Vascular bundle sap flow velocity sensor, vascular bundle sap flow velocity measuring device, and vascular bundle sap flow velocity measuring method

Abstract

To provide a vascular bundle liquid flow rate sensor capable of reducing mechanical or thermal damage to plants, a vascular bundle liquid flow rate measurement device, and a vascular bundle liquid flow rate measurement method.SOLUTION: A vascular bundle liquid flow rate sensor 1 has a heated temperature probe 20 having a first temperature sensor 21 and a heater 22 as a probe to pierce plants. The vascular bundle liquid flow rate measurement device includes: the vascular bundle liquid flow rate sensor 1; a power source that intermittently supplies the power to the heater 22; and a calculation unit for obtaining the vascular bundle liquid flow rate based on the temperature rise of the vascular bundle liquid due to the heating of the heater 22 measured by the first temperature sensor 21. Since the only the probe that pierces a plant is the temperature probe 20 with a heater, mechanical damage to the plant can be reduced. Since the heating by the heater 22 is intermittent, thermal damage to the plant can be reduced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vascular sap flow velocity sensor, a vascular sap flow velocity measuring device, and a vascular sap flow velocity measuring method, and more particularly to a sensor, device, and method for measuring the flow velocity of vascular sap flowing through the details of a plant, such as the shoot ends and fruit stalks of a plant. [Background technology]

[0002] In the production of crops and fruit trees, it is desirable to irrigate and replenish nutrients at the appropriate time according to the plant's growth condition from the perspective of productivity. However, in many agricultural fields, irrigation and nutrient replenishment are currently carried out based on experience and intuition, such as the number of days without rain. This type of experience-dependent method requires skill, is laborious, and is time-consuming. Furthermore, because the benchmark indicators are based on personal experience, it is difficult for anyone to carry out this method easily.

[0003] In recent years, there has been a growing movement to introduce information technology into agriculture, such as smart agriculture. It is expected that information technology will enable optimal production based on physiological information from plants, without relying on humans.

[0004] Vascular sap flow velocity is physiological information of plants that is necessary for irrigation management. In particular, to improve the productivity and quality of crops and fruit trees, it is important to measure the vascular sap flow velocity in the details of plants, such as the ends of new shoots and fruit stalks. A sensor that measures the vascular sap flow velocity in the details of plants has already been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-145810 Summary of the Invention [Problem to be solved by the invention]

[0006] The sensor disclosed in Patent Document 1 measures the flow velocity of vascular sap using the Granier method. The Granier method requires two probes to be inserted into the plant and the vascular sap to be constantly heated with a heater. This method causes significant mechanical and thermal damage to the plant.

[0007] In addition to the Granier method, the heat pulse method is also known as a method for measuring vascular sap flow velocity. The heat pulse method applies heat intermittently, causing less thermal damage to plants. However, measuring vascular sap flow velocity using the heat pulse method requires piercing the plant with three probes, which causes more mechanical damage to the plant than the Granier method.

[0008] In view of the above circumstances, it is an object of the present invention to provide a vascular sap flow velocity sensor, a vascular sap flow velocity measuring device, and a vascular sap flow velocity measuring method that cause minimal mechanical or thermal damage to plants. [Means for solving the problem]

[0009] The vascular bundle sap flow velocity sensor of the first invention comprises a heater-equipped temperature probe provided with a first temperature sensor and a heater, a readout electrode pair consisting of a pair of electrodes arranged at a predetermined interval, a moisture content probe provided with a water-sensitive film spanning the pair of electrodes, and a heater-equipped temperature probe and a water content probe arranged in parallel. The base end of the heater-equipped temperature probe and the base end of the moisture content probe are connected to each other. and a support portion for supporting the water-sensitive film, the water-sensitive film being arranged on the water content probe from the arrangement portion of the read electrode pair. The aforementioned Over the base end, From the base end Furthermore, the support portion is provided so as to cover a partial area of ​​the support portion. The vascular sap flow velocity sensor of the second invention is the same as that of the first invention, and further comprises a second temperature sensor that measures the outside air temperature. The vascular bundle sap flow velocity sensor of the third invention is the same as that of the first or second invention, and further comprises an electrical conductivity probe provided with an electrical conductivity electrode pair consisting of a pair of electrodes arranged at a predetermined interval, and the electrical conductivity probe is arranged in parallel with the water content probe. The base endIt is characterized in that it is supported by the support part. The vascular bundle sap flow velocity sensor of the fourth invention is any one of the first to third inventions, further comprising a temperature probe provided with a third temperature sensor, and the temperature probe is arranged in parallel with the heater-equipped temperature probe. The base end It is characterized in that it is supported by the support part. The vascular bundle sap flow velocity measuring device of the fifth invention is characterized by comprising a vascular bundle sap flow velocity sensor of any of the first to fourth inventions, a power source that intermittently supplies power to the heater of the heater-equipped temperature probe, and a calculation unit that calculates the vascular bundle sap flow velocity based on the increase in temperature of the vascular bundle sap due to heating by the heater measured by the first temperature sensor of the heater-equipped temperature probe. The vascular bundle sap flow velocity measurement method of the sixth invention is characterized in that the heater-equipped temperature probe and the water content probe of the vascular bundle sap flow velocity sensor of any of the first to fourth inventions are inserted into a plant, power is intermittently supplied to the heater of the heater-equipped temperature probe, the increase in temperature of the vascular bundle sap due to heating by the heater of the heater-equipped temperature probe is measured with the first temperature sensor, and the vascular bundle sap flow velocity is calculated based on the increase in temperature. The seventh invention is a method for measuring vascular sap flow velocity, which is characterized in that, in the sixth invention, the impedance or capacitance between the pair of electrodes that constitute the readout electrode pair of the water content probe is measured, the water content of the plant is determined from the impedance measurement value or the capacitance measurement value, and the vascular sap flow velocity is determined based on the increased temperature and the water content. The vascular bundle sap flow velocity measurement method of the eighth invention is characterized in that the water content probe and the electrical conductivity probe of the vascular bundle sap flow velocity sensor of the third invention are inserted into a plant, the impedance or capacitance between the pair of electrodes that constitute the readout electrode pair of the water content probe is measured, the water content of the plant is determined from the impedance measurement value or the capacitance measurement value, the electrical conductivity is determined from the electrical resistance between the pair of electrodes that constitute the electrical conductivity electrode pair, and the water content measurement value is compensated using the electrical conductivity measurement value. The vascular sap flow velocity measurement method of the ninth invention is characterized in that, in the sixth or seventh invention, a natural temperature gradient is calculated from the temperature of the plant or the outside air temperature, and the rising temperature is corrected using the natural temperature gradient. [Effects of the Invention]

[0010] According to the first aspect of the present invention, the water content measured by the water content probe is taken into consideration, so that the vascular sap flow velocity can be measured with high accuracy. According to the second aspect of the present invention, the vascular sap flow velocity is calculated taking into consideration the natural temperature gradient calculated from the outside air temperature, thereby making it possible to improve robustness against the external environment. According to the third aspect of the present invention, the water content of a plant can be measured with high accuracy by compensating the measured water content value based on the electrical conductivity of the water in the plant measured by the electrical conductivity probe. According to the fourth aspect of the present invention, the vascular sap flow velocity is determined taking into consideration the natural temperature gradient measured by the third temperature sensor, thereby making it possible to improve robustness against the external environment. No. 5 According to the invention, the heating by the heater is intermittent, which reduces thermal damage to the plant. In addition, the flow rate of the vascular sap can be measured by inserting the heater-equipped temperature probe into the plant and obtaining the measurement value of the first temperature sensor. No. 6 According to the invention, the vascular sap flow velocity can be determined. Seventh According to the present invention, the vascular sap flow velocity can be determined with high accuracy by taking into account the plant water content. No. 8 According to the invention, the water content of a plant can be measured with high accuracy by compensating the water content measurement value based on the electrical conductivity of the water in the plant measured by the electrical conductivity probe. No. 9 According to the present invention, the robustness against the external environment can be improved by determining the vascular sap flow velocity in consideration of the natural temperature gradient determined from the plant temperature or the ambient temperature. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a plan view of the vascular bundle sap flow velocity sensor according to the first embodiment. [Figure 2] FIG. 2 is a side view of the vascular bundle sap flow velocity sensor according to the first embodiment. [Figure 3] FIG. 2 is an explanatory diagram of a state in which the vascular bundle sap flow velocity sensor according to the first embodiment is used. [Figure 4]1 is a graph showing temperature changes of vascular sap. [Figure 5] FIG. 1 is an explanatory diagram of a vascular sap flow velocity measuring device according to a first embodiment. [Figure 6] FIG. 10 is a plan view of a vascular sap flow velocity sensor according to a second embodiment. [Figure 7] FIG. 10 is a plan view of a vascular sap flow velocity sensor according to a third embodiment. [Figure 8] FIG. 1 is a longitudinal cross-sectional view of a moisture content probe. [Figure 9] Figure (A) shows the analytical model, and Figure (B) shows the temperature distribution. [Figure 10] 10 is a graph showing the relationship between heat pulse velocity and flow velocity obtained by thermal analysis. [Figure 11] 1 is a graph showing the relationship between heat pulse velocity and flow velocity obtained by a simulated plant test. [Figure 12] 1 is a graph showing the change over time in xylem sap flow velocity of tomatoes under growing conditions. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described with reference to the drawings. [First embodiment] The vascular sap flow velocity sensor 1 according to the first embodiment of the present invention can be attached to the small parts of a plant, such as the end of a new shoot, a fruit stalk, etc. The vascular sap flow velocity sensor 1 has the function of measuring the flow velocity and flow rate of vascular sap (xylem sap or phloem sap) in the small parts of a plant.

[0013] (vascular sap flow rate sensor) First, the configuration of the vascular sap flow velocity sensor 1 will be described. As shown in Figure 1, the vascular sap flow velocity sensor 1 has a support part 10. A heater-equipped temperature probe 20 is provided on the support part 10. The heater-equipped temperature probe 20 is inserted into the plant, thereby attaching the vascular sap flow velocity sensor 1 to the plant.

[0014] The support 10 and the heater-equipped temperature probe 20 are formed by processing a semiconductor substrate. Examples of semiconductor substrates include silicon substrates and SOI (Silicon on Insulator) substrates. Semiconductor substrates are processed using MEMS technology, which employs thin-film formation such as photolithography, etching, sputtering, and vapor deposition. The vascular sap flow velocity sensor 1 may be formed by methods other than MEMS technology, and the material is not limited to a semiconductor substrate.

[0015] ·Support part The support part 10 is a member that supports the heater-equipped temperature probe 20. The support part 10 is a plate material that is rectangular in plan view, and the heater-equipped temperature probe 20 is supported on one side thereof.

[0016] Heated temperature probe The heater-equipped temperature probe 20 is a rod-shaped member that is cantilevered on the edge of the support part 10. The tip of the heater-equipped temperature probe 20 is preferably pointed, such as triangular. If the tip of the heater-equipped temperature probe 20 is pointed, the insertion resistance when piercing the fine details of the plant can be reduced.

[0017] The heater-equipped temperature probe 20 is sized so that it can be inserted into the smallest part of a plant, such as the end of a new shoot or a fruit stalk, with a stem or stalk diameter of a few millimeters. The length of the heater-equipped temperature probe 20 (the length from the base end to the tip in the axial direction) is sized so that when inserted into the smallest part of a plant, its tip can be placed in the xylem or phloem of the plant. The length of the heater-equipped temperature probe 20 is, for example, 0.5 to 5 mm.

[0018] The width of the heater-equipped temperature probe 20 is not particularly limited, but is, for example, 50 to 500 μm. The narrower the width of the heater-equipped temperature probe 20, the less mechanical damage can be caused to the plant.

[0019] As shown in FIG. 2, the vascular bundle sap flow velocity sensor 1 is generally thin and plate-like. The thickness of the heater-equipped temperature probe 20 is set to be thinner than the width of the xylem and phloem of the plant. The thickness of the heater-equipped temperature probe 20 depends on the type of plant and the thickness of the stem to be measured, but is, for example, 50 to 300 μm. A thickness of 50 μm or more provides sufficient strength and prevents the heater-equipped temperature probe 20 from breaking when inserted into or removed from the plant stem. Furthermore, since the diameter of the xylem and phloem is approximately 100 to 400 μm depending on the type of plant, a thickness of 300 μm or less prevents the heater-equipped temperature probe 20 from blocking the xylem or phloem even when inserted into the xylem or phloem. The thinner the heater-equipped temperature probe 20, the less mechanical damage it causes to the plant. Therefore, it is more preferable that the heater-equipped temperature probe 20 be 100 μm or less in thickness. The thickness of the support portion 10 is not particularly limited, and may be the same as that of the heater-equipped temperature probe 20 or may be thicker than that of the heater-equipped temperature probe 20 .

[0020] As shown in FIG. 1, a first temperature sensor 21 is provided at the tip of the heater-equipped temperature probe 20. The first temperature sensor 21 has a function of sensing temperature and is not particularly limited as long as it is sized to be able to be disposed at the tip of the heater-equipped temperature probe 20. The first temperature sensor 21 can be a resistance temperature detector, a pn junction diode, a thermocouple, or the like. Because the vascular bundle sap flow velocity sensor 1 is expected to be used outdoors, it is preferable to use a resistance temperature detector that is not light-dependent as the first temperature sensor 21. Furthermore, two electrode pads 21e, 21e connected to the first temperature sensor 21 via wiring are provided on the upper surface of the support part 10.

[0021] The resistance thermometer sensor is formed by depositing a thin film of a metal suitable for the resistance thermometer sensor, such as Au, on a semiconductor substrate using, for example, sputtering or vapor deposition. The electrical resistance of the resistance thermometer sensor increases as the temperature rises. A constant current source is connected between the two electrode pads 21e, 21e. The constant current source supplies a constant current to the resistance thermometer sensor, and the voltage is measured with a voltmeter. The temperature can be calculated from the voltage measured by the voltmeter.

[0022] The heater-equipped temperature probe 20 is also provided with a heater 22. The heater 22 may be located at any position other than the tip, as long as it can supply heat to the heater-equipped temperature probe 20. The heater 22 is not particularly limited as long as it is large enough to be mounted on the heater-equipped temperature probe 20. For example, a microheater (referred to as a "filament heater" in this specification) formed by forming a thin film of Au (gold), Pt (platinum), Ti (titanium), Cr (chromium), or the like by a sputtering method, vapor deposition method, or the like, and processing it into a thin filament shape can be used as the heater 22. Alternatively, a pn junction diode formed using an oxidation diffusion furnace may be used as the heater 22.

[0023] Two electrode pads 22e, 22e connected via wiring to the heater 22 are disposed on the upper surface of the support 10. A constant DC power supply is connected between the two electrode pads 22e, 22e. Heat can be generated by passing a current through the heater 22.

[0024] (Method for measuring vascular fluid flow velocity) Next, a method for measuring the vascular sap flow velocity using the vascular sap flow velocity sensor 1 will be described.

[0025] ·attachment First, the vascular sap flow velocity sensor 1 is attached to the shoot end, fruit stalk, etc. of the plant to be measured. Specifically, as shown in Figure 3, the heater-equipped temperature probe 20 of the vascular sap flow velocity sensor 1 is attached by piercing it into the plant.

[0026] When the heater-equipped temperature probe 20 is inserted into the plant, the tip of the heater-equipped temperature probe 20 passes through the plant cortex CO and reaches the phloem PH. When inserted further, the tip of the heater-equipped temperature probe 20 reaches the xylem XY and then the pith PI. When measuring the flow rate of the phloem sap, the tip of the heater-equipped temperature probe 20 is placed in the phloem PH. When measuring the flow rate of the xylem sap, the tip of the heater-equipped temperature probe 20 is placed in the xylem XY. Below, an example of measuring the flow rate of the xylem sap will be explained.

[0027] With the heater-equipped temperature probe 20 inserted into the plant, power is intermittently supplied to the heater 22. That is, a pulsed current is passed through the heater 22. The time width (pulse width) for which power is supplied to the heater 22 is determined in advance.

[0028] When the heater 22 is driven intermittently, the xylem sap is heated only while the heater 22 is driven. In this case, the temperature of the xylem sap changes over time as shown in Figure 4. That is, the temperature of the xylem sap rises while it is being heated by the heater 22, and drops when the heating ends.

[0029] The temperature of the xylem sap at the start of heating by the heater 22, t1, is defined as T1. The temperature of the xylem sap at the end of heating by the heater 22, t2, is defined as T2. The temperature rise ΔT of the xylem sap due to heating by the heater 22 is calculated by subtracting T1 from T2. The temperature rise ΔT of the xylem sap at the end of heating by the heater 22, t3, is defined as T3, a predetermined time after heating by the heater 22 has ended. The temperature rise ΔT of the xylem sap due to heating by the heater 22 may also be calculated by subtracting T3 from T2. The time from t2 to t3 is set to allow the temperature of the xylem sap to drop sufficiently. In either case, the temperature of the xylem sap can be measured by the first temperature sensor 21, so the temperature rise ΔT can be calculated from the measurement value of the first temperature sensor 21.

[0030] Solving the heat transfer residence equation, the heat pulse velocity V h is expressed by the following equation (1): In equation (1), D is the thermal diffusivity of the vessel [m 2 / s], ΔT u is the temperature rise of the xylem sap [℃], ΔT0 is the temperature rise of the xylem sap when the flow rate is 0 [℃], and t is the heating time [s]. u is a measured value obtained by the first temperature sensor 21. The thermal diffusivity D and the temperature rise ΔT0 of the xylem sap when the flow velocity is 0 are constants that depend on the plant being measured and are determined in advance by experiment, etc. The heating time t is set to a time that is optimal for measuring the xylem sap flow velocity depending on the plant. The heating time t is, for example, 20 to 40 seconds.

number

[0031] Inserting the heater-equipped temperature probe 20 into the vessel disrupts the flow of vessel fluid, so this effect may be corrected. For example, the corrected heat pulse velocity V c In equation (2), a, b, and c are correction coefficients, which are determined in advance by experiment or the like.

number

[0032] The xylem liquid flow velocity u is proportional to the heat pulse velocity. In other words, the xylem liquid flow velocity u is obtained by equation (3). In equation (3), α is a coefficient that is determined in advance through experiments, etc. V is the heat pulse velocity V before correction. h or the corrected heat pulse velocity V c is.

number

[0033] The flow rate can be calculated from the flow velocity of the xylem fluid. As shown in equation (4), the flow rate Q of the xylem fluid is calculated by multiplying the flow velocity u [m / s] by the cross-sectional area A [m 2 ] is obtained by multiplying

number

[0034] According to the above principle, the temperature rise ΔT of the xylem sap measured by the first temperature sensor 21 is u The flow velocity u and flow rate Q of the xylem sap can be determined based on the above. Note that the flow velocity and flow rate of the phloem sap can be determined by placing the tip of the heater-equipped temperature probe 20 in the phloem PH of the plant. When monitoring the vascular sap flow velocity over a long period of time, the heater 22 is driven at predetermined intervals, and the vascular sap flow velocity is determined each time. There are no particular limitations on the interval at which the heater 22 is driven. Shortening the interval increases the time resolution of the flow velocity.

[0035] In the vascular bundle sap flow velocity sensor 1 of this embodiment, the only probe that is inserted into the plant is the heater-equipped temperature probe 20. Because there is no need to insert multiple probes into the plant, mechanical damage to the plant can be reduced. Also, because heating by the heater 22 is intermittent, thermal damage to the plant can be reduced compared to constant heating. Furthermore, because the heater 22 is driven intermittently, the power consumption of the vascular bundle sap flow velocity sensor 1 can be reduced. For example, the vascular bundle sap flow velocity sensor 1 can be continuously operated by a battery over the plant cultivation period, which can last from several months to half a year.

[0036] (Vascular fluid flow rate measuring device) Next, the vascular sap flow velocity measuring device AA will be explained. As shown in FIG. 5, the vascular sap flow velocity measuring device AA has a vascular sap flow velocity sensor 1. For example, multiple vascular sap flow velocity sensors 1 are attached to multiple plants in an agricultural field. The vascular sap flow velocity sensors 1 may be attached to multiple locations on a single plant, or may be attached to all or some specimens of multiple plants. Also, only one vascular sap flow velocity sensor 1 may be used.

[0037] A data logger DR is connected to the vascular bundle sap flow velocity sensor 1, and supplies power and collects measurements. The data logger DR intermittently supplies power to the heater 22. Therefore, the data logger DR corresponds to the "power source" in the claims. The data logger DR also has a built-in wireless communication device.

[0038] The server device SV is installed in a building adjacent to the agricultural field. A wireless communication device is connected to the server device SV, and it is configured to be able to communicate wirelessly with the data logger DR.

[0039] The data logger DR transmits the measurement data of the vascular bundle sap flow velocity sensor 1 to the server device SV via the wireless communication device. The server device SV analyzes the received measurement data and calculates the vascular bundle sap flow velocity. The details are as described above. Therefore, the server device SV corresponds to the "calculation unit" recited in the claims.

[0040] The connection between the data logger DR and the server device SV is not limited to wireless but may be wired. Data accumulated in the data logger DR may be saved to a storage medium, and the storage medium may be read by the server device SV. The power source is not limited to the data logger DR as long as it can supply power to the heater 22. The calculation unit is also not limited to the server device SV as long as it can determine the vascular bundle sap flow velocity.

[0041] Second Embodiment Next, a vascular sap flow velocity sensor 2 according to a second embodiment of the present invention will be described. 6, the vascular bundle sap flow velocity sensor 2 has a heater-equipped temperature probe 20 and a support part 10, similar to the first embodiment. Members similar to those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0042] A second temperature sensor 11 is provided on the support part 10. The second temperature sensor 11 can be the same as the first temperature sensor 21. Two electrode pads 11e, 11e connected to the second temperature sensor 11 via wiring are provided on the upper surface of the support part 10. The second temperature sensor 11 can measure temperature in the same way as the first temperature sensor 21.

[0043] The second temperature sensor 11 is for measuring the outside air temperature around the plant. To prevent the heat from the heater 22 from being transmitted to the second temperature sensor 11, the heater-equipped temperature probe 20 and the second temperature sensor 11 are insulated from each other.

[0044] For example, the vascular bundle sap flow velocity sensor 2 is formed by processing an SOI substrate consisting of a support substrate (Si), an oxide layer (SiO2), and an active layer (Si). The first temperature sensor 21, heater 22, and second temperature sensor 11 are formed on the surface of the active layer. The active layer between the heater-equipped temperature probe 20 and the second temperature sensor 11 is then removed, leaving an oxide layer between them. This allows thermal insulation between the heater-equipped temperature probe 20 and the second temperature sensor 11.

[0045] (natural temperature gradient compensation) A natural temperature gradient occurs when a heater is turned on in a greenhouse where plants are grown, or when the solar radiation or wind around the plants changes. The natural temperature gradient affects the measurement value of the first temperature sensor 21, reducing the accuracy of measuring the vascular sap flow velocity. Therefore, in this embodiment, the outside air temperature measured by the second temperature sensor 11 is used to correct for the effect of the natural temperature gradient.

[0046] As described above, when measuring the vascular bundle sap flow velocity, the heater 22 is driven intermittently. The first temperature sensor 21 measures the temperature rise ΔT1 of the vascular bundle sap due to heating by the heater 22. At the same time, the second temperature sensor 11 measures the natural temperature gradient ΔT2. If the temperature rise ΔT1 is the difference in the measurements taken by the first temperature sensor 21 between t1 and t2, the natural temperature gradient ΔT2 can be calculated as the difference in the measurements taken by the second temperature sensor 11 between t1 and t2. If the temperature rise ΔT1 is the difference in the measurements taken by the first temperature sensor 21 between t2 and t3, the natural temperature gradient ΔT2 can be calculated as the difference in the measurements taken by the second temperature sensor 11 between t2 and t3.

[0047] Then, as shown in equation (5), the natural temperature gradient ΔT2 is used to correct the temperature rise ΔT1.

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[0048] Corrected temperature rise ΔT u Using this, the heat pulse velocity V is calculated according to equation (1). h By calculating the vascular sap velocity, the influence of the natural temperature gradient can be eliminated. In this way, by calculating the vascular sap velocity taking into account the natural temperature gradient calculated from the outside air temperature, robustness against the external environment can be improved.

[0049] The second temperature sensor 11 does not have to be provided on the support part 10. That is, a temperature sensor that is physically independent from the heater-equipped temperature probe 20 may be used as the second temperature sensor 11. Therefore, the second temperature sensor may be a separate component from the vascular bundle sap flow velocity sensor.

[0050] Third Embodiment Next, a vascular sap flow velocity sensor 3 according to a third embodiment of the present invention will be described. As shown in Figure 7, the vascular bundle sap flow velocity sensor 3 is the vascular bundle sap flow velocity sensor 1 of the first embodiment with the addition of a water content probe 30, an electrical conductivity probe 40, and a temperature probe 50. The remaining configuration is the same as in the first embodiment, so the same members are given the same reference numerals and their explanations will be omitted.

[0051] The water content probe 30 is used to measure the water content of the plant. The measured water content is used to compensate for the measured water content. If compensation based on water content is not necessary, the vascular bundle sap flow velocity sensor 3 does not need to be provided with the water content probe 30. The electrical conductivity probe 40 is used to measure the electrical conductivity of water within the plant. The measured electrical conductivity is used to compensate for the measured water content. If compensation based on electrical conductivity is not necessary, the vascular bundle sap flow velocity sensor 3 does not need to be provided with the electrical conductivity probe 40. The temperature probe 50 is used to measure the temperature of the plant. The measured temperature is used to compensate for some or all of the measured water velocity, water content, and electrical conductivity. If compensation based on temperature is not necessary, the vascular bundle sap flow velocity sensor 3 does not need to be provided with the temperature probe 50.

[0052] The probes 20, 30, 40, and 50 are arranged parallel to one another on the same plane, with their base ends supported on one side of the support 10. The order in which the probes 20, 30, 40, and 50 are arranged is not particularly limited. However, it is preferable to arrange the temperature probe 50 at a position separated from the heater-equipped temperature probe 20. This makes it difficult for heat from the heater 22 to be transmitted to the temperature probe 50, allowing for accurate measurement of the natural temperature gradient. For example, it is preferable to arrange the probes in the following order: heater-equipped temperature probe 20, moisture content probe 30, electrical conductivity probe 40, and temperature probe 50.

[0053] Moisture content probe A readout electrode pair 31 is provided at the tip of the moisture content probe 30. The readout electrode pair 31 consists of a pair of electrodes 32, 32 arranged at a predetermined distance. Two electrode pads 32e, 32e connected to the two electrodes 32, 32 via wiring are arranged on the upper surface of the support part 10. In addition, the moisture content probe 30 is provided with a water-sensitive film 33.

[0054] When the water content probe 30 is inserted into a plant, the water in the plant is absorbed into the water-sensitive film 33. The amount of water absorbed by the water-sensitive film 33 is read out as the impedance or capacitance between the electrodes 32, 32. This allows the water content of the plant to be measured.

[0055] 8, a pair of electrodes 32, 32 are formed on the surface of a semiconductor substrate SS that constitutes the moisture content probe 30. There are no particular limitations on the size of the electrode 32, as long as it can be placed at the tip of the moisture content probe 30. The electrode 32 is formed by depositing a thin metal film of Au, Al, or the like on the semiconductor substrate SS by, for example, sputtering or vapor deposition.

[0056] The water-sensitive film 33 is formed on the pair of electrodes 32, 32 so as to span them. The water-sensitive film 33 has the function of absorbing moisture and is made of a material with a lower dielectric constant than water. In this specification, the term "water-sensitive film" refers to a film that has the function of absorbing moisture and is made of a material with a lower dielectric constant than water. Since the dielectric constant of water at a temperature of 20°C is approximately 80, the dielectric constant of the water-sensitive film 33 should only be smaller than 80. However, since the greater the difference between the dielectric constant of the water-sensitive film 33 and the dielectric constant of water, the higher the accuracy of measuring the moisture content. Therefore, the dielectric constant of the water-sensitive film 33 is preferably 1 to 3.

[0057] The material of the water-sensitive film 33 is preferably insoluble in water and thermally and chemically stable. Materials that can be used for the water-sensitive film 33 include lithium chloride, metal oxides, ceramics, and polymeric materials. However, lithium chloride is toxic to plants and therefore not particularly suitable for use with plants. Examples of metal oxides and ceramics include aluminum oxide (Al2O3) and silicon dioxide (SiO2). Metal oxides and ceramics are insoluble in water. However, metal oxides and ceramics are hard and require high-temperature heat treatment during the manufacturing process. In contrast, polymeric materials are suitable for use with plants and are also soft. Examples of polymeric materials include polyimide and polyvinyl alcohol. Among these, polyimide is preferred for its ease of mounting on semiconductor Si substrates. Furthermore, polyimide is less soluble in water, making it suitable for long-term measurement of water content in plants. Therefore, if the water-sensitive film 33 is made of polyimide, it is less likely to dissolve in water within plants, enabling long-term measurement.

[0058] When the water-sensitive film 33 is made of a polymer material, the surface of the water-sensitive film 33 may be hydrophilized. This makes it easier for the water-sensitive film 33 to absorb water from within the plant, thereby increasing the response speed of water content measurement. For example, when the water-sensitive film 33 is made of polyimide, the surface of the water-sensitive film 33 may be oxygen plasma treated. Oxygen plasma treatment of the polyimide surface introduces carbonyl groups, making the polyimide surface hydrophilic. This also has the effect of increasing the surface area of ​​the polyimide. As the water-sensitive film 33 is made hydrophilic and its surface area increases, it becomes easier for the water-sensitive film 33 to absorb water from within the plant, thereby increasing the response speed of water content measurement.

[0059] Electrical conductivity probe As shown in Fig. 7, an electrical conductivity electrode pair 41 is provided at the tip of the electrical conductivity probe 40. The electrical conductivity electrode pair 41 consists of a pair of electrodes 42, 42 arranged at a predetermined distance. The electrical conductivity electrode pair 41 is used to measure the electrical conductivity of water (vascular bundle sap, etc.) present between the electrodes 42, 42. There are no particular limitations on the size of the electrode 42, as long as it can be placed at the tip of the electrical conductivity probe 40. The electrode 42 is formed, for example, by depositing a thin metal film of Au, Al, etc. on the semiconductor substrate SS by sputtering, vapor deposition, or the like.

[0060] Two electrode pads 42e, 42e connected to the two electrodes 42, 42 via wiring are disposed on the upper surface of the support part 10. Electrical conductivity can be measured by an AC two-electrode method. That is, an AC power supply and an ammeter are connected in series between a pair of electrode pads 42e, 42e corresponding to the pair of electrodes 42, 42. A current is supplied between the electrodes 42, 42 by the AC power supply, and the current flowing between the electrodes 42, 42 is measured by the ammeter. Based on Ohm's law, the electrical resistance between the electrodes 42, 42 is calculated from the current measured by the ammeter, and the electrical conductivity is determined from the electrical resistance.

[0061] To measure the electrical conductivity of water within a plant, it is preferable that the measurement range of electrical conductivity is at least 0 to 10 mS / cm. The measurement range of electrical conductivity using the AC two-electrode method depends on the cell constant K of the electrode pair. Here, the cell constant K is calculated by dividing the inter-electrode distance L by the electrode surface area S. In other words, the measurement range of electrical conductivity depends on the shape of the electrode 42. The shape of the electrode 42 can be selected from various shapes, such as a three-dimensional electrode, a comb-shaped electrode, or a flat electrode.

[0062] Temperature probe A third temperature sensor 51 is provided at the tip of the temperature probe 50. The third temperature sensor 51 can be the same as the first temperature sensor 21. Two electrode pads 51e, 51e connected to the third temperature sensor 51 via wiring are provided on the upper surface of the support part 10. The third temperature sensor 51 can measure temperature in the same way as the first temperature sensor 21.

[0063] The moisture content probe 30, the electrical conductivity probe 40, and the temperature probe 50 may each be configured as separate probes, or some or all of them may be configured as a single probe. For example, the electrical conductivity probe 40 and the temperature probe 50 may be integrated into one probe by mounting the electrical conductivity electrode pair 41 and the third temperature sensor 51 on a single probe.

[0064] (Method for measuring vascular fluid flow velocity) Next, a method for measuring the vascular sap flow velocity using the vascular sap flow velocity sensor 3 will be described.

[0065] ·attachment First, the vascular sap flow velocity sensor 3 is attached to the shoot end, fruit stalk, or other part of the plant to be measured. Specifically, as shown in Figure 7, all of the probes 20, 30, 40, and 50 of the vascular sap flow velocity sensor 3 are pierced and attached to the plant. At this time, the probes 20, 30, 40, and 50 are positioned along the xylem XY and phloem PH of the plant. When measuring the flow velocity of the phloem sap, the tips of the probes 20, 30, 40, and 50 are positioned in the phloem PH. When measuring the flow velocity of the xylem sap, the tips of the probes 20, 30, 40, and 50 are positioned in the xylem XY. Below, an example of measuring the flow velocity of the xylem sap is explained.

[0066] The water-sensitive film 33 only needs to be formed in an area that covers at least the readout electrode pair 31. However, it is preferable that the water-sensitive film 33 be provided from the position where the readout electrode pair 31 is located to the base end of the water content probe 30. It is even more preferable that the water-sensitive film 33 be provided so as to cover a portion of the upper surface of the support part 10 from the base end of the water content probe 30. In this way, a portion of the water-sensitive film 33 is positioned outside the plant.

[0067] The water-sensitive membrane 33 absorbs water according to the amount of water in the plant. To detect a decrease in water content in the plant, the water that the water-sensitive membrane 33 has absorbed must be dehydrated. If a portion of the water-sensitive membrane 33 is placed outside the plant, dehydration is promoted from this portion that is exposed to the outside air. As dehydration from the water-sensitive membrane 33 is smooth, the response speed when the water content decreases becomes faster.

[0068] Moisture content measurement (impedance method) When the water content probe 30 is inserted into a plant, the water in the plant is absorbed by the water-sensitive film 33. The amount of water absorbed by the water-sensitive film 33 changes depending on the amount of water in the plant. Also, the impedance between the electrodes 32, 32 that make up the readout electrode pair 31 changes depending on the amount of water absorbed by the water-sensitive film 33.

[0069] The relationship between the impedance Z [kΩ] between the electrodes 32 and 32 and the water content WC [%] of the plant is expressed by equation (6), where Z0 is the impedance [kΩ] when the water-sensitive film 33 does not absorb water, and B is a coefficient representing the sensitivity of the sensor.

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[0070] Z0 and B are determined in advance by testing. When measuring the water content of a plant, the impedance Z between the electrodes 32, 32 is measured. Then, the water content WC of the plant is calculated from the measured impedance Z based on equation (6).

[0071] Moisture content measurement (capacitance method) As the amount of water absorbed by the water-sensitive film 33 increases, the capacitance between the electrodes 32, 32 that make up the readout electrode pair 31 also increases. In particular, if the material of the water-sensitive film 33 is appropriately selected, there is a linear relationship between the amount of water absorbed by the water-sensitive film 33 and the capacitance between the electrodes 32, 32. This relationship is determined in advance through testing. When measuring the water content of a plant, the capacitance C between the electrodes 32, 32 is measured. Then, based on the relationship between the capacitance and the water content, the water content WC of the plant is calculated from the measured capacitance C.

[0072] As described above, the water content of a plant can be measured by inserting water content probe 30 into the plant and reading out the impedance or capacitance from readout electrode pair 31.

[0073] Electrical conductivity compensation The measured water content value obtained by the water content probe 30 depends on the electrical conductivity of the water in the plant. Therefore, it is preferable to compensate the measured water content value with the electrical conductivity. The electrical conductivity of the water (mainly xylem sap) in the plant can be measured by the electrical conductivity electrode pair 41 of the electrical conductivity probe 40. The measured water content value is compensated based on the electrical conductivity measured by the electrical conductivity probe 40. This allows the water content of the plant to be measured with high accuracy.

[0074] For example, when determining the water content from the impedance between electrodes 32, 32, the sensor sensitivity coefficient B in equation (6) is calculated in advance using solutions with various electrical conductivities. When measuring the water content of a plant, the electrical conductivity of the water inside the plant is measured at the same time. The plant's water content WC is calculated from the impedance Z based on equation (6), which applies the sensor sensitivity coefficient B corresponding to the measured electrical conductivity. In this way, the measured water content can be compensated by calculating the sensor sensitivity coefficient B from the measured electrical conductivity.

[0075] Furthermore, the sensor sensitivity coefficient B is linearly dependent on the electrical conductivity σ. Therefore, the impedance Z is measured in advance using the moisture content probe 30 using solutions with various electrical conductivities σ to determine the sensor sensitivity coefficient B in equation (6), and the relationship between the electrical conductivity σ and the sensor sensitivity coefficient B is fitted with a linear function. In other words, the coefficients a and b are determined in advance in the relationship between the electrical conductivity σ and the sensor sensitivity coefficient B, expressed by equation (7) below.

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[0076] When measuring the water content of a plant, the impedance Z is measured using the water content probe 30, and the electrical conductivity σ is measured using the electrical conductivity probe 40. The sensor sensitivity coefficient B is calculated from the measured electrical conductivity value σ based on equation (7). The plant water content WC is calculated from the impedance Z based on equation (6) to which the calculated sensor sensitivity coefficient B is applied.

[0077] Similarly, when determining the water content from the capacitance between the electrodes 32, 32, solutions of various electrical conductivities are used to determine in advance the relationship between the amount of water absorbed by the water-sensitive film 33 and the capacitance between the electrodes 32, 32. When measuring the water content of the plant, the electrical conductivity of the water in the plant is measured at the same time. Based on the water content-capacitance relationship corresponding to the measured electrical conductivity, the water content WC of the plant is determined from the capacitance C.

[0078] ·Temperature compensation The electrical conductivity measurements obtained by the electrical conductivity probe 40 depend on temperature. Generally, electrical conductivity measurements change by 1 to 3% per 1°C. Therefore, it is preferable to temperature compensate the electrical conductivity measurements. The temperature of the water (mainly xylem sap) within the plant can be measured by the third temperature sensor 51 of the temperature probe 50. The electrical conductivity measurements are compensated based on the temperature measured by the temperature probe 50. This allows the electrical conductivity of the water within the plant to be determined with high accuracy. The water content can be determined with high accuracy by further compensating the water content measurement using the temperature-compensated electrical conductivity.

[0079] Temperature compensation of the measured electrical conductivity is performed, for example, by the following procedure: Based on equation (8), the measured electrical conductivity is converted to the electrical conductivity σ at a reference temperature of 25°C. 25 where β is the temperature coefficient, T is the temperature of the liquid being measured [°C], and σ is the measured electrical conductivity [S / m].

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[0080] The temperature coefficient β is calculated using equation (9), where T1 is a temperature [°C] other than 25°C and T2, T2 is a temperature [°C] other than 25°C and T1, σ1 is the measured electrical conductivity [S / m] at T1, and σ2 is the measured electrical conductivity [S / m] at T2.

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[0081] When the water-sensitive film 33 is made of polyimide, the moisture content measured by the moisture content probe 30 is independent of temperature. However, when the water-sensitive film 33 is made of another material, the moisture content measurement may be temperature dependent. In such cases, the moisture content measurement may be temperature compensated. That is, the moisture content measurement is directly compensated based on the temperature measured by the temperature probe 50. This allows for accurate measurement of the moisture content.

[0082] ·Vessel liquid flow rate measurement The measurement of the xylem liquid flow velocity is basically the same as in the first embodiment. That is, power is intermittently supplied to the heater 22 of the heated temperature probe 20, and the temperature rise ΔT of the xylem liquid due to heating by the heater 22 is measured. u is measured by the first temperature sensor 21. Then, the temperature rise ΔT u Calculate the xylem sap flow velocity u from

[0083] Here, the xylem sap flow velocity u and the heat pulse velocity V h There is a relationship between these two as shown in equation (10). b is the dry density of the vessel [g / cm 3 ], ρ s is the density of the xylem sap [g / cm 3 ], WC is the moisture content [%], c s is the specific heat capacity of the vessel when dry [J / gK], c dw is the specific heat capacity of the vessel fluid [J / gK]. b , ρ s , c s , c dw is a constant that depends on the plant to be measured and is determined in advance by experiment or the like.

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[0084] That is, the coefficient α in equation (3) depends on the water content WC, as shown in equation (11).

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[0085] Therefore, the coefficient α is calculated from the measured water content WC based on equation (11). Using this value of α, the xylem sap flow velocity u is calculated based on equation (3). That is, the temperature rise ΔT measured by the heater-equipped temperature probe 20 is calculated based on the coefficient α. u In addition, the vascular sap flow velocity u is calculated based on the water content WC measured by the water content probe 30. In this way, by taking the water content into consideration, the vascular sap flow velocity u can be measured with high accuracy.

[0086] Natural temperature gradient compensation The natural temperature gradient can be measured by the third temperature sensor 51 of the temperature probe 50. That is, the natural temperature gradient ΔT2 is calculated from the measurement value (plant temperature) of the third temperature sensor 51. The natural temperature gradient ΔT2 is used to correct the temperature rise ΔT1. This is the same as in the second embodiment. By calculating the vascular sap flow velocity taking into account the natural temperature gradient calculated from the plant temperature, robustness to the external environment can be improved. [Example]

[0087] (thermal analysis) A thermal analysis of the vascular sap flow velocity sensor was performed using the modeling software ANSYS. Figure 9(A) shows the analysis model. The vascular sap flow velocity sensor only has a heated temperature probe. The heated temperature probe is equipped with a filament heater with a resistance of 130 Ω. The tip of the heated temperature probe was inserted into a 3 mm diameter tube that resembled a plant. Water was flowed through the tube.

[0088] After supplying 45.2 mW of power to the filament heater for 30 seconds, the power supply was stopped for 150 seconds. Figure 9(B) shows the temperature distribution when power is supplied to the filament heater. The temperature rise ΔT was calculated from the difference between the water temperature at the start of heating by the heater and the water temperature at the end of heating. u Calculate the heat pulse velocity V according to equation (1). h where the thermal diffusivity D is the value of water, 1.47 × 10 -7 m 2 / s.

[0089] The flow rate of the water flowing through the tube was changed in the range of 0 to 4 mm / s, and the heat pulse velocity V was measured using the above procedure. h The calculated heat pulse velocity V h The correction coefficient for equation (2) was determined by analyzing the above. As a result, the correction coefficient for equation (2) was determined as a = 0.78 × 10 2 , b=-1.47×10 3 , c=7.84×10 3 It was decided.

[0090] The corrected heat pulse velocity V c Figure 10 shows the relationship between the flow velocity and the vascular sap velocity. From Figure 10, it was confirmed that the vascular sap flow velocity sensor can measure changes in flow velocity in the range of 0 to 4 mm / s.

[0091] (Sensor manufacturing) Next, we fabricated a vascular sap flow velocity sensor with the configuration shown in Figure 1. First, a wet oxidation treatment was performed for two hours to form an oxide film on the surface of the silicon wafer, which served as an insulating layer. Next, a 0.04 μm thick Cr layer was applied as an adhesive layer on top of the insulating layer, and a 0.2 μm thick corrosion-resistant Au layer was formed on top of the adhesive layer by sputtering. Next, the resistance temperature sensor and a filament heater with a resistance of 130 Ω were patterned, and photoresist (SU-8 3005) was patterned as a protective film for the wiring. Finally, a needle-shaped probe was fabricated by dry etching using the resist (PMER) as a mask.

[0092] The support part of the vascular sap flow velocity sensor measures 5mm x 4mm. The heated temperature probe is 3mm long and 480µm wide. The tip of the heated temperature probe is angled at 60°. The support part is packaged in insulating material to reduce the effects of external temperature changes during use.

[0093] (sensor calibration) Next, the fabricated vascular bundle sap flow velocity sensor was calibrated. The tip of the heater-equipped temperature probe was inserted into a 3 mm diameter tube, and water was injected using a syringe pump. 45.2 mW of power was supplied to the filament heater for 30 seconds, and then the power supply was stopped for 150 seconds. The temperature rise ΔT was calculated from the difference between the measured values ​​of the resistance thermometer at the start and end of heating. u Calculate the heat pulse velocity V according to equation (1). h where the thermal diffusivity D is the value of water, 1.47 × 10 -7 m 2 / s.

[0094] The flow rate of the water flowing through the tube was changed in the range of 0 to 4 mm / s, and the heat pulse velocity V was measured using the above procedure. h The calculated heat pulse velocity V h The correction coefficient for equation (2) was determined by analyzing the above. As a result, the correction coefficient for equation (2) was determined as a = 1.10 × 10 2 , b=-3.10×10 3 , c=2.35×10 4 It was decided.

[0095] Figure 11 shows the corrected heat pulse velocity V c Figure 11 shows the relationship between the flow velocity and the vascular sap velocity. From Figure 11, it was confirmed that the vascular sap flow velocity sensor can measure changes in flow velocity in the range of 0 to 4 mm / s.

[0096] (Measurement under growing conditions) Next, we measured the water content of tomatoes (Solanum lycopersicum L.) in a natural growing environment. Seeds were sown in potting soil (420036, DCM Holdings Co., Ltd.) and grown in a climate chamber (NC-410HC, Nippon Medical and Chemical Machinery Manufacturing Co., Ltd.). A vascular sap flow rate sensor was attached to the stem of the tomato. The sensor was attached 150 mm from the soil surface. The environment inside the climate chamber was set to a temperature of 25°C, humidity of 50%, and a carbon dioxide concentration of 500 ppm. The light intensity inside the climate chamber was adjusted to match the actual time.

[0097] The time change in xylem sap flow velocity measured with the vascular sap flow velocity sensor is shown in Figure 12. Figure 12 confirms that the xylem sap flow velocity changes depending on the amount of light. This is thought to be because an increase or decrease in light intensity (promotion / inhibition of transpiration) changes the way water is absorbed from the culture soil, causing a change in the xylem sap flow velocity. This confirms that the vascular sap flow velocity sensor can measure the vascular sap flow velocity of plants in real time without destructive damage. [Explanation of symbols]

[0098] 1, 2, 3 Vascular bundle sap flow velocity sensor 10 Support part 11 Second temperature sensor 20 Heated temperature probe 21 First temperature sensor 22 Heater 30 Moisture Probes 31 readout electrode pair 33 Water sensitive membrane 40 Electrical Conductivity Probe 41 Electrical conductivity electrode pair 50 temperature probes 51 Third temperature sensor

Claims

1. a heater-equipped temperature probe provided with a first temperature sensor and a heater; a moisture content probe provided with a readout electrode pair consisting of a pair of electrodes arranged at a predetermined interval and a water-sensitive film spanning the pair of electrodes; a support portion that supports a base end portion of the heater-equipped temperature probe and a base end portion of the moisture content probe while the heater-equipped temperature probe and the moisture content probe are arranged in parallel, The water-sensitive film extends from the portion where the read electrode pair is disposed to the base end of the moisture content probe, and extends from the base end to cover a partial area of ​​the support portion. A vascular bundle sap flow velocity sensor characterized by:

2. A second temperature sensor is provided to measure the outside air temperature.

2. The vascular sap flow velocity sensor according to claim 1.

3. an electrical conductivity probe provided with an electrical conductivity electrode pair consisting of a pair of electrodes arranged at a predetermined interval; The electrical conductivity probe is supported at its base end by the support in a state where it is aligned parallel to the moisture content probe.

3. The vascular sap flow velocity sensor according to claim 1 or 2.

4. a temperature probe provided with a third temperature sensor; The temperature probe is supported at its base end by the support part in a state where it is aligned in parallel with the heater-equipped temperature probe.

4. The vascular sap flow velocity sensor according to claim 1, wherein the sensor is a sensor for detecting a flow rate of a vascular sap.

5. The vascular sap flow velocity sensor according to any one of claims 1 to 4, a power supply that intermittently supplies power to the heater of the heated temperature probe; a calculation unit that calculates a vascular bundle sap flow rate based on the temperature rise of the vascular bundle sap due to heating by the heater, the temperature rise being measured by the first temperature sensor of the heater-equipped temperature probe; A vascular bundle sap flow velocity measuring device characterized by:

6. The heater-equipped temperature probe and the water content probe of the vascular sap flow velocity sensor according to any one of claims 1 to 4 are inserted into a plant, intermittently supplying power to the heater of the heated temperature probe; measuring the temperature rise of the vascular bundle sap caused by heating by the heater of the heater-equipped temperature probe with the first temperature sensor; Calculate the vascular sap flow rate based on the temperature rise A method for measuring vascular sap flow velocity.

7. measuring the impedance or capacitance between the pair of electrodes constituting the readout electrode pair of the moisture content probe; determining the water content of the plant from the impedance or capacitance measurements; Calculating the vascular sap flow rate based on the increased temperature and the water content 7. The method for measuring vascular sap flow velocity according to claim 6.

8. The water content probe and the electrical conductivity probe of the vascular sap flow velocity sensor according to claim 3 are inserted into a plant, measuring the impedance or capacitance between the pair of electrodes constituting the readout electrode pair of the moisture content probe; determining the water content of the plant from the impedance or capacitance measurements; determining electrical conductivity from the electrical resistance between the pair of electrodes constituting the electrical conductivity electrode pair; Electrical conductivity measurements are used to compensate moisture content measurements A method for measuring vascular sap flow velocity.

9. A natural temperature gradient is calculated from the temperature of the plant or the outside air temperature; Correcting the elevated temperature using the natural temperature gradient 8. The method for measuring vascular sap flow velocity according to claim 6 or 7.

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