.

[0104] Step 2: Synchronously measure the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of plants in the target area, and construct a light response curve. Calculate the actual photosynthetic efficiency based on the integral of the light response curve. Measure the nitrogen uptake rate of mycelium at different nitrogen concentrations through in vitro mycelial culture experiments. Use the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index. Combine the actual photosynthetic efficiency with the fitted results of the mycelial nitrogen uptake rate to calculate the carbon-nitrogen coupling factor.

[0105] The logic for simultaneously measuring the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of the target plant and constructing the light response curve is as follows:

[0106] Use a portable photosynthetic meter to measure the photosynthetic rate of plants in the target area during the average daily light period. The measurement parameters are: the net photosynthetic rate is set as P n , photosynthetically active radiation is set as PAR, and leaf temperature is set as T leaf and the stomatal conductance is set to g s , each time point was measured three times, and the average was taken after removing outliers;

[0107] For the light response curve, a non-rectangular hyperbolic model was used to fit P n The relationship with PAR is based on the formula:

[0108]

[0109] in, is the apparent quantum efficiency, which characterizes the light energy conversion efficiency under weak light, P max is the maximum photosynthetic rate, reflecting the CO fixation capacity at light saturation. is the dark respiration rate, the amount of CO consumed by plants under lightless conditions, i.e., respiratory consumption under lightless conditions, which represents the energy consumption to maintain metabolism;

[0110] It is the efficiency of converting light energy into photosynthetic products under weak light conditions with PAR < 200. PAR is the light quantum flux density in the wavelength range of 400-700nm and is the key factor driving the light reaction. n It is the net amount of CO fixed per unit leaf area per unit time, reflecting the combined results of photosynthesis and respiration;

[0111] P n Characterizes the actual photosynthetic capacity of plants under specific light conditions. PAR directly affects the light reaction rate. R max ,R d Adjust R n ; In low light, PAR→0, Linear dependence on PAR; under strong light R n ≈R max -R d , reaches saturation; R max The larger the value, the higher the light saturation point. d The larger it is, the lower the net photosynthetic benefit;

[0112] P n >0, indicating that photosynthesis exceeds respiratory consumption and plants accumulate organic matter, P n <0, that is, respiration is dominant under extremely weak light or no light, and carbon is lost; The larger the value, the more efficient the plant is in utilizing light energy under weak light conditions, such as the characteristics of shade plants, P max The larger it is, the stronger its CO assimilation capacity is when light is saturated, such as C4 plants are better than C3 plants;

[0113] Based on the light response curve, the actual photosynthetic efficiency α is calculated by integration of the formula:

[0114]

[0115] Among them, the integration time window is the average daily light period, t day =4h, t is the time variable, PAR(t) is the photosynthetic active radiation value that changes with time, P n (t) is the net photosynthetic rate that changes with time;

[0116] α is the actual photosynthetic efficiency, which is the total carbon assimilation of plants during the daily average light period, reflecting the daily productivity of plants. n α(t) and PAR(t) are the net photosynthetic rate and photosynthetically active radiation that change with time and require synchronous high-frequency measurement; α integrates light intensity, light response characteristics and time to quantify carbon accumulation capacity, P n (t) is dynamically coupled with PAR(t), and the instantaneous rate is converted into a total amount by integration;

[0117] The larger the α, the stronger the plant's daily carbon fixation capacity, which may support higher biomass accumulation or stress resistance, which is regulated by the shape of the light response curve, such as high P max Plants contribute more during periods of high light intensity;

[0118] The nitrogen uptake rate of mycelium under different nitrogen concentrations was measured by in vitro mycelial culture experiments. The logic of fitting the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index was as follows:

[0119] The isolated mycelium was cultured in agar medium and NH4 + The concentration gradient was 0, 50, 100, 150, 200 μM, and each concentration was repeated 3 times. 32 The P-ATP labeling method was used to determine the nitrogen uptake rate of mycelium. The specific steps included 32 P-labeled ATP and NH4 + The solution was mixed and the mycelia were incubated for 30 minutes. The mycelia were counted using a liquid scintillation counter. 32 P radioactivity intensity, converted to nitrogen uptake rate;

[0120] The Michaelis-Menten equation was used to fit the nitrogen absorption rate:

[0121]

[0122] Where V is the nitrogen absorption rate of mycelium at a specific nitrogen concentration, reflecting the ability of mycelium to absorb nitrogen per unit time; [N] is the nitrogen concentration in the environment, indicating the effective nitrogen level in the environment where the mycelium is located; V max K is the maximum nitrogen absorption rate, which is the nitrogen absorption capacity of mycelium at saturated nitrogen concentration and reflects the nitrogen absorption potential of mycelium. m is the half-saturation constant, which characterizes the affinity of mycelium to nitrogen, K m The smaller the value, the higher the affinity;

[0123] V is directly dependent on the ambient nitrogen concentration [N] and the intrinsic properties of mycelium V max ,K m ; Low nitrogen [N]<<K m When V≈(V max / K m )·[N], the rate is linearly related to the concentration; high nitrogen [N]>>K m When V≈V max , the rate is saturated and limited by the amount of carrier protein;

[0124] V max The larger the K is, the stronger the nitrogen absorption potential of the hyphae in a nitrogen-rich environment, such as the expression of highly active transport proteins; m The smaller the hyphae, the more competitive they are in low-nitrogen environments, such as AM fungi adapted to poor soils;

[0125] The Levenberg-Marquardt algorithm was used for nonlinear least squares fitting, requiring the coefficient of determination to be greater than or equal to 0.95, and PAR < 200 μmol / m 2 / s low-light data points to avoid noise interference;

[0126] The soil available nitrogen concentration [N soil ]: Fresh soil samples were mixed with 1MKCl solution at a ratio of 1:5, shaken for 30 minutes and then centrifuged. The supernatant was measured by flow analyzer for NH4 + -N and NO3 - -N concentration, sum to get [N soil ];

[0127] The nitrogen availability index is Among them, [N soil ] is the available nitrogen concentration in soil, K m is the half-saturation constant, which indicates the concentration at which nitrogen effectiveness reaches 50% of the maximum value. It is calibrated through plant absorption kinetics experiments. When [N soil ] is much larger than K m When [N soil ] is much smaller than K m When [N soil ]=K m When the nitrogen availability index is 0.5, it means that the nitrogen availability is in a critical state;

[0128] The index value ranges from [0,1] and quantifies the matching degree between soil nitrogen supply and mycelial absorption capacity, which is determined by K m and [N soil ] are jointly determined to reflect the nitrogen utilization efficiency of hyphae in a specific soil;

[0129] When [N soil ]>>K m When the index → 1, nitrogen is highly available, and the mycelium absorbs nitrogen close to V max ; When [N soil ]<<K m When the index → 0, nitrogen limitation is significant, and the nitrogen absorption rate is affected by [N soil ] Strictly restricted;

[0130] When the index is close to 1, the soil nitrogen is sufficient, the mycelium has high nitrogen absorption efficiency, and the plant may reduce its own root nitrogen absorption investment; when the index is close to 0, the soil nitrogen is scarce, the mycelium nitrogen absorption is limited, and the plant may activate other nitrogen acquisition strategies, such as organic acid secretion;

[0131] The carbon-nitrogen coupling factor C N The calculation formula is:

[0132]

[0133] in, is the nitrogen availability index, f(T leaf ,g s ) is the photosynthetic efficiency environmental correction function, specifically: in is the temperature response function, which suppresses the metabolic efficiency when the temperature deviates from the optimal temperature, T leaf It's Ye Wen, T opt =25℃ is the optimum temperature for mycelium, τ=10℃ is the temperature decay constant, which controls the rate of efficiency decrease when the temperature deviates from the optimum temperature. is the regulation of stomatal conductance, g s,max is the historical maximum stomatal conductance observation, which is used to normalize the limitation of current stomatal aperture on CO supply;

[0134] α is the actual photosynthetic efficiency, which provides carbon skeleton for mycelium-plant nitrogen metabolism. Adjust the allocation weight of carbon to nitrogen absorption; C N The carbon assimilation capacity, nitrogen availability and environmental suitability were integrated to quantify the carbon and nitrogen synergistic efficiency of the plant-mycelium system. N Positively correlated with α, photosynthetic carbon supply is the coupling basis; C N It is positively correlated with the nitrogen availability index; the higher the nitrogen availability, the higher the conversion efficiency of carbon to nitrogen metabolism;

[0135] f(T leaf ,g s ) When the leaf temperature deviates from 25°C, the efficiency index decreases. For example, high temperature inhibits mycelial activity and reduces stomatal conductance. For example, under drought stress, the CO supply decreases, inhibiting carbon-nitrogen coupling.

[0136] C N The larger the size, the stronger the carbon and nitrogen metabolism synergy of the plant-hypha system in a specific environment, which may support a higher growth rate or stress tolerance, which is restricted by multiple factors, such as high temperature T leaf >35℃ or low stomatal conductance g s <0.1, which can significantly reduce C N ; High α, combined with high nitrogen availability index, drives C N Improve and promote mycelium-plant mutualism; if C N Sustained low temperatures may trigger plants to reduce their dependence on mycelium and turn to independent nitrogen absorption by the roots; opt Even if α and nitrogen availability index are high, C N It may still be due to f(T leaf ,gs ) is attenuated and limited, stomatal conductance g s Decrease, such as drought reduces both α and f(T leaf ,g s ), dual inhibition of carbon-nitrogen coupling.

[0137] Step 3: Collect morphological parameters of hyphae in the target area, including hyphal branching degree, hyphal diameter, and fractal dimension. Based on the relationship between hyphal diameter and hyphal transport rate, establish a diameter-transport rate equation, and combine it with hyphal branching degree to calculate the total flux of the hyphal network.

[0138] The logic for collecting the morphological parameters of target crop mycelium, including mycelial branching degree, mycelial tube diameter, and fractal dimension, is as follows:

[0139] Three-dimensional reconstruction of the hyphal network was performed using confocal microscopy combined with fluorescence staining, with a spatial resolution of 0.2 μm / pixel. The branching degree, B, was defined as the number of branch nodes per cubic millimeter of hyphal volume. Hyphae with diameters between 0.5 μm and 3 μm and lengths between 5 μm and 200 μm were counted as valid hyphal segments, excluding aging or abnormally enlarged hyphae. The cross-sectional diameters of each hypha in the valid hyphal segment were measured using transmission electron microscopy, and the mean was taken as the hyphal tube diameter d. The path of the hyphae in the valid hyphal segment was marked pixel by pixel along its central axis, and the actual length was calculated using the three-dimensional Euclidean distance formula. Outliers that deviated from the mean ±3 times the standard deviation were eliminated, and the arithmetic mean of the remaining valid hyphal segments was taken to obtain the average hyphal length, L.

[0140] The fractal dimension D was calculated using the box counting method. The box size gradient was set to ∈ = [2 μm, 32 μm], and the minimum number of boxes N(∈) that covered the mycelial network for each size ∈ was counted. The formula used was:

[0141]

[0142] Where N(∈1) is the minimum number of boxes covering the mycelial network when the box size is ∈1, ∈1=2μm,∈2=32μm is the box size, and D∈[1,2] quantifies the spatial expansion efficiency. The closer D is to 2, the denser and more efficient the network is.

[0143] N(∈) is the minimum number of boxes required to cover the entire mycelial network when the box size is ∈, reflecting the spatial distribution density of the network. The box size ∈ is the side length of the cube used to segment the mycelial network. The gradient is set to capture multi-scale structural features. The fractal dimension D quantifies the complexity and spatial expansion efficiency of the mycelial network, with a value range of 1 for a simple linear structure to 2 for completely filling the two-dimensional plane.

[0144] D characterizes the fractal properties of the hyphal network, namely its self-similarity and space-filling ability. N(∈) and ∈ reveal the hierarchical complexity of the network structure through the number of covering boxes at different scales. If the hyphal network is denser, that is, with more branches and frequent crossings, the N(∈) of the small box ∈→0 will grow faster, causing D to approach 2. If the hyphae are sparse, such as a single trunk extension, the growth rate of N(∈) as ∈ decreases will be slower, and D will approach 1.

[0145] When D ≈ 2, the hyphal network is highly complex and has high spatial expansion efficiency, which may enhance the ability to explore soil resources, such as multiple branches and frequent crossings. When D ≈ 1, the hyphae extend linearly and have a simple structure, which may be limited by environmental stresses, such as soil compaction or hyphae aging.

[0146] Based on the modified Poiseuille law, the transport rate v of a single hypha is:

[0147]

[0148] Where ΔP = ψ root -ψ soil is the osmotic pressure difference at the root-soil interface, which drives the flow of water and solutes from the soil to the roots, and the root water absorption potential ψ root =-0.5MPa, soil water potential ψ soil = -0.1 MPa, μ is the cytoplasmic viscosity, which is related to the metabolic state of hyphae, such as the intracellular solute concentration, and L is the average hyphal length, measured by CLSM three-dimensional reconstruction;

[0149] ΔP=ψ root -ψ soil =-0.5MPa-(-0.1MPa)=-0.4MPa

[0150] v is the amount of water or solute that passes through a single mycelium per unit time, reflecting the transport capacity of a single mycelium and directly affecting the total flux of the mycelial network; d 4 It is the fourth power amplification effect of the tube diameter. A slight increase in the thickening of the hyphae can significantly increase the transport rate. For example, if d increases from 2 μm to 3 μm, v increases by 5 times. The larger the water potential difference ΔP, such as ψ soil The lower it is, the stronger the transport driving force is; if μ and L increase the cytoplasmic viscosity or the hyphae are too long, which increases the flow resistance, then v should be reduced;

[0151] The larger v is, the higher the transport efficiency of a single hypha, which may support faster nutrient transport, such as phosphorus, nitrogen, and water, to the plant roots. If d < 0.5 μm, that is, abnormal hyphae are excluded, v approaches 0 due to the small flow cross-sectional area, and the transport function is lost.

[0152] Total flux of mycelial network Q total The calculation formula is:

[0153] Qtotal =v·B·D 2

[0154] Among them, the single hypha velocity v provides the basic transport capacity, the branching degree B increases the transport path density, and the fractal dimension squared D 2 Amplify the synergistic effects of complex networks;

[0155] The branch number B is the number of hyphal branch nodes per unit volume, which is quantified by three-dimensional reconstruction using confocal microscopy to quantify the path density of the hyphal network. The fractal dimension squared D 2 , amplifying the synergistic effect of the fractal network, reflecting the gain of the complex structure on the transport efficiency, the total flux Q total It reflects the overall transport capacity of the hyphal network, integrating single hyphal rate, branching density and network complexity;

[0156] Q total Characterizes the maximum transport potential of the mycelial network per unit time and space. v is the basic transport capacity, which is dominated by the mycelial tube diameter and water potential difference. The higher the branching degree B, the more transport paths there are, and the flux increases linearly. The fractal dimension squared D 2 Reflect nonlinear gains in network complexity, such as dense crossings shortening transport paths;

[0157] Q total The larger the mycelial network, the stronger its overall transport capacity, which may significantly improve the efficiency of plant water and nutrient absorption. When the high D of the complex network is combined with the high B of the multi-branched network, Q total It grows exponentially, far exceeding the contribution of a single factor; if D or B is low, such as when environmental stress inhibits mycelial growth, even if v is high, Q total May still be restricted;

[0158] Through v is proportional to d 4 Dominate single hyphae transport, is to improve Q total The core morphological parameters, branching degree B and fractal dimension D, jointly determine the spatial expansion strategy of the network. High B and high B may reflect the adaptability of hyphae in resource heterogeneous soils, such as multiple branches exploring barren areas; soil water potential ψ siol If it decreases, such as during drought, ΔP will increase and v will be raised, but hyphae growth may be inhibited, i.e., B and D will be reduced. The net effect needs to be weighed;

[0159] This model can be used to evaluate the functional efficiency of AM fungi in different soil environments, providing a quantitative basis for agricultural management, such as inoculant screening and irrigation strategy optimization. For example, under drought conditions, strains with larger d and higher D are preferentially selected to maximize Q. total and alleviate plant water stress.

[0160] Step 4: Based on the difference in nitrogen uptake between the experimental and control groups and the total amount of external nitrogen input, the original nitrogen utilization rate was calculated. This was then combined with the carbon-nitrogen coupling factor and the total flux of the mycelial network to obtain the comprehensive efficiency factor. The transport persistence coefficient was then introduced to correct for the dynamic changes in transport efficiency, ultimately yielding the soil nitrogen utilization rate in the target area.

[0161] Based on the difference in nitrogen absorption between the experimental and control groups and the total amount of external nitrogen input, the original nitrogen utilization rate was calculated. The logic of the comprehensive efficiency factor was calculated by combining the carbon-nitrogen coupling factor with the total flux of the mycelial network:

[0162] Based on the difference in nitrogen absorption between the experimental group and the control group, combined with the total amount of external nitrogen input, the original utilization rate NUE was calculated. base The formula is:

[0163]

[0164] Among them, N con is the nitrogen absorption of the soil in the control group, reflecting the independent nitrogen absorption capacity of plant roots. AM is the amount of soil nitrogen uptake in the experimental group, which was determined by 1N isotope labeling and LA-ICP-MS spatial imaging, and by 1N isotope labeling and LA-ICP-MS imaging, N inp is the total amount of external nitrogen input, including fertilizers, mineralized nitrogen, and atmospheric wet deposition nitrogen;

[0165] NUE base The original nitrogen utilization rate represents the ratio of the net gain of nitrogen absorption by AM fungi to the external input nitrogen, reflecting the contribution rate of the nitrogen absorption efficiency improved by AM fungi relative to the external input nitrogen;

[0166] When N AM -N con >0, that is, AM fungi promote nitrogen absorption, NUE base >0, when N AM -N con = 0, no net contribution of AM fungi, NUE base =0;NUE base With N AM -N con Positively correlated with N inp Negative correlation; NUE base When NUE > 0.5, AM fungi significantly improve nitrogen use efficiency and may reduce dependence on chemical fertilizers. base When <0.1, the AM fungi have a weak effect and the strain or environmental conditions need to be optimized. If there is no external input, that is, N inp As it approaches 0, the formula becomes invalid and the absolute absorption amount needs to be used for evaluation;

[0167] The comprehensive efficiency factor F is calculated by combining the carbon-nitrogen coupling factor and the total flux of the mycelial network. eff , based on the formula:

[0168] F eff =NUE base Q total ·C N

[0169] Among them, C N is the carbon-nitrogen coupling factor, characterizing the synergistic effect of photosynthetic carbon supply and mycelial nitrogen uptake efficiency, Q total is the total flux of the mycelial network, quantifying the physical transport capacity of the mycelial network;

[0170] Q total is the total flux of the hyphal network, which is determined by the hyphal transport rate, branching degree and fractal dimension. N is the carbon-nitrogen coupling factor, integrating photosynthetic carbon supply, nitrogen availability, and environmental correction, F eff is the comprehensive efficiency factor, which quantifies the overall effectiveness of AM fungi in carbon and nitrogen synergy and physical transport; F eff The larger the value, the stronger the synergy of the mycelium-plant system in integrating and transporting carbon and nitrogen resources, and the higher the sustainability of the system.

[0171] F eff F reflects the comprehensive efficiency of the mycelial network in carbon supply, nitrogen absorption and transport. eff With NUE base ,Q total ,C N If any factor approaches 0, such as mycelium death Q total →0 or low temperature inhibition C N →0, will be significantly reduced;

[0172] Live hyphae were marked green and dead hyphae were marked red by fluorescent double staining, and the proportion of surviving hyphae was recorded by confocal microscopy, and an exponential decay model was fitted:

[0173] S(t)=e -λt

[0174] Where S(t) is the survival rate of hyphae at time t, λ is the decay rate constant, and t is the time variable; it is defined as t act The time when the survival rate drops to 50%, S(t act )=0.5, calculated

[0175] λ is the mycelial mortality rate per unit time, which is fitted by time series imaging of fluorescent double staining (live mycelia green / dead mycelia red), t actis the time (half-life) when the survival rate drops to 50%, characterizing the average active lifespan of the mycelial population; S(t) is the proportion of surviving mycelia at time t, reflecting the dynamic changes in the persistence of mycelial function;

[0176] S(t) depends on time t and the intrinsic decay characteristic λ of the hyphae. The larger λ is, the faster the hyphae die. act The shorter the ideal strain is, the shorter the strain is when λ→0, t act →∞, mycelium remains active for a long time;

[0177] The formula for calculating the transport continuity coefficient is:

[0178]

[0179] Among them, k is the environmental pressure coefficient, which is used to quantify the intensity of the external environment's inhibition on the persistence of hyphal transport. The range of PC is [0,1], which quantifies the probability that hyphae can maintain transport function during their active lifespan. It is affected by the life span of mycelium. When the life span of mycelium is extremely short, that is, t act →0, PC→1, the transport persistence can be ignored, when the mycelium life is long, that is, t act →∞, PC→0, transport continues to be efficient;

[0180] It is the environmental pressure inhibition. The larger the k value, the stronger the environmental pressure, such as drought, pathogen attack, nutrient competition, etc., and the mycelium needs a longer survival time t act In order to maintain the continuity of transportation, the smaller the k value, the more suitable the environment, and the mycelium can achieve efficient transportation in a shorter survival time;

[0181] k is calibrated by fitting experimental data: mycorrhizae are cultured under different environmental conditions, such as different humidity, temperature, and microbial competition intensity. The proportion of surviving hyphae S(t) is measured regularly by fluorescent double staining, such as every 24 hours, and the time series data is recorded. The exponential decay model S(t) = e is fitted to the data under each environment. -λt , get the decay rate constant λ and calculate the half-life t act , through isotope tracer method, such as 1N labeling, to determine the nitrogen transport efficiency under different environments, define the actual transport continuity, assuming that under ideal conditions (no environmental pressure) the actual transport continuity is 1, and under extremely harsh conditions the actual transport continuity is 0, and substitute the experimental data into the correction formula Solve k by least squares fitting;

[0182] λ reflects the aging rate of the hyphae itself, and k reflects the external environmental pressure. The two together determine the transport persistence PC. In a harsh environment, even if the hyphae itself has a long life span, that is, λ is small, if the k value is large, the PC will still decrease.

[0183] The soil utilization rate is based on the formula:

[0184]

[0185] Among them, N AM is the soil nitrogen absorption of the experimental group, N con is the nitrogen absorption of the soil in the control group, N inp is the total amount of external nitrogen input, including fertilizers, mineralized nitrogen, and atmospheric deposition; α is the actual photosynthetic efficiency, which is calculated by integrating the light response curve and reflects the carbon supply capacity of plants; K m is the half-saturation constant of nitrogen uptake by mycelium, which was obtained by fitting the experimental data of in vitro mycelium by Michaelis-Menten equation, [N soil ] is the effective nitrogen concentration in the soil, which determines the availability of nitrogen, and f(T leaf ,g s ) is the environmental correction function for photosynthetic efficiency;

[0186] d is the diameter of hyphae, measured by transmission electron microscopy, which directly affects the transport rate; ΔP is the osmotic pressure difference at the root-soil interface, calculated from the difference between the root water uptake potential and the soil water potential; μ is the cytoplasmic viscosity, with a default value of 0.001; L is the average hyphae length; B is the hyphae branching degree; D is the fractal dimension, which quantifies the fractal dimension, and 1≤D≤2; PC is the transport persistence coefficient;

[0187] When PC→0, transport is interrupted; when PC≈1, mycelium transports nitrogen stably throughout its life cycle, which is suitable for drought or poor soils; when PC≈0, the transport capacity is short-lived, and other nitrogen acquisition mechanisms, such as root secretion of organic acids, are required;

[0188] It is the direct effect of AM fungi on nitrogen utilization, It is a synergistic effect of photosynthetic carbon supply and nitrogen availability. is the network physical transport potential, PC is the time weight of mycelial activity maintenance, and NUE is the final output indicator, which comprehensively quantifies the nitrogen resource utilization efficiency of the AM fungus-plant system in a specific environment;

[0189] NUE is affected by all input parameters and reflects the result of the synergistic effect of multiple factors. When NUE>1, the system nitrogen utilization efficiency exceeds the external input, which may rely on internal circulation or mycelium to efficiently activate the residual nitrogen in the soil. When NUE≈0, the system nitrogen utilization is completely ineffective, and environmental stress needs to be checked, such as extreme pH inhibition of mycelium or measurement error.

[0190] The model integrates biological processes such as mycelial nitrogen uptake and photosynthesis with physical transport such as fractal networks and environmental responses such as temperature and stomatal conductance through hierarchical nested formulas, and ultimately outputs NUE as a comprehensive efficiency indicator for the AM fungus-plant symbiotic system. Its core value lies in distinguishing the specific contributions of various factors, such as mycelial morphology, carbon supply, and active lifespan to nitrogen utilization, providing optimization targets for agricultural practices such as inoculation of microbial agents and irrigation / fertilization strategies, such as prioritizing the improvement of d and locating potential limiting factors through the decline of NUE, such as low temperature inhibition of C. N Or compacting the soil reduces D.

[0191] See also Figure 2 The present invention further provides a system for calculating soil nitrogen utilization rate under the action of arbuscular mycorrhizae, wherein the system is used to execute the above-mentioned method for calculating soil nitrogen utilization rate under the action of arbuscular mycorrhizae, comprising:

[0192] A data acquisition module is used to synchronously acquire experimental group data and control group data in the target area within a preset time window, wherein the experimental group data is the soil nitrogen uptake measured by the arbuscular mycorrhizal fungus inoculated group, and the control group data is the soil nitrogen uptake measured by the uninoculated group, and record the total amount of external nitrogen input in the target area;

[0193] A coupled calculation module is used to simultaneously measure the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of plants in the target area, construct a light response curve, calculate the actual photosynthetic efficiency based on the integral of the light response curve, measure the nitrogen uptake rate of mycelium at different nitrogen concentrations through in vitro mycelial culture experiments, and use the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index. The actual photosynthetic efficiency is combined with the fitting results of the mycelial nitrogen uptake rate to calculate the carbon-nitrogen coupling factor;

[0194] The mycelial network module is used to collect morphological parameters of mycelium in the target area, including mycelial branching degree, mycelial diameter, and fractal dimension. Based on the relationship between mycelial diameter and mycelial transport rate, a diameter-transport rate equation is established, and the total flux of the mycelial network is calculated in combination with mycelial branching degree.

[0195] The comprehensive results module is used to calculate the original nitrogen utilization rate based on the difference in nitrogen absorption between the experimental group and the control group, combined with the total amount of external nitrogen input, and combine it with the carbon-nitrogen coupling factor and the total flux of the mycelial network to calculate the comprehensive efficiency factor. The transport sustainability coefficient is then introduced to correct the dynamic changes in transport efficiency, and finally the soil nitrogen utilization rate in the target area is obtained.

[0196] The above formulas are all dimensionless and numerical calculations. The formulas are obtained by collecting a large amount of data and performing software simulation to obtain the most recent real situation. The preset parameters in the formulas are set by technicians in this field according to actual conditions.

[0197] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software depends on the specific application and design constraints of the technical solution.

[0198] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, and may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment as needed.

[0199] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

Claims

1. A method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae, characterized in that: The specific steps include: Step 1: Within a preset time window, synchronously acquire experimental group data and control group data in the target area, wherein the experimental group data is the soil nitrogen uptake measured by the arbuscular mycorrhizal fungus inoculation group, and the control group data is the soil nitrogen uptake measured by the uninoculated group, and record the total amount of external nitrogen input in the target area; Step 2: Synchronously measure the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of plants in the target area, and construct a light response curve. Calculate the actual photosynthetic efficiency based on the integral of the light response curve. Measure the nitrogen uptake rate of mycelium at different nitrogen concentrations through in vitro mycelial culture experiments. Use the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index. Combine the actual photosynthetic efficiency with the fitted results of the mycelial nitrogen uptake rate to calculate the carbon-nitrogen coupling factor. Step 3: Collect morphological parameters of hyphae in the target area, including hyphal branching degree, hyphal diameter, and fractal dimension. Based on the relationship between hyphal diameter and hyphal transport rate, establish a diameter-transport rate equation, and combine it with hyphal branching degree to calculate the total flux of the hyphal network. Step 4: Based on the difference in nitrogen uptake between the experimental and control groups and the total amount of external nitrogen input, the original nitrogen utilization rate was calculated. This was then combined with the carbon-nitrogen coupling factor and the total flux of the mycelial network to obtain the comprehensive efficiency factor. The transport persistence coefficient was then introduced to correct for the dynamic changes in transport efficiency, ultimately yielding the soil nitrogen utilization rate in the target area. The formula for calculating the soil nitrogen utilization efficiency NUE is: Among them, N AM is the soil nitrogen absorption of the experimental group, N con is the nitrogen absorption of the soil in the control group, N inp is the total amount of external nitrogen input, α is the actual photosynthetic efficiency, K m is the half-saturation constant of nitrogen absorption by mycelium, [N soil ] is the soil available nitrogen concentration, f(T leaf ,g s ) is the environmental correction function for photosynthetic efficiency; d is the mycelial diameter, ΔP is the osmotic pressure difference at the root-soil interface, μ is the cytoplasmic viscosity, L is the average mycelial length, B is the mycelial branching degree, and D is the fractal dimension; PC is the transport persistence coefficient.

2. The method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae according to claim 1, characterized in that: The logic for synchronously acquiring experimental and control group data in the target area within the preset time window is as follows: The preset time window is the hyphae expansion period of the plant growing season in the target area. The experimental group is the rhizosphere soil sample of the plant inoculated with arbuscular mycorrhizal fungi, and the control group is the rhizosphere soil sample of the plant not inoculated. The specific steps for obtaining the soil nitrogen absorption are as follows: Rhizosphere soil samples were collected from the 0-30 cm rhizosphere layer. During the active period of AM fungi symbiotic with plant roots, rhizosphere soil samples were collected once a week. Using the 1N isotope pulse labeling method, 1N-labeled NHCl and KNO solutions were injected into the experimental group soil weekly at labeling concentrations of 10 mg / kg and 15 mg / kg, respectively. The control group was treated simultaneously with equal amounts of unlabeled NHCl and KNO solutions to eliminate interference from fertilization itself. Spatially resolved isotope analysis of hyphae and plant roots was performed by laser ablation inductively coupled plasma mass spectrometry to distinguish ammonium nitrogen specifically absorbed by hyphae. 15 NH4 + Nitrate 15 NO3 - content; Calculate the soil nitrogen absorption N in the experimental group AM : in and The nitrogen absorption amount of the control soil was obtained by measuring the amount of nitrogen absorbed by the roots in the same soil without mycorrhiza inoculation using the same method. con ; Total external nitrogen input N inp It is calculated by the accumulation of atmospheric wet deposition nitrogen, fertilizer input and mineralized nitrogen. Precipitation is collected by rain gauge and NO3 in precipitation is determined by chemiluminescence method. - -N and NH4 + -N concentration was used to calculate the amount of atmospheric wet nitrogen deposition, and the total amount of nitrogen applied was calculated by fertilization records, and the NH4 in fertilizers was determined by flow injection analysis. + -N and NO3 - -N content was used to calculate the fertilizer input, and the mineralized nitrogen content was determined by anaerobic culture combined with KCl extraction-colorimetry.

3. The method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae according to claim 1, characterized in that: The logic for simultaneously measuring the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of the target plant and constructing the light response curve is as follows: Use a portable photosynthetic meter to measure the photosynthetic rate of plants in the target area during the average daily light period. The measurement parameters are: the net photosynthetic rate is set as P n , photosynthetically active radiation is set as PAR, and leaf temperature is set as T leaf and the stomatal conductance is set to g s , each time point was measured three times, and the average was taken after removing outliers; For the light response curve, a non-rectangular hyperbolic model was used to fit P n The relationship with PAR is based on the formula: in, is the apparent quantum efficiency, P max is the maximum photosynthetic rate, R d is the dark respiration rate; Based on the light response curve, the actual photosynthetic efficiency α is calculated by integration of the formula: Among them, the integration time window is the average daily light period, t day =4h, t is the time variable, PAR(t) is the photosynthetic active radiation value that changes with time, P n (t) is the net photosynthetic rate that changes with time.

4. The method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae according to claim 3, characterized in that: The nitrogen uptake rate of mycelium under different nitrogen concentrations was measured by in vitro mycelial culture experiments. The logic of fitting the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index was as follows: The isolated mycelium was cultured in agar medium and NH4 + The concentration gradient was 0, 50, 100, 150, 200 μM, and each concentration was repeated 3 times. The nitrogen uptake rate of mycelium was determined by 32P-ATP labeling method. The specific steps included: 32P-labeled ATP was mixed with NH4 + The solutions were mixed and the mycelia were incubated for 30 min. The 32P radioactivity intensity in the mycelia was measured using a liquid scintillation counter and converted into nitrogen uptake rate; The Michaelis-Menten equation was used to fit the nitrogen absorption rate: Where V is the nitrogen absorption rate of mycelium at a specific nitrogen concentration, [N] is the nitrogen concentration in the environment, and V max is the maximum nitrogen absorption rate, K m is the half-saturation constant; The Levenberg-Marquardt algorithm was used for nonlinear least squares fitting, requiring the coefficient of determination to be greater than or equal to 0.95, and PAR < 200 μmol / m 2 / s low-light data points to avoid noise interference; The soil available nitrogen concentration [N soil ]: Fresh soil samples were mixed with 1M KCl solution at a ratio of 1:5, shaken for 30 minutes and then centrifuged. The supernatant was measured by flow analyzer for NH4 + -N and NO3 - -N concentration, sum to get [N soil ]; The nitrogen availability index is Among them, [N soil ] is the available nitrogen concentration in soil, K m is the half-saturation constant; When [N soil ] is much larger than K m When [N soil ] is much smaller than K m When , it means that soil nitrogen is severely limited and the nitrogen availability index approaches 0; The carbon-nitrogen coupling factor C N The calculation formula is: in, is the nitrogen availability index, f(T leaf ,g s ) is the environmental correction function for photosynthetic efficiency; f9T leaf ,g s ) Specifically: in, is the temperature response function, T leaf It's Ye Wen, T opt =25℃ is the optimum temperature for mycelium, τ=10℃ is the temperature decay constant, is the regulation of stomatal conductance, g s,max It is the highest historical observed value of pore conductance.

5. The method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae according to claim 1, characterized in that: The logic for collecting the morphological parameters of target crop mycelium, including mycelial branching degree, mycelial tube diameter, and fractal dimension, is as follows: The three-dimensional reconstruction of the hyphal network was performed using confocal microscopy combined with fluorescence staining, with a spatial resolution of 0.2 μm / pixel. Hyphae with diameters between 0.5 μm and 3 μm and lengths between 5 μm and 200 μm were counted as effective hyphal segments, excluding aging or abnormally enlarged hyphae. The cross-sectional diameters of each hypha in the effective hyphal segment were measured using transmission electron microscopy, and the mean was taken as the hyphal tube diameter d. The path of the hyphae in the effective hyphal segment was marked pixel by pixel along its central axis, and the actual length was calculated using the three-dimensional Euclidean distance formula. Outliers that deviated from the mean by ±3 times the standard deviation were eliminated, and the arithmetic mean of the remaining effective hyphal segments was taken to obtain the average hyphal length. The hyphal branching degree B is defined as the number of branch nodes per cubic millimeter of hyphal volume. The fractal dimension D was calculated using the box counting method. The box size gradient was set to ∈ = [2 μm, 32 μm], and the minimum number of boxes N(∈) that covered the mycelial network for each size ∈ was counted. The formula used was: Where N(∈1) is the minimum number of boxes covering the mycelial network when the box size is ∈1, ∈1=2μm,∈2=32μm is the box size, and D∈[1,2] quantifies the spatial expansion efficiency. The closer D is to 2, the denser and more efficient the network is. Based on the modified Poiseuille law, the transport rate v of a single hypha is: Where ΔP = ψ root -ψ soil is the osmotic pressure difference at the root-soil interface, and the root water absorption potential ψ root =-0.5MPa, soil water potential ψ soil =-0.1MPa, μ is the cytoplasmic viscosity, L is the average length of hyphae; Total flux of mycelial network Q total The calculation formula is: Q total =v·B·D 2 Among them, the single hypha velocity v provides the basic transport capacity, the branching degree B increases the transport path density, and the fractal dimension squared D 2 Amplifying the synergistic effects of complex networks.

6. The method for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae according to claim 5, characterized in that: Based on the difference in nitrogen absorption between the experimental and control groups and the total amount of external nitrogen input, the original nitrogen utilization rate was calculated. The logic of the comprehensive efficiency factor was calculated by combining the carbon-nitrogen coupling factor with the total flux of the mycelial network: Based on the difference in nitrogen absorption between the experimental group and the control group, combined with the total amount of external nitrogen input, the original utilization rate NUE was calculated. base The formula is: Among them, N con is the nitrogen absorption of the soil in the control group, N AM is the soil nitrogen absorption of the experimental group, N inp is the total amount of external nitrogen input; The comprehensive efficiency factor F is calculated by combining the carbon-nitrogen coupling factor and the total flux of the mycelial network. eff , based on the formula: F eff =NUE base ·Q total ·C N Among them, C N is the carbon-nitrogen coupling factor, Q total is the total flux of the hyphal network; Live hyphae were marked green and dead hyphae were marked red by fluorescent double staining, and the proportion of surviving hyphae was recorded by confocal microscopy, and an exponential decay model was fitted: S(t)=e -λt Among them, S(t) is the survival rate of hyphae at time t, λ is the decay rate constant, t is the time variable, and t is defined as act is the time when the survival rate drops to 50%, that is, S(t act )=0.5, calculated The formula for calculating the transport continuity coefficient is: Where k is the environmental pressure coefficient, It is affected by the life span of mycelium. It is environmental pressure suppression.

7. A system for calculating soil nitrogen utilization efficiency under the action of arbuscular mycorrhizae, characterized by: The system is used to execute the method for calculating soil nitrogen utilization rate under the action of arbuscular mycorrhizae according to any one of claims 1 to 6, comprising: A data acquisition module is used to synchronously acquire experimental group data and control group data in the target area within a preset time window, wherein the experimental group data is the soil nitrogen uptake measured by the arbuscular mycorrhizal fungus inoculated group, and the control group data is the soil nitrogen uptake measured by the uninoculated group, and record the total amount of external nitrogen input in the target area; A coupled calculation module is used to simultaneously measure the net photosynthetic rate, photosynthetically active radiation, leaf temperature, and stomatal conductance of plants in the target area, construct a light response curve, calculate the actual photosynthetic efficiency based on the integral of the light response curve, measure the nitrogen uptake rate of mycelium at different nitrogen concentrations through in vitro mycelial culture experiments, and use the Michaelis-Menten equation to obtain the half-saturation constant and nitrogen availability index. The actual photosynthetic efficiency is combined with the fitting results of the mycelial nitrogen uptake rate to calculate the carbon-nitrogen coupling factor; The mycelial network module is used to collect morphological parameters of mycelium in the target area, including mycelial branching degree, mycelial diameter, and fractal dimension. Based on the relationship between mycelial diameter and mycelial transport rate, a diameter-transport rate equation is established, and the total flux of the mycelial network is calculated in combination with mycelial branching degree. The comprehensive results module is used to calculate the original nitrogen utilization rate based on the difference in nitrogen absorption between the experimental group and the control group, combined with the total amount of external nitrogen input, and combine it with the carbon-nitrogen coupling factor and the total flux of the mycelial network to calculate the comprehensive efficiency factor. The transport sustainability coefficient is then introduced to correct the dynamic changes in transport efficiency, and finally the soil nitrogen utilization rate in the target area is obtained.

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