WO2023074362A1

WO2023074362A1 - Vascular sap flow rate sensor, vascular sap flow rate measuring device, and vascular sap flow rate measuring method

Info

Publication number: WO2023074362A1
Application number: PCT/JP2022/037981
Authority: WO
Inventors: 房男下川; 郁也飯尾
Original assignee: 国立大学法人香川大学
Priority date: 2021-10-25
Filing date: 2022-10-12
Publication date: 2023-05-04
Also published as: JP2023063920A

Abstract

Provided are a vascular sap flow rate sensor, a vascular sap flow rate measuring device, and a vascular sap flow rate measuring method that cause little mechanical or thermal damage to a plant.　A vascular sap flow rate sensor (1) includes, as a probe that pierces the plant, only a heater-attached temperature probe (20) provided with a first temperature sensor (21) and a heater (22). The vascular sap flow rate measuring device includes: the vascular sap flow rate sensor (1); a power source for supplying power intermittently to the heater (22); and a calculating unit for obtaining a vascular sap flow rate on the basis of a rising temperature of vascular sap resulting from heating by the heater (22), said rising temperature being measured by the first temperature sensor (21). Since the only probe that pierces the plant is the heater-attached temperature probe (20), 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.

Description

Vascular Fluid Flow Velocity Sensor, Vascular Fluid Flow Velocity Measuring Device, and Vascular Fluid Flow Velocity Measuring Method

The present invention relates to a vascular bundle liquid flow velocity sensor, a vascular bundle liquid flow velocity measuring device, and a vascular bundle liquid flow velocity measuring method. More particularly, the present invention relates to sensors, devices and methods for measuring the flow rate of vascular fluid through plant details such as plant shoot ends, fruit stalks, and the like.

In the production of crops and fruit trees, from the perspective of productivity, it is desirable to irrigate and supply nutrients at the appropriate time according to the growth conditions of the plants. However, in many agricultural fields, the current situation is that irrigation and nutrient supply are carried out based on experience and intuition based on the number of days without rain. Such empirical methods require skill and are laborious and time consuming. In addition, since the standard index is based on personal experience, it is difficult for everyone to easily implement it.

In recent years, there has been an active movement to introduce information technology into agriculture, such as smart agriculture. It is expected that information technology will enable optimal production based on the physiological information of plants without relying on humans.

Physiological information of plants required for irrigation management is vascular flux flow rate. In particular, in order to improve the productivity and quality of crops and fruit trees, it is important to measure the vascular fluid flow velocity in details of plants such as shoot ends and fruit stalks. A sensor for measuring vascular fluid flow velocity in plant details has already been proposed (US Pat.

JP 2015-145810 A

The sensor disclosed in Patent Document 1 measures the vascular fluid flow rate by the Granier method. In the Granier method, it is necessary to pierce the plant with two probes and constantly heat the vascular fluid with a heater. Therefore, mechanical and thermal damage to plants is great.

In addition to the Granier method, the heat pulse method is also known as a method for measuring the vascular flux flow velocity. Since the heat pulse method applies heat intermittently, the heat damage given to plants is small. However, the heat pulse method requires three probes to be pierced into the plant to measure the vascular fluid flow rate, which causes greater mechanical damage to the plant than the Granier method.

In view of the above circumstances, it is an object of the present invention to provide a vascular bundle liquid flow velocity sensor, a vascular bundle liquid flow velocity measuring device, and a vascular bundle liquid flow velocity measuring method that cause less damage to plants mechanically or thermally.

The vascular bundle liquid flow rate sensor of the first aspect is characterized in that it has only a heater-equipped temperature probe provided with a first temperature sensor and a heater as a probe to be pierced into the plant.
The vascular bundle liquid flow rate sensor of the second aspect is characterized in that, in the first aspect, it has a second temperature sensor that measures the ambient temperature.
A vascular bundle liquid flow rate measuring device according to a third aspect comprises a vascular bundle liquid flow rate sensor having a heater-equipped temperature probe provided with a first temperature sensor and a heater, a support portion supporting the heater-equipped temperature probe, and characterized by comprising a power source that intermittently supplies power to a heater, and a computing unit that obtains a vascular bundle fluid flow rate based on the temperature rise of the vascular bundle fluid due to heating of the heater measured by the first temperature sensor. do.
The vascular bundle liquid flow rate measuring device of the fourth aspect is characterized in that, in the third aspect, it is equipped with a second temperature sensor that measures the outside air temperature.
A fifth aspect of the vascular bundle fluid flow velocity measuring device is the third or fourth aspect, wherein the vascular bundle fluid flow velocity sensor comprises a pair of readout electrodes arranged at a predetermined interval; a moisture content probe provided with a water-sensitive membrane that spans electrodes, and the moisture content probe is supported by the support part in a state of being aligned in parallel with the temperature probe with heater. Characterized by
A sixth aspect of the vascular bundle liquid flow rate measuring device is the fifth aspect, wherein the vascular bundle liquid flow rate sensor is provided with an electrical conductivity electrode pair consisting of a pair of electrodes arranged at a predetermined interval. a conductivity probe, and the electrical conductivity probe is supported by the supporting portion in a state of being aligned in parallel with the moisture content probe.
The vascular bundle liquid flow rate measuring device of the seventh aspect is the vascular bundle liquid flow rate measuring device according to any one of the third to sixth aspects, wherein the vascular bundle liquid flow rate sensor has a temperature probe provided with a third temperature sensor, and the temperature probe is the It is characterized in that it is supported by the support portion while being aligned in parallel with the temperature probe with heater.
The vascular bundle liquid flow velocity measuring method of the eighth aspect includes piercing a plant with a heater-equipped temperature probe provided with a first temperature sensor and a heater, intermittently supplying power to the heater, and heating the vascular bundle by heating the heater. The method is characterized in that the temperature rise of the liquid is measured by the first temperature sensor, and the vascular bundle liquid flow velocity is obtained based on the temperature rise.
A vascular bundle liquid flow velocity measuring method of a ninth aspect is the eighth aspect, wherein a reading electrode pair consisting of a pair of electrodes arranged at a predetermined interval and a water-sensitive membrane bridged over the pair of electrodes are The water content probe provided is pierced into the plant, the impedance or capacitance between the pair of electrodes constituting the readout electrode pair is measured, and the water content of the plant is determined from the impedance measurement value or the capacitance measurement value. and determining a vascular fluid flow rate based on said elevated temperature and said moisture content.
In the ninth aspect, the vascular bundle liquid flow velocity measuring method of the tenth aspect is characterized by piercing the plant with 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 is obtained from the electrical resistance between the pair of electrodes constituting the electrical conductivity electrode pair, and the electrical conductivity measurement is used to compensate the moisture content measurement.
The vascular bundle liquid flow velocity measuring method of the eleventh aspect is, in any one of the eighth to tenth aspects, obtaining a natural temperature gradient from the temperature of the plant or the ambient temperature, and correcting the elevated temperature using the natural temperature gradient. It is characterized by

According to the first aspect, the only probe that pierces the plant is the heater-equipped temperature probe, so that mechanical damage to the plant can be reduced.
According to the second aspect, it is possible to improve the robustness against the external environment by obtaining the vascular bundle liquid flow velocity in consideration of the natural temperature gradient obtained from the outside air temperature.
According to the 3rd aspect, since the heating by a heater is intermittent, the thermal damage inflicted on a plant can be made small. Further, by piercing a plant with a temperature probe with a heater and acquiring a measurement value of the first temperature sensor, the vascular bundle liquid flow velocity can be measured.
According to the fourth aspect, by obtaining the vascular bundle liquid flow velocity in consideration of the natural temperature gradient obtained from the outside air temperature, the robustness against the external environment can be enhanced.
According to the fifth aspect, the vascular bundle liquid flow velocity can be measured with high accuracy by considering the water content measured by the water content probe.
According to the sixth aspect, the water content of the 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.
According to the seventh aspect, by obtaining the vascular bundle liquid flow velocity in consideration of the natural temperature gradient measured by the third temperature sensor, it is possible to enhance the robustness against the external environment.
According to the eighth aspect, the vascular bundle liquid flow rate can be determined.
According to the ninth aspect, the vascular bundle liquid flow rate can be obtained with high accuracy by considering the plant water content.
According to the tenth aspect, the water content of the plant can be accurately measured by compensating the water content measurement value based on the electrical conductivity of the water in the plant measured by the electrical conductivity probe.
According to the eleventh aspect, by determining the vascular bundle liquid flow rate in consideration of the natural temperature gradient determined from the temperature of the plant or the ambient temperature, the robustness to the external environment can be enhanced.

1 is a plan view of a vascular bundle liquid flow rate sensor according to a first embodiment; FIG. FIG. 2 is a side view of the vascular bundle liquid flow rate sensor according to the first embodiment; FIG. 2 is an explanatory diagram of a usage state of the vascular bundle liquid flow rate sensor according to the first embodiment; 4 is a graph showing temperature changes of vascular fluid. 1 is an explanatory diagram of a vascular bundle liquid flow rate measuring device according to a first embodiment; FIG. FIG. 11 is a plan view of a vascular bundle liquid flow rate sensor according to a second embodiment; FIG. 11 is a plan view of a vascular bundle liquid flow rate sensor according to a third embodiment; 1 is a vertical cross-sectional view of a moisture content probe; FIG. FIG. (A) is a diagram showing an analysis model. FIG. (B) is a temperature distribution map. 4 is a graph showing the relationship between heat pulse velocity and flow velocity obtained by thermal analysis. It is a graph which shows the relationship between the heat pulse velocity calculated|required by the simulated plant test, and the flow velocity. It is a graph which shows the time change of the vessel liquid flow velocity of the tomato under a growing environment.

Next, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
The vascular bundle liquid flow rate sensor 1 according to the first embodiment of the present invention can be attached to details of a plant such as the terminal of a new shoot or fruit stalk. The vascular fluid flow sensor 1 has the function of measuring the flow velocity and volume of vascular fluid (vascular fluid or phloem fluid) in plant details.

(vascular flux sensor)
First, the configuration of the vascular bundle liquid flow rate sensor 1 will be described.
As shown in FIG. 1 , the vascular bundle liquid flow rate sensor 1 has a support portion 10 . A temperature probe 20 with a heater is provided on the supporting portion 10 . The vascular bundle liquid flow velocity sensor 1 is attached to the plant by piercing the plant with the heater-equipped temperature probe 20 .

The supporting portion 10 and the temperature probe 20 with heater are formed by processing a semiconductor substrate. Semiconductor substrates include silicon substrates and SOI (Silicon on Insulator) substrates. In addition to photolithography and etching, MEMS techniques using thin film formation such as sputtering and vapor deposition are used for processing semiconductor substrates. Note that the vascular bundle liquid flow rate sensor 1 may be formed by a method other than the MEMS technology, and the material is not limited to a semiconductor substrate.

Supporting Portion The supporting portion 10 is a member that supports the temperature probe 20 with heater. The supporting portion 10 is a rectangular plate in plan view, and the heater-equipped temperature probe 20 is supported on one side of the supporting portion 10 .

·Temperature Probe with Heater The temperature probe with heater 20 is a bar-shaped member and is provided in a cantilever shape on the edge of the support section 10 . The shape of the tip of the temperature probe 20 with heater is preferably a pointed shape such as a triangle. If the tip of the heater-equipped temperature probe 20 has a sharp shape, it is possible to reduce the penetration resistance when sticking into the details of the plant.

The heater-equipped temperature probe 20 is sized so that it can be placed by piercing into details of a plant, such as the end of a plant's new shoots and fruit stalks, which have a stem diameter or shaft diameter of several millimeters. The length of the heater-equipped temperature probe 20 (the length from the proximal end to the distal end in the axial direction) is such that when the probe is pierced into the details of the plant and installed, the tip is placed in the vessel or phloem of the details of the plant. sized to obtain. The length of the temperature probe 20 with heater is, for example, 0.5 to 5 mm.

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 smaller the mechanical damage to the plant.

As shown in FIG. 2, the vascular bundle liquid flow rate sensor 1 is a thin plate as a whole. The thickness of the heater-equipped temperature probe 20 is set thinner than the width of the vessel and phloem of the plant. The thickness of the heater-equipped temperature probe 20 is, for example, 50 to 300 μm, depending on the type of plant to be measured and the thickness of the stem. If the thickness is 50 μm or more, the strength is sufficient, and there is no risk of breakage when the heater-equipped temperature probe 20 is inserted into or removed from the stem of a plant or the like. In addition, although it depends on the type of plant, the diameter of the vessel and the sieve canal is about 100 to 400 μm. blockage can be suppressed. The thinner the heater-equipped temperature probe 20 is, the less mechanical damage is given to the plant. Therefore, it is more preferable to set the thickness of the temperature probe 20 with heater to 100 μm or less. The thickness of the supporting portion 10 is not particularly limited, and may be the same thickness as the temperature probe 20 with heater, or may be thicker than the temperature probe 20 with heater.

As shown in FIG. 1, a first temperature sensor 21 is provided at the tip of the temperature probe 20 with heater. The first temperature sensor 21 has a function of sensing temperature, and is not particularly limited as long as it has a size that can be arranged at the tip of the temperature probe 20 with heater. As the first temperature sensor 21, a resistance temperature detector, a pn junction diode, a thermocouple, or the like can be used. Since the vascular bundle liquid flow rate sensor 1 is assumed to be used outdoors, it is preferable to use a resistance temperature detector that does not depend on light as the first temperature sensor 21 . Two

electrode pads

21e, 21e connected to the first temperature sensor 21 via wiring are arranged on the upper surface of the supporting portion 10. As shown in FIG.

The resistance temperature detector is formed by depositing a thin film of a metal such as Au, which is suitable as a resistance temperature detector, on a semiconductor substrate by, for example, a sputtering method, a vapor deposition method, or the like. A resistance temperature detector increases its electrical resistance as the temperature rises. A constant current source is connected between the two

electrode pads

21e, 21e. A constant current source is used to supply a constant current to the RTD, and a voltmeter is used to measure the voltage. The temperature can be calculated from the voltage measured by the voltmeter.

A heater 22 is provided in the heater-equipped temperature probe 20 . The position of the heater 22 is not limited to the tip as long as it can supply heat to the temperature probe 20 with heater. The heater 22 is not particularly limited as long as it has a size that can be arranged in the temperature probe 20 with heater. For example, thin films of Au (gold), Pt (platinum), Ti (titanium), Cr (chromium), etc. are formed by sputtering, vapor deposition, etc., and processed into thin thread micro heaters (herein referred to as "filament heaters"). ) can be employed as the heater 22 . Alternatively, a pn junction diode formed using an oxidation diffusion furnace may be employed as the heater 22 .

Two

electrode pads

22e, 22e connected to the heater 22 via wiring are provided on the upper surface of the support portion 10. A DC constant power supply is connected between the two

electrode pads

22e, 22e. Heat can be generated by applying an electric current to the heater 22 .

(Vascular bundle liquid flow rate measurement method)
Next, a method for measuring the vascular bundle liquid flow rate by the vascular bundle liquid flow rate sensor 1 will be described.

- Attachment First, the vascular bundle liquid flow rate sensor 1 is attached to the end of a shoot, fruit stalk, or the like of a plant to be measured. Specifically, as shown in FIG. 3, the temperature probe 20 with heater of the vascular bundle liquid flow velocity sensor 1 is attached by piercing the plant.

When the heater-equipped temperature probe 20 is pierced into the plant, the tip of the heater-equipped temperature probe 20 passes through the cortical layer CO of the plant and reaches the phloem PH. Further, when the tip of the heater-equipped temperature probe 20 is pierced deeply, it reaches the vessel XY and then the pith PI. When measuring the flow velocity of the phloem liquid, the tip of the heater-equipped temperature probe 20 is placed on the phloem PH. When measuring the flow velocity of vessel fluid, the tip of heater-equipped temperature probe 20 is placed in vessel XY. An example of measuring the flow velocity of a vessel fluid will be described below.

Electric power is intermittently supplied to the heater 22 while the temperature probe 20 with heater is pierced into the plant. That is, a pulsed current is supplied to the heater 22 . A time width (pulse width) for supplying power to the heater 22 is predetermined.

When the heater 22 is driven intermittently, the vessel fluid is heated only while the heater 22 is driven. At this time, the temperature of the vessel fluid changes with time as shown in FIG. That is, the temperature of the vascular fluid increases while being heated by the heater 22, and the temperature of the vascular fluid decreases when the heating ends.

Let T ₁ be the temperature of the vessel fluid at the time t ₁ when heating by the heater 22 is started. In addition, the temperature of the vessel fluid at the time _t2 when heating by the heater 22 ends is defined as _T2 . The temperature rise ΔT of the vascular fluid due to heating by the heater 22 is obtained by subtracting T ₁ from T ₂ . Let _T3 be the temperature of the vessel fluid at time _t3 when a predetermined time has passed since the end of heating by the heater 22. The temperature rise ΔT of the vascular fluid due to heating by the heater 22 may be obtained by subtracting _T3 from _T2 . Note that the time from _t2 to _t3 is set to a time during which the temperature of the vessel fluid is sufficiently lowered. In any case, since the temperature of the vessel fluid can be measured by the first temperature sensor 21, the temperature rise .DELTA.T can be obtained from the measured value of the first temperature sensor 21. FIG.

Solving the heat transfer retention 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 vessel fluid [°C], and ΔT ₀ is the temperature rise of the vessel fluid when the flow velocity is 0 [ °C], and t is the heating time [s]. The increased temperature ΔT _u is a measured value obtained by the first temperature sensor 21 . The thermal diffusivity D and the temperature rise ΔT ₀ of the vascular fluid when the flow velocity is 0 are constants depending on the plant to be measured, and are determined in advance by experiments or the like. The heating time t is set to the optimum time for measuring the vascular fluid flow rate depending on the plant. Heating time t is, for example, 20 to 40 seconds.

Since the insertion of the heated temperature probe 20 into the vessel disrupts the flow of vessel fluid, this effect may be corrected. For example, the heat pulse velocity V _c after correction may be obtained based on the following equation (2). In formula (2), a, b, and c are correction coefficients, which are determined in advance by experiments or the like.

The vessel fluid flow velocity u is proportional to the heat pulse velocity. That is, the vascular fluid flow velocity u is obtained by Equation (3). In Equation (3), α is a coefficient, which is determined in advance by experiments or the like. V is the heat pulse velocity V _h before correction or the heat pulse velocity V _c after correction.

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

According to the above principle, the flow velocity u and the flow rate Q of the vascular fluid can be obtained based on the temperature rise ΔT _u of the vascular fluid measured by the first temperature sensor 21 . If the tip of the heater-equipped temperature probe 20 is placed on the phloem PH of the plant, the velocity and flow rate of the phloem sap can be obtained. When monitoring the vascular bundle fluid flow rate for a long period of time, the heater 22 is driven at predetermined intervals, and the vascular bundle liquid flow rate is obtained each time. The interval at which the heater 22 is driven is not particularly limited. If the interval is shortened, the time resolution of the flow velocity can be increased.

In the vascular bundle liquid flow rate sensor 1 of this embodiment, the temperature probe 20 with heater is the only probe that pierces the plant. Since there is no need to pierce the plant with multiple probes, mechanical damage to the plant can be reduced. Moreover, since the heating by the heater 22 is intermittent, it is possible to reduce the thermal damage to the plants as compared with constant heating. Furthermore, since the heater 22 is driven intermittently, the power consumption of the vascular bundle liquid flow velocity sensor 1 can be reduced. For example, the vascular bundle liquid flow rate sensor 1 can be continuously driven by a battery for several months to half a year, which is the plant cultivation period.

(Vascular bundle fluid velocity measuring device)
Next, the vascular bundle liquid flow rate measuring device AA will be described.
As shown in FIG. 5 , the vascular fluid flow velocity measuring device AA has a vascular fluid flow velocity sensor 1 . For example, a plurality of vascular bundle liquid flow velocity sensors 1 are attached to a plurality of plants in an agricultural field. The vascular bundle fluid flow velocity sensor 1 may be attached to a plurality of locations on one plant, or may be attached to all or a portion of specimens of a plurality of plants. Alternatively, only one vascular bundle liquid flow velocity sensor 1 may be provided.

A data logger DR is connected to the vascular bundle fluid flow rate sensor 1 to supply power and collect measured values. A data logger DR supplies power to the heater 22 intermittently. Therefore, the data logger DR corresponds to the "power source" described in the claims. Also, the data logger DR has a built-in wireless communication device.

A server device SV is installed in a building, etc., adjacent to an agricultural site. A wireless communication device is connected to the server device SV, and is configured to be able to wirelessly communicate with the data logger DR.

The data logger DR transmits the measurement data of the vascular bundle fluid flow rate sensor 1 to the server device SV via the wireless communication device. The server device SV analyzes the received measurement data and determines the vascular fluid flow rate. The details are as described above. Therefore, the server device SV corresponds to the "computing section" described in the claims.

The connection between the data logger DR and the server device SV is not limited to wireless, and may be wired. Data accumulated in the data logger DR may be stored in 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 not limited to the server device SV as long as it can obtain the vascular bundle liquid flow velocity.

[Second embodiment]
Next, a vascular bundle liquid flow rate sensor 2 according to a second embodiment of the present invention will be described.
As shown in FIG. 6, the vascular bundle liquid flow rate sensor 2 has a temperature probe 20 with a heater and a support portion 10 as in the first embodiment. The same reference numerals are given to the same members as in the first embodiment, and the description thereof is omitted.

A second temperature sensor 11 is provided on the support portion 10 . A sensor similar to the first temperature sensor 21 can be employed as the second temperature sensor 11 . Two

electrode pads

11e, 11e connected to the second temperature sensor 11 via wiring are arranged on the upper surface of the supporting portion 10. As shown in FIG. The temperature can be measured by the second temperature sensor 11 in the same manner as the first temperature sensor 21 .

The second temperature sensor 11 is for measuring the outside air temperature around the plant. Heat insulation is provided between the heater-equipped temperature probe 20 and the second temperature sensor 11 so that the heat of the heater 22 is less likely to be transmitted to the second temperature sensor 11 .

For example, the vascular flux sensor 2 is formed by processing an SOI substrate consisting of a support substrate (Si), an oxide film layer (SiO ₂ ) and an active layer (Si). A first temperature sensor 21, a heater 22 and a second temperature sensor 11 are formed on the surface of the active layer. Then, the active layer between the heater-equipped temperature probe 20 and the second temperature sensor 11 is removed so that an oxide film layer is interposed therebetween. Thereby, heat insulation can be provided between the temperature probe 20 with heater and the second temperature sensor 11 .

(natural temperature gradient correction)
A natural temperature gradient occurs when a heater is activated in a greenhouse where plants are grown, or when sunlight or wind changes around the plants. A natural temperature gradient affects the measurement value of the first temperature sensor 21, degrading the measurement accuracy of the vascular fluid flow rate. Therefore, in this embodiment, the outside air temperature measured by the second temperature sensor 11 is used to correct the influence of the natural temperature gradient.

As described above, the heater 22 is intermittently driven when measuring the vascular fluid flow rate. Then, the temperature rise ΔT ₁ of the vascular bundle fluid due to heating by the heater 22 is measured by the first temperature sensor 21 . At the same time, the second temperature sensor 11 measures the natural temperature gradient ΔT ₂ . If the temperature rise ΔT ₁ is the difference in the measured values of the first temperature sensor 21 between t ₁ and _{t 2} , then the natural temperature gradient ΔT ₂ is the difference in the measured values of the second temperature sensor 11 between t ₁ and _{t 2} . is required as If the temperature rise ΔT ₁ is the difference in the measured values of the first temperature sensor 21 between t ₂ and _{t 3} , then the natural temperature gradient ΔT ₂ is the difference in the measured values of the second temperature sensor 11 between t ₂ and _{t 3} . is required as

Then, as shown in equation (5), the temperature rise ΔT ₁ is corrected using the natural temperature gradient ΔT ₂ .

If the heat pulse velocity V _h is obtained according to the equation (1) using the corrected temperature rise ΔT _u , the vascular bundle liquid flow velocity can be obtained by removing the influence of the natural temperature gradient. Thus, the robustness against the external environment can be enhanced by obtaining the vascular bundle liquid flow velocity in consideration of the natural temperature gradient obtained from the outside air temperature.

Note that the second temperature sensor 11 may not be provided on the support portion 10. That is, a temperature sensor physically independent of the temperature probe 20 with heater may be used as the second temperature sensor 11 . Therefore, the second temperature sensor may be a separate member from the vascular bundle liquid flow velocity sensor.

[Third embodiment]
Next, a vascular bundle liquid flow rate sensor 3 according to a third embodiment of the present invention will be described.
As shown in FIG. 7, the vascular bundle liquid flow rate sensor 3 is obtained by adding a moisture content probe 30, an electrical conductivity probe 40 and a temperature probe 50 to the vascular bundle liquid flow rate sensor 1 of the first embodiment. Since the rest of the configuration is the same as that of the first embodiment, the same reference numerals are assigned to the same members and the description thereof is omitted.

The water content probe 30 is used to measure the water content of plants. The measured water content is used to compensate for the vascular flux measurements. If no moisture content compensation is required, the vascular fluid flow rate sensor 3 may not be provided with the moisture content probe 30 . Electrical conductivity probe 40 is used to measure the electrical conductivity of water in plants. The measured electrical conductivity is used to compensate for moisture content measurements. If compensation by electrical conductivity is not required, the electrical conductivity probe 40 may not be provided in the vascular bundle liquid flow rate sensor 3 . The temperature probe 50 is used for temperature measurement of plants. The measured temperature is used to compensate for some or all of the vascular flux measurements, moisture content measurements and electrical conductivity measurements. The temperature probe 50 may not be provided in the vascular bundle liquid flow rate sensor 3 when there is no need for temperature compensation.

The base ends of the

probes

20, 30, 40, and 50 are supported on one side of the support portion 10 while being arranged in parallel on the same plane. The order in which the

probes

20, 30, 40, and 50 are arranged is not particularly limited. However, the temperature probe 50 is preferably arranged at a position distant from the temperature probe 20 with heater. This makes it difficult for the heat of the heater 22 to be conducted to the temperature probe 50, so that the natural temperature gradient can be accurately measured. For example, it is preferable to arrange the temperature probe 20 with heater, the moisture content probe 30, the electrical conductivity probe 40, and the temperature probe 50 in this order.

Moisture Content Probe A reading 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 interval. Two

electrode pads

32e, 32e connected to the two

electrodes

32, 32 via wiring are arranged on the upper surface of the support portion 10. As shown in FIG. Also, the water content probe 30 is provided with a water sensitive film 33 .

When the water content probe 30 is pierced into the plant, the water inside the plant is absorbed by the water-sensitive membrane 33 . The amount of water absorbed by the water-sensitive film 33 is read out as impedance or capacitance between the

electrodes

32,32. This allows the water content of the plant to be measured.

As shown in FIG. 8, a pair of

electrodes

32, 32 are formed on the surface of the semiconductor substrate SS that constitutes the moisture content probe 30. As shown in FIG. The size of the electrode 32 is not particularly limited as long as it has a size that can be arranged at the tip of the moisture content probe 30 . The electrode 32 is formed, for example, by depositing a metal thin film such as Au or Al on the semiconductor substrate SS by sputtering, vapor deposition, or the like.

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 a function of absorbing water and is made of a material having a dielectric constant lower than that of water. As used herein, the term "water-sensitive film" means a film having a function of absorbing moisture and formed of a material having a lower relative dielectric constant than water. Since the dielectric constant of water at a temperature of 20.degree. However, the relative permittivity of the water-sensitive film 33 is preferably 1 to 3, because the larger the difference between the relative permittivity of the water-sensitive film 33 and the relative permittivity of water, the higher the accuracy of measurement of the water content.

The material of the water-sensitive film 33 is preferably insoluble in water and thermally and chemically stable. Lithium chloride, metal oxides, ceramics, polymer materials, and the like can be used as materials for the water sensitive film 33 . However, since lithium chloride is toxic to plants, it cannot be said to have excellent applicability to plants. Metal oxides and ceramics include aluminum oxide (Al ₂ O ₃ ) and silicon dioxide (SiO ₂ ). Metal oxides and ceramics are insoluble in water. However, metal oxides and ceramics are hard materials and require high-temperature heat treatment during the manufacturing process. On the other hand, polymer materials have excellent applicability to plants and are soft. Examples of polymer materials include polyimide and polyvinyl alcohol. Among these, polyimide is preferable from the viewpoint of ease of mounting on a semiconductor Si substrate. In addition, since polyimide does not easily dissolve in water, it is suitable for long-term measurement of water content in plants. Therefore, if the water-sensitive film 33 is made of polyimide, the water-sensitive film 33 is difficult to dissolve in the water in the plant, and long-term measurement is possible.

When forming the water-sensitive film 33 with 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 the water in the plant, thereby increasing the response speed of the 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 treated with oxygen plasma. When the surface of polyimide is treated with oxygen plasma, carbonyl groups are introduced to make the surface of polyimide hydrophilic. There is also the effect of increasing the surface area of polyimide. Since the surface area of the water-sensitive membrane 33 increases as the water-sensitive membrane 33 becomes hydrophilic, the moisture in the plant is easily absorbed by the water-sensitive membrane 33, and the response speed of water content measurement increases.

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 interval. The electrical conductivity electrode pair 41 is for measuring the electrical conductivity of moisture (such as vascular fluid) present between the

electrodes

42,42. The size of the electrode 42 is not particularly limited as long as it has a size that can be arranged at the tip of the electrical conductivity probe 40 . The electrode 42 is formed, for example, by depositing a metal thin film such as Au or Al on the semiconductor substrate SS by sputtering, vapor deposition, or the like.

Two

electrode pads

42e, 42e connected to the two

electrodes

42, 42 via wiring are provided on the upper surface of the support portion 10. Electrical conductivity can be measured by the AC two-electrode method. That is, between a pair of

electrode pads

42e, 42e corresponding to the pair of

electrodes

42, 42, an AC power supply and an ammeter are connected in series. A current is supplied between the

electrodes

42, 42 with an AC power source, and the current flowing between the

electrodes

42, 42 is measured with an 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 obtained from the electrical resistance.

　In order to measure the electrical conductivity of water in plants, it is preferable that the electrical conductivity measurement range is at least 0 to 10 mS/cm. The measurement range of electrical conductivity by the AC two-electrode method depends on the cell constant K of the electrode pair. Here, the cell constant K is obtained by dividing the distance L between the electrodes by the surface area S of the electrodes. That is, the electrical conductivity measurement range 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-teeth electrode, and a planar electrode.

- Temperature probe A third temperature sensor 51 is provided at the tip of the temperature probe 50 . A sensor similar to the first temperature sensor 21 can be employed as the third temperature sensor 51 . Two

electrode pads

51e, 51e connected to the third temperature sensor 51 via wiring are arranged on the upper surface of the supporting portion 10. As shown in FIG. The temperature can be measured by the third temperature sensor 51 in the same manner as the first temperature sensor 21 .

The moisture content probe 30, electrical conductivity probe 40, and temperature probe 50 may be configured as separate probes, or a part or all of them may be configured as a single probe. For example, the electrical conductivity electrode pair 41 and the third temperature sensor 51 may be mounted on one probe, and the electrical conductivity probe 40 and the temperature probe 50 may be integrated.

(Vascular bundle liquid flow rate measurement method)
Next, a method for measuring the vascular bundle liquid flow rate by the vascular bundle liquid flow rate sensor 3 will be described.

- Attachment First, the vascular bundle liquid flow rate sensor 3 is attached to the shoot end, fruit stalk, or the like of the plant to be measured. Specifically, as shown in FIG. 7, all the

probes

20, 30, 40, 50 of the vascular bundle liquid flow velocity sensor 3 are attached by piercing the plant. At this time, probes 20, 30, 40, 50 are placed along vessel XY and phloem PH of the plant. When measuring the flow velocity of the sieve canal, the tips of the

probes

20, 30, 40, 50 are placed on the sieve canal PH. When measuring the flow rate of vessel fluid, the tips of

probes

20, 30, 40, 50 are placed in vessel XY. An example of measuring the flow velocity of a vessel fluid will be described below.

By the way, the water-sensitive film 33 only needs to be formed in a region covering at least the readout electrode pair 31 . However, it is preferable that the water-sensitive film 33 is provided from the arrangement portion of the readout electrode pair 31 to the proximal end portion of the moisture content probe 30 . Moreover, it is more preferable that the water-sensitive film 33 is provided so as to cover a part of the upper surface of the support portion 10 from the base end portion of the moisture content probe 30 . In this way, part of the water-sensitive membrane 33 is arranged outside the plant.

The water-sensitive film 33 absorbs water according to the amount of water in the plant. In order to capture the decrease in water in the plant, it is necessary to dehydrate the water absorbed by the water-sensitive membrane 33 . If part of the water-sensitive membrane 33 is arranged outside the plant, dehydration is promoted from this part exposed to the outside air. Since dehydration from the water-sensitive film 33 is smoothly performed, the response speed when the water content decreases is increased.

・Measurement of moisture content (impedance method)
When the water content probe 30 is pierced into the plant, water in the plant is absorbed by the water sensitive membrane 33 . The amount of water absorbed by the water-sensitive film 33 changes according to the amount of water in the plant. Also, the impedance between the

electrodes

32 , 32 forming the readout electrode pair 31 changes according to the amount of water absorbed by the water-sensitive film 33 .

The relationship between the impedance Z [kΩ] between the

electrodes

32, 32 and the water content WC [%] of the plant is represented by Equation (6). In equation (6), Z ₀ is the impedance [kΩ] when the water-sensitive film 33 does not absorb moisture, and B is a coefficient representing the sensitivity of the sensor.

Z ₀ and B are determined in advance by testing. The impedance Z between the

electrodes

32, 32 is measured when measuring the water content of the plant. Then, the water content WC of the plant is obtained from the impedance measurement value Z based on Equation (6).

・Measurement of moisture content (method using capacitance)
There is a relationship that when the amount of water absorbed by the water-sensitive film 33 increases, the capacitance between the electrodes 32 constituting the readout electrode pair 31 increases. In particular, if the material of the water-sensitive film 33 is appropriately selected, the amount of water absorbed by the water-sensitive film 33 and the capacitance between the

electrodes

32, 32 have a linear relationship. This relationship is obtained in advance by testing. The capacitance C between the

electrodes

32, 32 is measured when measuring the water content of the plant. Then, the water content WC of the plant is obtained from the capacitance measurement value C based on the relationship between the capacitance and the water content.

As described above, the water content of the plant can be measured by piercing the water content probe 30 into the plant and reading the impedance or capacitance from the readout electrode pair 31 .

• Electrical Conductivity Compensation The water content measurements obtained by the water content probe 30 are dependent on the electrical conductivity of water within the plant. Therefore, it is preferable to compensate the moisture content measurements with electrical conductivity. The electrical conductivity of the water (mainly vascular fluid) in the plant can be measured by the electrical conductivity electrode pair 41 of the electrical conductivity probe 40 . The moisture content measurements are compensated based on the conductivity measured by the conductivity probe 40 . Thereby, the water content of the plant can be measured with high accuracy.

For example, when determining the water content from the impedance between the

electrodes

32, 32, the sensor sensitivity coefficient B in the formula (6) is determined in advance using solutions with various electric conductivities. When measuring the water content of the plant, the electric conductivity of the water inside the plant is measured at the same time. The water content WC of the plant is determined from the impedance Z based on equation (6) applying the sensor sensitivity coefficient B corresponding to the measured electrical conductivity. Thus, by determining the sensor sensitivity coefficient B from the electrical conductivity measurement, the moisture content measurement can be compensated.

Also, the sensor sensitivity coefficient B linearly depends on the electrical conductivity σ. Therefore, the impedance Z is measured in advance by the moisture content probe 30 using solutions with various electric conductivities σ, and the sensor sensitivity coefficient B in the equation (6) is obtained, and the electric conductivity σ and the sensor sensitivity coefficient B is fitted with a linear function. That is, the coefficients a and b of the relational expression between the electric conductivity σ and the sensor sensitivity coefficient B expressed by the following equation (7) are obtained.

When measuring the water content of the plant, the water content probe 30 measures the impedance Z and the electrical conductivity probe 40 measures the electrical conductivity σ. Based on equation (7), the sensor sensitivity coefficient B is obtained from the electrical conductivity measurement value σ. The water content WC of the plant is obtained from the impedance Z based on Equation (6) to which the obtained sensor sensitivity coefficient B is applied.

Similarly, when the water content is determined from the capacitance between the

electrodes

32, 32, solutions with various electric conductivities are used in advance to determine the amount of water absorbed by the water-sensitive film 33 and the static electricity between the

electrodes

32, 32. Find the relationship with capacitance. When measuring the water content of the plant, the electrical conductivity of the water of 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 obtained from the capacitance C.

• Temperature Compensation The electrical conductivity measurements obtained by the electrical conductivity probe 40 are temperature dependent. In general, conductivity measurements vary by 1-3% per degree Celsius. Therefore, it is preferable to temperature compensate the electrical conductivity measurements. The temperature of water (mainly vascular fluid) in the plant can be measured by the third temperature sensor 51 of the temperature probe 50 . The conductivity measurements are compensated based on the temperature measured by the temperature probe 50 . As a result, the electrical conductivity of water in the plant can be obtained with high accuracy. By further compensating the water content measurement using the temperature-compensated electrical conductivity, the water content can be determined with high accuracy.

Temperature compensation of the electrical conductivity measurement value is performed, for example, by the following procedure. That is, based on equation (8), the electrical conductivity measurement value is converted into electrical conductivity σ ₂₅ [S/m] at a reference temperature of 25°C. Here, β is the temperature coefficient, T is the temperature of the liquid to be measured [°C], and σ is the electrical conductivity measurement value [S/m].

The temperature coefficient β is obtained from equation (9). Here, T ₁ is the temperature other than 25° C. and T ₂ [° C.], T ₂ is the temperature other than 25° C. and T ₁ [° C.], and σ ₁ is the electrical conductivity measurement value at T ₁ [S/m]. , σ ₂ is the conductivity measurement [S/m] at T ₂ .

When the water-sensitive film 33 is made of polyimide, the moisture content measured by the moisture content probe 30 does not depend on the temperature. However, if the water-sensitive membrane 33 is made of other materials, the measured moisture content may be temperature dependent. In such cases, the moisture content measurements may be temperature compensated. That is, the moisture content measurements are directly compensated based on the temperature measured by the temperature probe 50 . Thereby, the water content can be measured with high accuracy.

- Vascular fluid flow velocity measurement The vessel fluid velocity measurement is basically the same as in the first embodiment. That is, power is intermittently supplied to the heater 22 of the temperature probe 20 with heater, and the first temperature sensor 21 measures the temperature rise ΔT _u of the vascular fluid due to the heating of the heater 22 . Then, the vascular liquid flow velocity u is obtained from the temperature rise ΔT _u according to equations (1), (2) and (3).

Here, there is a relationship represented by Equation (10) between the vessel liquid flow velocity u and the heat pulse velocity _Vh . In equation (10), ρ _b is the dry density of the vessel [g/cm ³ ], ρ _s is the density of the vessel liquid [g/cm ³ ], WC is the water content [%], and c _s is The dry specific heat capacity of the vessel [J/gK], _cdw is the specific heat capacity of the vessel liquid [J/gK]. ρ _b , ρ _s , c _s , and _cdw are constants that depend on the plant to be measured, and are determined in advance by experiments or the like.

That is, the coefficient α in formula (3) depends on the water content WC as shown in formula (11).

Therefore, based on the equation (11), the coefficient α is obtained from the measured water content WC. Using this value of α, the vascular fluid flow velocity u is determined based on the equation (3). That is, the vascular bundle liquid flow velocity u is determined based on the water content WC measured by the water content probe 30 in addition to the temperature rise ΔT _u measured by the temperature probe 20 with heater. Thus, by considering the water content, the vascular bundle liquid flow velocity u can be measured with high accuracy.

- Natural temperature gradient correction A natural temperature gradient can be measured by the third temperature sensor 51 of the temperature probe 50 . That is, the natural temperature gradient ΔT ₂ is obtained from the measured value (plant temperature) of the third temperature sensor 51 . The natural temperature gradient ΔT ₂ is used to correct the elevated temperature ΔT ₁ . The details are the same as in the second embodiment. Robustness to the external environment can be enhanced by determining the vascular flux flow rate by considering the natural temperature gradient obtained from the plant temperature.

(thermal analysis)
Thermal analysis of the vascular flux sensor was performed using the modeling software ANSYS. FIG. 9A shows an analysis model. The probe of the vascular flux sensor is only a temperature probe with a heater. A filament heater with a resistance value of 130Ω was mounted on the temperature probe with heater. The tip of the heater-equipped temperature probe was pierced into a 3 mm diameter tube that simulated a plant. Water was run through the tube.

A power of 45.2 mW was supplied to the filament heater for 30 seconds and then turned off for 150 seconds. FIG. 9B shows the temperature distribution when power is supplied to the filament heater. The temperature rise ΔT _u was obtained from the difference between the water temperature at the start of heating by the heater and the water temperature at the end of heating, and the heat pulse velocity V _h was obtained according to Equation (1). Here, the thermal diffusivity D was set to 1.47×10 ⁻⁷ m ² /s, which is the value of water.

The heat pulse velocity V _h was determined by the above procedure while changing the flow rate of water flowing through the tube in the range of 0 to 4 mm/s. The obtained heat pulse velocity _Vh was analyzed to determine the correction coefficient of equation (2). As a result, the correction coefficients of equation (2) are a=0.78×10 ² , b=−1.47×10 ³ , and c=7.84×10 ³ .

FIG. 10 shows the relationship between the corrected heat pulse velocity V _c and the flow velocity. From FIG. 10, it was confirmed that the vascular bundle liquid flow velocity sensor can measure changes in flow velocity in the range of 0 to 4 mm/s.

(Sensor production)
Next, a vascular bundle liquid flow velocity sensor having the configuration shown in FIG. 1 was manufactured. First, a wet oxidation treatment was performed for 2 hours to form an oxide film on the surface of the silicon wafer to form an insulating layer. Next, a Cr layer having a thickness of 0.04 μm was provided as an adhesive layer on the insulating layer, and a corrosion-resistant Au layer having a thickness of 0.2 μm was formed on the adhesive layer by sputtering. Next, a temperature-measuring resistor and a filament heater with a resistance value of 130Ω were patterned, and a photoresist (SU-8 3005) was patterned as a wiring protective film. Finally, using a resist (PMER) as a mask, a needle-like probe was produced by dry etching.

The dimensions of the supporting part of the vascular bundle liquid flow rate sensor are 5 mm x 4 mm. The heated temperature probe is 3 mm long and 480 μm wide. The angle of the tip of the temperature probe with heater is 60°. In addition, the support was packaged with an insulating material to reduce the effects of external temperature changes during use.

(sensor calibration)
Next, we calibrated the manufactured vascular bundle liquid flow velocity sensor. The tip of the heater-equipped temperature probe was pierced into a tube with a diameter of 3 mm, and water was injected using a syringe pump. A power of 45.2 mW was supplied to the filament heater for 30 seconds and then turned off for 150 seconds. The temperature rise ΔT _u was obtained from the difference between the measured value of the temperature sensor at the start of heating and the measured value of the temperature sensor at the end of heating, and the heat pulse velocity V _h was determined according to equation (1). Here, the thermal diffusivity D was set to 1.47×10 ⁻⁷ m ² /s, which is the value of water.

The heat pulse velocity V _h was determined by the above procedure while changing the flow rate of water flowing through the tube in the range of 0 to 4 mm/s. The obtained heat pulse velocity _Vh was analyzed to determine the correction coefficient of equation (2). As a result, the correction coefficients of equation (2) are a=1.10×10 ² , b=−3.10×10 ³ , and c=2.35×10 ⁴ .

FIG. 11 shows the relationship between the corrected heat pulse velocity V _c and the flow velocity. From FIG. 11, it was confirmed that the vascular bundle liquid flow velocity sensor can measure changes in flow velocity in the range of 0 to 4 mm/s.

(Measurement under growing environment)
Next, the water content was measured using tomatoes (Solanum lycopersicum L.) under growing conditions. Tomatoes were seeded in potting soil (420036, DCM Holdings Co., Ltd.) and grown in an artificial climate chamber (NC-410HC, Nihon Ika Kikai Seisakusho Co., Ltd.). Here, the attachment position of the vascular bundle liquid flow velocity sensor was set at a position 150 mm from the soil surface. The environment inside the artificial climate chamber was set at a temperature of 25° C., a humidity of 50%, and a carbon dioxide concentration of 500 ppm. The amount of light in the artificial weather device was changed according to the actual time.

Fig. 12 shows the change over time in the vascular fluid flow rate measured by the vascular bundle liquid flow rate sensor. From FIG. 12, it was confirmed that the vessel fluid flow rate changed depending on the amount of light. This is thought to be due to changes in the amount of light (promotion/suppression of transpiration) in the state of absorbing water from the potting soil, and thus changes in vessel liquid flow velocity. From this, it was confirmed that the vascular bundle fluid flow rate sensor can measure the plant vascular bundle liquid flow rate in real time in a non-destructive manner.

Reference Signs List

1, 2, 3 vascular fluid flow rate sensor 10 support 11 second temperature sensor 20 temperature probe with heater 21 first temperature sensor 22 heater 30 moisture content probe 31 readout electrode pair 33 water sensitive membrane 40 electrical conductivity probe 41 electricity conductivity electrode pair 50 temperature probe 51 third temperature sensor

Claims

A vascular bundle liquid flow rate sensor, characterized in that it has only a heater-equipped temperature probe provided with a first temperature sensor and a heater as a probe to be pierced into a plant.
2. The vascular fluid flow rate sensor of claim 1, further comprising a second temperature sensor for measuring ambient temperature.
a vascular bundle liquid flow rate sensor having a heater-equipped temperature probe provided with a first temperature sensor and a heater, and a support for supporting the heater-equipped temperature probe;
a power source that intermittently supplies power to the heater;
A vascular bundle liquid flow rate measuring device, comprising: a computing unit that calculates a vascular bundle liquid flow rate based on the temperature rise of the vascular bundle liquid due to heating of the heater measured by the first temperature sensor.
4. The vascular bundle liquid flow rate measuring device according to claim 3, further comprising a second temperature sensor for measuring the ambient temperature.
The vascular fluid flow rate sensor has 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 membrane bridging the pair of electrodes. death,
5. The vascular bundle liquid flow rate measuring device according to claim 3, wherein said water content probe is supported by said support portion in a state of being aligned in parallel with said temperature probe with heater.
The vascular fluid flow velocity sensor has an electrical conductivity probe provided with an electrical conductivity electrode pair consisting of a pair of electrodes arranged at a predetermined interval,
6. The vascular bundle liquid flow rate measuring device according to claim 5, wherein said electrical conductivity probe is supported by said support portion in a state of being aligned in parallel with said water content probe.
The vascular fluid flow rate sensor has a temperature probe provided with a third temperature sensor,
7. The vascular bundle liquid flow rate measuring device according to claim 3, wherein said temperature probe is supported by said support portion in a state of being aligned in parallel with said temperature probe with heater.
piercing a plant with a heater-equipped temperature probe provided with a first temperature sensor and a heater;
intermittently supplying power to the heater;
measuring the temperature rise of the vascular bundle liquid due to heating by the heater with the first temperature sensor;
A vascular bundle liquid flow rate measuring method, wherein the vascular bundle liquid flow rate is determined based on the elevated temperature.
piercing the plant with a water content probe provided with a readout electrode pair consisting of a pair of electrodes arranged at a predetermined interval and a water-sensitive membrane spanning the pair of electrodes;
measuring the impedance or capacitance between the pair of electrodes constituting the readout electrode pair;
determining the water content of the plant from impedance measurements or capacitance measurements;
9. The vascular bundle liquid flow rate measuring method according to claim 8, wherein the vascular bundle liquid flow rate is determined based on the elevated temperature and the water content.
piercing the plant with an electrical conductivity probe provided with an electrical conductivity electrode pair consisting of a pair of electrodes arranged at a predetermined interval;
Obtaining the electrical conductivity from the electrical resistance between the pair of electrodes constituting the electrical conductivity electrode pair,
10. The method of claim 9, wherein electrical conductivity measurements are used to compensate for water content measurements.
Obtaining a natural temperature gradient from the temperature of the plant or the ambient temperature,
11. The vascular bundle liquid flow rate measuring method according to claim 8, wherein the temperature rise is corrected using the natural temperature gradient.