A method for in-situ calibration of carbon isotopes of rice plants in the field

Abstract

The present invention provides a carbon isotope in-situ calibration system for rice plants, comprising the following components: a carbon marker releasing device, including a motor, a screw rod, a sliding member and a syringe, wherein the motor is in transmission connection with the screw rod for driving the screw rod to rotate, and the sliding member is respectively connected to the screw rod and the syringe for sliding under the drive of the screw rod so as to extrude and release the carbon marker in the syringe; a marking box, which is hollow and has an opening at the bottom, and the marking box is communicated with the syringe through a carbon marker release pipe; and a motor controller, which is connected to the motor through a first signal line for sending a signal for driving the screw rod to rotate to the motor. The present invention further provides a method for carbon isotope in-situ calibration of rice plants. The method for carbon isotope in-situ calibration of rice plants provided by the present invention performs in-situ calibration of <supgt;13< / supgt;C on rice plants under in-situ field conditions, with a controllable process, accurate measurement, reduced human interference, and reduced <supgt;13< / supgt;C labeling cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of plant isotope labeling, and relates to a method for in-situ calibration of carbon isotopes of rice plants in the field, specifically to a method for accurately quantifying rice plants using 13 C isotope labeling under in-situ field conditions. Background Art

[0002] The stable carbon isotope ( 13 C) tracer technique is an important technical means in the study of carbon fixation, distribution, and transformation in rice. The application of 13 C isotope tracer technique can be used for safe and reliable test implementation and measurement. According to 13 the different 13 C labeling frequencies, there are currently three main methods internationally: single pulse labeling, repeated pulse labeling, and continuous labeling. Pulse labeling is a technical method of injecting a single sufficient amount of 13 C label. Compared with other labeling techniques, pulse labeling has multiple advantages, is suitable for research related to photosynthetic carbon distribution and transport in plants, and can also provide information on the distribution and transformation of photosynthetic carbon at different growth stages of plants, dynamically monitor the transformation of photosynthetic products in the soil, and accurately reflect the transformation and migration process of carbon in the atmosphere-plant-soil system.

[0003] First of all, currently 13 most of the experimental studies related to 13 C plant labeling focus on laboratory research, and there are relatively few in-situ field test observations, mainly due to the lack of relevant experimental technical support. Currently, the 13 C isotope calibration technology for rice plants all needs to be carried out under laboratory culture conditions. Related patents such as: Chinese Invention Patent (Application No. 200610019742), Chinese Invention Patent (Application No. 201020608969), Chinese Invention Patent (Application No. 201420390240), Chinese Invention Patent (Application No. 201520633964), Chinese Invention Patent (Application No. 201721161687) all need to carry out 13 C isotope calibration on rice plants in culture vessels such as potted plants or seedling trays. In the above calibration methods, since single plants or several rice plants grow in culture vessels, the soil, light, water, and fertilizer conditions for the growth of rice plants are very different from the environmental conditions of field-grown rice plants in groups. Therefore, it is impossible to overcome the edge effect caused by the culture container on the growth and development of rice plants, and it is difficult to accurately simulate the physiological process of rice plants under actual field planting conditions.

[0004] Secondly, existing patents all use chemical reactions to generate 13 CO2 labels. The common method is to add 13 C-labeled Na2 13A chemical reaction between CO3 and HCl is carried out to obtain 13 C-labeled CO2. Related patents include: Chinese Invention Patent (Application No. 200610019742), Chinese Invention Patent (Application No. 201721161687). In addition, besides Na2 13 CO3, Ba 13 CO3 has also been used as 13 a reaction carrier for C-labeled substances. Related patents include: Chinese Invention Patent (Application No. 201020608969), Chinese Invention Patent (Application No. 201420390240). In the above patents 13 in the CO2 labeling device, the related chemical reaction rate is fast, and the CO2 release process is difficult to accurately control. Therefore, it is difficult to control the CO2 concentration level in the calibration container. A large number of studies have shown that drastic changes in environmental CO2 concentration will affect the photosynthesis and related physiological processes of rice plants. Therefore, it is difficult to reflect the response of the physiological and material transport processes of rice plants under real field environmental conditions. In addition, due to the existing 13 C isotope labeling technology, the labeling mechanism is a drop-controlled chemical reaction device, which is complex in structure and unstable in gas supply, and it is difficult to monitor the progress of the reaction accurately in real time. At the same time, the supply of labeled substances and the recovery of remaining labeled substances in the existing patented technologies do not involve accurate quantification under field conditions. Therefore, it is difficult to carry out 13 accurate quantitative research on C isotope labeling under field conditions only with the existing related patented technologies.

[0005] Finally, 13 the C isotope calibration research technology has little impact on plants and can better reflect the migration and transformation processes of specific physiological activities and related products of plants by measuring the metabolites of different stable isotope labeled substances in plants and the environment. Since 13 the C calibration process requires isolating the gas exchange between the calibration container and the environment, all kinds of 13 C isotope calibration technologies need to be carried out in a closed chamber. Related patents: Chinese Invention Patent (Application No. 201020608969), Chinese Invention Patent (Application No. 201520633964), Chinese Invention Patent (Application No. 201721161687), all of which are equipped with environmental parameter reading devices such as thermometers, hygrometers, and CO2 concentration sensors in the calibration container either simultaneously or partially. Since 13C calibration requires plants to assimilate and fix CO2, so the calibration process has certain requirements for the lighting conditions in the container. At the same time, considering that there is no gas exchange between the calibration container and the external environment, the temperature and humidity in the box will also change accordingly due to light during the calibration process. Existing isotope calibration technology makes it difficult to accurately control the temperature and humidity in the calibration container. In actual field operations, the temperature of the calibration container without effective temperature control measures can rise to 42°C. Excessive temperature will cause great disturbances to the physiological processes of the labeled objects, and even cause irreversible damage to the labeled crops. The impact of this labeling process is against 13 The original intention of C isotope calibration is to reduce disturbance to the experimental objects and more accurately reflect the physiological laws of the observed objects under natural conditions. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for in-situ field calibration of carbon isotopes of rice plants, which is used to solve the problem that the prior art lacks a stable carbon isotope that can be controlled and accurately quantified. 13 C calibration method problem.

[0007] To achieve the above-mentioned and other related purposes, the present invention provides, in a first aspect, a carbon isotope field in-situ calibration system for rice plants, comprising the following components:

[0008] A carbon marker release device, the carbon marker release device comprising a motor, a screw, a sliding member and a syringe, the motor is connected to the screw for driving the screw to rotate, the sliding member is connected to the screw and the syringe respectively for sliding under the drive of the screw to squeeze and release the carbon marker in the syringe;

[0009] A marking box, which is hollow and has an open bottom, and is connected to the syringe via a carbon marker release tube;

[0010] A controller is connected to the motor via a first signal line and is used to send a signal to the motor to drive the screw to rotate.

[0011] Preferably, the sliding part includes a slider and a slide rail, the syringe includes a barrel and a piston core rod in the barrel, the slider is connected to the rod end of the piston core rod, and is rotationally connected to the screw rod, and is slidingly connected to the slide rail, and is used to drive the slider to slide on the slide rail through the rotation of the screw rod, thereby pushing the piston core rod to squeeze and release the carbon marker in the barrel.

[0012] More preferably, the sliding block is rotationally connected to the screw rod, which means that the lower portion of the sliding block is threadedly connected to the screw rod, and the sliding block is driven to move horizontally by the rotation of the screw rod.

[0013] Further preferably, the internal thread of the slider is 0.9 - 1.1 mm. Most preferably, the internal thread of the slider is 1.0 mm.

[0014] Further preferably, the pitch of the screw rod is 0.9 - 1.1 mm. Most preferably, the pitch of the screw rod is 1.0 mm.

[0015] More preferably, a limiting rod for fixing the cylinder body is provided outside the cylinder body.

[0016] More preferably, the capacity range of the cylinder body is 0 - 200 ml.

[0017] More preferably, the needle end interface of the cylinder body is connected to one end of the carbon marker release tube through a check valve.

[0018] Preferably, a limiter is provided at one end of the screw rod away from the motor.

[0019] Preferably, a three-way valve is provided on the carbon marker release tube.

[0020] Preferably, the thickness of the marker box is 3.8 - 4.2 mm. More preferably, the thickness of the marker box is 4 mm.

[0021] Preferably, a fan is provided at the top inside the marker box, and the fan is connected to the controller through a second signal line, and the controller is used to send a signal for driving the fan to rotate to the fan.

[0022] More preferably, the second signal line penetrates through the top of the marker box, and a sealing plug sleeved outside the second signal line is provided at the position where the second signal line penetrates through the top of the marker box.

[0023] Preferably, a CO2 concentration sensor and a temperature sensor are provided at the top inside the marker box.

[0024] Preferably, a pneumatic balancer is provided on one side of the marker box.

[0025] Preferably, a circulating sampling gas path is provided on the marker box, and both ends of the pipeline of the circulating sampling gas path penetrate through the two side walls of the marker box and are inserted into the marker box to form a circulating loop, and a sampling valve is provided on the circulating sampling gas path.

[0026] More preferably, a gas sampling bag can be externally connected to the circulating sampling gas path through the sampling valve. The sampling valve can be a three-way electronic valve.

[0027] More preferably, an air pump is connected to the pipeline of the circulating sampling gas path.

[0028] More preferably, a sealing ring sleeved outside the circulating sampling gas path is provided at the position where the pipeline of the circulating sampling gas path penetrates through the side wall of the marker box.

[0029] Preferably, a base matching the marking box is provided below the marking box. The base includes a support frame and a fixing groove located at the top of the support frame. The lower end of the side wall of the marking box can be sleeved in the fixing groove of the base.

[0030] Preferably, a condenser is provided on one side of the marking box. The condenser includes heat dissipation fins and a condensing pipe. The heat dissipation fins and the condensing pipe are located inside the marking box. The condensing pipe is located between the heat dissipation fins and the side wall of the marking box. Both ends of the condensing pipe penetrate through the side wall of the marking box and are provided with circulating pump interfaces.

[0031] More preferably, heat-insulating liner pipes are sleeved outside both ends of the condensing pipe.

[0032] More preferably, the condensing pipe is connected to a circulating pump through the circulating pump interface.

[0033] More preferably, a condensate water diversion groove is provided below the condenser. The upper part of the condensate water diversion groove matches the positions of the heat dissipation fins and the condensing pipe, and the lower part of the condensate water diversion groove matches the fixing groove.

[0034] Preferably, the controller is connected to the battery through a power supply wire.

[0035] Preferably, the controller is a commonly used stepper motor controller. The stepper motor controller precisely controls the rotation angle of the stepper motor rotor by outputting uniform electrical pulse signals. Those skilled in the art all understand that the calculation, comparison, judgment, and output instruction processes of the controller can all be implemented by using integrated circuit modules, programmable logic devices, other hardware, or installing corresponding software modules in the prior art. For example, specifically, the controller is the 42-type stepper motor controller TB6600 produced by Risym Company, which can precisely control the stepping rate of the stepper motor used in the present invention (step angle 1.8°, 200 steps / revolution).

[0036] The second aspect of the present invention provides a method for in-situ calibration of carbon isotopes of rice plants in the field. This method uses the above calibration system for measurement and includes the following steps:

[0037] 1) Determine the paddy field area where the rice plants to be calibrated are located by setting the base;

[0038] 2) Sleeve the marking box on the base and seal it. First, set the sampling time periods at different daytime, and respectively measure the volume CO2 concentration C1 of the marking box at the beginning of the sampling time period and the volume CO2 concentration C2 at the end of the sampling time period, and synchronously measure the light intensity in each corresponding sampling time period of the marking box. Calculate the net CO2 assimilation rate F of the rice plants to be calibrated in different time periods respectively according to formula (1) npr ,

[0039] The formula (1) is: F npr = (C1 × V chamber - C2 × V chamber ) / T duration ,

[0040] In formula (1), F npr is the net CO2 assimilation rate of the rice plants to be calibrated during the corresponding time period, cm 3 ·h -1 ; C1 is the volume CO2 concentration of the labeling chamber at the start of the sampling time period, ppmv; C2 is the volume CO2 concentration of the labeling chamber at the end of the sampling time period, ppmv; V chamber is the air volume inside the labeling chamber, cm 3 ; T duration is the duration of the sampling time period, h;

[0041] 3) Obtain the net CO2 assimilation rate and light intensity according to step 2). Using light intensity as the abscissa and net CO2 assimilation rate as the ordinate, obtain the net CO2 assimilation rate curve, and determine the maximum net CO2 assimilation rate of the rice plants to be calibrated under light saturation conditions and its time period;

[0042] 4) During the time period when the maximum net CO2 assimilation rate determined in step 3) appears, after sleeving the labeling chamber on the base and sealing it, input 13 CO2 gas of C, so that 13 C-CO2 gradually replaces 12 C-CO2. After calibrating for T labelling time, measure the volume CO2 concentration C CO2 in the remaining gas in the labeling chamber and 13 the absolute atomic abundance F 13C of C-CO2, and then calculate the content n 13 of the C-labeled substance in the rice plants according to formulas (2) and (3), 13C ,

[0043] The formula (2) is: n 13C = (p × V 13C ) / (R × T),

[0044] In formula (2), n 13C is the content of the C-labeled substance in the rice plants, mol; p is the atmospheric pressure during calibration, Pa; V 13 is the total volume of C-CO2 fixed by the plants at the end of calibration, dm 13C ; R is the gas constant, and its value is 8.314 J / mol·K; T is the thermodynamic temperature value of the air temperature in the labeling chamber at the end of calibration, K; 13 ; R is the gas constant, with a value of 8.314 J / mol·K; T is the thermodynamic temperature value of the air temperature in the labeling chamber at the end of calibration, K; 3 ; R is the gas constant, with a value of 8.314 J / mol·K; T is the thermodynamic temperature value of the air temperature in the labeling chamber at the end of calibration, K;

[0045] The formula (3) is: V 13C = T labelling × R NAR – C CO2 × V chamber × F 13C ,

[0046] In formula (3), V 13C is the total volume of C-CO2 fixed by the plant at the end of calibration, dm 13 ; T 3 is the calibration duration, h; R labelling is the maximum net CO2 assimilation rate of the rice plant, ml·h NAR ; C -1 is the concentration of the remaining volume of CO2 in the labeling chamber after the end of calibration, ppmv; V CO2 is the air volume in the labeling chamber, cm chamber ; F 3 is the absolute abundance value of C-CO2 in the remaining CO2 in the labeling chamber after the end of calibration, atom%. 13C 13

[0047] Preferably, in step 1), the base is fixed in the paddy soil through a support frame, and the paddy field area where the rice plant to be calibrated is located is surrounded in the middle of the base.

[0048] Preferably, in step 1), determining the paddy field area where the rice plant to be calibrated is located is carried out 40 - 50 h before the formal calibration. More preferably, determining the paddy field area where the rice plant to be calibrated is located is carried out 48 h before the formal calibration.

[0049] Preferably, in step 2), the time periods of different time intervals during the day are 0.5 h or 1 h.

[0050] More preferably, the time periods of different time intervals during the day are 1 h.

[0051] Further preferably, the time periods of different time intervals during the day are respectively 7:00 - 8:00, 8:00 - 9:00, 9:00 - 10:00, 10:00 - 11:00, 11:00 - 12:00, 12:00 - 13:00, 13:00 - 14:00, 14:00 - 15:00, 15:00 - 16:00, 16:00 - 17:00.

[0052] Preferably, in step 2), the duration of different time intervals during the day is not less than the duration of the corresponding sampling time interval.

[0053] ​​Preferably, in step 2), the determination of the volumetric CO2 concentration and / or light intensity is carried out 20 - 30 h before the formal calibration. More preferably, the determination of the volumetric CO2 concentration and / or light intensity is carried out 24 h before the formal calibration.

[0054] Preferably, in step 2), the light intensity is measured using a portable digital illuminometer. The light intensity is the average value measured during the sampling period.

[0055] Preferably, in step 2) or 4), the ambient temperature inside the labeling chamber also needs to be measured, and the ambient temperature inside the labeling chamber ≤ 38 °C. The ambient temperature inside the labeling chamber is measured using a temperature sensor.

[0056] Preferably, in step 2) or 4), the CO2 concentration inside the labeling chamber is maintained at 350 ± 50 ppmv.

[0057] Preferably, in step 3), in the net CO2 assimilation rate curve, the unit of the light intensity is lx, and the unit of the net CO2 assimilation rate is cm 3 ·h -1 。

[0058] Preferably, in step 2) or 4), the 13 CO2 gas enriched with C is in the barrel of the syringe and is input into the labeling chamber by the carbon marker release device through the carbon marker release tube.

[0059] Preferably, in step 2) or 4), the volumetric CO2 concentration inside the labeling chamber is collected with a gas sampling bag and then measured by gas chromatography.

[0060] Preferably, in step 4), the 13 absolute atomic abundance of C-CO2 inside the labeling chamber is collected with a gas sampling bag and then measured by gas isotope mass spectrometry.

[0061] As described above, a method for in-situ calibration of carbon isotope of rice plants provided by the present invention, through an in-situ calibration system for carbon isotope of rice plants with a preferred structure, combined with the calibration steps and conditions with preferred conditions, can measure the carbon assimilation rate of rice plants under certain light intensity conditions in-situ in the field, and draw a carbon assimilation rate curve, and adjust the release rate of CO2 gas calibrated with C into the chamber according to the carbon assimilation rate curve to maintain the CO2 concentration inside the transparent chamber at a relatively stable level, complete the in-situ 13 C labeling in the field, measure the CO2 concentration of the remaining gas inside the transparent chamber and 13 C atomic abundance, and the accurate labeling amount of C in the rice plant can be obtained after calculation. It has the following beneficial effects: 13 C atomic abundance, and the accurate labeling amount of C in the rice plant can be obtained after calculation. It has the following beneficial effects: 13 C in the rice plant. It has the following beneficial effects:

[0062] (1) The present invention provides a method for in-situ field calibration of carbon isotopes of rice plants, which involves calibrating the carbon isotopes of rice plants in the field. 13 C in situ calibration makes the research results closer to the actual physiological process responses of rice plants in field environments.

[0063] (2) The present invention provides a method for in-situ calibration of carbon isotopes of rice plants in the field, which is process controllable and can continuously and accurately release carbon isotopes quantitatively through a stepper motor and a controller. 13 C-labeled CO2 was used to control the growth of rice plants in situ in the field. 13 The rate of C isotope labeling is controllable, making the labeling process stable and continuous, and the transformation and migration of related photosynthetic products can be quantitatively analyzed in subsequent experiments.

[0064] (3) The present invention provides a method for in-situ field calibration of carbon isotopes of rice plants, which can quantitatively analyze the carbon isotopes in the calibration process on the basis of process controllability. 13 C markers, thereby achieving the target rice plants 13 Accurate determination of the amount of C labeling.

[0065] (4) The present invention provides a method for in-situ field calibration of carbon isotopes of rice plants, wherein the temperature in the calibration box can be checked and controlled during the calibration process. 13 During the C labeling process, the CO2 concentration and temperature in the equipment remain relatively constant, which significantly reduces the artificial interference of large CO2 concentration changes in previous labeling technologies on the photosynthesis physiological process of crops, and can significantly improve the crop's 13 C calibrates the CO2 fixation efficiency, greatly reducing the previous 13 The C calibration process is the impact of human disturbance of environmental factors on rice plants.

[0066] (5) The present invention provides a method for in-situ field calibration of carbon isotopes of rice plants, 13 C markers, all equipment and materials of this technology can be reused many times, greatly reducing the risk of rice plants. 13 C marks the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 Shown is a schematic structural diagram of a carbon isotope field in-situ calibration system for rice plants according to the present invention.

[0068] Figure 2 Shown is a schematic diagram of the process of an in-situ field calibration method for carbon isotopes of rice plants according to the present invention.

[0069] Reference numerals

[0070] 1 Carbon marker release device

[0071] 11 Motor

[0072] 12 Screw

[0073] 13 Slider

[0074] 131 Slide block

[0075] 132 Slide rail

[0076] 14 Syringe

[0077] 141 Barrel

[0078] 142 Piston core rod

[0079] 15 Limit rod

[0080] 16 Limiter

[0081] 2 Marker box

[0082] 21 Fan

[0083] 22 CO2 concentration sensor

[0084] 23 Temperature sensor

[0085] 24 Air pressure balancer

[0086] 3 Controller

[0087] 4 Carbon marker release pipe

[0088] 41 Check valve

[0089] 42 Three-way valve

[0090] 5 First signal line

[0091] 6 Second signal line

[0092] 61 Sealing plug

[0093] 7 Circulating sampling gas path

[0094] 71 Sealing ring

[0095] 8 Base

[0096] 81 Support frame

[0097] 82 Fixed slot

[0098] 9 Condenser

[0099] 91 Heat sink

[0100] 92 Condensing pipe

[0101] 93 Circulation pump interface

[0102] 94 Heat preservation liner

[0103] 95 Condensate water diversion trough

[0104] 10 Battery

[0105] 101 Power supply wire Specific implementation manners

[0106] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the protection scope of the present invention.

[0107] The following illustrates the implementation manners of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0108] As Figure 1 described, a carbon isotope field in-situ calibration system for rice plants provided by the present invention includes the following components:

[0109] Carbon marker release device 1, the carbon marker release device 1 includes a motor 11, a screw 12, a sliding member 13 and a syringe 14. The motor 11 is in transmission connection with the screw 12 for driving the screw 12 to rotate. The sliding member 13 is respectively connected to the screw 12 and the syringe 14 for sliding under the drive of the screw 12 to squeeze and release the carbon marker in the syringe 14;

[0110] Marker box 2, the marker box 2 is hollow and has an open bottom. The marker box 2 is communicated with the syringe 14 through a carbon marker release pipe 4;

[0111] Controller 3, the controller 3 is connected to the motor 11 through a first signal wire 5 for sending a signal to the motor 11 to drive the screw 12 to rotate.

[0112] In a preferred embodiment, the motor 11 is a commonly used stepper motor and can be obtained from the market. Specifically, the stepper motor is a 42BYG34-401A type stepper motor (torque 0.28 N, step angle 1.8°) produced by Risym Company. The motor 11 is powered by a battery 10, and the battery 10 is a 12V lead-acid battery.

[0113] In a preferred embodiment, as Figure 1As shown, the slider 13 includes a sliding block 131 and a slide rail 132. The syringe 14 includes a barrel 141 and a piston core rod 142 inside the barrel 141. The sliding block 131 is connected to the rod end of the piston core rod 142, and is rotationally connected to the screw 12 and slidably connected to the slide rail 132, and is used to drive the sliding block 131 to slide on the slide rail 132 by the rotation of the screw 12 so as to push the piston core rod 142 to extrude and release the carbon marker in the barrel 141.

[0114] Further, the rotational connection between the sliding block 131 and the screw 12 means that the lower part of the sliding block 131 is threadedly connected to the screw 12, and the rotation of the screw 12 drives the sliding block 131 to move horizontally. Thus, the rotary motion output by the stepping motor is converted into a linear motion, which is used to drive the sliding block 131 to slide on the slide rail 132, push the piston core rod 142 to extrude, and realize the precise speed control and quantitative release of the carbon marker in the barrel 141.

[0115] Specifically, the internal thread of the sliding block 131 is 0.9 - 1.1 mm, preferably 1.0 mm.

[0116] Specifically, the pitch of the screw 12 is 0.9 - 1.1 mm, preferably 1.0 mm.

[0117] Further, as Figure 1 shown, a limiting rod 15 for fixing the barrel 141 is provided outside the barrel 141, which is used to fix the position of the barrel 141 to prevent the barrel 141 from moving when the piston core rod 142 extrudes the barrel 141 to release the carbon marker, thus resulting in inaccurate control of the release rate of the carbon marker.

[0118] Further, the material of the barrel 141 is PVC.

[0119] Further, the capacity range of the barrel 141 is 0 - 200 ml.

[0120] Further, as Figure 1 shown, the needle end interface of the barrel 141 is connected to one end of the carbon marker release tube 4 through a check valve 41. The needle end interface of the barrel 141 is a standard Luer interface. The check valve 4 is used to prevent the carbon marker in the barrel 141 from flowing back.

[0121] In a preferred embodiment, as Figure 1 shown, a stopper 16 is provided at one end of the screw 12 away from the motor 11. The stopper 16 is used to fix the position of the screw 12.

[0122] In a preferred embodiment, the carbon marker is 13 C-labeled CO2.

[0123] In a preferred embodiment, as Figure 1 shown, a three-way valve 42 is provided on the carbon marker release tube 4. The three-way valve 42 is a standard Luer port three-way valve. The three-way valve 42 controls the release of the carbon marker in the cylinder body 141 through the carbon marker release tube 4 by opening and closing.

[0124] In a preferred embodiment, the material of the marker box 2 is transparent acrylic sheet.

[0125] In a preferred embodiment, the light transmittance of the marker box 2 is 96-98%, preferably 97%.

[0126] In a preferred embodiment, the thickness of the marker box 2 is 3.8-4.2 mm, preferably 4 mm.

[0127] In a preferred embodiment, as Figure 1 shown, a fan 21 is provided at the top inside the marker box 2. The fan 21 is connected to the controller 3 via the second signal line 6. The controller 3 is used to send a signal to drive the fan 21 to rotate to the fan 21. The fan 21 is used to mix the gas inside the marker box 2 after the carbon marker is input into the marker box 2.

[0128] Further, as Figure 1 shown, the second signal line 6 penetrates through the top of the marker box 2. A sealing plug 61 sleeved outside the second signal line 6 is provided at the position where the second signal line 6 penetrates through the top of the marker box 2. It plays a sealing role.

[0129] In a preferred embodiment, as Figure 1 shown, a CO2 concentration sensor 22 and a temperature sensor 23 are provided at the top inside the marker box 2. The CO2 concentration sensor 22 is a commonly used CO2 concentration sensor and can be purchased from the market. Specifically, the CO2 concentration sensor 22 is a K30 type CO2 concentration sensor produced by SenseAir Company. The temperature sensor 23 is a commonly used temperature sensor and can be purchased from the market. Specifically, the temperature sensor 23 is a BMP180 type temperature sensor produced by BOSCH Company. The CO2 concentration sensor 22 and the temperature sensor 23 can be externally connected to a computer through a data line and used to monitor the relative CO2 concentration and temperature inside the marker box 2 through a display.

[0130] In a preferred embodiment, as Figure 1As shown, a pneumatic balancer 24 is provided on one side of the marking box 2. The pneumatic balancer 24 is a communicating vessel made of an aluminum foil air bag, which is used to balance the air pressure inside and outside the marking box 2 to ensure that the air pressure inside and outside the marking box 2 is the same. The materials used for the pneumatic balancer 24 can be obtained by purchasing from the market. Specifically, the pneumatic balancer 24 is made of a 200 ml model aluminum foil air bag produced by Dalian Delin Technology Co., Ltd.

[0131] In a preferred embodiment, as Figure 1 shown, a circulating sampling gas path 7 is provided on the marking box 2. The two ends of the pipeline of the circulating sampling gas path 7 penetrate through the side walls on both sides of the marking box 2 and are inserted into the marking box 2 to form a circulation loop. A sampling valve is provided on the circulating sampling gas path 7. It is used to make the gas in the marking box 2 circulate and flow back through the pipeline of the circulating sampling gas path 7.

[0132] Furthermore, the circulating sampling gas path 7 can be externally connected with a gas sampling bag through the sampling valve. The sampling valve can be a three-way electronic valve. The gas sampling bag is a vacuum aluminum foil air bag, and its brand and model are the same as the air bag used for the pneumatic balancer 24. The gas sampling bag can be used to collect the gas in the circulating sampling gas path 7.

[0133] Furthermore, an air pump is connected to the pipeline of the circulating sampling gas path 7. The air pump is used to drive the gas flow in the circulating sampling gas path 7.

[0134] Furthermore, a sealing ring 71 sleeved outside the circulating sampling gas path 7 is provided at the position where the pipeline of the circulating sampling gas path 7 penetrates through the side wall of the marking box 2. Thus, it plays a sealing role to prevent gas leakage.

[0135] In a preferred embodiment, as Figure 1 shown, a base 8 matching the marking box 2 is provided below the marking box 2. The base 8 includes a support frame 81 and a fixing groove 82 located at the top of the support frame 81. The lower end of the side wall of the marking box 2 can be sleeved in the fixing groove 82 of the base 8. The fixing groove 82 can be filled with liquid for liquid seal.

[0136] In a preferred embodiment, as Figure 1 shown, a condenser 9 is provided on one side of the marking box 2. The condenser 9 includes a heat sink 91 and a condensing pipe 92. The heat sink 91 and the condensing pipe 92 are located inside the marking box 2. The condensing pipe 92 is located between the heat sink 91 and the side wall of the marking box 2. Both ends of the condensing pipe 92 penetrate through the side wall of the marking box 2 and are provided with circulating pump interfaces 93. The condenser 9 can be used to adjust the temperature inside the marking box 2 to make the ambient temperature inside the marking box 2 lower than 38°C.

[0137] Further, heat-insulating lining pipes 94 are sleeved outside both ends of the condenser pipe 93. The heat-insulating lining pipes 94 can be used for heat preservation. The heat-insulating lining pipes 94 are heat-insulating lining pipes made of foamed plastics. The condenser pipe 94 is a copper pipe.

[0138] Further, the condenser pipe 94 is connected to a circulation pump through a circulation pump interface 93, and condensed water is conveyed to the condenser 9 through the circulation pump for cooling.

[0139] Further, as Figure 1 shown, a condensed water diversion groove 95 is provided below the condenser 9. The upper part of the condensed water diversion groove 95 is matched with the positions of the heat sink 91 and the condenser pipe 92, and the lower part of the condensed water diversion groove 95 is matched with the fixed groove 82. The upper part of the condensed water diversion groove 95 is matched with the positions of the heat sink 91 and the condenser pipe 92, which is convenient for guiding the condensed water, so that the condensed water generated by the heat sink 91 and the condenser pipe 92 can accurately flow into the condensed water diversion groove 95 without splashing onto the rice plants to be calibrated. The lower part of the condensed water diversion groove 95 is matched with the fixed groove 82, which is convenient for guiding the condensed water, so that the condensed water generated by the heat sink 91 and the condenser pipe 92 falls into the fixed groove 82 through the condensed water diversion groove 95 without splashing onto the rice plants to be calibrated, and at the same time, the water required for liquid sealing is increased.

[0140] In a preferred embodiment, as Figure 1 shown, the controller 3 is connected to the battery 10 through a power supply line 101. The battery 10 is a 12V lead-acid battery.

[0141] In a preferred embodiment, as Figure 1 shown, the controller 3 is a commonly used stepper motor controller. The stepper motor controller accurately controls the rotation angle of the stepper motor rotor by outputting uniform electrical pulse signals. Those skilled in the art all understand that the calculation, comparison, judgment, and output instruction processes of the controller can all be realized by using integrated circuit modules, programmable logic devices, other hardware or installing corresponding software modules in the prior art. For example, specifically, the controller 3 is a type 42 stepper motor controller TB6600 produced by Risym Company, which can accurately control the stepping rate of the stepper motor used in the present invention (step angle 1.8°, 200 steps / revolution).

[0142] Next, in combination with Figure 1-2 , a method for in-situ calibration of carbon isotope of rice plants in the present invention will be described. This method is measured by using the above calibration system and includes the following steps:

[0143] 1) Determine the paddy field area where the rice plants to be calibrated are located by setting the base;

[0144] 2) Place the labeled box on the base and seal it. First, set the sampling time periods for different daytime hours, and measure and obtain the volumetric CO2 concentration C1 of the labeled box at the start of the sampling time period and the volumetric CO2 concentration C2 at the end of the sampling time period respectively. At the same time, measure the light intensity within each corresponding sampling time period of the labeled box, and calculate and obtain the net CO2 assimilation rate F of the rice plants to be calibrated for different time periods according to formula (1). npr ,

[0145] The said formula (1) is: F npr =(C1×V chamber - C2×V chamber ) / T duration ,

[0146] In formula (1), F npr is the net CO2 assimilation rate of the rice plants to be calibrated for the corresponding time period, cm 3 ·h -1 ; C1 is the volumetric CO2 concentration of the labeled box at the start of the sampling time period, ppmv; C2 is the volumetric CO2 concentration of the labeled box at the end of the sampling time period, ppmv; V chamber is the air volume inside the labeled box, cm 3 ; T duration is the duration of the sampling time period, h;

[0147] 3) According to the net CO2 assimilation rate and light intensity obtained in step 2), with the light intensity as the abscissa and the net CO2 assimilation rate as the ordinate, obtain the net CO2 assimilation rate curve, and determine the maximum net CO2 assimilation rate of the rice plants to be calibrated under light saturation conditions and its time period;

[0148] 4) During the time period when the maximum net CO2 assimilation rate determined in step 3) appears, after placing the labeled box on the base and sealing it, input 13 CO2 gas of 13 C-CO2 to gradually replace 12 C-CO2. After calibrating for T labelling time, measure the volumetric CO2 concentration C CO2 in the remaining gas inside the labeled box and 13 the absolute atomic abundance F 13C of 13 C-labeled substances in the rice plants, and then calculate the content n 13C of

[0149] The said formula (2) is: n 13C =(p×V 13C ) / (R×T),

[0150] In formula (2), n 13CTo calibrate in a rice plant 13 The content of the C marker, mol; p is the atmospheric pressure during calibration, Pa; V 13C is the total volume of C-CO2 fixed by the plant at the end of calibration 13 , dm 3 ; R is the gas constant, with a value of 8.314 J / mol·K; T is the thermodynamic temperature value of the air temperature in the marker box at the end of calibration, K;

[0151] The formula (3) is: V 13C = T labelling × R NAR – C CO2 × V chamber × F 13C ,

[0152] In formula (3), V 13C is the total volume of C-CO2 fixed by the plant at the end of calibration 13 , dm 3 ; T labelling is the calibration duration, h; R NAR is the maximum net CO2 assimilation rate of the rice plant, ml·h -1 ; C CO2 is the concentration of the remaining volume of CO2 in the marker box after calibration, ppmv; V chamber is the air volume in the marker box, cm 3 ; F 13C is the absolute abundance value of C-CO2 in the remaining CO2 in the marker box after calibration 13 , atom%.

[0153] In a specific embodiment, in step 1), the base is fixed in the paddy soil through a support frame, and the paddy field area where the rice plant to be calibrated is located is surrounded in the middle of the base.

[0154] In a specific embodiment, in step 1), determining the paddy field area where the rice plant to be calibrated is located is carried out 40 - 50 h before the formal calibration. More preferably, determining the paddy field area where the rice plant to be calibrated is located is carried out 48 h before the formal calibration.

[0155] In a specific embodiment, in step 2), the time intervals for different daytime periods are 0.5 h or 1 h, preferably 1 h.

[0156] Specifically, the time periods of different time intervals during the day are 7:00 - 8:00, 8:00 - 9:00, 9:00 - 10:00, 10:00 - 11:00, 11:00 - 12:00, 12:00 - 13:00, 13:00 - 14:00, 14:00 - 15:00, 15:00 - 16:00, and 16:00 - 17:00 respectively, which are used to determine the net CO2 assimilation rate of the rice plants to be calibrated.

[0157] In a specific embodiment, in step 2), the duration of the different time intervals during the day is not less than the duration of the corresponding sampling time interval.

[0158] In a specific embodiment, in step 2) or 3), the measurement of the volumetric CO2 concentration and / or light intensity is carried out 20 - 30 h before the formal calibration. More preferably, the measurement of the volumetric CO2 concentration and / or light intensity is carried out 24 h before the formal calibration.

[0159] In a specific embodiment, in step 3), the light intensity is measured using a portable digital illuminometer. The light intensity is the average value measured during the sampling time interval.

[0160] In a specific embodiment, in step 2) or 4), the environmental temperature inside the marking box also needs to be measured, and the environmental temperature inside the marking box ≤ 38 °C. The environmental temperature inside the marking box is measured using a temperature sensor. When the environmental temperature inside the marking box is too high, the condenser is started to input ice - water mixture to reduce the environmental temperature inside the marking box, making the temperature inside the box relatively constant.

[0161] In a specific embodiment, in step 2) or 4), the CO2 concentration inside the marking box is maintained at 350 ± 50 ppmv. The CO2 concentration range inside the marking box can be monitored through a CO2 concentration sensor.

[0162] In a specific embodiment, in step 3), in the net CO2 assimilation rate curve, the unit of the light intensity is lx, and the unit of the net CO2 assimilation rate is cm 3 ·h -1 。

[0163] In a specific embodiment, in step 2) or 4), the marking box is sleeved on the base and sealed with a liquid seal. The liquid seal is to add paddy - field water into the fixed groove of the base to seal the marking box. The liquid seal seals between the marking box and the base, preventing gas exchange inside and outside the marking box and affecting the accuracy of the calibration result.

[0164] In a specific embodiment, in step 3), the light saturation refers to the light intensity when the CO2 concentration of the rice plants to be labeled no longer changes in the labeling chamber. At this light intensity, the rice plants to be labeled have the maximum net CO2 assimilation rate.

[0165] In a specific embodiment, in step 4), the 13 CO2 gas of C is enriched in the barrel of the syringe and is input into the labeling chamber by the carbon label releasing device through the carbon label releasing tube.

[0166] In a specific embodiment, in step 2) or 4), the volume CO2 concentration in the labeling chamber is collected by a gas sampling bag and determined by gas chromatography.

[0167] In a specific embodiment, in step 4), the 13 absolute atomic abundance of 13C-CO2 is collected by a gas sampling bag and determined by gas isotope mass spectrometry.

[0168] For specific calibration, the user obtains a carbon isotope in-situ calibration system for rice plants as shown in Figure 1 and conducts the calibration process as shown in Figure 2 . 40 - 50 h before the start of calibration, first fix the base in the soil of the paddy field to be calibrated, that is, fix the support frame in the soil of the paddy field to be calibrated, so as to enclose the paddy field area where the rice plants to be calibrated are located in the middle of the base.

[0169] Then, 20 - 30 h before the formal calibration, sleeve the labeling chamber on the base to seal it, that is, sleeve the lower end of the side wall of the labeling chamber into the fixing groove of the base, cover the rice plants to be calibrated into the labeling chamber, and pour the field water into the fixing groove of the base, so as to conduct liquid sealing between the labeling chamber and the base to prevent gas exchange inside and outside the labeling chamber and affect the accuracy of the calibration result. At different daytime time periods, the time period is 0.5 h or 1 h. Set the sampling time periods at different daytime time periods, and respectively measure the volume CO2 concentration C1 at the start of the sampling time period and the volume CO2 concentration C2 at the end of the sampling time period of the labeling chamber, and synchronously measure the light intensity in each corresponding sampling time period of the labeling chamber. Calculate the net CO2 assimilation rate F of the rice plants to be calibrated in different time periods respectively according to formula (1) npr , and C1 and C2 are determined by collecting the CO2 concentration through a gas sampling bag by a circulating sampling gas path through a sampling valve and then by gas chromatography. The average value of the light intensity in the sampling time period is measured by a portable digital illuminometer. With the light intensity (unit: lx) as the abscissa and the net CO2 assimilation rate (cm 3 ·h -1 ) as the ordinate, obtain the net CO2 assimilation rate curve, and determine the maximum net CO2 assimilation rate and its time period of the rice plants to be calibrated under light saturation conditions.

[0170] Calibration is carried out according to the time period when the determined maximum net CO2 assimilation rate appears. During the time period when the maximum net CO2 assimilation rate appears, after the labeling chamber is sleeved on the base and closed, the lower end of the side wall of the labeling chamber is sleeved in the fixing groove of the base, and the rice plant to be calibrated is covered into the labeling chamber, and the field water is poured into the fixing groove of the base, so as to seal the space between the labeling chamber and the base, prevent gas exchange inside and outside the labeling chamber, and affect the accuracy of the calibration result. Then, input 13 CO2 gas labeled with 13 C, that is, a signal for driving the screw to rotate is sent to the motor through the first signal line by a controller powered by a battery, so that the motor drives the screw to rotate. By the rotation of the screw, the slider is driven to slide on the slide rail, and then the piston end of the piston core rod is pushed to squeeze and release the 13 C-labeled CO2 marker enriched in the cylinder. The 13 C-labeled CO2 marker in the cylinder flows into the labeling chamber through the carbon marker release pipe, so that 12 C-CO2 is gradually replaced by

[0171] After calibrating for labelling time T, measure the volume CO2 concentration C CO2 and 13 the absolute atomic abundance F 13C of 13 C-CO2 in the remaining gas in the labeling chamber. That is, the CO2 concentration in the remaining gas in the labeling chamber is collected through a circulating sampling gas path by a sampling valve through a gas sampling bag for CO2 and 13 C-labeled CO2. The volume CO2 concentration is measured by a gas chromatograph, and the absolute atomic abundance of 13 C-labeled CO2 is measured by a gas isotope mass spectrometer. Then, calculate the content n 13C of the

[0172] After the measurement is completed, turn off the machine and promptly open the labeling box. During the calibration process, measure the ambient temperature inside the labeling box through a temperature sensor ≤ 38°C. When the ambient temperature inside the labeling box is too high, use a circulating water pump to start the condenser to input ice-water mixture to reduce the ambient temperature inside the labeling box and make the temperature inside the box relatively constant. At the same time, a fan can be used to mix the CO2 gas inside the labeling box.

[0173] Example 1

[0174] The user obtains a carbon isotope in-situ calibration system for rice plants as shown in Figure 1 and conducts the calibration process as shown in Figure 2 Before the start of calibration for 48 h, first fix the base in the paddy soil to be calibrated, that is, fix the support frame in the paddy soil to be calibrated, so as to enclose the paddy field area where the rice plants to be calibrated are located in the middle of the base.

[0175] Then, 24 h before the formal calibration, sleeve the labeling box on the base to seal it, that is, sleeve the lower end of the side wall of the labeling box into the fixing groove of the base, cover the rice plants to be calibrated into the labeling box, and pour field water into the fixing groove of the base, so as to conduct liquid sealing between the labeling box and the base to prevent gas exchange inside and outside the labeling box and affect the accuracy of the calibration result. At different time periods during the day, the time period is 1 h, specifically 7:00 - 8:00, 8:00 - 9:00, 9:00 - 10:00, 10:00 - 11:00, 11:00 - 12:00, 12:00 - 13:00, 13:00 - 14:00, 14:00 - 15:00, 15:00 - 16:00, 16:00 - 17:00. Then, set the sampling time period to 30 min, measure the volume CO2 concentration C1 at the start of the sampling time period and the volume CO2 concentration C2 at the end of the sampling time period of the labeling box respectively, and synchronously measure the light intensity in each corresponding sampling time period of the labeling box, and calculate the net CO2 assimilation rate F of the rice plants to be calibrated in different time periods according to formula (1) npr , and C1 and C2 are measured for the CO2 concentration by gas chromatography after being collected by a circulating sampling gas path through a sampling valve and collected in a sampling bag.

[0176] Use a portable digital illuminometer to measure the average value of the light intensity during the sampling time period. With the light intensity (unit: lx) as the abscissa and the net CO2 assimilation rate (cm 3 ·h -1 ) as the ordinate, obtain the net CO2 assimilation rate curve, and determine the maximum net CO2 assimilation rate and its time period of the rice plants to be calibrated under light saturation conditions.

[0177] Taking the time period from 10:00 to 11:00 in the morning as an example, gas samples in the labeling chamber were collected at 0 min when sampling started and 30 min when sampling ended (i.e., the sampling time period). The volume CO2 concentration was measured by gas chromatography, and it was obtained that C1 was 400 ppmv at 0 min and C2 was 250 ppmv at 30 min. Since the volume of the labeling chamber is 1 m 3 , substituting the above values into formula (1): F npr =(C1×V chamber -C2×V chamber ) / T duration , it was obtained that within the time period from 10:00 to 11:00 in the morning, the net CO2 assimilation rate of the rice plants to be calibrated was: 300 cm3·h -1 . A portable digital illuminometer was used to synchronously measure the light intensity within 30 min, and the average value of the light intensity was obtained as 65000 lx. By analogy, C1 and C2 values of each time period during the day were measured respectively, and the corresponding net CO2 assimilation rates of the calibrated rice plants were calculated according to formula (1) respectively. The light intensity within the corresponding sampling time period was measured synchronously. With the light intensity (unit: lx) as the abscissa and the net CO2 assimilation rate (cm 3 ·h -1 ) as the ordinate, a net CO2 assimilation rate curve was obtained. By comparing the net CO2 assimilation rates of the rice plants to be calibrated at different time periods, it was concluded that the net CO2 assimilation rate of the rice plants increased with the increase of light intensity. When the light intensity was greater than 55000 lx, although the light intensity continued to rise, the net CO2 concentration of the rice plants no longer changed. Then it could be determined that the light saturation point of the rice plants at this time was 55000 lx, and the rice plants reached the maximum net CO2 assimilation rate at this time. The maximum net CO2 assimilation rate of the rice plants to be calibrated under light saturation conditions during the day was 300 cm3·h -1 , and the time period when the maximum net CO2 assimilation rate occurred was from 9:00 in the morning to 16:00 in the afternoon.

[0178] Within the time period when the maximum net CO2 assimilation rate occurred, after the labeling chamber was sleeved on the base and closed, the lower end of the side wall of the labeling chamber was sleeved into the fixed groove of the base, and the rice plants to be calibrated were covered into the labeling chamber. Field water was poured into the fixed groove of the base to seal the space between the labeling chamber and the base, preventing gas exchange inside and outside the labeling chamber and affecting the accuracy of the calibration result. Then, input 13 CO2 gas of C, that is, through a controller powered by a battery, a signal to drive the screw to rotate was sent to the motor through the first signal line, causing the motor to drive the screw to rotate. By the rotation of the screw, the slider was driven to slide on the slide rail, and then the piston end of the piston core rod was pushed to squeeze and release the 13 C-labeled CO2 marker enriched in the cylinder. The 13The C-labeled CO2 marker flows into the labeling chamber through the carbon marker release tube, so that 13 C-CO2 is gradually replaced 12 by C-CO2. A fan can be used to mix the CO2 gas in the labeling chamber. Since the motor is a stepper motor, the 13 release rate of the C-labeled CO2 can be adjusted to a CO2 assimilation rate of 300 cm3·h -1 , and the calibration is completed within the time period from 9:00 am to 4:00 pm. Measure the volume CO2 concentration C in the remaining gas in the labeling chamber CO2 and 13 the absolute atomic abundance F of C-CO2 13C , that is, the CO2 concentration in the remaining gas in the labeling chamber is collected through a circulating sampling gas path, and CO2 and 13 C-labeled CO2 are collected through a gas sampling bag. The volume CO2 concentration is measured by a gas chromatograph, and the absolute atomic abundance of 13 C-labeled CO2 is measured by a gas isotope mass spectrometer. Since the volume of the labeling chamber is 1 m 3 , the measured CO2 concentration in the remaining gas in the labeling chamber is 400 ppmv, and the 13 absolute abundance value of C in CO2 is 10.0 atom%. Then, calculate the content n of the 13 C-labeled marker in the rice plant according to formulas (2) and (3) 13C , and the total amount of the 13 C-labeled marker obtained from this calibration is: 1.045×10 -2 mol.

[0179] After the measurement is completed, turn off the machine and open the labeling chamber in time. During the calibration process, the ambient temperature in the labeling chamber is measured by a temperature sensor to be 30°C ≤ 38°C, and the atmospheric pressure is 101.325 kPa.

[0180] As can be seen from the above calibration system and its calibration method, compared with the existing pot experiments and laboratory cultures, the calibration system and its calibration method can perform in-situ labeling in actual fields, and the measurement results are a true reflection of the actual growth process of the plants. For the calibration system and its calibration method, the entire labeling process is precisely controllable, environmental factors such as temperature are relatively controllable during the labeling process, and the closed environment has little artificial interference on the plants, 13 the total amount of C-labeling can be accurately quantified, and the labeling result is accurate.

[0181] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0182] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for in-situ field calibration of carbon isotopes of rice plants, using a calibration system for measurement, comprising the following steps: 1) Determine the rice field area where the rice plants to be calibrated are located by setting a base; 2) Put the marking box on the base and close it. Set the sampling time periods at different time periods during the day, and measure the volume CO2 concentration C1 of the marking box at the beginning of the sampling time period and the volume CO2 concentration C2 at the end of the sampling time period. And synchronously measure the light intensity in each corresponding sampling time period of the marking box, and respectively calculate the net CO2 assimilation rate F of the rice plants to be calibrated in different time periods according to formula (1). npr , The formula (1) is: F npr = (C1 × V chamber - C2 × V chamber ) / T duration , In formula (1), F npr is the net CO2 assimilation rate of the rice plants to be calibrated during the corresponding time period, cm 3 ·h -1 ; C1 is the volume CO2 concentration at the start of the sampling period of the labeling chamber, ppmv; C2 is the volume CO2 concentration at the end of the sampling period of the labeling chamber, ppmv; V chamber is the air volume in the labeling chamber, cm 3 ; T duration is the duration of the sampling time period, h; 3) According to step 2), the net CO2 assimilation rate and light intensity are obtained, and a net CO2 assimilation rate curve is obtained with light intensity as the horizontal coordinate and net CO2 assimilation rate as the vertical coordinate, so as to determine the maximum net CO2 assimilation rate and time period of the rice plant to be calibrated under light saturation conditions; 4) During the time period when the maximum net CO2 assimilation rate determined in step 3) appears, after enclosing the labeled chamber by sleeving it onto the base, input 13 CO2 gas of 13 C to gradually replace 12 C-CO2. After calibrating for T labelling time, measure the volume CO2 concentration C CO2 in the remaining gas in the labeled chamber, as well as 13 the absolute atomic abundance F 13C of 13 C-CO2, and then calculate the content n 13C of the 13 C-labeled substance in the rice plant according to formulas (2) and (3). The formula (2) is: n 13C = (p × V 13C ) / (R × T), In formula (2), n 13C is the content of the 13 C marker in the rice plant, in mol; p is the atmospheric pressure during calibration, in Pa; V 13C is the total volume of 13 C-CO2 fixed by the plant at the end of calibration, in dm 3 ; R is the gas constant, with a value of 8.314 J / (mol·K); T is the thermodynamic temperature value of the air temperature in the marker box at the end of calibration, in K; The formula (3) is: V 13C = T labelling × R NAR – C CO2 × V chamber × F 13C , In formula (3), V 13C is the total volume of C-CO2 fixed by the plant at the end of calibration 13 , dm 3 ; T labelling is the calibration duration, h; R NAR is the maximum net CO2 assimilation rate of the rice plant, ml·h -1 ; C CO2 is the concentration of the remaining volume of CO2 in the labeling chamber after calibration, ppmv; V chamber is the air volume in the labeling chamber, cm 3 ; F 13C is the absolute abundance value of 13 C-CO2 in the remaining CO2 in the labeling chamber after calibration, atom%; The carbon isotope field in-situ calibration system for rice plants includes the following components: A carbon marker releasing device (1), the carbon marker releasing device (1) comprising a motor (11), a screw (12), a sliding member (13) and a syringe (14), the motor (11) being transmission-connected to the screw (12) for driving the screw (12) to rotate, the sliding member (13) being respectively connected to the screw (12) and the syringe (14) for sliding under the drive of the screw (12) so as to squeeze and release the carbon marker in the syringe (14); A marking box (2), wherein the marking box (2) is hollow and has an opening at the bottom, and the marking box (2) is connected to the injector (14) via a carbon marker release tube (4); A controller (3), the controller (3) being connected to the motor (11) via a first signal line (5) and being used for sending a signal to the motor (11) for driving the screw rod (12) to rotate; A base (8) matching the marking box (2) is provided below the marking box (2); the base (8) comprises a support frame (81) and a fixing groove (82) located at the top of the support frame (81); the lower end of the side wall of the marking box (2) can be sleeved in the fixing groove (82) of the base (8).

2. The in-situ calibration method of carbon isotope of a rice plant according to claim 1, characterized in that, The sliding member (13) includes a slider (131) and a slide rail (132), and the syringe (14) includes a barrel (141) and a piston core rod (142) in the barrel (141). The slider (131) is connected to the rod end of the piston core rod (142), and is rotationally connected to the screw (12), and is slidingly connected to the slide rail (132), and is used to drive the slider (131) to slide on the slide rail (132) through the rotation of the screw (12), thereby pushing the piston core rod (142) to squeeze and release the carbon marker in the barrel (141).

3. The in-situ calibration method of carbon isotope of rice plants according to claim 2, characterized in that The cylinder (141) includes any one or more of the following conditions: A1) a limiting rod (15) for fixing the cylinder (141) is provided outside the cylinder (141); A2) the capacity range of the cylinder (141) is 0-200 ml; A3) The needle end interface of the cylinder (141) is connected to one end of the carbon marker release tube (4) via a check valve (41).

4. A method for in-situ calibration of carbon isotope of rice plants according to claim 1, characterized in that The marking box (2) includes any one or more of the following conditions: B1) A fan (21) is provided at the top inside the marking box (2). The fan (21) is connected to the controller (3) via a second signal line (6). The controller (3) is configured to send a signal for driving the fan (21) to rotate to the fan (21); B2) A CO2 concentration sensor (22) and a temperature sensor (23) are provided at the top inside the marking box (2); B3) A pressure balancer (24) is provided on one side of the marking box (2); B4) A circulating sampling gas path (7) is provided on the marking box (2). The two ends of the pipeline of the circulating sampling gas path (7) penetrate through the two side walls of the marking box (2) respectively and are inserted into the marking box (2) to form a circulating loop. A sampling valve is provided on the circulating sampling gas path (7).

5. A method for in-situ calibration of carbon isotope of rice plants according to claim 1, characterized in that, A condenser (9) is provided on one side of the marking box (2). The condenser (9) includes a heat sink (91) and a condensing pipe (92). The heat sink (91) and the condensing pipe (92) are located inside the marking box (2). The condensing pipe (92) is located between the heat sink (91) and the side wall of the marking box (2). Both ends of the condensing pipe (92) penetrate through the side wall of the marking box (2) and are provided with circulating pump interfaces (93).

6. A method for in-situ calibration of carbon isotope of rice plants according to claim 5, characterized in that The condenser includes any one or more of the following conditions: C1) Heat-insulating liner pipes (94) are sleeved outside both ends of the condensing pipe (92); C2) A condensate water diversion trough (95) is provided below the condenser (9). The upper part of the condensate water diversion trough (95) is matched with the positions of the heat sink (91) and the condensing pipe (92). The lower part of the condensate water diversion trough (95) is matched with the fixing groove (82).

7. A method for in-situ calibration of carbon isotopes of rice plants according to claim 1, characterized in that, The controller (3) is connected to the battery (10) via a power supply line (101).

8. A method for in-situ calibration of carbon isotope of rice plants according to claim 1, characterized in that, In step 1), determining the paddy field area where the rice plants to be calibrated are located is carried out 40 - 50 h before the formal calibration. In step 2) or 3), the measurement of the volumetric CO2 concentration and / or light intensity is carried out 20 - 30 h before the formal calibration.

9. A method for in-situ calibration of carbon isotope of rice plants according to claim 1, characterized in that, The duration of different time periods during the day is 0.5 h or 1 h, and the duration of different time periods during the day is not less than the duration of the corresponding sampling time period.

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