Method and device for measuring carbon dioxide compensation point

Abstract

To provide a measurement method and a measurement device, capable of measuring a carbon dioxide compensation point of a plant.SOLUTION: A measurement method comprises the steps of: setting a leaf so as to come into contact with a gas in a chamber; causing the leaf to undergo photosynthesis with the leaf set in the chamber and with the chamber sealed; measuring the CO2 concentration in the sealed chamber by a CO2 sensor over time while the set leaf is undergoing photosynthesis; and determining the carbon dioxide compensation point by using the measurement values obtained by the CO2 sensor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for determining the carbon dioxide compensation point of a plant. [Background technology]

[0002] For example, in plant research, the photosynthetic rate of plants is sometimes measured using a photosynthesis measuring device. There are two types of photosynthesis measuring devices: a closed type disclosed in Patent Document 1 and an open type disclosed in Patent Document 2. The closed type device can measure the photosynthetic rate in a much shorter time than the open type device.

[0003] In recent years, there has been interest in research into converting C3 plants into C4 plants in order to improve crop yields and quality. In this research, measurements of the carbon dioxide compensation point (hereafter referred to as gamma value or Γ value) are sometimes used. It is known that the Γ value of C4 plants is much smaller than that of C3 plants.

[0004] The Γ value is unique to plants. It is defined as the CO2 concentration (ppm) at the equilibrium state between the photosynthetic reaction and the respiratory reaction. The photosynthetic reaction is expressed as the following equation 1, and the respiratory reaction is expressed as the following equation 2. Although the two appear to be chemical equilibrium reactions, they are independent reaction systems. TIFF2025062396000002.tif20151

[0005] Currently, an open-type photosynthesis measuring device as disclosed in Patent Document 2 is used to measure the Γ value (see FIG. 7 of Patent Document 2, etc.). A plant to be measured is placed in a chamber called an assimilation chamber in a state in which it can photosynthesize. The assimilation chamber has an inlet and an outlet. A pump is provided to circulate air through the assimilation chamber through the inlet and the outlet. In addition, a CO2 sensor and a flow meter are disposed upstream of the inlet, and another CO2 sensor is disposed downstream of the outlet.

[0006] The measurement method is as follows: first, air is circulated through the assimilation chamber via the inlet and outlet using a pump, while light is irradiated on the plants to cause photosynthesis in the chamber. Then, the CO2 concentration measured by the CO2 sensor on the outlet side starts to decrease and stabilizes after a certain amount of time has passed. After stabilization, the measurement value of the CO2 sensor on the outlet side is used to measure the Γ value.

[0007] In this measurement method, it takes 40 to 50 minutes for the concentration measured by the CO2 sensor on the outlet side to stabilize. In other words, it takes at least 40 to 50 minutes to measure the Γ value.

[0008] Therefore, there is a need for a method to measure the Γ value quickly and easily. If the Γ value could be measured quickly, it is expected that this would lead to more efficient research into the conversion of C4 plants. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. WO2016 / 208424 [Patent Document 2] JP 2022-36854 A Summary of the Invention

[0010] The present invention provides a measurement method and a measurement device that enable measurement of the carbon dioxide compensation point in a short period of time.

[0011] The method for measuring the carbon dioxide compensation point of a plant is as follows: placing the leaf in the chamber such that the leaf is in contact with gas within the chamber; allowing the leaf to photosynthesize while the leaf is set in the chamber and the chamber is sealed; Measuring the CO2 concentration in the sealed chamber over time with a CO2 sensor while the set leaves are photosynthesizing; and and determining the carbon dioxide compensation point using measurements obtained by the CO2 sensor.

[0012] The method may use the measurements obtained by the CO2 sensor to determine both the carbon dioxide compensation point and the photosynthetic rate of the plant.

[0013] The gas filled in the chamber when the chamber is sealed may be atmospheric air.

[0014] The measurement method includes: introducing a dilution gas into the chamber to dilute the CO2 concentration in the chamber while the leaves are photosynthesizing; determining the photosynthetic rate using the measurements obtained by the CO sensor prior to the introduction of the diluent gas; The measurements taken by the CO2 sensor after introduction of the diluent gas may be used to determine the carbon dioxide compensation point.

[0015] The measurement method may include filling the chamber with a gas having a CO2 concentration lower than that of the atmosphere, and then sealing the chamber.

[0016] The measurement method may include filling the chamber with zero gas that does not contain CO2 and then sealing the chamber.

[0017] The measuring device for measuring the carbon dioxide compensation point of a plant is a sealable chamber having an opening that is covered by a leaf; an irradiation unit that irradiates light toward the opening of the chamber; a CO sensor disposed within the chamber to measure a CO concentration within the chamber over time; and a Γ value calculation unit that calculates the carbon dioxide compensation point based on the measurement value from the CO2 sensor.

[0018] The chamber may include a lower gasket provided along an edge of the opening. The irradiation unit may include a casing having an opening, and an upper gasket provided along the opening of the casing for sandwiching the leaf together with the lower gasket.

[0019] The lower gasket may be formed from a gel sheet.

[0020] The gel sheet may have an Asker F hardness of, for example, 30 or more and 80 or less.

[0021] The Asker F hardness of the gel sheet is more preferably 30 or more and 40 or less. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 shows a schematic diagram of the measurement device and method. [Diagram 2] FIG. 2 shows a schematic cross-sectional view of a chamber of the measurement device of FIG. [Diagram 3] FIG. 3 is a block diagram of the measurement device. [Figure 4] FIG. 4 shows a graph of the measurement results of Γ value measurement test A. [Diagram 5] FIG. 5 shows a table of the measurement results of the Γ value measurement test A. [Figure 6] FIG. 6 shows the determined Γ value in Γ value measurement test A. [Figure 7] FIG. 7 shows a graph of the measurement results of Γ value measurement test B. [Figure 8] FIG. 8 shows another graph of the measurement results of Γ value measurement test B. [Figure 9] FIG. 9 shows a table of the measurement results of the Γ value measurement test B. [Figure 10] FIG. 10 shows a graph of the measurement results of Γ value measurement test C. [Figure 11] FIG. 11 shows a table of the measurement results of the Γ value measurement test C. [Figure 12]FIG. 12 shows a graph and a table of the measurement results of Γ value measurement test D. [Figure 13] FIG. 13 shows a graph and a table of the measurement results of the Γ value measurement test E. [Figure 14] FIG. 14 shows a graph of the dilution test results and the relationship between injection volume and O2 concentration. [Figure 15] FIG. 15A illustrates the leak between the sponge gasket and the leaf, FIG. 15B illustrates the intimate contact between the gel sheet gasket and the leaf, and FIG. 15C shows the preferred orientation relationship between the gasket and the leaf. [Figure 16] FIG. 16 shows the results of a test to confirm the sealing performance of the gasket. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, embodiments of the present application will be described with reference to the drawings.

[0024] In the following, an example of a method and an apparatus for measuring the carbon dioxide compensation point (hereinafter, referred to as Γ value) of a plant P as shown in Fig. 1 will be described. For example, the measuring apparatus shown in Fig. 1 is used. The apparatus includes an analysis unit 1 and an operation unit 2.

[0025] The analysis unit 1 is shown in detail in Fig. 2. The measurement device includes a chamber 3 and an irradiation unit 4. The chamber 3 is made of, for example, an aluminum alloy. The chamber 3 has an upward opening 30. A lower gasket 31 is provided along the edge of the opening 30.

[0026] The irradiation unit 4 includes a casing 42. The casing 42 has an opening 40. An upper gasket 41 is provided along the edge of the opening 40. The openings 30 and 40 have the same shape, for example, both rectangular. The size is, for example, 2 cm x 3 cm.

[0027] The illumination unit 4 includes, as a light source, one or more LEDs 43 in a casing 42. The illumination unit 4 emits light for photosynthesis from the LEDs 43 toward the opening 40.

[0028] The irradiation unit 4 can open and close the chamber 3 (its opening 30) by being moved by the handle 10 in Fig. 1. As shown in Fig. 2, when the irradiation unit 4 closes the chamber 3 (its opening 30), the openings 30 and 40 are aligned, and therefore the gaskets 31 and 41 are also aligned.

[0029] 1 and 2, the leaf L to be measured is sandwiched between the chamber 3 and the irradiation unit 4 so that the leaf L covers the entire opening 30. When the leaf L is set in the chamber 3 in this way so as to come into contact with the gas in the chamber 3, the irradiation unit 4 can irradiate the leaf L with light through the opening 40. The set leaf L comes into contact with the gas in the chamber 3, and can therefore respire and / or photosynthesize using the gas in the chamber 3.

[0030] The lower gasket 31 and the upper gasket 41 sandwich the leaf L, thereby sealing the gap between the opening 30 of the chamber 3 and the set leaf L. Normally, the leaf L is set so that the front surface of the leaf L faces upward toward the irradiation unit 4 and the back surface of the leaf L faces downward toward the chamber 3.

[0031] As described later, the airtightness of the chamber 3 is important in measuring the Γ value. When the leaf L is sandwiched between the chamber 3 and the irradiation unit 4, leakage from between the leaf L and the lower gasket 31 should be particularly prevented. This is because the veins of the leaf form unevenness on the back surface of the leaf L, which is likely to cause leakage and affect the measurement. Therefore, the lower gasket 31 that comes into contact with the back surface of the leaf L is preferably a gel sheet made of silicon polymer, polystyrene, or the like. For example, the hardness of the gasket is preferably 2 to 4 degrees, or less than 2 degrees. The upper gasket 41 may be a conventional sponge (for example, a silicon sponge) or a gel sheet similar to the lower gasket 31.

[0032] Furthermore, the measurement device includes a CO2 sensor 11 in the chamber 3. The CO2 sensor 11 is configured to measure the CO2 concentration in the chamber 3 over time in order to determine the photosynthetic rate (hereinafter, referred to as A value) and Γ value of the plant P, as described below. Such a CO2 sensor 11 may be, for example, an NDIR type infrared sensor. More specifically, the infrared sensor disclosed in Patent Document 1 may be used.

[0033] Furthermore, the measurement device includes a temperature sensor 12 and a humidity sensor 13 in the chamber 3. The temperature sensor 12 is configured to measure the temperature in the chamber 3. The humidity sensor 13 is configured to measure the humidity in the chamber 3. These measured values ​​are used to measure the A value.

[0034] The measurement device may include a fan (not shown) for circulating the gas within the chamber 1.

[0035] Furthermore, the measurement device includes at least one supply port 32 provided in the chamber 3, and an on-off valve 14 assigned to the supply port 32. As described below, the measurement device can supply various gases to the chamber 3 from the supply port 32. The on-off valve 14 can open and close the supply port 32.

[0036] The measurement device further includes an exhaust port 33 provided in the chamber 3, and an on-off valve 15 assigned to the exhaust port 33. The measurement device can exhaust gas from the chamber 3 through the exhaust port 33. The on-off valve 15 can open and close the exhaust port 33.

[0037] Therefore, when the leaf L is set in the chamber 3 as described above and air-tightly covers the opening 30, the chamber 3 can be sealed by closing the supply opening 32 and the discharge opening 33 with the opening / closing valves 14, 15.

[0038] Furthermore, by opening the supply port 32 and the exhaust port 33, gas can be supplied into the chamber 3 even when the leaf L is set in the chamber 3 as described above and covers the opening 30, making gas exchange and gas dilution possible.

[0039] More specifically, this measurement device can supply air to the chamber 3 through the supply port 32 using a pump (not shown).

[0040] The measuring device can also supply a gas that does not contain CO2 (hereinafter referred to as zero gas) to the chamber 3. For example, the measuring device can obtain zero gas by passing the gas through a CO2 removal column (e.g., a column containing soda lime as a removal agent) and supply the zero gas to the chamber 3 through the supply port 32. The measuring device may supply N2 gas as the zero gas from a cylinder through the supply port 32 to the chamber 3.

[0041] The measurement device can supply a calibration gas (eg, N 2 gas, zero gas, span gas) for calibrating the CO 2 sensor 11 to the chamber 3 through the supply port 32.

[0042] In addition, the user can connect a syringe (not shown) to supply port 32 and manually supply a dilution gas (e.g., the above-mentioned zero gas) for diluting the CO2 concentration or O2 concentration in chamber 3 from the syringe to chamber 3 through supply port 32.

[0043] Although one supply port 32 is shown in FIG. 2, a plurality of supply ports 32 may be provided, such as for introducing air, introducing zero gas, introducing calibration gas, and introducing a syringe.

[0044] The above pumps and columns are mounted in the operation unit 2.

[0045] 3 is a block diagram of the measurement device. In the operation unit 2, the measurement device includes an operation display section 20, a storage section 21, and a speed calculation section 22.

[0046] The operation and display unit 20 includes a user interface such as a button or a touch panel. A user can operate the user interface to realize the functions of the measurement device. The operation and display unit 20 also includes an indicator (e.g., a display) that displays the measurement value (instruction) of the CO2 sensor 11 and the measured A value and Γ value described below.

[0047] The storage unit 21 is a storage medium that records the measured values ​​obtained by the sensors 11 to 13 and stores the measured A and Γ values. The storage unit 21 may include a semiconductor memory element such as a RAM or a flash memory, a hard disk, a data logger, and the like.

[0048] The speed calculation unit 22 measures the A value. For example, as shown in FIG. 2, a leaf L is set in the chamber 3, covers the opening 30, and is sandwiched between the chamber 3 and the irradiation unit 4. Then, with the chamber 3 sealed, the irradiation unit 2 irradiates the leaf L with light. As a result, the set leaf L photosynthesizes using the CO2 in the sealed chamber 3. Therefore, when photosynthesis starts, the concentration of CO2 in the sealed chamber 3 decreases significantly. The CO2 sensor 11 measures this change in concentration.

[0049] The rate calculation unit 22 calculates the time change in the CO2 concentration immediately after the start of photosynthesis, d[CO2] / dt(ppm·s -1 The rate calculation unit 22 calculates, for example, the time it takes for the CO2 concentration to decrease by 10 ppm from the start of photosynthesis. The rate measurement unit 22 then calculates the A value (molCO 2· m -2 ·s -1 ) is calculated based on the time change in CO2 concentration d[CO2] / dt and the state equation using the following equation 3. [Number 3] TIFF2025062396000003.tif28150

[0050] In equation 3, T (K) is the temperature of the gas introduced into the chamber 3 and is measured by the temperature sensor 12. S (cm 2) is the area of ​​the leaf L covering the opening 30 (i.e., the area of ​​the opening 30). V (cm 3 ) is the actual volume of the chamber 3 excluding the sensors 11 to 13, the fan, etc. The measurement value of the humidity sensor 13 is used for humidity correction, which will not be described in detail here.

[0051] The above configuration is substantially the same as the closed type photosynthesis measuring device disclosed in Patent Document 1. Such a measuring device may be, for example, Massa International Corporation's photosynthesis measuring device (product name MIC-100).

[0052] The measurement device of the present application further includes a Γ value measuring section 23, and the Γ value can be calculated using the above-mentioned closed type photosynthesis measurement device. The basic principle for measuring the Γ value will be described below.

[0053] As in the measurement of the A value, the leaf L is set in the chamber 3 to cover the opening 30, and is sandwiched between the irradiation unit 4 and the chamber 3. The irradiation unit 4 then irradiates the leaf L with light, causing the leaf L to photosynthesize using the gas in the chamber 3. The memory unit 21 (e.g., a data logger) records the measurement value from the CO2 sensor and obtains data indicating the change in CO2 concentration in the chamber 3 over time.

[0054] As described above, the CO2 concentration in the chamber 3 decreases when photosynthesis begins. After a certain time has passed, the CO2 concentration in the chamber 3 stabilizes and becomes almost constant. The leaves L are respiring while photosynthesizing. The reason the CO2 concentration stabilizes is that the photosynthetic reaction and the respiratory reaction are in equilibrium. Therefore, the CO2 concentration in the chamber 3 at this time can be taken as the Γ value (ppm).

[0055] Therefore, the Γ value calculation unit 23 analyzes the measured values ​​of the CO2 concentration measured by the CO2 sensor 11 and recorded in the memory unit 21, and calculates the Γ value using the measured values ​​where the CO2 concentration is stable. For example, the Γ value calculation unit 23 may calculate the average value of the measured values ​​where the measured values ​​are stable as the Γ value.

[0056] The gas filled in chamber 3 when it is sealed (the gas in chamber 3 at the start of measurement, hereafter referred to as the base gas) is generally air when measuring the A value. On the other hand, the base gas in measuring the Γ value may be air, or a gas with a lower CO2 concentration than air. Researchers may select the type of base gas. With this measurement device, the base gas (the concentration of its constituent gases) can be adjusted.

[0057] For example, when air is used as the base gas, air is sucked in by a pump and introduced into the chamber 3 through the supply port 32. The chamber 3 is then sealed.

[0058] It is possible to dilute or adjust the concentration of a particular gas in the chamber 3. For this purpose, the syringe may be used to supply a dilution gas (for example, zero gas) to the chamber 3 to dilute the CO2 concentration or O2 concentration.

[0059] 100% N2 gas may be introduced as the base gas into the chamber 3. In addition, when N2 gas is introduced as the base gas into the chamber 3, it is possible to calibrate the sensor 11 by checking whether the indication of the CO2 sensor 11 is 0 ppm.

[0060] The composition of the base gas in the chamber 3 can be changed. For example, the O2 concentration of the base gas can be changed. For example, it can be adjusted to 0, 5, 10, 15 or 20 Vol%. When the O2 concentration is 20 Vol%, gas with CO2 removed from the atmosphere can be introduced into the chamber and the chamber 3 can be sealed. When the O2 concentration is 0, N2 gas can be introduced. When the O2 concentration is 5, 10 or 15 Vol%, the chamber 3 is first filled with the atmosphere, and then N2 gas is introduced using a syringe to dilute and adjust the O2 concentration.

[0061] As described later, the A value and the Γ value can be measured at the same time (in one operation). In this case, the O2 concentration of the base gas may be changed. However, in order to measure the A value, the base gas must contain a CO2 concentration of about 400 ppm. Therefore, in this case, in addition to N2 gas, a span gas with a CO2 concentration of 400 ppm is required.

[0062] <Preparation for measurement> First, for the measurement, each element of the measurement device is warmed up (warming up step). Then, the CO2 sensor 11 is calibrated as described above using zero gas (calibration step). Then, the measurement is started. In the following, the lower gasket 13 of the gel sheet is used.

[0063] <1st measurement method> After the calibration step, the leaf L to be measured is set in the chamber 3 (setting step). Therefore, the leaf L is sandwiched between the chamber 3 and the irradiation unit 4 with the leaf L covering the opening 30. In the first measurement method, air is used as the base gas. After the air is filled in the chamber 3, the chamber 3 is sealed (sealing step).

[0064] Next, measurement is started (measurement step). That is, the irradiation unit 4 irradiates the set leaves L with light. The CO2 sensor 11 measures the CO2 concentration in the chamber 3 over time (for example, every 15 seconds). The memory unit 21 records the measured CO2 concentration.

[0065] The CO2 concentration in the chamber 3 decreases significantly immediately after the start of the measurement, and then stabilizes and becomes almost constant. The Γ value measurement unit 23 calculates the Γ value using the measurement value of the stable CO2 concentration recorded in the memory unit 21. When the Γ value is calculated, the memory unit 21 stops recording the CO2 concentration.

[0066] <Second measurement method> The procedure for measuring the A value and the procedure for measuring the Γ value are the same. Therefore, the second measurement method measures both the A value and the Γ value in one operation.

[0067] Immediately after the measurement is started (immediately after the leaves L are irradiated with light), the CO2 concentration in the chamber 3 decreases significantly. The rate measurement unit 22 measures the A value by utilizing the period during which the CO2 concentration decreases rapidly. For example, the rate measurement unit 22 may measure the time when the CO2 concentration decreases by 10 ppm from the start of the measurement, and calculate the A value using the above equation 3. After the rapid decrease, the CO2 concentration stabilizes and becomes almost constant. The Γ value calculation unit 23 calculates the Γ value as described above.

[0068] <Third measurement method> In the third measurement method, as in the second measurement method, both the A value and the Γ value are measured in one operation. However, after the CO2 concentration has decreased by a predetermined value from the start of measurement (for example, the concentration has decreased by 10 ppm from the starting concentration value), a dilution gas (zero gas) is introduced into the chamber 3 by a syringe to dilute the CO2 concentration. For example, the CO2 concentration may be diluted to 150 ppm. The CO2 concentration after dilution should be 1.5 to 2 times the expected Γ value.

[0069] The speed calculation unit 22 calculates the A value using the measurement values ​​obtained by the CO2 sensor 11 from the start of measurement to the introduction of the diluent gas. On the other hand, the Γ value calculation unit 23 calculates the Γ value using the measurement values ​​obtained by the CO2 sensor 11 after the introduction of the diluent gas.

[0070] <4th measurement method> In the fourth measurement method, the A value is not measured, but only the Γ value is measured. In the fourth measurement method, after the setting step, the zero gas calibration step is performed again. That is, after the leaf L is set in the chamber 3, zero gas is supplied as a calibration gas to fill the chamber 3, and the CO2 sensor 11 is calibrated again. Then, in the fourth measurement method, the chamber 3 is sealed and the set leaf L is allowed to photosynthesize. That is, in the fourth measurement method, zero gas (CO2 concentration is zero) is used as the base gas.

[0071] In this case, at the start of photosynthesis, the CO2 concentration in the sealed chamber 3 is zero, but due to the respiration reaction of the leaf L, the CO2 concentration in the chamber 3 gradually increases. Then, when the respiration reaction and the photosynthesis reaction reach equilibrium, the CO2 concentration stabilizes and becomes almost constant. Similar to other measurement methods, the Γ value measurement unit 23 determines the Γ value using the measured value at the point where the CO2 concentration is stable.

[0072] <Fifth Measurement Method> The fifth measurement method does not use air as the base gas. Therefore, in the fifth measurement method, after setting the leaf L in the chamber 3, the CO2 concentration and O2 concentration in the chamber 3 are adjusted using the above-mentioned dilution gas or the like (concentration adjustment step). For example, as described above, the O2 concentration in the chamber 3 may be adjusted to 0, 5, 10, 15, or 20 Vol% using the dilution gas or span gas. After the concentration adjustment step, the fifth measurement method seals the chamber 3, causes the set leaf L to perform photosynthesis, and measures the Γ value. Note that in the fifth measurement method, the A value may also be measured with the CO2 concentration of the base gas at around 400 ppm. Also, in the fifth measurement method, the CO2 concentration of the base gas may be adjusted to be higher than the CO2 concentration of the air.

[0073] <Gamma Value Measurement Test A> The Γ values of actual plants were measured by the above first to third measurement methods. Spinach, a C3 plant, was used. FIG. 4 is a diagram showing the time change of the CO2 concentration in the chamber in the first to third measurement methods. The time t = 0 is when the data logger (an example of the storage unit 22) starts recording the CO2 sensor. In the first measurement method, the data logger starts recording the CO2 concentration at the start of photosynthesis. In the second measurement method, after obtaining the measured values necessary for measuring the A value, the data logger starts recording the CO2 concentration. In the third measurement method, after diluting the CO2 concentration to about 150 ppm with zero gas, the data logger starts recording the CO2 concentration. FIG. 5 is a table showing the data for 4 minutes after the start of recording. The data logger recorded the CO2 concentration at 15-second intervals.

[0074] Regarding the measurement of the Γ value, for example, among the recorded continuous measurement values (indicated values), the point where it becomes ±1 ppm / min may be regarded as the stabilization of the CO2 concentration, and the average value of the measurement values may be used as the Γ value. That is, the Γ value may be the average value of four consecutive measurement values within the range of ±1 ppm (refer to the underlined part of the table in Fig. 5). This method is called the ±1 ppm averaging method. Alternatively, the minimum measurement value among these four consecutive values may be used as the Γ value. This is called the minimum point method. Fig. 6 shows the Γ values obtained by these determination methods. The Γ value calculation unit 23 may adopt either of the above two determination methods to calculate the Γ value.

[0075] <Gamma value measurement test B> For one leaf, its Γ value was measured multiple times using different measurement methods. First, the Γ value of the leaf of purslane was measured using the fourth measurement method (the first time). The data logger started recording the CO2 concentration after the zero gas recalibration step. Fig. 7 shows the measurement results. Also, the Γ value of the same purslane leaf was measured three times using the fifth measurement method (the second to fourth times). The CO2 concentrations of the base gases were 630 ppm, 530 ppm, and 540 ppm respectively, which were adjusted to be higher than the CO2 concentration in the atmosphere. The measurement results are shown in Fig. 8.

[0076] As shown in Fig. 7, in the fourth measurement method, immediately after the start of measurement, the CO2 concentration increased due to the respiratory reaction of the leaf. Then, as the respiratory reaction and the photosynthesis reaction reached equilibrium, the CO2 concentration stabilized. The Γ value obtained using the fourth measurement method was 69.0 ppm. It was confirmed that the Γ value could be measured in the same way as the first measurement method even when the CO2 concentration of the base gas was zero.

[0077] As shown in Figs. 8 and 9, the Γ values obtained using the fifth measurement method were 69.5 ppm, 70.5 ppm, and 68.0 ppm respectively. Therefore, the average value was 69.3 ppm, which had almost no difference from the 69.0 ppm of the measurement result of the fourth measurement method in Fig. 7. It was confirmed that the Γ value could be measured in the same way as other measurement methods even when the CO2 concentration of the base gas was higher than the atmosphere.

[0078] The Γ value of one leaf may be measured multiple times by different measurement methods, and the average value may be adopted as the Γ value. For example, in measurement test B, 69.2 ppm, which is the average value of the Γ value of 69.0 ppm obtained by the fourth measurement method in FIG. 7 and the Γ value (average value) of 69.3 ppm obtained by the fifth measurement method in FIG. 8, may be adopted in data arrangement. Thereby, the Γ value can be obtained with higher accuracy.

[0079] <Gamma value measurement test C> The Γ values of two types of purslane were measured using the fifth measurement method. The CO2 concentration of the base gas used was 277 ppm for the first time and 330 ppm for the second time, which is lower than the CO2 concentration of the atmosphere (about 400 ppm). FIGS. 10 and 11 show the test results.

[0080] As shown in FIGS. 10 and 11, the Γ value can be measured in about 3 minutes. This is due to the fact that by lowering the CO2 concentration of the base gas, the time until the CO2 concentration stabilizes is shortened. It was confirmed that lowering the CO2 concentration of the base gas below that of the atmosphere contributes to further shortening the time required for measuring the Γ value.

[0081] <Gamma value measurement tests D and E> For two types of eggplants (C3 plants) and two types of corns (C4 plants), the Γ value was measured using the first measurement method. As shown in FIGS. 12 and 13, it was confirmed that the Γ value can be measured in the same way not only for purslane but also for other C3 plants and C4 plants. It was also confirmed that the Γ value can be measured even for those with a considerably smaller Γ value than C3 plants, such as C4 plants.

[0082] As described above, it was confirmed that the Γ value can be measured using a closed-type photosynthesis measurement device. None of the measurement methods requires 8 minutes from the start of measurement to determining the Γ value. This measurement time can be significantly shortened compared to the 40 to 50 minutes required by an open-type photosynthesis measurement device. Therefore, the present application contributes to improving the efficiency of research on the C4 conversion of C3 plants.

[0083] Also, the second and third measurement methods can measure both the Γ value and the A value in a single operation. If the Γ value and the A value are measured separately, operations such as adjusting the base gas need to be performed twice. The second and third measurement methods have a great advantage in eliminating this necessity. The burden on the user is significantly reduced.

[0084] In the case of a base gas with a CO2 concentration lower than that of the atmosphere, the Γ value can be measured in just 3 minutes (see <Gamma value measurement test C>). That is, in this case, the measurement time of the Γ value can be further shortened compared to when using the atmosphere as the base gas.

[0085] Note that the Γ value of C4 plants is very small as in the above tests. Therefore, when measuring the Γ value, it is preferable to calibrate the CO2 sensor 11 each time.

[0086] <Dilution test> While injecting zero gas (here N2 gas) into the chamber with a syringe, the CO2 concentration in the chamber was confirmed. The graph in Fig. 14 shows the relationship between the injection volume (ml) and the CO2 concentration (ppm) in the chamber. The table in Fig. 14 shows the relationship between the injection volume (ml), the dilution rate (%), and the O2 concentration (%).

[0087] It was confirmed that the CO2 concentration and the O2 concentration of the base gas can be adjusted. The user can adjust the base gas by referring to the graph in Fig. 14. This is effective when implementing the third and fifth measurement methods. However, this graph is specific to the chamber. When using a different chamber, a different reference graph is required.

[0088] <Regarding the sealing performance of the gasket> As described above, measurement of the Γ value requires detection of a CO2 concentration of 100 ppm or less in the chamber 3. Therefore, the airtightness (sealing) of the chamber 3 during measurement is important. This is particularly important when the volume of the chamber 3 is small or when measuring C4 plants with low Γ values, because even a small leak can affect the measurement results. Therefore, leaks should be prevented.

[0089] Leaks are particularly likely to occur between the lower gasket 31 of the chamber 3 and the set leaf L. This is because the underside of the leaf L is uneven due to the veins. In particular, as shown in Figure 15A, the thickness of the leaf L at the position of the mid-vein MV is greater than other parts. At the position of this mid-vein MV, a gap G that can cause leakage may occur between the sponge gasket 31 and the leaf L.

[0090] Therefore, the lower gasket 31 is preferably formed from a material with low hardness, such as a gel sheet, that can closely fit the irregularities on the back surface of the leaf L without any gaps. The gel sheet may be made of a silicon polymer-based or polystyrene-based material. The hardness of the gel sheet is, for example, 30 or more and 80 or less in Asker F hardness. A gasket formed from a gel sheet with a hardness in this range can prevent leakage without any problems even with a vein MV of a normal thickness, such as up to about 1.0 mm. More preferably, the hardness of the gel sheet is 30 or more and 40 or less in Asker F hardness. A gasket formed from a gel sheet with a hardness in this range can sufficiently prevent leakage even with a vein MV of a large thickness, such as about 2.0 mm.

[0091] <Gasket sealing performance confirmation test> A test was conducted to confirm the sealing ability between the lower gasket and the leaf as follows. A leaf was sandwiched between the upper and lower gaskets, and it was confirmed whether a gap occurred between the lower gasket and the underside of the leaf at the position of the mid-vein. When the leaf was sandwiched between the upper and lower gaskets, the longitudinal direction of the rectangular gasket was aligned with the longitudinal direction of the leaf (see FIG. 15C). When the lower gasket and the leaf were in close contact with each other without any gaps at the mid-vein of the leaf, it was evaluated as "Good". On the other hand, when a gap occurred and leakage could not be prevented, it was evaluated as "Poor".

[0092] A sealing performance confirmation test was conducted on each of the sponge gasket, the gel sheet A gasket, and the gel sheet B gasket. The sponge is a comparative example, and is a silicone sponge with an Asker C hardness of about 15. Gel sheet A is made of silicone polymer and has an Asker F hardness of about 73 (average value of measurements at multiple points). Gel sheet B is made of polystyrene and has an Asker F hardness of about 34 (average value of measurements at multiple points).

[0093] FIG. 16 shows the measurement results. The leaf thickness shown in FIG. 16 is the thickness at the mid-vein position. The sponge gasket could not prevent leakage even with 0.5 mm thick molokheiya (C3 plant). Gel sheet A prevented leakage with molokheiya up to 1.0 mm thick. Gel sheet B showed high adhesion and prevented leakage even with 2.0 mm thick corn (C4 plant). Therefore, it was confirmed that a gel sheet with an Asker F hardness of 30 or more and 40 or less, like Gel sheet B, can sufficiently prevent leakage in most types of leaves. In other words, if such a gel sheet is used, the Γ value can be measured more accurately. [Explanation of symbols]

[0094] 1 Analysis Unit 11 Carbon dioxide sensor (CO2 sensor) 2 Operation unit 23 Gamma value measurement section 3. Chamber 30 Chamber opening 31 Lower gasket 4 Irradiation unit 40 Irradiation unit opening 41 Upper gasket P plant L leaf

Claims

1. A method for measuring the carbon dioxide compensation point of a plant, comprising the steps of: placing the leaf in the chamber such that the leaf is in contact with gas within the chamber; allowing the leaf to photosynthesize while the leaf is set in the chamber and the chamber is sealed; While the leaves were photosynthesizing, CO was released from the sealed chamber. ２ Concentration of CO ２ measuring with a sensor over time; and The CO ２ determining said carbon dioxide compensation point using measurements obtained by a sensor.

2. The CO ２ using the measurements obtained by the sensor to determine both the carbon dioxide compensation point and the photosynthetic rate of the plant; The measurement method according to claim 1.

3. The gas filled in the chamber when the chamber is sealed is atmospheric air. The measurement method according to claim 1.

4. While the leaves are photosynthesizing, a diluent gas is introduced into the chamber to measure CO ２ Dilute the concentration Before the introduction of the diluent gas, ２ using the measurements obtained by the sensor to determine the photosynthetic rate; After the introduction of the diluent gas, ２ using the measurements obtained by the sensor to determine the carbon dioxide compensation point; The measurement method according to claim 3.

5. CO2 than air ２ filling the chamber with a low concentration gas and then sealing the chamber; The measurement method according to claim 1.

6. CO ２ filling the chamber with a zero gas that does not contain The measurement method according to claim 1.

7. A measuring device for measuring a carbon dioxide compensation point of a plant, comprising: a sealable chamber having an opening that is covered by a leaf; an irradiation unit that irradiates light toward the opening of the chamber; CO in the chamber ２ CO placed in the chamber to measure its concentration over time. ２ A sensor; The CO ２ A Γ value calculation unit that calculates the carbon dioxide compensation point based on a measurement value from a sensor. Measuring equipment.

8. the chamber includes a lower gasket disposed along an edge of the opening; The irradiation unit includes a casing having an opening, and an upper gasket provided along the opening of the casing and for sandwiching the leaf together with the lower gasket.

8. The measuring device according to claim 7.

9. The lower gasket is formed from a gel sheet.

9. The measuring device according to claim 8.

10. The Asker F hardness of the gel sheet is 30 or more and 80 or less.

10. The measuring device according to claim 9.

11. The Asker F hardness of the gel sheet is 30 or more and 40 or less.

10. The measuring device according to claim 9.

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