Device and method for measuring rice plant mediated methane transmission rate

Abstract

The invention discloses a device and method for measuring the transmission rate of mediated methane in the whole and different parts of a rice plant.The device comprises a bottom basin, a cultivation container and a dark box, firstly, a methane-nitrogen mixed gas is injected into a nutrient solution in a nutrient solution barrel, the nutrient solution is injected into the cultivation container, the rice plant is transplanted into the cultivation container, and then the rice plant is transplanted into the dark box; the root system of the rice plant is immersed in the nutrient solution; the dark box is reversely buckled and covers the cultivation container, and the dark box is sealed in the mode that water is injected into the bottom pot; collecting gas samples in the camera obscura at different time points after the camera obscura is sealed; a gas chromatograph is used for measuring the methane concentration in each gas sample, the methane transmission rate of the plant is calculated according to the change relation of the methane concentration along with time, and the relative contribution degree of each organ to the methane transmission of the plant can be quantified through step-by-step shearing treatment of the root system, the stem, the leaf and other parts and comparison of the transmission rates before and after shearing. The method has the advantages of strong controllability, good repeatability, high determination precision and the like.

Description

Technical Field

[0001] This invention relates to the field of greenhouse gas emission monitoring technology, and in particular to an apparatus and method for measuring the methane transport rate mediated by the whole rice plant and different organs (such as roots, stems, and leaves). Background Technology

[0002] Methane is a significant greenhouse gas, and paddy fields are a major source of agricultural methane emissions. The rice plant's own transport pathways (aerenchyma) are the primary route for methane emissions from the soil to the atmosphere, contributing 80% to 98% during the growing season. Currently, the traditional static field chamber method is the standard approach for estimating methane emission flux from paddy fields. However, this method cannot distinguish the effects of various factors, including soil methane production, oxidation processes, and external environmental conditions, making it difficult to accurately quantify the plant's own methane transport capacity. Furthermore, existing technologies lack effective means to systematically assess the differences in methane transport contributions among different rice varieties, growth stages, and different plant organs (such as roots, stems, and leaves). This severely restricts the breeding of low-methane-emitting rice varieties and the development of targeted emission reduction measures. Therefore, there is an urgent need in this field to develop an experimental apparatus and method that is easy to operate, has good sealing properties, can accurately control rhizosphere methane concentration, and can effectively separate and measure the transport contributions of various plant organs. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide an apparatus and method for measuring the rate of methane transport mediated by rice plants.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a device for measuring the rate of methane transport mediated by rice plants, comprising a base basin, a cultivation container, and a dark box; the upper part of the cultivation container has a sponge body with openings for storing rice plants, the lower part of the cultivation container is used to hold nutrient solution, the cultivation container is placed on the bottom surface of the base, the dark box is semi-closed with one end open, the opening of the dark box is inverted on the bottom surface of the base without being sealed, the cultivation container is placed inside the dark box, the box body part opposite to the opening direction of the dark box is provided with a gas sampling port and has a built-in fan for mixing the gas inside the box, and the dark box is sealed by injecting water into the base basin.

[0005] Furthermore, the exterior of the darkroom is covered with a heat insulation layer, which protects the temperature inside the darkroom from solar radiation, thus ensuring a relatively stable temperature inside the chamber.

[0006] Furthermore, the gas sampling port on the dark box is a three-way valve gas sampling port, which facilitates the timed extraction of gas samples for gas chromatography analysis.

[0007] Furthermore, the insulation layer is made of sponge aluminum foil, which has good heat insulation properties and is easy to install.

[0008] Furthermore, the top of the cultivation container is equipped with an opening for a container lid, which has a fixing hole. The container lid and the sponge work together to fix the plant in place.

[0009] A method for determining the rate of methane transport mediated by rice plants, based on the aforementioned device for determining the rate of methane transport mediated by rice plants, includes the following steps: Step 1) Injecting a methane-nitrogen mixture into the nutrient solution in the nutrient solution tank while stirring simultaneously, so that the methane concentration in the nutrient solution reaches a stable state; Step 2) Injecting the methane-rich nutrient solution into a cultivation container, then transplanting the rice plants into the cultivation container, ensuring that the roots of the rice plants are immersed in the methane-rich nutrient solution, sealing and fixing the base of the rice plant stems in the cultivation container using a sponge, and pre-treating for 30 minutes. Step 3) Invert the dark box onto the bottom surface of the base and cover the rice plants in the cultivation container. Seal the dark box by injecting water into the bottom basin. Step 4) Turn on the fan inside the dark box and collect gas samples from inside the box at different time points after sealing through the gas sampling port. Step 5) Use a gas chromatograph to determine the methane concentration in each gas sample. Calculate the overall methane transport rate of the rice plant based on the change in methane concentration over time. This method can evaluate the overall methane transport rate of rice plants of different varieties and at different growth stages.

[0010] Furthermore, the methane transport rate F mentioned in step 5) is calculated according to the following formula:

[0011] Where F represents the methane transport rate of rice plants, in μg plant -1 h -1 M is the molecular weight of methane; V is the molar volume of methane under standard conditions, in L / mol. -1 ; The change rate of methane concentration in the dark chamber is expressed in ppmv / h. -1 ; The volume of the dark box is in meters (m). 3 T is the average temperature inside the dark chamber during sampling, in °C.

[0012] Furthermore, the bottom of the nutrient solution tank is connected to a gas supply pipe, and the top of the nutrient solution tank is provided with a sealing cap. A stirrer is fixed on the sealing cap, and the stirring part of the stirrer extends through the sealing cap to the bottom of the nutrient solution tank to achieve stirring and mixing. This structure is simple and low in cost.

[0013] Furthermore, the method includes the following steps: Step 7) performing stepwise pruning of the rice plant's roots, root length, stems, or leaves; Step 8) repeating steps 3) to 5) of claim 6 on the pruned rice plant to determine its methane transport rate; Step 9) calculating the relative contribution of the pruned organ to methane transport based on the change in methane transport rate before and after pruning. This technical feature allows for stepwise pruning of the roots, stems, leaves, etc., and by comparing the transport rates before and after pruning, the relative contribution of each organ to the plant's methane transport can be quantified.

[0014] Compared with the prior art, the beneficial effects of the present invention are: (1) by injecting exogenous methane into a sealed nutrient solution tank, the methane concentration in the nutrient solution can be controlled, avoiding interference in the soil cultivation process; (2) the present invention has high measurement accuracy and excellent linear fitting (R²). 2 (3) It can be used for experiments on the differences in methane concentration in different genotypes of rice, different developmental stages, different organs and nutrient solutions, and has strong functions; (4) It can truly reflect the methane transport capacity of the plant itself. Attached Figure Description

[0015] Figure 1 The diagram shown is a structural schematic of the measuring device of the present invention.

[0016] Figure 2 The image shown is a partial schematic diagram of the top of the measuring device of the present invention.

[0017] Figure 3 The figure shown is a cross-sectional view of the measuring device of the present invention.

[0018] Figure 4 The diagram shown is a schematic representation of the structure of the cultivation container of the measuring device of the present invention.

[0019] Figure 5 A comparison graph showing the change in methane concentration in a dark chamber over time during the growth of rice (genotype: Jingui Simiao) at the heading stage under nutrient solutions with different methane concentrations.

[0020] Figure 6 This is a comparison graph showing the change in methane concentration over time in a sealed dark chamber between rice plants (genotype: Jingui Simiao) and those without rice plants under the same methane concentration nutrient solution conditions (after 30 minutes of aeration).

[0021] Among them, chassis 1, dark box 2, dark box handle 2-1, gas sampling port 2-2, fan power interface 2-3, risk 2-4, cultivation container 3, sponge 3-1, through hole 3-2, rice plant 4, temperature measuring device 5. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed.

[0023] Example 1, such as Figure 1 - Figure 4 As shown, a device for measuring the rate of methane transport mediated by rice plants includes a base basin 1, a cultivation container 3, and a dark box 2. A sponge 3-1 is built into the upper part of the cultivation container 3, and the sponge 3-1 has a through hole 3-2 for placing rice plants 4 inside. The lower part of the cultivation container 3 is used to hold nutrient solution. The cultivation container 3 is placed on the bottom surface of the base basin 1. The dark box 2 is semi-closed with an opening at one end. The opening of the dark box 2 is not sealed and is placed upside down on the bottom surface of the base basin 1 for convenience. The dark box 2 has a handle 2-1 on its side. The cultivation container 3 is located inside the dark box 2. The part of the dark box 2 opposite to the opening direction has a gas sampling port 2-2 and a built-in fan 2-4 for mixing the gas inside the box. The dark box 2 is sealed by injecting water into the bottom basin 1. Preferably, the fan 2-4 is fixed to the inner surface of the top of the dark box 2 by a fixing bracket. The power interface 2-3 of the fan 2-4 passes through the top of the dark box 2 and is sealed. The dark box is made of PVC pipe material. Preferably, a temperature measuring device 5 is fixedly installed on the top of the dark box 2. The probe of the temperature measuring device 5 passes through the top of the dark box 2 and extends into the box to measure the internal temperature of the dark box.

[0024] Working Principle: A methane-rich nutrient solution is injected into the cultivation container 3. Rice plants 4 are then transplanted into the cultivation container 3, ensuring the roots of the rice plants 4 are immersed in the methane-rich nutrient solution. The base of the rice plant stem is sealed and fixed in the cultivation container 3 using a sponge 3-1. The dark box 2 is inverted on the bottom surface of the base plate 1, covering the rice plants 4 in the cultivation container 3. The dark box 2 is sealed by injecting water into the base plate 1. An external power supply is connected to the power interface 2-3 of the fan 2-4. The fan 2-4 inside the dark box 2 is activated to agitate the gas inside, preventing gas stratification. Gas samples are collected from the dark box at different time points after sealing through the gas sampling port 2-2. The methane concentration in each gas sample is determined using a gas chromatograph. This invention's measuring device can achieve high-precision and highly repeatable methane concentration measurement, laying the foundation for calculating methane concentration transfer rate.

[0025] Preferably, the gas sampling port 2-2 on the dark chamber 2 is a three-way valve gas sampling port, which facilitates the periodic extraction of gas samples for gas chromatography analysis. The fan 2-4 inside the dark chamber 2 is a small DC fan, which is used to mix the headspace gas in the dark chamber and avoid gas stratification that could lead to concentration measurement errors.

[0026] Preferably, the top of the cultivation container 3 is also provided with a container lid, and the container lid has a fixing hole. When the rice plant is transplanted into the cultivation container, the stem of the rice plant passes through the fixing hole of the container lid and the through hole of the sponge, thereby fixing the plant.

[0027] Preferably, the outer surface of the darkroom 2 is covered with a heat insulation layer. This layer protects the internal temperature from interference by solar radiation, ensuring a relatively stable internal temperature and reducing temperature fluctuations, thus stabilizing the increase in methane concentration. Specifically, the heat insulation layer uses sponge aluminum foil insulation material, preferably 2-3 cm thick, to reduce the impact of external temperature changes on the internal gas concentration changes of the darkroom 2. This provides good insulation, low cost, and easy maintenance.

[0028] Example 2: A method for determining the rate of methane transport mediated by rice plants, based on the aforementioned device for determining the rate of methane transport mediated by rice plants, includes the following steps:

[0029] Step 1) Inject a methane-nitrogen mixture into the nutrient solution in the nutrient solution tank while stirring simultaneously to stabilize the methane concentration. The nutrient solution tank has a gas supply pipe connected to its bottom and a sealing cap at its top. A stirrer is fixed to the sealing cap, and the stirring part of the stirrer extends through the sealing cap to the bottom of the nutrient solution tank for mixing. Specifically, in Step 1), add 45 L of nutrient solution to a 50 L nutrient solution tank. Introduce a methane-nitrogen mixture (20% methane, 80% nitrogen) through the 6 mm diameter gas supply pipe at the bottom of the nutrient solution tank. The gas flow rate is controlled at 3.1 L / min, and an electric stirrer is used at 150 r / min to enhance methane dissolution. Aeration continues for 30 min to allow the nutrient solution to reach a stable methane concentration (approximately 78 μmol / L).

[0030] The methane ratio is selected to be suitable for mixing and dissolving methane in the nutrient solution. Based on this, the aeration flow control and the stirring of the electric stirrer work together to enhance the efficient dissolution of methane into the nutrient solution, thereby improving the efficiency of the methane concentration in the nutrient solution reaching a stable state.

[0031] By introducing exogenous methane into the nutrient solution and maintaining its uniformity with a stirrer, a stable and consistent rhizosphere methane environment can be constructed in a short time, unaffected by soil oxidation-production processes. This stable and consistent rhizosphere methane environment ensures a stable and consistent growth environment for the rice plant roots in the measuring device, reduces disturbance to the plants, and enables accurate measurement of the methane transport rate of rice plants.

[0032] Step 2) Inject methane-rich nutrient solution into cultivation container 3, then transplant rice plants into the container, ensuring the roots are submerged in the methane-rich nutrient solution. Seal and fix the base of the rice plant stem in the container using a sponge and pre-treat for 30 minutes. After the methane concentration stabilizes, partially inject nutrient solution into the cultivation container, then immerse the rice plant roots in the nutrient solution. Secure the base of the rice plant stem using a sponge and the container lid, and pre-treat for 30 minutes.

[0033] The specific implementation method is as follows: Rice plants are transferred into a cultivation container containing 3 L of methane-rich nutrient solution. A 3.5 cm diameter fixing hole is made in the container lid. The base of the plant stem passes through the fixing hole in the container lid, and a moistened sponge is wrapped around the base of the plant stem. The sponge is then placed in the cultivation container, and the container lid is connected to the cultivation container to achieve fixation and relative sealing of the plant. The root system of the plant must be completely immersed in the nutrient solution. The plant needs to be pretreated in the methane-rich nutrient solution for 30 minutes to form a stable methane diffusion flow within its body. The pretreatment step ensures that the methane gradient inside the plant is fully established.

[0034] Step 3) Invert the dark box onto the bottom surface of the base and cover the rice plants in the cultivation container. Seal the dark box by injecting water into the base. The dark box, together with the base, creates the environment for measuring the methane transport rate of the rice plants through a water seal. The dark box is made of PVC pipe with a volume of 0.84 L. The small volume of the dark box (0.84 L) allows for a rapid increase in methane concentration, facilitating linear fitting.

[0035] Step 4) Activate the fan inside the dark chamber to agitate the gas and prevent stratification. Collect gas samples from the chamber at different time points after sealing through the gas sampling port. Specifically, samples are taken at 0, 10, 20, and 30 minutes through the three-way valve sampling port. The fan agitation and heat insulation structure improve the linearity of the concentration-time curve. The sampling time interval can be adjusted according to linear stability (usually every 10 minutes). A blank group of "water only, no plants" can be set to correct for background methane changes. The methane transfer rate is calculated based on the concentration-time slope.

[0036] Step 5) Use a gas chromatograph to determine the methane concentration in each gas sample. Based on the change in methane concentration over time, calculate the overall methane transport rate of the rice plant. This method can evaluate the methane transport rate of different rice varieties and rice plants at different growth stages, and can be used for the breeding of low-methane-emission rice varieties and the development of methane emission reduction strategies for rice plants.

[0037] Specifically, the methane transport rate F mentioned in step 5) is calculated using the following formula:

[0038]

[0039] Where F represents the methane transport rate of rice plants, in μg plant -1 h -1 M is the molecular weight of methane; V is the molar volume of methane under standard conditions, in L / mol. -1 ; The change rate of methane concentration in the dark chamber is expressed in ppmv / h. -1 ; The volume of the dark box is in meters (m). 3 T is the average temperature inside the dark chamber during sampling, in °C.

[0040] Figure 5 This chart shows the changes in methane concentration in a dark chamber over time during the heading stage of rice (genotype: Jingui Simiao) cultivated in nutrient solutions with different methane concentrations. The different methane concentrations were achieved by controlling the duration of methane gas introduction. The red curves represent the methane concentration change in the chambers corresponding to 0 minutes (0T) of methane gas introduction; the green curves represent the methane concentration change in the chambers corresponding to 10 minutes (10T); and the green curves represent the methane concentration change in the chambers corresponding to 30 minutes (30T). This demonstrates that this measuring device can accurately measure the methane transport rate of rice plants cultivated in nutrient solutions with different methane concentrations. The invention exhibits high measurement accuracy and excellent linear fitting.

[0041] Figure 6 This is a comparison graph showing the change in methane concentration over time in a sealed dark chamber between rice plants (genotype: Jingui Simiao) and those without rice plants under the same methane concentration nutrient solution conditions (after 30 minutes of aeration).

[0042] Therefore, this measuring device and method can be used for experiments on the differences in methane concentration in nutrient solutions of different rice genotypes, and can truly reflect the methane transport capacity of the plant itself.

[0043] Preferably, based on Example 2, the measurement method of the present invention further includes the following steps: Step 7) performing stepwise pruning treatment on the rice plant, including the root system, root length, stem, or leaves; Step 8) repeating steps 3) to 5) on the pruned rice plant to measure its methane transport rate; Step 9) calculating the relative contribution rate of the pruned organ to methane transport based on the change in methane transport rate before and after pruning.

[0044] Specifically, in step 9), the relative contribution rate of the sheared organ to methane transport is calculated using the following formula: Total efficiency = Root efficiency + Stem efficiency + Leaf efficiency; Relative contribution rate = 100% * Sheared organ efficiency / Total efficiency.

[0045] This invention establishes four treatment methods for organ pruning. In each method, a complete methane transport rate measurement is performed after each step to achieve stepwise pruning treatment through roots, stems, and leaves, and to compare the transport rates before and after pruning, thereby quantifying the relative contribution of each organ to the plant's methane transport. The four treatment methods for organ pruning are as follows: First, root biomass pruning sequence (A): Step A1: Intact root system; Step A2: Remove 1 / 3 of the root system; Step A3: Remove another 1 / 3 of the root system based on A2; Step A4: Remove all roots. Root length pruning sequence (B): Step B1: Intact plant; Step B2: Horizontal root pruning to 15 cm; Step B3: Pruning to 10 cm; Step B4: Pruning to 5 cm. Leaf and stem height cutting sequence (C): Step C1: Intact plant; Step C2: Remove all leaves and seal the cut; Step C3: Remove 1 / 3 of the stem and seal; Step C4: Remove 2 / 3 of the stem and seal; Step C5: Retain only the base 5 cm of the stem. Finally, leaf number cutting sequence (D): Step D1: Intact plant; Step D2: Retain only 1 leaf, remove the rest and seal; Step D3: Completely remove all leaves; Step D4: Completely remove all leaves and seal.

[0046] The method in this embodiment can perform stepwise shearing of parts such as roots, stems and leaves, and compare the transport rates before and after shearing to quantitatively calculate the relative contribution rate of each organ to the methane transport of the plant.

[0047] The embodiments in this specification are written in a progressive manner, with each embodiment focusing on its differences from other embodiments. The same or similar parts can be referred to each other.

[0048] It will be apparent to those skilled in the art, upon reading the foregoing disclosure, that the present invention can be implemented or used. Various modifications to these embodiments will be readily apparent, and the general principles defined herein may be implemented in other embodiments without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should cover the maximum extent consistent with the principles and innovative features of the invention, and is not limited to the embodiments listed herein.

Claims

1. A device for measuring the rate of methane transport mediated by rice plants, characterized in that, The device includes a base basin, a cultivation container, and a dark box. The upper part of the cultivation container has a built-in sponge with openings for storing rice plants. The lower part of the cultivation container is used to hold nutrient solution. The cultivation container is placed on the bottom surface of the base. The dark box is semi-closed with an opening at one end. The opening of the dark box is not sealed and is placed upside down on the bottom surface of the base. The cultivation container is placed inside the dark box. The part of the dark box opposite to the opening direction has a gas sampling port and a built-in fan for mixing the gas inside the box. The dark box is sealed by injecting water into the base basin.

2. The apparatus for measuring the rate of methane transport mediated by rice plants as described in claim 1, characterized in that, The dark box is covered with a heat insulation layer.

3. The apparatus for measuring the rate of methane transport mediated by rice plants as described in claim 1 or 2, characterized in that, The gas sampling port on the dark box is a three-way valve gas sampling port.

4. The apparatus for measuring the rate of methane transport mediated by rice plants as described in claim 2, characterized in that, The heat insulation layer is made of sponge aluminum foil.

5. The apparatus for measuring the rate of methane transport mediated by rice plants as described in claim 1 or 2, characterized in that, The cultivation container is also equipped with a container lid on top, and the container lid has a fixing hole.

6. A method for determining the rate of methane transport mediated by rice plants, based on the apparatus for determining the rate of methane transport mediated by rice plants as described in claim 1, characterized in that, Includes the following steps: Step 1) Inject a methane-nitrogen mixture into the nutrient solution in the nutrient solution tank and stir at the same time to make the methane concentration in the nutrient solution reach a stable state. Step 2) Inject the methane-rich nutrient solution into the cultivation container, then transplant the rice plants into the cultivation container, ensuring that the roots of the rice plants are immersed in the methane-rich nutrient solution. Seal and fix the base of the rice plant stems in the cultivation container with a sponge and pre-treat for 30 minutes. Step 3) Place the dark box upside down on the bottom surface of the base and cover the rice plants in the cultivation container. Seal the dark box by injecting water into the bottom basin. Step 4) Turn on the fan inside the dark chamber and collect gas samples from inside the chamber at different time points after the dark chamber is sealed through the gas sampling port; Step 5) Use a gas chromatograph to determine the methane concentration in each gas sample, and calculate the overall methane transport rate of the rice plant based on the relationship between methane concentration and time.

7. The method for determining the rate of methane transport mediated by rice plants as described in claim 6, characterized in that, The methane transport rate F mentioned in step 5) is calculated using the following formula: Where F is the methane transport rate of rice plants; M is the molecular weight of methane; and V is the molar volume of methane under standard conditions. The rate of change of methane concentration inside the dark box; Let T be the volume of the dark chamber, and T be the average temperature inside the dark chamber during sampling.

8. The method for determining the rate of methane transport mediated by rice plants as described in claim 6, characterized in that, The bottom of the nutrient solution tank is connected to a gas supply pipe, and the top of the nutrient solution tank is equipped with a sealing cap. A stirrer is fixed on the sealing cap, and the stirring part of the stirrer extends through the sealing cap to the bottom of the nutrient solution tank to achieve stirring and mixing.

9. The method for determining the rate of methane transport mediated by rice plants as described in claim 6, characterized in that, It also includes the following steps: Step 7) Perform stepwise pruning of the rice plant, including the root system, root length, stem, or leaves. Step 8) Repeat steps 3) to 5) of claim 6 on the cut rice plants and measure their methane transport rate; Step 9) Calculate the relative contribution of the organ to methane transport based on the change in methane transport rate before and after shearing.

10. The method for determining the rate of methane transport mediated by rice plants as described in claim 9, characterized in that, In step 9), the relative contribution rate of the sheared organ to methane transport is calculated using the following formula: Total efficiency = Root efficiency + Stem efficiency + Leaf efficiency; Relative contribution rate = 100% * Sheared organ efficiency / Total efficiency.

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